vtec vs displacement

I can appreciate the genious behond vtec, but i wish honda would give us larger displacement (not on a luxury car).

Or american car companies should impliment variable valve timing more.

Sliding cams on the next camaro? thatd melt my face

displacement or vtec? a 220hp american V8 or a 220 hp honda k series?

Not many american V8's only make 220 hp anymore, at least none I can think of, The least I can think of is the 4.7L Dodge Truck engine that makes around 260 hp. Also, some American brands DO use Variable Valve Timing. The only V8 with it though is the Cadillac Northstar. Also, Honda has slowly been increasing displacement, the civic has gone from 1.6L to 1.8L over the last 5 years and the Integra went from 1.8 to 2.0. The CRV went from 2.0 to 2.4 and the Accord 4 cyl from 2.3 to 2.4.

theres no replacement for displacment. if they would combine valve timing with more displacement their cars would be a force to be reconed with.

they are going to impliment vvt on the next gmt-900's, but see theseare pushrod motors, not sohc, or dohc, the reason they call it a small block is because u can fit it int he space of a bmw inline six, making more power with way fewer parts, pushrod motors only have one cam, so when ppl say that foreign cars are better cuz they can make so much power out of a smaller motor, in terms of displacement yes, but the smallblock still takes up less space under the hood, plus dohc motors are more costly to make, cadillac came out with the first quad cam V8 in 1992.

I think some of the Ecotecs use VVT.

I still like displacement, but I'm not knocking anything away from Honda's Vtec. Its a great design, and it allows their small engines to breath better throughout the powerband. Throwing it in larger engines would only increase output futher. Combining that with variable intake and exhaust setups will only continue to push the envelope. Of coarse this is costly and more space engaging, but there is always a trade off. Bigger engines can afford to be simpler and still provide plenty of power and linear performance.

I guess it all depends on what you like. If your taste is small engines that offer 'peaky' characteristics, then a small Honda engine is the perfect match. If your out for larger engines that pull harder down low and continues pulling in a linear fashion, then maybe a small block V8 is your answer.

cadillac came out with the first quad cam V8 in 1992.
Ferrari's were using quad cams in the 80s, so they definately weren't the first. Maybe that was their first although I thought the Northstar was introduced in 93?

It would be a very nice engine indeed. But I would still prefer a SOHV setup. Did you know that DOHC engines have a way higher center of gravity? If handling is important to you(which many import tuners argue... lol) then a SOHV engine would be more suitable assuming the car can be made to accept it.

Although it isn't variable valve timing, something that can greatly increase top end power is this:

AFR Hydra-Rev (http://www.airflowresearch.com/pages/hydra_rev.htm)

I can't vouch for how well it works or what effect it has on engine life, I've heard many accounts of it doing its job and adding mad hp up top.

Variable valve timing just isn't necessary with large displacement engines. The whole purpose of it is to extend the powerband of small engines by using a low lift/duration cam profile for low-end power and switching to a higher lift/duration profile at high rpm to get a broader power band. If you take the new Z06 engine for instance with it's 7lt v8 which inherently has a huge powerband, what would vvt gain?? You've got an engine that makes loads of power from ~2k all the way to redline, so why switch cam profiles along the way? People like to see these bells and whistles (which is what the cadillac northstar is intended to show) but why have them when it they aren't beneficial?

any engine can benefit from vvt, maybe just some more than others. the z06 7.0 is very powerful, but vvt would still make it more powerful through the whole range. still, i guess thats a case of having so much power, it doesnt really matter how efficiently or how smoothly it does it. Its also easier for them to just bore an LS2 or something than to develop vvt for it to get extra power. if an LT1 had vvt maybe it wouldnt loose power so soon, and still have the low end.

and yea when i said 220 V8 i was talking kinda old, I didnt want to say V6 because V8 is a better representative for displacement.

oh yea ecotecs do have vvt, i like that.

Do overhead cams really raise the center of gravity THAT much? camshafts dont really weigh a ton and the lifters and pushrods in a pushrod add some weight (not as much as an extra cam i guess). A pushrod vvt is still cool to think about, but i dont know if combining vvt (which tends to be ohc) and the pushrod/lower center of gravity idea would be that beneficial. It seems like it might end up less than the sum of its parts. to my understanding pushrod engines are generally kinda sloppy.

Ive realized that honda is increasing displacement, awesome, but what about a wicked 5 liter vtec thats not an RL or something? I suppose honda likes to slowly advance and perfect each step on the way. They also make such small "sporty" cars that in a practical sense dont need large engines.

ferrari has those 3d lobes and sliding cams, i love that. I guess the keyword there is ferrari

I saw this thread and a couple of comments came to mind...

