Pushrod vs DOHC
Neutrino
06-09-2003, 07:49 PM
Ok from what i know a DOHC setup is complettely superior to a pushrod one....it alowes for faster reving less moving parts and you can tune the exaust and intake timing and lift independently......
so why do american big V8 still use pushrods...i mean american companies obviously have the technology for using DOHC but they keep insisting on pushrods....even high tech modern V8's as the LS6 or the new 5.7 hemi still use them.....i guess only the quadcam in the new mach 1 and the cobra uses a DOHC setup
is there some advantage of using pushrods that i'm not aware of.....are they trying to keep the design more simple or keep the prices down....or are they afraid of making those engines too powerfull:confused:
so why do american big V8 still use pushrods...i mean american companies obviously have the technology for using DOHC but they keep insisting on pushrods....even high tech modern V8's as the LS6 or the new 5.7 hemi still use them.....i guess only the quadcam in the new mach 1 and the cobra uses a DOHC setup
is there some advantage of using pushrods that i'm not aware of.....are they trying to keep the design more simple or keep the prices down....or are they afraid of making those engines too powerfull:confused:
Moppie
06-10-2003, 05:57 AM
The LS6 and others use Pushrods for several reasons:
1, On a low revving engine large capacity with a flat torque curve and lots of grunt there is little advantage to be gained from useing an over head cam set up.
2, its simple. Two heads and 8 cylinders = 4 cams, AND lots of moving parts, which means lots of extra expense to manufactor, especialy when you are having lots of differnt versions of the same engine.
(note Lotus designed Twin Cam heads for the LS1, which was used in the Elise GT1, I think a special version of the Corvette, and as expensive extras from Chevy.
3, Americans are old fashioned, and speaking generaly somewhat naive when it comes to how and engine works, and what it means to be American. As a general market enough ppl assicaite lots of technology like Twin Cams with non American products, i.e. Cars from Japan.
Also a lot of American V8 owners like to tune thier engines, with things like new Cams etc.
By useing a single Cam pushrod engine Chevy keeps it "American" and makes it cheap and simple to add a new aftermarket cam. (think what 4 new cams would cost!)
(NOTE: This comes from a GM Marketing survey, and comments made by a GM engine designer to the Australian Motor Magazine)
4, Space. Twin cam heads simply take up a lot of space, especialy when you have two of them on an already large engine. Its ok in the frount f a truck, but when you want to squeeze it into a Van, or a Corvette?
Quite simply Chevy, stuck with greater displacement as and simple head and valve train design to produce more than acceptable amounts of power.
Quite simply its how thier enginers and company philosophy likes to build engines. It has its disadvantages, but it also has it advantages, but most importantly it works, and it works very well.
1, On a low revving engine large capacity with a flat torque curve and lots of grunt there is little advantage to be gained from useing an over head cam set up.
2, its simple. Two heads and 8 cylinders = 4 cams, AND lots of moving parts, which means lots of extra expense to manufactor, especialy when you are having lots of differnt versions of the same engine.
(note Lotus designed Twin Cam heads for the LS1, which was used in the Elise GT1, I think a special version of the Corvette, and as expensive extras from Chevy.
3, Americans are old fashioned, and speaking generaly somewhat naive when it comes to how and engine works, and what it means to be American. As a general market enough ppl assicaite lots of technology like Twin Cams with non American products, i.e. Cars from Japan.
Also a lot of American V8 owners like to tune thier engines, with things like new Cams etc.
By useing a single Cam pushrod engine Chevy keeps it "American" and makes it cheap and simple to add a new aftermarket cam. (think what 4 new cams would cost!)
(NOTE: This comes from a GM Marketing survey, and comments made by a GM engine designer to the Australian Motor Magazine)
4, Space. Twin cam heads simply take up a lot of space, especialy when you have two of them on an already large engine. Its ok in the frount f a truck, but when you want to squeeze it into a Van, or a Corvette?
Quite simply Chevy, stuck with greater displacement as and simple head and valve train design to produce more than acceptable amounts of power.
Quite simply its how thier enginers and company philosophy likes to build engines. It has its disadvantages, but it also has it advantages, but most importantly it works, and it works very well.
FYRHWK1
06-10-2003, 06:18 AM
Originally posted by Neutrino
Ok from what i know a DOHC setup is complettely superior to a pushrod one....it alowes for faster reving less moving parts and you can tune the exaust and intake timing and lift independently......
nope, more moving parts in a DOHC setup, MANY more, compare the LT5 to the LS6, 3 more cams, twice as many valves, springs and rockers (I believe it uses rockers anyway, if not then lifters) The comparable friction is completely lopsided, the DOHC setup will lose MUCH more power through friction, and that slows down the speed at which the engine revs, in this case DOHC is the worst setup available, in terms of friction, engine acceleration and power loss.
do american big V8 still use pushrods...i mean american companies obviously have the technology for using DOHC but they keep insisting on pushrods....even high tech modern V8's as the LS6 or the new 5.7 hemi still use them.....i guess only the quadcam in the new mach 1 and the cobra uses a DOHC setup
because believe it or not, pushrod setups are JUST as good within their operating range. They may not be able to spin as high, but look at the size of the engines, there's no need to rev over 6500 RPM and if they wanted to, they could anyway. Pushrod engines are lighter, are less complicated, have less valvetrain friction and less moving parts. The engines are shorter in height as well being the single cam is housed in block, this makes for a lower hoodline and lower center of gravity. They cost less to make, and cost less to maintain and fix, did i mention they're lighter? by a good 40-60 lbs, all from the nose of the car.
Look at it this way, the Z06 can lap and run with the lighter 360 modena and heavier 911 turbo, get better gas mileage then both and has less aerodynamic drag, why? its engine is smaller in exterior size, it's likely lighter then the 360 modena V8 although i don't have its specs because of the fact that pushrod engines have less components, less heavy ones at that. GM has one of the BEST DOHC V8s around, the northstar, while you havent heard anything about it it's been in numerous SAE articles for its capability, now if they have one of the best DOHC motors around, why wouldn't they put it in the corvette? Dave Hill will do ANYTHING to lap faster and run better, tradition be damned, if the DOHC engine would work (and there isnt any other DOHC engine that exists thats actually better then what GM has available) better why wouldn't he use it?
As for valve timing, well thy can use single cam variable valve timing to help keep the powerband flat but its much less flexible then the DOHC versions, this is one place where DOHC has advantages. GM has a dual in-block cam motor prototype that runs, produces 450 HP & TQ, passes all emissions tetsing if bodied in a Fbody or corvette type car (weight and aeerodynamics mostly) and has variable valve timing. The motor uses a greater then 2V per cylinder arrangement though how many noone knows, likely 3V. Maintains all of the advantages of a pushrod setup and the second biggest advantage of DOHC, the first being its high RPM stability of course, beauty is in a 6.4L motor you dont need high RPMs.
Both engines have their place and i'm not knocking DOHC, but its far from better in every way, in alot of ways it's worse.
