roller rocker cams

does anyone know when these jwt cams will be available and what kind of gains can i expect to the wheels and is it worth the money

Originally posted by dav2215
does anyone know when these jwt cams will be available and what kind of gains can i expect to the wheels and is it worth the money

No

dave:
That question has been asked 10 million times...
and yes we are still waiting :p

I need those damn S3 cams damnit. HURRY UP JWT!!!

i actually want the C2 cams :D

geo : do you know how much does JWT want for the C2 cams? and the valve springs?

oh hang on..are they actually available?

Roller rockers? Then they aren't available. :( Try Jun. :confused:

Originally posted by pche059
i actually want the C2 cams :D

geo : do you know how much does JWT want for the C2 cams? and the valve springs?

oh hang on..are they actually available?

I think they run around $1,100 US for the cams and valve springs. You must use the JWT valve springs with these cams. But, the valve springs are so good that they actually made 2 hp with stock cams!

That's actually scary to think about because it tells you that the stock springs will float with the stock cams.

i am new to this forum i didnt know everbody went over this. owell

i think toda or Jun juss came out with the roller cam for the sr20de while i was surfing there site...Im not sure so visit there site for urself.

Originally posted by P10DET

That's actually scary to think about because it tells you that the stock springs will float with the stock cams.

For a high port....u think the S3 's or C series cams are better...and would it be wise to put the new valve springs on for the new cams? :sun:

Originally posted by A380Driver
For a high port....u think the S3 's or C series cams are better...and would it be wise to put the new valve springs on for the new cams? :sun:

C series will be better. The C series require the valve springs.

hey geo what will be the differences be with the C2 cams compare to the S3 cams?
coz I remember someone said they give out similiar max power
correct me if i am wrong ?
as well is the engine likely to gain more torque? (max torque)
or is it just a shift in power band range

for auto tranny P11
which ones are better?
:D
thx

Originally posted by pche059
hey geo what will be the differences be with the C2 cams compare to the S3 cams?
coz I remember someone said they give out similiar max power
correct me if i am wrong ?
as well is the engine likely to gain more torque? (max torque)
or is it just a shift in power band range

for auto tranny P11
which ones are better?
:D
thx

I don't have all the answers you are looking for, but the C series cams tend to be peakier than the S series. Given that, I'd guess the S series cams would generally be better on a car with an automatic.

I do think the C2 and the S3 have similar peak power output.

JWT told me the new cams (s variety) may be ready by Dec 21.

Typically, high-lift short-duration cams make more torque across the RPM range, so I don't think a 'C' cam would be peaky compared to an 's'.

a 'C' cam may not be the answer if you are running higher compression, as you don't get the cylinder pressure reduction realized from a longer duration cam at low-mid RPMs. But the 'C' may be just the ticket if you live at altitude and don't wish to lose what little bottom end you already have.

JWT told me the new cams (s variety) may be ready by Dec 21.

OH REALLY?!?
YEAH!!!!!

finally
would you know how much they are going for? and what kinda power gain is it likely to give?

Typically, high-lift short-duration cams make more torque across the RPM range, so I don't think a 'C' cam would be peaky compared to an 's'.

well just out of interest...would you have any ideas what would the power output curve and the torque curve look like with these C cams?

:)
so cool that i can finally change my cams :D

Pche,

Only the 'S' cam will be available shortly, as far as I know.
JWT didn't quote any numbers, as they were still in R&D. But I would expect a minimum of 8-10 rear-wheel HP. Also, the roller rockers may enable JW to make the cam ramps more aggressive without putting strain on the valvetrain.

One of the compact car mags did a comparo with various JWT grinds, hopefully another member can recall the exact issue.

Generally speaking, here's what you can expect from two cams with similar durations

1) The cam with less aggressive ramps (to allow for the use of stock springs and retainers) will have less torque and less peak HP.

2) The cam with more aggressive ramps (translated: valves open fast) and more total lift (sometimes with a few degrees LESS duration) will make more torque throughout the majority of the RPM range.

hope this helps

Originally posted by manzano
But I would expect a minimum of 8-10 rear-wheel HP.
That is VERY, VERY impressive! Impossibly impressive I'd have to say. ;)

Average dyno gains on their pre-00 SR20 cams is 8 rw hp with no other mods, and they can squeeze another few ponies if they can take advantage of the roller rockers to add some more lift while keeping their 260 duration.

And don't be surprised if that's what JWT pulls off. Maybe there is a Santa Claus...

OR

you can have the same lift and duration, and build more aggressive ramps, so the valve sits longer on the 'nose' of the cam. Roller cams use this technique.

For instance, one cam's lobe looks 'pointy', so max lift +- 10% is realized for, say, only 20 degrees of rotation. (this is just an example!)

The other cam's lobe ramps up faster, then levels off to form a nice, wide nose on top. Max lift for this cam (+- 10%) is realized for 30% of rotation. Guess which cam makes more power?

Originally posted by manzano
Average dyno gains on their pre-00 SR20 cams is 8 rw hp with no other mods

I'll bet you $100 they gain ZERO rwhp.

Originally posted by manzano
...and they can squeeze another few ponies if they can take advantage of the roller rockers to add some more lift while keeping their 260 duration.

It's not likely the roller cams with gain more than the regular cams due to the lower redline of the roller engine.

P10,

No bet. How 'bout front wheel horsepower?

Originally posted by manzano
No bet. How 'bout front wheel horsepower?

I won't bet against that. I'm sure they will get that. I've talked with Mike Kojima and he tells me the prototypes are already showing nice gains. They are still trying to get a bit more out of them.

P10,

Sorry about the RHP thing. I'm old, and get confused easily!