As far as domestic V8s and variable valve timing are concerned, don't the 5.4 and 4.6 liter modular motors in the Ford lineup use variable valve timing in their three valve heads? Maybe I'm hallucinating, but I swear that I've read that information somewhere.

Also, there are some lager displacement V8s in the Nissan, Mercedes and BMW lineups that make use of variable valve timing, right?

As far as the reasons for using pushrods in a smallblock V8 are concerned, I've read numerous reasons. The higher center of gravity possessed by an overhead cam motor probably isn't too huge an issue-especially when lightweight aluminum heads are used. I have, however, read that simple packaging and cost issues are the primary motivator for using pushrod designs. They originally considered using a overhead cam design for the new Z06 (a la ZR1), but it was pretty pointless since the lightwieght LS2 block could still be bored over (to 427 cubes with appropriate cylinder liners!) to make a load of power and still fit under the very low Corvette cowl.

BTW, if anyone here is really interested in anything I am saying or this argument as a whole, the following article by Car and Driver's Larry Webster is really worth a read:
http://www.caranddriver.com/article.asp?section_id=27&article_id=8025

As far as Vtec in general is concerned, it's a great system, but Honda isn't really at the forefront of that technology anymore. BMW's double Vanos system with variable length intake runners is a pretty big deal, and Toyota's VVT-i system keeps getting more advanced. Don't get me wrong- iVtec is a good design, too. I'm just saying that Honda isn't the standout in the art of head design that it once was.

As a side note, as far as engine tech goes, I know what really impresses me: Volkswagen group's direct injection system. Here soon we are going to get to see some turbo motors running outrageous compression ratios. I can't wait till someone adapts that system for a turbo V6.

big deal, and Toyota's VVT-i system keeps getting more advanced. Don't get me wrong- iVtec is a good design, too. I'm just saying that Honda isn't the standout in art of head design that it once was.



iVTEC is still several steps ahead of Toyotas VVT-i system.
And at the moment BMW and Honda are the only two main stream manufactors to fit thier entire range with variable timing AND lift.

But your right that the rest of the automotive comunity is catching up with Honda, and it won't be long for iVTEC like systems are common place.
But Honda has always been an innovator, and Im sure will have something else up its sleave.
Look at the engine in the Japanese version of the Fit, its a lean burning, double spark plug, direct injection iVTEC sewing machine.

Untill a few days ago I knew very little about VANOS (not to mention double VANOS), but I looked into it and its an impressive design. I understand that many companies are employing VVT and i started this thread as basically a spinoff of "america vs japan", using raw displacement american V8s with heads that arent necessarily sophisticated against the very detailed and wonderfully designed but puny engines of Japan's poster child - honda.

I hope that last sentence wasn't a complete cluster-F.

MclarenF1 had a great response and I liked that C&D article. I know ford has a vvt system, but I'm not sure what engines/cars it's applied to. I would like to see vvt on many more engines - which is likely soon to happen.

I think I'll look into how mitsu's MIVEC works, ive only heard that it changes lift. Maybe one of you dudes can enlighten me.

I think I'll look into how mitsu's MIVEC works, ive only heard that it changes lift. Maybe one of you dudes can enlighten me.


Its VTEC built under license with a few small detail changes :)

you also have to realize that the entire vtec systems can be diregarded if you just change to a more aggressive cam setup...if you don't mind losing a bit of drivability.

Both...
Nothing like the sound of a Ferrari and 8000 rpm+!
But a viper also sounds great, I love the sound of a V10 with an h or X pipe, the new M5 also sounds great.
It's better to make engine power at lower revs though for engine reliability.
I'd rather have a 200HP V6 than a 200HP I4 though since the displacement is so little there isn't any power off the line and if you fall off the vtec range you're screwed.
A 200HP v8 is kinda boring though since it would only rev to a bit over 4000 like the old 5.0 v8s and sohc 4.6s, but they'll shove you back in your seat.
But the new sohc 3 valve is nice.. 300HP base v8 finally.
DOHC V8> any n/a 4 banger though.
Having to constantly keep the revs up can be a irritating task.

Personally, I prefer a higher reving, smaller displacement in my cars because

1) When I dont want to race and I want my car to be civil its civil
2) much better fuel economy because I cant afford gas
3) nice light short clutch because I am WAY to lazy to shift a heavy long clutch in traffic

Notice though that my perference for smaller engines have nothing to do with racing

For a track car or a car I want to drive steadily fast I want a larger displacement engine, and DOHC or SOHC does help the engine breathe much better then pushrods, and advanced VVT helps you achieve the max out of your engine everywhere on the powerband (if you set it like that)

However, an LS2, or an LS7 with its pushrods and no VVT can keep up with the big boys who have advanced timing systems and DOHC...also look at the Hemi, it puts out more Hp and slightly less torque with pushrods then Nissans 5.6L endurance V8 with VVT and DOHC

Last thing I wanna say is the BMW gets the most out of its engines, and just from a 4.8L V8 it puts out more hp than a Hemi or an Endurance

Chrysler/Mitsubishi/Hyundai's new world engine has duel VVT and its hp torque ration seems to characterize a Honda engine more.