BTW moppie, the Lotus/GM designed engine was the LT5, found in the ZR-1 corvettes from 90-95, great engine as the car held the 24 hr speed record for like 14 years until the W12 supercar beat it, but it was terrible for a daily motor, rebuilds cost 10K+, the valvecovers from one engine cant be swapped onto another for some reason, i forget what, but it has to do with the valvetrain falling apart if it isnt the same. Also was very finnicky, required alot of chain tensioners and guides, the first 2 or 3 years were known for needing an overhaul after 40-50K because the chains would loosen and rattle around. Nice design overall but you'll notice its the only time GM ever let lotus design a motor with them :tongue:
Ok from what i know a DOHC setup is complettely superior to a pushrod one....it alowes for faster reving less moving parts and you can tune the exaust and intake timing and lift independently......
nope, more moving parts in a DOHC setup, MANY more, compare the LT5 to the LS6, 3 more cams, twice as many valves, springs and rockers (I believe it uses rockers anyway, if not then lifters) The comparable friction is completely lopsided, the DOHC setup will lose MUCH more power through friction, and that slows down the speed at which the engine revs, in this case DOHC is the worst setup available, in terms of friction, engine acceleration and power loss.
do american big V8 still use pushrods...i mean american companies obviously have the technology for using DOHC but they keep insisting on pushrods....even high tech modern V8's as the LS6 or the new 5.7 hemi still use them.....i guess only the quadcam in the new mach 1 and the cobra uses a DOHC setup
because believe it or not, pushrod setups are JUST as good within their operating range. They may not be able to spin as high, but look at the size of the engines, there's no need to rev over 6500 RPM and if they wanted to, they could anyway. Pushrod engines are lighter, are less complicated, have less valvetrain friction and less moving parts. The engines are shorter in height as well being the single cam is housed in block, this makes for a lower hoodline and lower center of gravity. They cost less to make, and cost less to maintain and fix, did i mention they're lighter? by a good 40-60 lbs, all from the nose of the car.
Look at it this way, the Z06 can lap and run with the lighter 360 modena and heavier 911 turbo, get better gas mileage then both and has less aerodynamic drag, why? its engine is smaller in exterior size, it's likely lighter then the 360 modena V8 although i don't have its specs because of the fact that pushrod engines have less components, less heavy ones at that. GM has one of the BEST DOHC V8s around, the northstar, while you havent heard anything about it it's been in numerous SAE articles for its capability, now if they have one of the best DOHC motors around, why wouldn't they put it in the corvette? Dave Hill will do ANYTHING to lap faster and run better, tradition be damned, if the DOHC engine would work (and there isnt any other DOHC engine that exists thats actually better then what GM has available) better why wouldn't he use it?
As for valve timing, well thy can use single cam variable valve timing to help keep the powerband flat but its much less flexible then the DOHC versions, this is one place where DOHC has advantages. GM has a dual in-block cam motor prototype that runs, produces 450 HP & TQ, passes all emissions tetsing if bodied in a Fbody or corvette type car (weight and aeerodynamics mostly) and has variable valve timing. The motor uses a greater then 2V per cylinder arrangement though how many noone knows, likely 3V. Maintains all of the advantages of a pushrod setup and the second biggest advantage of DOHC, the first being its high RPM stability of course, beauty is in a 6.4L motor you dont need high RPMs.
Both engines have their place and i'm not knocking DOHC, but its far from better in every way, in alot of ways it's worse.
BTW moppie, the Lotus/GM designed engine was the LT5, found in the ZR-1 corvettes from 90-95, great engine as the car held the 24 hr speed record for like 14 years until the W12 supercar beat it, but it was terrible for a daily motor, rebuilds cost 10K+, the valvecovers from one engine cant be swapped onto another for some reason, i forget what, but it has to do with the valvetrain falling apart if it isnt the same. Also was very finnicky, required alot of chain tensioners and guides, the first 2 or 3 years were known for needing an overhaul after 40-50K because the chains would loosen and rattle around. Nice design overall but you'll notice its the only time GM ever let lotus design a motor with them :tongue:
Hudson
06-10-2003, 09:37 AM
Assuming you're comparing similar engine setups (2-valve per cylinder), a pushrod engine would have fewer camshafts, but add in the additional hardware that moves the valves and you'll have more parts in the OHV engine. Of course a 4-valve/cylinder engine is going to have twice as many valves...but compare apples to apples.
An OHV engine is typically smaller. In the late 1980s, Lotus was developing a DOHC setup for the Corvette engine but it proved too wide to fit in the engine bay of the car (Corvette's get their engines from the bottom and the engine wouldn't fit between the frame rails). Lotus needed to develop the DOHC LT5 engine from the ground up instead. And the reason why the LT5 costs so much to rebuild is that it's a low-volume engine...not necessarily because it's a DOHC engine.
As for OHC setups not being well suited to vans (I've already answered the Corvette problem), Ford uses SOHC engines in their Econoline/Club Wagon vans. GM does not (yet) use any OHC engines in their larger trucks and Dodge's van is going out of production, so there's no need to put the newer OHC engines in it. There would be no problem placing a SOHC or DOHC engine in a van...no more of a problem than a big OHV V8, which have been available.
Ford, Cadillac, Oldsmobile (until recently), and a number of imports use DOHC V8 engines. Ford and Dodge trucks use SOHC V8 engines (Dodge also has OHV V8s).
That survey quoted by GM, as with most all marketing materials, is to support the idea of GM's continued use of OHV engine in the face of global competition moving toward OHC designs. Using the small-block design saves GM money because they haven't had to design an all new engine in fifty years. If I were in business and the world asked me why I did a certain thing that seemed counter to the market, I would provide some sort of research backing my decision as well.
An OHV engine is typically smaller. In the late 1980s, Lotus was developing a DOHC setup for the Corvette engine but it proved too wide to fit in the engine bay of the car (Corvette's get their engines from the bottom and the engine wouldn't fit between the frame rails). Lotus needed to develop the DOHC LT5 engine from the ground up instead. And the reason why the LT5 costs so much to rebuild is that it's a low-volume engine...not necessarily because it's a DOHC engine.
As for OHC setups not being well suited to vans (I've already answered the Corvette problem), Ford uses SOHC engines in their Econoline/Club Wagon vans. GM does not (yet) use any OHC engines in their larger trucks and Dodge's van is going out of production, so there's no need to put the newer OHC engines in it. There would be no problem placing a SOHC or DOHC engine in a van...no more of a problem than a big OHV V8, which have been available.
Ford, Cadillac, Oldsmobile (until recently), and a number of imports use DOHC V8 engines. Ford and Dodge trucks use SOHC V8 engines (Dodge also has OHV V8s).
That survey quoted by GM, as with most all marketing materials, is to support the idea of GM's continued use of OHV engine in the face of global competition moving toward OHC designs. Using the small-block design saves GM money because they haven't had to design an all new engine in fifty years. If I were in business and the world asked me why I did a certain thing that seemed counter to the market, I would provide some sort of research backing my decision as well.
FYRHWK1
06-10-2003, 05:21 PM
Originally posted by Hudson
Assuming you're comparing similar engine setups (2-valve per cylinder), a pushrod engine would have fewer camshafts, but add in the additional hardware that moves the valves and you'll have more parts in the OHV engine. Of course a 4-valve/cylinder engine is going to have twice as many valves...but compare apples to apples.
but its also got 3 more cam gears, springs, retainers and rockers on top of the valves, which in any case the valves are unnecessary unless you're going to use higher RPMs, the current LS6 heads flow more power then they can use up until 6500 RPM, people are making 30-50+ HP on just a cam swap as thats how GM limited it. the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
Assuming you're comparing similar engine setups (2-valve per cylinder), a pushrod engine would have fewer camshafts, but add in the additional hardware that moves the valves and you'll have more parts in the OHV engine. Of course a 4-valve/cylinder engine is going to have twice as many valves...but compare apples to apples.
but its also got 3 more cam gears, springs, retainers and rockers on top of the valves, which in any case the valves are unnecessary unless you're going to use higher RPMs, the current LS6 heads flow more power then they can use up until 6500 RPM, people are making 30-50+ HP on just a cam swap as thats how GM limited it. the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
Neutrino
06-10-2003, 05:37 PM
Originally posted by FYRHWK1
but its also got 3 more cam gears, springs, retainers and rockers on top of the valves, which in any case the valves are unnecessary unless you're going to use higher RPMs, the current LS6 heads flow more power then they can use up until 6500 RPM, people are making 30-50+ HP on just a cam swap as thats how GM limited it. the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
but its also got 3 more cam gears, springs, retainers and rockers on top of the valves, which in any case the valves are unnecessary unless you're going to use higher RPMs, the current LS6 heads flow more power then they can use up until 6500 RPM, people are making 30-50+ HP on just a cam swap as thats how GM limited it. the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
76_cobra
06-10-2003, 05:58 PM
OHC engines are much larger than OHV motors the Ford SOHC 4.6L V8 used in the current mustangs is actually physically larger than a 428ci big block u couldn't fit a 4.6L V8 into the old mustangs that had big blocks in them my dad and I were giong to buy a 4.6 from a mercury marquis to put into my sister's 67 mustang but the engine compartment was much too small for the motor and back then u could order a 428 for those mustangs.
Moppie
06-10-2003, 08:14 PM
Originally posted by Hudson
As for OHC setups not being well suited to vans (I've already answered the Corvette problem), ....................
Didn't say they dont fit, just that since they are smaller on top it's easier for them to fit. IT also allows more interior room inside the van, something I would consider more important than how many cams and valves the engine has. :)
Originally posted by Hudson
That survey quoted by GM, as with most all marketing materials, is to support the idea of GM's continued use of OHV engine in the face of global competition moving toward OHC designs.
Yes, good point. Anyone that has done even a basic study of statistics should know that with the right manipulation you can have a survey represent anything you want.
:cool:
As for OHC setups not being well suited to vans (I've already answered the Corvette problem), ....................
Didn't say they dont fit, just that since they are smaller on top it's easier for them to fit. IT also allows more interior room inside the van, something I would consider more important than how many cams and valves the engine has. :)
Originally posted by Hudson
That survey quoted by GM, as with most all marketing materials, is to support the idea of GM's continued use of OHV engine in the face of global competition moving toward OHC designs.
Yes, good point. Anyone that has done even a basic study of statistics should know that with the right manipulation you can have a survey represent anything you want.
:cool:
2strokebloke
06-10-2003, 08:15 PM
Originally posted by Neutrino
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
Not so much inertia, but engineers do have to take into account how much the pushrods will flex (another reason OHC became popular)
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
Not so much inertia, but engineers do have to take into account how much the pushrods will flex (another reason OHC became popular)
454Casull
06-10-2003, 09:22 PM
Originally posted by 76_cobra
OHC engines are much larger than OHV motors the Ford SOHC 4.6L V8 used in the current mustangs is actually physically larger than a 428ci big block u couldn't fit a 4.6L V8 into the old mustangs that had big blocks in them my dad and I were giong to buy a 4.6 from a mercury marquis to put into my sister's 67 mustang but the engine compartment was much too small for the motor and back then u could order a 428 for those mustangs.
Name an OHC engine that does not have OHV.
OHC engines are much larger than OHV motors the Ford SOHC 4.6L V8 used in the current mustangs is actually physically larger than a 428ci big block u couldn't fit a 4.6L V8 into the old mustangs that had big blocks in them my dad and I were giong to buy a 4.6 from a mercury marquis to put into my sister's 67 mustang but the engine compartment was much too small for the motor and back then u could order a 428 for those mustangs.
Name an OHC engine that does not have OHV.
454Casull
06-10-2003, 09:31 PM
One of the more important reasons is because the cost of R&D is simply too high, especially since GM's current line of engines doesn't really have anything to address. However, GM is developing a new line of engines with contemporary technologies like variable valve timing, DOHC, etc.
IIRC, it's not so much the reciprocating mass that keeps the RPMs so low, but the fact that 2-valve heads can't breathe at higher RPMs. The higher stroke (compared to displacement) compensates.
FYRHWK1 - inline 4s use only 2 cam gears, and the same amount of springs per valve. And I do believe you're using OHV and in-block camshaft interchangeably.
IIRC, it's not so much the reciprocating mass that keeps the RPMs so low, but the fact that 2-valve heads can't breathe at higher RPMs. The higher stroke (compared to displacement) compensates.
FYRHWK1 - inline 4s use only 2 cam gears, and the same amount of springs per valve. And I do believe you're using OHV and in-block camshaft interchangeably.
Moppie
06-10-2003, 09:37 PM
Originally posted by 454Casull
Name an OHC engine that does not have OHV.
I actualy know of one.
There was a company here in NZ that developed a totaly modular all alloy engine that used double over head cams and Side Valves.
Unforunalty it was mostly a front to steal grant money from the Government, and while the engine worked, it didnt exatly work as well as claimed, and of course the whole project was shut down, and the directors prosecuted.
Name an OHC engine that does not have OHV.
I actualy know of one.
There was a company here in NZ that developed a totaly modular all alloy engine that used double over head cams and Side Valves.
Unforunalty it was mostly a front to steal grant money from the Government, and while the engine worked, it didnt exatly work as well as claimed, and of course the whole project was shut down, and the directors prosecuted.
Moppie
06-10-2003, 09:47 PM
Originally posted by 454Casull
One of the more important reasons is because the cost of R&D is simply too high, especially since GM's current line of engines doesn't really have anything to address.
Remember that GM is currently the worlds largest company, and has under its wing some of the worlds leading car manufactors, and access to a lot of technology.
Infact outside of the US the only GM car I can think of that dosnt use an Over head cam engine is the Holden, and they use engine designs sourced from the US anyway.
Lotus already makes an excellent and compant DOHC V8 engine that still has plenty of life left in it, and plenty of room for development, they also have the resouces and knowledge to design a larger V8 for GM, at very little cost, since they are some what desperate for the work.
SAAB is also world leader in engine deisgns, and while they have little experiance with V8's Im sure they could be of great help.
And of course GM currently has a deal going with Honda where GMs desiel technology (Izuzu) is being exchanged for Hondas Hybrid and lean buring engine designs.
They also have a good relationship with Toyota, and have done a lot of Platform sharing over the last 15 years, they have even invested a few $$ here and there in Toyota projects.
I think there must be more to it than R&D costs.
I think keeping it simple, and control and prediction of the market are far better reasons.
One of the more important reasons is because the cost of R&D is simply too high, especially since GM's current line of engines doesn't really have anything to address.
Remember that GM is currently the worlds largest company, and has under its wing some of the worlds leading car manufactors, and access to a lot of technology.
Infact outside of the US the only GM car I can think of that dosnt use an Over head cam engine is the Holden, and they use engine designs sourced from the US anyway.
Lotus already makes an excellent and compant DOHC V8 engine that still has plenty of life left in it, and plenty of room for development, they also have the resouces and knowledge to design a larger V8 for GM, at very little cost, since they are some what desperate for the work.
SAAB is also world leader in engine deisgns, and while they have little experiance with V8's Im sure they could be of great help.
And of course GM currently has a deal going with Honda where GMs desiel technology (Izuzu) is being exchanged for Hondas Hybrid and lean buring engine designs.
They also have a good relationship with Toyota, and have done a lot of Platform sharing over the last 15 years, they have even invested a few $$ here and there in Toyota projects.
I think there must be more to it than R&D costs.
I think keeping it simple, and control and prediction of the market are far better reasons.
ivymike1031
06-11-2003, 12:00 AM
Originally posted by FYRHWK1
the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
Ahhh, but a pushrod engine requires a much higher valve spring force to achieve a particular operating speed... so you end up with a whole lot more friction for each valve. On a per-valve basis, a pushrod system also has way more moving parts, especially when compared to a direct-attack valvetrain.
Originally posted by 454Casull However, GM is developing a new line of engines with contemporary technologies like variable valve timing, DOHC, etc.
I'm curious to know where you heard about this. Was it in a magazine somewhere? I can say (on a tip from a very reliable source) that you're correct, but I wasn't aware that the knowledge was so widespread.