However, the reason why Honda engines have less displacement and torque is because they sacrificed that so they can affectively stroke them more or give the piston rotation a wider and thus more movement. This means that engines rev higher and quicker so therefore they can reach their maximum power figures faster. Combine that with the right gearing and that could mean many things from more fuel efficiency as well as far better midway accerleration from a small engine, mainly sacrificing torque.

Extreme low-end as well as high-end has always been a problem with these type of engines though. But that is why Honda developed their Variable Valve Timing and Lift Electronic Control technology. It doesn't competely overcome as much as helps the engine achieve a good high-end. There has been nothing down about the extreme low-end as of yet (at least when it comes to NA production engines), but the Chrysler world hopes to address that.

In other words, Honda automobile engines have more in common with their motorcycle engines (which they made first) than other automobile engines.

If you want to see a good example of a highly stroked being utilized effectively look no further than the Nissan Skyline GT-R. With 350hp pumping out of a 2.5l I6, with the help of two turbos, but the increased stroke actually helps the engine spule up the turbochargers quicker.

Also, people tend to say and are somewhat valid that they respond great to some comparitively smaller tuning such as a CAI since you can feel the difference faster. But the same can be said for a large displacement engine once someone removes the cats and does and exhaust upgrade. They are just piston engines with different methods of achieving one of the two final results, sending power to the wheels.

Personally, I prefer a higher reving, smaller displacement in my cars because

1) When I dont want to race and I want my car to be civil its civil
2) much better fuel economy because I cant afford gas
3) nice light short clutch because I am WAY to lazy to shift a heavy long clutch in traffic

Notice though that my perference for smaller engines have nothing to do with racing

For a track car or a car I want to drive steadily fast I want a larger displacement engine, and DOHC or SOHC does help the engine breathe much better then pushrods, and advanced VVT helps you achieve the max out of your engine everywhere on the powerband (if you set it like that)

However, an LS2, or an LS7 with its pushrods and no VVT can keep up with the big boys who have advanced timing systems and DOHC...also look at the Hemi, it puts out more Hp and slightly less torque with pushrods then Nissans 5.6L endurance V8 with VVT and DOHC

Last thing I wanna say is the BMW gets the most out of its engines, and just from a 4.8L V8 it puts out more hp than a Hemi or an Endurance
Speaking of LS engines, they get 25MPG+ on the highway
:evillol:
Low end torque= make good use of the 6 speed's .50 6th gear ratio so it's just going above idle at 80 MPH.
A viper gets 20MPG highway also thanks to low end torque to that end, but gets horrible city gas, like 11 I think.
With a smaller engine you have to be turnin some rpms on the freeway so you're burning more gas :2cents:

I know ford has a vvt system, but I'm not sure what engines/cars it's applied to. I would like to see vvt on many more engines - which is likely soon to happen.

Ford has a variable valve timing system on the inline 6 used in the Ford Falcons sold in Australia. They call it Dual Independent Variable Cam Timing (DIVCT).

Current model Ford Falcon (http://www.ford.com.au/range/falcon/models/xtsedan.asp)

As far as I know, the 6cyl Falcons have always had some kind of variable valve and/or cam timing system since the introduction of the AU Falcon in 1998.

Not to mention the Ford Focus SVT and now ST170 has VVT.

I know this is off base because mainly you are only stating facts about large displacement V8's and little 4 bangers. But what about Nissan's RB26DETT or Toyota's 2JZ-GTE's? These are smaller relitive displacement engines compaired to the 4.7-7.0 liter Domestics and are only about 2.6-3.0 but produce around 300hp. The 4.7's and 5.7's can make around 750-850 realistically, and so can these two motors. So really it's a matter of fuel economy and since both these motors are regularly mated with a 6speed as in the Supra and Skyline, I give it to Jap's on this matter, their engineering is just a little bit better with their straight 6's.

they have forced induction..
You have have a 2 liter engine make 800HP, but it won't make full boost until a certain rpm.. like say 4500rpm so under the threshold it's quite slow.
Also there may be some turbo lag, not to be confused with that I just talking about, as in at say 5000rpm you hit the gas and there's a moment before it really kicks in.

yeah true, i was just kinda throwing it out there, domestics are built fast stock and imports arent usually, more economy. but when tuning both are capable around the same area, of course not a 1.6l miata motor or anything but power to weight they are close.