Originally posted by 454Casull yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
The pushrod does have some amount of inertia, but it's usually pretty small compared to some of the other components. It's also on the "light" side of the rocker arm (rocker ratio means that the pr moves less than the valve does, so its mass is relatively less significant). In order of significance to dynamic performance due to inertia, I'd rank the valvetrain components for a pushrod valvetrain as follows:
1) rocker arm (mass ~160gm, inertia ~130 kg*mm^2)
2) valve + retainer + top of spring (mass ~90gm)
3) hydraulic lifter (mass ~90gm)
4) pushrod (mass ~60gm)
In order of significance due to flexibility, I'd rank them as follows:
1) rocker arm or hydraulic lifter depending on system
2) the other one (of the two above)
3) pushrod
the OHV does have alot of moving parts, lifters, rockers, pushrods and springs, retainers etc. but theres less friction inherent.
Ahhh, but a pushrod engine requires a much higher valve spring force to achieve a particular operating speed... so you end up with a whole lot more friction for each valve. On a per-valve basis, a pushrod system also has way more moving parts, especially when compared to a direct-attack valvetrain.
Originally posted by 454Casull However, GM is developing a new line of engines with contemporary technologies like variable valve timing, DOHC, etc.
I'm curious to know where you heard about this. Was it in a magazine somewhere? I can say (on a tip from a very reliable source) that you're correct, but I wasn't aware that the knowledge was so widespread.
Originally posted by 454Casull yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
The pushrod does have some amount of inertia, but it's usually pretty small compared to some of the other components. It's also on the "light" side of the rocker arm (rocker ratio means that the pr moves less than the valve does, so its mass is relatively less significant). In order of significance to dynamic performance due to inertia, I'd rank the valvetrain components for a pushrod valvetrain as follows:
1) rocker arm (mass ~160gm, inertia ~130 kg*mm^2)
2) valve + retainer + top of spring (mass ~90gm)
3) hydraulic lifter (mass ~90gm)
4) pushrod (mass ~60gm)
In order of significance due to flexibility, I'd rank them as follows:
1) rocker arm or hydraulic lifter depending on system
2) the other one (of the two above)
3) pushrod
FYRHWK1
06-11-2003, 02:04 AM
Originally posted by 454Casull
Name an OHC engine that does not have OHV.
all of them, the OHC monicker stands for overhead cam, meaning the cam is over the valves, the OHV setup obviously has the valves over the cam.
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
actually they're hollow, but it does become a problem at high RPM, not only the springing action (flex like 2 stroke said) but keeping it in contact with the rocker and lifter.
Ahhh, but a pushrod engine requires a much higher valve spring force to achieve a particular operating speed... so you end up with a whole lot more friction for each valve. On a per-valve basis, a pushrod system also has way more moving parts, especially when compared to a direct-attack valvetrain.
That happens when you're causing a force to change direction nearly 180 degrees, it's the biggest downfall of the pushrod system i'll admit, and on a per valve basis it does have more friction, but overall power loss is still less, it's like the HP/liter argument, brings up some good points but in the end the overall is what matters.
I'm curious to know where you heard about this. Was it in a magazine somewhere? I can say (on a tip from a very reliable source) that you're correct, but I wasn't aware that the knowledge was so widespread.
The new 3,6L V6, the XV8, the XV12 are all new engines that come with all of that stock, the XV8 & 12 come with cylinder deactivation (DOD) and are meant for large passenger sedans, if those are the engines he's talking about. Rgiht now what I want to know is how far GM and BMW are along in the solenoid valvetrain issue.
In terms of powertrain GM is probably the #1 company for cost effective powerplants and transmissions, even BMW buys automatics for their 5 series from them, they have acess to DOHC motors that are very potent and make one thats world class in its abilities, noen of them outperform the LS6 as of now and the newly designed LS2 will be even better in design, for their application pushrods are perfect.
Name an OHC engine that does not have OHV.
all of them, the OHC monicker stands for overhead cam, meaning the cam is over the valves, the OHV setup obviously has the valves over the cam.
yeah but doesn't the pushrod itself care a lot of inertia...i mean its quite long and pretty solid too.....
actually they're hollow, but it does become a problem at high RPM, not only the springing action (flex like 2 stroke said) but keeping it in contact with the rocker and lifter.
Ahhh, but a pushrod engine requires a much higher valve spring force to achieve a particular operating speed... so you end up with a whole lot more friction for each valve. On a per-valve basis, a pushrod system also has way more moving parts, especially when compared to a direct-attack valvetrain.
That happens when you're causing a force to change direction nearly 180 degrees, it's the biggest downfall of the pushrod system i'll admit, and on a per valve basis it does have more friction, but overall power loss is still less, it's like the HP/liter argument, brings up some good points but in the end the overall is what matters.
I'm curious to know where you heard about this. Was it in a magazine somewhere? I can say (on a tip from a very reliable source) that you're correct, but I wasn't aware that the knowledge was so widespread.
The new 3,6L V6, the XV8, the XV12 are all new engines that come with all of that stock, the XV8 & 12 come with cylinder deactivation (DOD) and are meant for large passenger sedans, if those are the engines he's talking about. Rgiht now what I want to know is how far GM and BMW are along in the solenoid valvetrain issue.
In terms of powertrain GM is probably the #1 company for cost effective powerplants and transmissions, even BMW buys automatics for their 5 series from them, they have acess to DOHC motors that are very potent and make one thats world class in its abilities, noen of them outperform the LS6 as of now and the newly designed LS2 will be even better in design, for their application pushrods are perfect.
ivymike1031
06-11-2003, 10:06 AM
Originally posted by FYRHWK1
That happens when you're causing a force to change direction nearly 180 degrees, it's the biggest downfall of the pushrod system i'll admit, and on a per valve basis it does have more friction, but overall power loss is still less, it's like the HP/liter argument, brings up some good points but in the end the overall is what matters.
The total valvetrain friction is not always less, and it is often more. If you compare an overhead cam valvetrain with 2 valves/cyl to a pushrod valvetrain with 2 valves/cyl, your safest bet would be to say that the overhead cam engine has less total valvetrain friction.
The original question was about pushrod vs DOHC, and in that case it's tough for me to say which would have the higher total valvetrain friction. Possibly the DOHC engine, but I'd hesitate to make a blanket statement.
That happens when you're causing a force to change direction nearly 180 degrees, it's the biggest downfall of the pushrod system i'll admit, and on a per valve basis it does have more friction, but overall power loss is still less, it's like the HP/liter argument, brings up some good points but in the end the overall is what matters.
The total valvetrain friction is not always less, and it is often more. If you compare an overhead cam valvetrain with 2 valves/cyl to a pushrod valvetrain with 2 valves/cyl, your safest bet would be to say that the overhead cam engine has less total valvetrain friction.
The original question was about pushrod vs DOHC, and in that case it's tough for me to say which would have the higher total valvetrain friction. Possibly the DOHC engine, but I'd hesitate to make a blanket statement.
454Casull
06-11-2003, 11:41 AM
Originally posted by ivymike1031
The pushrod does have some amount of inertia, but it's usually pretty small compared to some of the other components. It's also on the "light" side of the rocker arm (rocker ratio means that the pr moves less than the valve does, so its mass is relatively less significant). In order of significance to dynamic performance due to inertia, I'd rank the valvetrain components for a pushrod valvetrain as follows:
1) rocker arm (mass ~160gm, inertia ~130 kg*mm^2)
2) valve + retainer + top of spring (mass ~90gm)
3) hydraulic lifter (mass ~90gm)
4) pushrod (mass ~60gm)
In order of significance due to flexibility, I'd rank them as follows:
1) rocker arm or hydraulic lifter depending on system
2) the other one (of the two above)
3) pushrod
That last quote of yours in your post wasn't mine. :)
The pushrod does have some amount of inertia, but it's usually pretty small compared to some of the other components. It's also on the "light" side of the rocker arm (rocker ratio means that the pr moves less than the valve does, so its mass is relatively less significant). In order of significance to dynamic performance due to inertia, I'd rank the valvetrain components for a pushrod valvetrain as follows:
1) rocker arm (mass ~160gm, inertia ~130 kg*mm^2)
2) valve + retainer + top of spring (mass ~90gm)
3) hydraulic lifter (mass ~90gm)
4) pushrod (mass ~60gm)
In order of significance due to flexibility, I'd rank them as follows:
1) rocker arm or hydraulic lifter depending on system
2) the other one (of the two above)
3) pushrod
That last quote of yours in your post wasn't mine. :)
454Casull
06-11-2003, 11:44 AM
all of them, the OHC monicker stands for overhead cam, meaning the cam is over the valves, the OHV setup obviously has the valves over the cam.
WTF? OverHead Cam means the cams are over the heads, and OverHead Valves means the valves are over the heads. Now excepting that example Moppie gave, cams over the head actuate valves over the head, therefore OHC tends to have OHV.
WTF? OverHead Cam means the cams are over the heads, and OverHead Valves means the valves are over the heads. Now excepting that example Moppie gave, cams over the head actuate valves over the head, therefore OHC tends to have OHV.
Hudson
06-11-2003, 12:43 PM
While OHV does technically mean "overhead valve" which all production automotive piston engines qualify as, OHV in modern terminology is used to refer to engines with their camshaft not over the cylinder heads. But you all knew that already.
Originally posted by Moppie
Remember that GM is currently the worlds largest company, and has under its wing some of the worlds leading car manufactors, and access to a lot of technology.
"World's largest company is actually wrong. Even "world's largest automotive company" can be called into question depending on how you define it. GM does make more automobiles and trucks than any other company (toy companies aside).
Originally posted by Moppie
Lotus already makes an excellent and compant DOHC V8 engine that still has plenty of life left in it, and plenty of room for development, they also have the resouces and knowledge to design a larger V8 for GM, at very little cost, since they are some what desperate for the work.
I'm a little confused here. GM hasn't owned Lotus in about a decade.
Originally posted by Moppie
SAAB is also world leader in engine deisgns, and while they have little experiance with V8's Im sure they could be of great help.
Actually, if you look at it...Saab is using GM engines more and more. It's only a matter of time (about three years) before all engines used in Saabs will be based on GM designs...which have come from Germany.
Originally posted by Moppie
Remember that GM is currently the worlds largest company, and has under its wing some of the worlds leading car manufactors, and access to a lot of technology.
"World's largest company is actually wrong. Even "world's largest automotive company" can be called into question depending on how you define it. GM does make more automobiles and trucks than any other company (toy companies aside).
Originally posted by Moppie
Lotus already makes an excellent and compant DOHC V8 engine that still has plenty of life left in it, and plenty of room for development, they also have the resouces and knowledge to design a larger V8 for GM, at very little cost, since they are some what desperate for the work.
I'm a little confused here. GM hasn't owned Lotus in about a decade.
Originally posted by Moppie
SAAB is also world leader in engine deisgns, and while they have little experiance with V8's Im sure they could be of great help.
Actually, if you look at it...Saab is using GM engines more and more. It's only a matter of time (about three years) before all engines used in Saabs will be based on GM designs...which have come from Germany.
ivymike1031
06-11-2003, 01:35 PM
"World's largest company is actually wrong. Even "world's largest automotive company" can be called into question depending on how you define it. GM does make more automobiles and trucks than any other company (toy companies aside).
More than DaimlerChrylser (freightliner, mitsu, etc)?
More than DaimlerChrylser (freightliner, mitsu, etc)?
Hudson
06-11-2003, 02:32 PM
The most recent numbers I have show that GM produces far more vehicles than even the second place company...
1. General Motors
2. Ford Motor Company
3. Toyota Motor Corporation
4. Volkswagen AG
5. Renault SA/Nissan Motor
6. DaimlerChrysler
7. PSA Peugeot-Citroen
8. Honda Motor Company
9. Hyundai Group, including Kia Motors Corporation
10. Fiat SpA, including Fiat Auto and Ferrari SpA
1. General Motors
2. Ford Motor Company
3. Toyota Motor Corporation
4. Volkswagen AG
5. Renault SA/Nissan Motor
6. DaimlerChrysler
7. PSA Peugeot-Citroen
8. Honda Motor Company
9. Hyundai Group, including Kia Motors Corporation
10. Fiat SpA, including Fiat Auto and Ferrari SpA
FYRHWK1
06-12-2003, 03:11 AM
Originally posted by 454Casull
all of them, the OHC monicker stands for overhead cam, meaning the cam is over the valves, the OHV setup obviously has the valves over the cam.
WTF? OverHead Cam means the cams are over the heads, and OverHead Valves means the valves are over the heads. Now excepting that example Moppie gave, cams over the head actuate valves over the head, therefore OHC tends to have OHV.
sorry bucky, but that would make no sense at all, all OHC motors would also be OHV as well, OHC refers to the cams being over the valves, OHV is the valves over the heads, it's pretty simple...
The total valvetrain friction is not always less, and it is often more. If you compare an overhead cam valvetrain with 2 valves/cyl to a pushrod valvetrain with 2 valves/cyl, your safest bet would be to say that the overhead cam engine has less total valvetrain friction.
Nothing is always, but on the whole it's fairly safe to say that a DOHC V8 will have a good amount of extra friction involved, you're talking 4 times the bearing surfaces, gears and all the rest that goes with it.
all of them, the OHC monicker stands for overhead cam, meaning the cam is over the valves, the OHV setup obviously has the valves over the cam.
WTF? OverHead Cam means the cams are over the heads, and OverHead Valves means the valves are over the heads. Now excepting that example Moppie gave, cams over the head actuate valves over the head, therefore OHC tends to have OHV.
sorry bucky, but that would make no sense at all, all OHC motors would also be OHV as well, OHC refers to the cams being over the valves, OHV is the valves over the heads, it's pretty simple...
The total valvetrain friction is not always less, and it is often more. If you compare an overhead cam valvetrain with 2 valves/cyl to a pushrod valvetrain with 2 valves/cyl, your safest bet would be to say that the overhead cam engine has less total valvetrain friction.
Nothing is always, but on the whole it's fairly safe to say that a DOHC V8 will have a good amount of extra friction involved, you're talking 4 times the bearing surfaces, gears and all the rest that goes with it.
Hudson
06-12-2003, 11:21 AM
Originally posted by FYRHWK1
Nothing is always, but on the whole it's fairly safe to say that a DOHC V8 will have a good amount of extra friction involved, you're talking 4 times the bearing surfaces, gears and all the rest that goes with it.
Two points:
One: OHC engines are, for the most part, also OHV engines...technically. As you said, OHV means the valves are in the heads and OHC means the cams are over the heads. All OHC engines that I've seen have valves in the heads as well. OHV was originally designed to differentiate flat-head (valve-in-block, L-head) engines from the more efficient valve-in-head design. Today, OHV typically refers to and engine who's camshaft is in the block...where the OHC name refers to engine who's camshaft is in the head.
Two: I don't think "it's fairly safe to say that a DOHC V8 will have a good amount of extra friction." In addition to the bearing surfaces, you're missing the friction associated with all of the hardware necessary to move the valvetrain that is reduced in an OHC design. Additionally, there is the inertia of all the pushrod parts that are lacking in an OHC design. If there are "four times the bearing surfaces," this just means that the DOHC V8 would run smoother than a pushrod with more flex in its camshaft.
Nothing is always, but on the whole it's fairly safe to say that a DOHC V8 will have a good amount of extra friction involved, you're talking 4 times the bearing surfaces, gears and all the rest that goes with it.