The exception of big engine= bad mpg is the LS series engines from GM...
LT1 got pretty good milage also IIRC.
But now adays with good fuel injection you can get good highway milage on any v8 now as long as you keep the rpms down and your foot off the gas :nono:
Just the ls1 and the like are the king of mpg and high performance.

Speaking of LS engines, they get 25MPG+ on the highway
:evillol:
Low end torque= make good use of the 6 speed's .50 6th gear ratio so it's just going above idle at 80 MPH.
A viper gets 20MPG highway also thanks to low end torque to that end, but gets horrible city gas, like 11 I think.
With a smaller engine you have to be turnin some rpms on the freeway so you're burning more gas :2cents:


But to be honest with you, on a flat, average size freeway on-ramp, I can get my dinky Mazda Protege to highway speed with the automatic shifting at 3500rpm, and merging is such a short sequence theres really no noticable gas mileage lost, unless of course your merging on 6 different highways a trip

and I thought the motive of Vtec was more about keeping fuel effeciency at lower RPM's, than giving performance at high RPM's...please correct me if im wrong

But to be honest with you, on a flat, average size freeway on-ramp, I can get my dinky Mazda Protege to highway speed with the automatic shifting at 3500rpm, and merging is such a short sequence theres really no noticable gas mileage lost, unless of course your merging on 6 different highways a trip

and I thought the motive of Vtec was more about keeping fuel effeciency at lower RPM's, than giving performance at high RPM's...please correct me if im wrong
I mean your rpms will be higher than in a v8 because of your torque curve, v8s get good highway gas milage since they have torque way down low.

If honda didn't have vtec and just had their "big" cam, it would have a real lumpy idle(likely would need like 1200+idle rpm) and would have even less torque, and would get horrible emissions at low engine speeds :nono:
And like you said, gas milage would be shit.

vtec has economy/environmental and performance advantages.

Australia gets some cool cars, i hope to see that falcon in the states. It took us long enough to get the holden monaro (GTO).

that n/a 3.2 inline 6 (double VANOS) in the M3 makes 333hp. I'd say thats getting a lot out of an engine.

Someone mentioned that the whole vtec system can be disregarded if you just switch to a more agressive cam setup. Well there would be the idle issues and such that were mentioned and also VVT runs off the idea that faster engine speeds require earlier valve operation. The intake valve needs to open before TDC on the exhaust stroke to get an appropriate amount into the cylinder. The extra lift
(which may just be an agressive cam and not necessarily vvt) allows for more fuel/air to enter, which can be difficult at high rpms on weak lobe profile. The best systems use both ideas.

VVT can make great power... but it's gotta be way up there.

ie: Supra...
http://img.photobucket.com/albums/v294/flatlander757/Misc/31450-651-23091.jpg

1200rpm loppy idle in 1.6L sohc with slightly aggressive cam, pulleys, light flywheel, stage 1 clutch, i/h/e, is not that much of an issue. Avg. 30+mpg with spirited city driving and a substantial amount of highway driving. Si tranny with short gears makes for 75-80mph at around 4k rpms but that is right in the power band so not much gas is needed. It's all personal preference and how much money you want to spend into what you like.

I can't make heads or tails of this thread. What are y'all talking about? Well here's my take on what I've gathered. VTEC is a great thing but you're missing the boat as to what the real purpose is. It isn't just about fuel economy, it's about having a flat torque curve and a broad power band. The low lift profile provides a nice amount of pull at low rpm, then an oil jet kicks in at a certain rpm to change cam profiles to keep pulling at high rpm. People wonder why there isn't a lot of motivation to incorporate variable valve timing in to large v8's and the answer is simple, they don't need it. Large displacement engines inherently have a broad power band, it just goes with the territory, so the expense of variable valve timing is unnecessary. Also, there is no comparing the engine from the Skyline GTR to VTEC. And, it's a 2.6 liter, not a 2.5. Turbocharged engines also don't need variable valve lift or timing. When you crank up the boost, you're achieving the same sort of benefit you receive from a high lift cam. More air and fuel per compression stroke, therefore more output.

if you read the thread more clearly you would understand that at a point we went to American vs. Japanese...and the RB25DETT is a 2.5L and the RB26DETT is a 2.6L both are in the Skyline, so it doesn't watter what liter I or somebody else posted...it WAS vtec vs. displacement, then it evolved...

The 2.5L skyline is the GTs-T with an RB25DET i.e. single turbo.

And isn't VTEC more comparable to VVTL rather than just VVT? Since VTEC is variable lift as well as timing whereas VVT is just vriable timing.