Two points:
One: OHC engines are, for the most part, also OHV engines...technically. As you said, OHV means the valves are in the heads and OHC means the cams are over the heads. All OHC engines that I've seen have valves in the heads as well. OHV was originally designed to differentiate flat-head (valve-in-block, L-head) engines from the more efficient valve-in-head design. Today, OHV typically refers to and engine who's camshaft is in the block...where the OHC name refers to engine who's camshaft is in the head.
Two: I don't think "it's fairly safe to say that a DOHC V8 will have a good amount of extra friction." In addition to the bearing surfaces, you're missing the friction associated with all of the hardware necessary to move the valvetrain that is reduced in an OHC design. Additionally, there is the inertia of all the pushrod parts that are lacking in an OHC design. If there are "four times the bearing surfaces," this just means that the DOHC V8 would run smoother than a pushrod with more flex in its camshaft.
Moppie
06-12-2003, 08:45 PM
Originally posted by Hudson
1. "World's largest company is actually wrong. Even "world's largest automotive company" can be called into question depending on how you define it.
2, I'm a little confused here. GM hasn't owned Lotus in about a decade.
1, Hmmm its way OT to argue, but I always thought that GM and GE have been swapping the title for some time, and that with the fall in Airline useage in the last couple of years GM had taken the top spot?
(of course someother large multinational could have risen from the depths that Im unaware of)
2, Tell that to Lotus. GM still has some share in the company, and Lotus still use GM's engine managment on the V8 Esprit. (theres a diagnostic comp at work for the V8 that will also read codes from nearly any GM 6 or 8cyl engine from the last 10 years).
And even if they are no wholy or partly owned by GM, lotus engienering has a long history of doing development work for GM, and there is no reason for it to stop.
And yes the SAAB's are becoming more and more Opelised but SABB is still supplying a lot of the R&D that is going into the Opel engines, and platforms.
SAAB you have to remember along with the likes of Lotus has been one of the most inovative manufactors in the last 50 years.
1. "World's largest company is actually wrong. Even "world's largest automotive company" can be called into question depending on how you define it.
2, I'm a little confused here. GM hasn't owned Lotus in about a decade.
1, Hmmm its way OT to argue, but I always thought that GM and GE have been swapping the title for some time, and that with the fall in Airline useage in the last couple of years GM had taken the top spot?
(of course someother large multinational could have risen from the depths that Im unaware of)
2, Tell that to Lotus. GM still has some share in the company, and Lotus still use GM's engine managment on the V8 Esprit. (theres a diagnostic comp at work for the V8 that will also read codes from nearly any GM 6 or 8cyl engine from the last 10 years).
And even if they are no wholy or partly owned by GM, lotus engienering has a long history of doing development work for GM, and there is no reason for it to stop.
And yes the SAAB's are becoming more and more Opelised but SABB is still supplying a lot of the R&D that is going into the Opel engines, and platforms.
SAAB you have to remember along with the likes of Lotus has been one of the most inovative manufactors in the last 50 years.
FYRHWK1
06-12-2003, 11:58 PM
Originally posted by Hudson
Two points:
One: OHC engines are, for the most part, also OHV engines...technically. As you said, OHV means the valves are in the heads and OHC means the cams are over the heads. All OHC engines that I've seen have valves in the heads as well. OHV was originally designed to differentiate flat-head (valve-in-block, L-head) engines from the more efficient valve-in-head design. Today, OHV typically refers to and engine who's camshaft is in the block...where the OHC name refers to engine who's camshaft is in the head.
Two: I don't think "it's fairly safe to say that a DOHC V8 will have a good amount of extra friction." In addition to the bearing surfaces, you're missing the friction associated with all of the hardware necessary to move the valvetrain that is reduced in an OHC design. Additionally, there is the inertia of all the pushrod parts that are lacking in an OHC design. If there are "four times the bearing surfaces," this just means that the DOHC V8 would run smoother than a pushrod with more flex in its camshaft.
Yes both have the valves in the head above the chamber, but if you're going to use the terms OHV and OHC to differ them in comparison then it wouldn't really work if OHC were both of them.
the OHC design eliminates the pushrod and either the rocker or the lifter, maybe both of those last 2 if it uses a replacable shim over the valvestem, it still has 4 times the bearing friction and twice as much spring pressure to overcome, if you add the VVT syste m into the mix then it's an even bigger gap with the compleexity of the added gears. Run smoother? cam flex? how could you possibly get cam flex in an OHV design? the torsional stress being put on it would hardly be enough to flex it, and being theres more then enough main bearings to support it Flex is nigh unmeasureable, the crank is a different story altogether.
Two points:
One: OHC engines are, for the most part, also OHV engines...technically. As you said, OHV means the valves are in the heads and OHC means the cams are over the heads. All OHC engines that I've seen have valves in the heads as well. OHV was originally designed to differentiate flat-head (valve-in-block, L-head) engines from the more efficient valve-in-head design. Today, OHV typically refers to and engine who's camshaft is in the block...where the OHC name refers to engine who's camshaft is in the head.
Two: I don't think "it's fairly safe to say that a DOHC V8 will have a good amount of extra friction." In addition to the bearing surfaces, you're missing the friction associated with all of the hardware necessary to move the valvetrain that is reduced in an OHC design. Additionally, there is the inertia of all the pushrod parts that are lacking in an OHC design. If there are "four times the bearing surfaces," this just means that the DOHC V8 would run smoother than a pushrod with more flex in its camshaft.
Yes both have the valves in the head above the chamber, but if you're going to use the terms OHV and OHC to differ them in comparison then it wouldn't really work if OHC were both of them.
the OHC design eliminates the pushrod and either the rocker or the lifter, maybe both of those last 2 if it uses a replacable shim over the valvestem, it still has 4 times the bearing friction and twice as much spring pressure to overcome, if you add the VVT syste m into the mix then it's an even bigger gap with the compleexity of the added gears. Run smoother? cam flex? how could you possibly get cam flex in an OHV design? the torsional stress being put on it would hardly be enough to flex it, and being theres more then enough main bearings to support it Flex is nigh unmeasureable, the crank is a different story altogether.
Hudson
06-13-2003, 12:55 AM
Originally posted by Moppie
...Tell that to Lotus. GM still has some share in the company, and Lotus still use GM's engine managment on the V8 Esprit. (theres a diagnostic comp at work for the V8 that will also read codes from nearly any GM 6 or 8cyl engine from the last 10 years).
And even if they are no wholy or partly owned by GM, lotus engienering has a long history of doing development work for GM, and there is no reason for it to stop.
I don't have to tell it to Lotus...they know who owns them.
Even if Lotus uses GM engine management systems, that doesn't mean there's any connection between the two companies. Engine manufacturers buy parts from other manufacturers all the time.
GM bought Lotus in the 1980s...and sold it in the early 1990s to Bugatti International. When Bugatti began to fail, they sold off most of Lotus to the Malaysian company Proton. The current ownership of Lotus is Proton at 80% and Bugatti International (Romano Artioli) at 20%. GM sold all of its interests in Lotus.
And Lotus does development work for many car companies...that's their main business.
...Tell that to Lotus. GM still has some share in the company, and Lotus still use GM's engine managment on the V8 Esprit. (theres a diagnostic comp at work for the V8 that will also read codes from nearly any GM 6 or 8cyl engine from the last 10 years).
And even if they are no wholy or partly owned by GM, lotus engienering has a long history of doing development work for GM, and there is no reason for it to stop.
I don't have to tell it to Lotus...they know who owns them.
Even if Lotus uses GM engine management systems, that doesn't mean there's any connection between the two companies. Engine manufacturers buy parts from other manufacturers all the time.
GM bought Lotus in the 1980s...and sold it in the early 1990s to Bugatti International. When Bugatti began to fail, they sold off most of Lotus to the Malaysian company Proton. The current ownership of Lotus is Proton at 80% and Bugatti International (Romano Artioli) at 20%. GM sold all of its interests in Lotus.
And Lotus does development work for many car companies...that's their main business.
SaabJohan
06-13-2003, 03:12 PM
Originally posted by Hudson
Actually, if you look at it...Saab is using GM engines more and more. It's only a matter of time (about three years) before all engines used in Saabs will be based on GM designs...which have come from Germany.
The Saab techs are calling them "frigolit engines" since they are so sensitive. So all those engines, both Opel and "global" engines must be redesigned before they can be used. For example the Opel 3.0 V6 engine failed Saabs durability test, it was redesigned, but still it wasn't a specially good engine. After a while it was taken out of production because of high fuel consumtion and exhaust emissions. It was later released with assymetric turbocharging and a more advanced EMS, which reduced the fuel consumtion and exhaust emissions. But still, it never became a popular choice. Now the story is similar with the new 9-3, the engine is GM:s global engine (I think the basic design is done by Lotus), and even that it has been equipped with stronger internal parts and a more advanced EMS the maximum output is 210 hp since the basic design is so weak. Sometimes GM is just trying to cut costs a little too much.
Actually, if you look at it...Saab is using GM engines more and more. It's only a matter of time (about three years) before all engines used in Saabs will be based on GM designs...which have come from Germany.
The Saab techs are calling them "frigolit engines" since they are so sensitive. So all those engines, both Opel and "global" engines must be redesigned before they can be used. For example the Opel 3.0 V6 engine failed Saabs durability test, it was redesigned, but still it wasn't a specially good engine. After a while it was taken out of production because of high fuel consumtion and exhaust emissions. It was later released with assymetric turbocharging and a more advanced EMS, which reduced the fuel consumtion and exhaust emissions. But still, it never became a popular choice. Now the story is similar with the new 9-3, the engine is GM:s global engine (I think the basic design is done by Lotus), and even that it has been equipped with stronger internal parts and a more advanced EMS the maximum output is 210 hp since the basic design is so weak. Sometimes GM is just trying to cut costs a little too much.
FYRHWK1
06-16-2003, 06:13 PM
I dout the ecotec 4 cylinder is lotus designed, it's actually reliable, but you may be right as i cant find any info on it now. Opels 3.0L V6 isnt a GM global engine, each division has its own incentive to make their own motors, GMs true global motors are the LS series V8, the ecotec and the new 3.6L v6, i dont believe i've ever seen the northstar used anywhere efore, but since it was only available in FWD configuration that may change now that it's redesigned for RWD app. Also, is htat 3L Opel V6 related to the POS 3.2L CTS motor? i know it's opel in design and a cheap piece to buy, that piece of junk is the reason they dropped the perfectly great 3.5L V6.
Moppie
06-16-2003, 11:15 PM
Originally posted by Hudson
I don't have to tell it to Lotus...they know who owns them.
.
I do a lot of part time work for the New Zealand Lotus agent, who of course has a lot of contact with Lotus UK, and Lotus Australia.
The 80-20 split your described is not totaly accurate, theres about a 10% stake that is either held by GM, or partly GM,and partly some other unknown party. :)
And I think that 20 years of first ownership, and then design work counts as a pretty close tie with another company.
:smile:
I don't have to tell it to Lotus...they know who owns them.
.
I do a lot of part time work for the New Zealand Lotus agent, who of course has a lot of contact with Lotus UK, and Lotus Australia.
The 80-20 split your described is not totaly accurate, theres about a 10% stake that is either held by GM, or partly GM,and partly some other unknown party. :)
And I think that 20 years of first ownership, and then design work counts as a pretty close tie with another company.
:smile:
Hudson
06-18-2003, 01:01 PM
Originally posted by Moppie
I do a lot of part time work for the New Zealand Lotus agent, who of course has a lot of contact with Lotus UK, and Lotus Australia.
The 80-20 split your described is not totaly accurate, theres about a 10% stake that is either held by GM, or partly GM,and partly some other unknown party. :)
And I think that 20 years of first ownership, and then design work counts as a pretty close tie with another company.
:smile:
If you can find a good source saying otherwise, I'll believe you. But from the research I've done, GM sold off its holdings in Lotus to Bugatti International around 1993 and GM doesn't have any significant amount of the company. The 80/20 ownership split is accurate (+/- 1%) as far as I've found.
I do a lot of part time work for the New Zealand Lotus agent, who of course has a lot of contact with Lotus UK, and Lotus Australia.
The 80-20 split your described is not totaly accurate, theres about a 10% stake that is either held by GM, or partly GM,and partly some other unknown party. :)
And I think that 20 years of first ownership, and then design work counts as a pretty close tie with another company.
:smile:
If you can find a good source saying otherwise, I'll believe you. But from the research I've done, GM sold off its holdings in Lotus to Bugatti International around 1993 and GM doesn't have any significant amount of the company. The 80/20 ownership split is accurate (+/- 1%) as far as I've found.
Hudson
06-18-2003, 01:10 PM
Originally posted by FYRHWK1
I dout the ecotec 4 cylinder is lotus designed, it's actually reliable, but you may be right as i cant find any info on it now. Opels 3.0L V6 isnt a GM global engine, each division has its own incentive to make their own motors, GMs true global motors are the LS series V8, the ecotec and the new 3.6L v6, i dont believe i've ever seen the northstar used anywhere efore, but since it was only available in FWD configuration that may change now that it's redesigned for RWD app. Also, is htat 3L Opel V6 related to the POS 3.2L CTS motor? i know it's opel in design and a cheap piece to buy, that piece of junk is the reason they dropped the perfectly great 3.5L V6.
Lotus probably did some engineering work on the L850/Ecotec (as they do work with many companies), but why does their involvement in the engine's design mean it wouldn't be reliable?
GM Europe and GM North America have, until recently, designed their own engines. In recent years, the two "divisions" of GM have been integrating their engineering work. Current global engines include the L850/Ecotec four-cylinder and the "High-Feature" V6.
GM Europe's "MV6" six-cylinder engine has been used in Opel/Vauxhall, Holden, Saab, Cadillac, and Saturn products, but I wouldn't necessarily call it a "global engine."
By the way, what is the "LS series V8?"
I dout the ecotec 4 cylinder is lotus designed, it's actually reliable, but you may be right as i cant find any info on it now. Opels 3.0L V6 isnt a GM global engine, each division has its own incentive to make their own motors, GMs true global motors are the LS series V8, the ecotec and the new 3.6L v6, i dont believe i've ever seen the northstar used anywhere efore, but since it was only available in FWD configuration that may change now that it's redesigned for RWD app. Also, is htat 3L Opel V6 related to the POS 3.2L CTS motor? i know it's opel in design and a cheap piece to buy, that piece of junk is the reason they dropped the perfectly great 3.5L V6.
Lotus probably did some engineering work on the L850/Ecotec (as they do work with many companies), but why does their involvement in the engine's design mean it wouldn't be reliable?
GM Europe and GM North America have, until recently, designed their own engines. In recent years, the two "divisions" of GM have been integrating their engineering work. Current global engines include the L850/Ecotec four-cylinder and the "High-Feature" V6.
GM Europe's "MV6" six-cylinder engine has been used in Opel/Vauxhall, Holden, Saab, Cadillac, and Saturn products, but I wouldn't necessarily call it a "global engine."
By the way, what is the "LS series V8?"
FYRHWK1
06-18-2003, 08:12 PM
The Lotus reliability remark was just poking fun, they don't have the best track record when working with GM, the LT5 was half designed by them and never was known as a high mileage motor. So the 3.2L is the 3.0 V6, allrigth, well then i can agree its a terrible POS, fortunatly the CTS will soon be getting the new 3.6L so we'll see how much better it performs. the LS series V8 would be the LS1, LS6 and upcoming LS2 and LS7 engines.
Hudson
06-18-2003, 11:19 PM
One engine is not a good measure of the expansive work Lotus has done with GM.
The "LS Series V8" as you call it is known as GM's Small Block family. The LS1/LS6 is related to the 4.8/5.3/6.0 V8s used in the trucks...and related to the previous generation "Chevrolet Small Block" family. These engines are hardly considered "global engines." If you're considering the fact that the V8s are used in North America and Australia, so is the 3.8L OHV V6....so is the MV6...
The "LS Series V8" as you call it is known as GM's Small Block family. The LS1/LS6 is related to the 4.8/5.3/6.0 V8s used in the trucks...and related to the previous generation "Chevrolet Small Block" family. These engines are hardly considered "global engines." If you're considering the fact that the V8s are used in North America and Australia, so is the 3.8L OHV V6....so is the MV6...
FYRHWK1
06-18-2003, 11:47 PM
well, while it is a smallblock chevy, it has nothing at all to do with the previous 2 generations at all so i've been tentative to simply call it that, and gen III smallblock doesnt usually get the point across. As to lotus, i've never known them to be a very good engine building company, their chassis are nice for small sportscars but powertrain wise nothing they've done ever really stood out in my mind.
Moppie
06-19-2003, 02:36 AM
Originally posted by FYRHWK1
As to lotus, i've never known them to be a very good engine building company, their chassis are nice for small sportscars but powertrain wise nothing they've done ever really stood out in my mind.
This is getting OT, but: You clearly have a limited experiance with Lotus engines. The Lotus Twin Cam, based on the ford 1600cc Kent Block is a great engine, one of the best 4cyl engines ever made infact. It formed the basis for the Cosworth 16v Twin Cam, which was then copied by Toyota to make the famous 4age 1600cc 4cyl engine.
The 2.2L lotus Twin Cam engine is totaly designed by Lotus, and is another great engine. Making over 260-270hp with a simple Turbo and blow through Carb set up it has an amazingly flat torque curve that rivals most fuel injected engines, and is amazingly strong, capable of revving well beyond the fueling limits of the carbs. It suffers from the usual english engine oil leaks, but otherwise is extremly reliable.
The new Lotus V8 is an even greater engine, with an amazingly flat torque curve and is extremly reliable.
The only weakness in Lotus drivelines is the Renult g/boxs, but blame Renult for that not Lotus. :)
As to lotus, i've never known them to be a very good engine building company, their chassis are nice for small sportscars but powertrain wise nothing they've done ever really stood out in my mind.
This is getting OT, but: You clearly have a limited experiance with Lotus engines. The Lotus Twin Cam, based on the ford 1600cc Kent Block is a great engine, one of the best 4cyl engines ever made infact. It formed the basis for the Cosworth 16v Twin Cam, which was then copied by Toyota to make the famous 4age 1600cc 4cyl engine.
The 2.2L lotus Twin Cam engine is totaly designed by Lotus, and is another great engine. Making over 260-270hp with a simple Turbo and blow through Carb set up it has an amazingly flat torque curve that rivals most fuel injected engines, and is amazingly strong, capable of revving well beyond the fueling limits of the carbs. It suffers from the usual english engine oil leaks, but otherwise is extremly reliable.
The new Lotus V8 is an even greater engine, with an amazingly flat torque curve and is extremly reliable.
The only weakness in Lotus drivelines is the Renult g/boxs, but blame Renult for that not Lotus. :)
FYRHWK1
06-19-2003, 05:04 AM
Extremely limited, but noone i know whos from europe has ever really mentioned them as top motors, good to hear theyre capable though.
SaabJohan
06-19-2003, 03:50 PM
Originally posted by FYRHWK1
I dout the ecotec 4 cylinder is lotus designed, it's actually reliable, but you may be right as i cant find any info on it now. Opels 3.0L V6 isnt a GM global engine, each division has its own incentive to make their own motors, GMs true global motors are the LS series V8, the ecotec and the new 3.6L v6, i dont believe i've ever seen the northstar used anywhere efore, but since it was only available in FWD configuration that may change now that it's redesigned for RWD app. Also, is htat 3L Opel V6 related to the POS 3.2L CTS motor? i know it's opel in design and a cheap piece to buy, that piece of junk is the reason they dropped the perfectly great 3.5L V6.
Sadly to say, the ecotec isn't that reliable. Well, maybe if it stays original but if you try to modify it things will start to fall apart already at low power outputs. Saab has three versions of this engines, 150, 175 and 210 hp. The 175 hp engine will start to break if the output is increase to around 210 hp. If the 210 hp engines power is increased to more than 220-230 hp the same thing will happend to that engine.
Known weaknesses are cylinder head, cylinderwalls and the "bridge" that carries the crankshaft. A guess is also that pistons and con-rods are weak too.
I dout the ecotec 4 cylinder is lotus designed, it's actually reliable, but you may be right as i cant find any info on it now. Opels 3.0L V6 isnt a GM global engine, each division has its own incentive to make their own motors, GMs true global motors are the LS series V8, the ecotec and the new 3.6L v6, i dont believe i've ever seen the northstar used anywhere efore, but since it was only available in FWD configuration that may change now that it's redesigned for RWD app. Also, is htat 3L Opel V6 related to the POS 3.2L CTS motor? i know it's opel in design and a cheap piece to buy, that piece of junk is the reason they dropped the perfectly great 3.5L V6.
Sadly to say, the ecotec isn't that reliable. Well, maybe if it stays original but if you try to modify it things will start to fall apart already at low power outputs. Saab has three versions of this engines, 150, 175 and 210 hp. The 175 hp engine will start to break if the output is increase to around 210 hp. If the 210 hp engines power is increased to more than 220-230 hp the same thing will happend to that engine.
Known weaknesses are cylinder head, cylinderwalls and the "bridge" that carries the crankshaft. A guess is also that pistons and con-rods are weak too.
FYRHWK1
06-20-2003, 01:57 AM
I've never heard of one going south myself, but then again i've never heard of a modified ecotec, stock they'll last as long as you like them to but i'd believe it that they'll fall apart at higher levels. Theres a new version coming out built for the sport compact tuner market that should improve the design, time will tell though. Doesnt the vauxhall VX220 turbo and opel speedster turbo run an ecotec? i'm sure those engines are a good bit stronger.
454Casull
06-20-2003, 04:05 PM
Originally posted by SaabJohan
Sadly to say, the ecotec isn't that reliable. Well, maybe if it stays original but if you try to modify it things will start to fall apart already at low power outputs. Saab has three versions of this engines, 150, 175 and 210 hp. The 175 hp engine will start to break if the output is increase to around 210 hp. If the 210 hp engines power is increased to more than 220-230 hp the same thing will happend to that engine.
Known weaknesses are cylinder head, cylinderwalls and the "bridge" that carries the crankshaft. A guess is also that pistons and con-rods are weak too.
Does the Ecotec use an aluminum block?
Sadly to say, the ecotec isn't that reliable. Well, maybe if it stays original but if you try to modify it things will start to fall apart already at low power outputs. Saab has three versions of this engines, 150, 175 and 210 hp. The 175 hp engine will start to break if the output is increase to around 210 hp. If the 210 hp engines power is increased to more than 220-230 hp the same thing will happend to that engine.
Known weaknesses are cylinder head, cylinderwalls and the "bridge" that carries the crankshaft. A guess is also that pistons and con-rods are weak too.
Does the Ecotec use an aluminum block?
FYRHWK1
06-20-2003, 06:21 PM
yes, all aluminum.
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