You figure 102 lb/ft of torque at the (drive) wheels :) at 6800 rpm is worth 132 wheel hp, which is 10-12 over all the (legit) baseline roller G20 dyno numbers I've seen. I wouldn't be surprised to see them get 105, which works out to be 136 hp.

Originally posted by manzano
Sorry about the RHP thing. I'm old, and get confused easily!


Hehe. You're not the only one. If you're older than me, you can get as confused as you like. BTW, tell me when I start drooling, OK? ;)

Originally posted by manzano
You figure 102 lb/ft of torque at the (drive) wheels :) at 6800 rpm is worth 132 wheel hp, which is 10-12 over all the (legit) baseline roller G20 dyno numbers I've seen. I wouldn't be surprised to see them get 105, which works out to be 136 hp.

OK.

Sounds like you're getting info from someone who is connected as well.

BTW, hp is a function of torque, but there was just a debate on the SE-R list how the Dynoject calculates hp. Rob Cadle thinks it calculates hp first and then converts to torque rather than the other way around like on a brake dyno.

So what torque figures are you quoting? Peak, or at max hp?

George,

Horsepower is merely a function of torque and RPM.

All a dyno knows is how much torque an engine is putting to the rollers. It then uses the following formula to calculate hp at each measuring interval. As far as where the engine reaches peak hp, it depends on how gradual torque declines after the peak, etc.

If you know how much torque an engine produces at, say, every 100 rpm interval, you can calculate the HP at the same engine speed. Then, just connect the torque and HP dots.

HP = T x N/5252

Since we are talking dyno, T will be torque put to the roller. H is horsepower, N = engine speed (RPM), 5252 is constant.

Knowing the SR20 engine with a cam will reach peak HP at or near redline, I worked backwards.

102 * (6800/5252) = 132 HP
104 * (6800/5252) = 136 HP

Originally posted by manzano
Horsepower is merely a function of torque and RPM.


Yes, I know. I basically said that.

Originally posted by manzano
All a dyno knows is how much torque an engine is putting to the rollers. It then uses the following formula to calculate hp at each measuring interval. As far as where the engine reaches peak hp, it depends on how gradual torque declines after the peak, etc.


Not necessarily true.

The Dynojet doesn't measure torque like a brake dyno does. It is an inertial dyno that measures a number of things to calculate hp and torque.

From Rob Cadle on the SE-R Mailing List:

Actually, the dynojet measures the change in drum RPM over a (small) time step. Change in rotational kinetic energy is then calculated from known drum inertia. Work is equal to the change in rotational kinetic energy. Average power is work divided by time.

So, drum velocity is measured (actually, drum position is probably measured, and velocity is derived). Drum acceleration is not measured, nor does it need to be determined to calculate wheel hp.

Once hp at the wheels in determined, torque is calculated from:

T = HP*5252/RPM

Where RPM is engine speed. This is why you can't get a torque curve for the car if the speed pickup isn't connected.

(and pasted from another messge by Rob)

Alright, now maybe I'm talking out of my ass, because I haven't thoroughly researched this. I may be wrong.

BUT, I *think* that the dynojet calculate HP and derives torque from that. If the dynojet calculated torque first, then it would have no way to determine hp if you didn't have an engine speed pickup connected.

In fact, when you do not have an engine speed pickup connected, the dynojet gives measured hp, not torque. This is why I'm pretty sure that it is hp that is measured, not torque.


Originally posted by manzano
If you know how much torque an engine produces at, say, every 100
rpm interval, you can calculate the HP at the same engine speed. Then, just connect the torque and HP dots.

HP = T x N/5252


Yes, I know.

Originally posted by manzano
Knowing the SR20 engine with a cam will reach peak HP at or near redline, I worked backwards.


Your assumptions are incorrect.

so manzano,
would you have any ideas if the redline of the roller rocker SR20 could be raise ? and how much higher if at all?

Originally posted by pche059
so manzano,
would you have any ideas if the redline of the roller rocker SR20 could be raise ? and how much higher if at all?

So far JWT has not attempted it. All of their testing has been with stock redline.

oh my god...crappie
according to my S-AFC meter....my redline is at 6680rpm....any attempt to go over that will result in hitting the rev limiter....bounching like crap

well...i don't think i 6680rpm is enough for a 2L na engine?
what do you guys think?

and geo.. what are the different ways to increase the max torque figure?
if it can be improved at all?
and how much improvement do you think it can be obtained?

won't bet against that. I'm sure they will get that. I've talked with Mike Kojima and he tells me the prototypes are already showing nice gains. They are still trying to get a bit more out of them.

hey geo..what sort of figures are we talking about here?
:p
more or less than the solid rocker s3 cams?

and hey i remember someone actually said that it is harder for the roller engine to rev as high as the solid rocker engine? is this right? and why is it if so?

yea, there are various types of dynos, but all use some method for measuring torque at a given RPM. That method may be hydraulic or roller timing, but Dynos only know torque and engine speed. It is impossible to measure HP without knowing engine speed, enough said on that topic.

Regardless of the type of dyno, the dyno's job is to plot torque points at various RPMs. Then, the connected PC (and software) calculates the HP at those measured engine speeds , and plots the HP points accordingly. The software joins the plots to give you torque and HP curves. (connect the dots)


The PC software also takes into account air density based on ambient temperature, barometric pressure and altitude. As these variables are entered by the operator, many dyno numbers are 'faked' by entering bogus altitudes and pressures.

So once again, no machine can measure HP without knowing engine speed.



;)

Pche,

As far as squeezing more torque out of the engine, it's gonna be tough. Given the SR20 has a square bore/stroke ratio, you can move the torque curve up the RPM range, but max torque will stay about the same. Hotter cams at best will add a few lb/ft at max, and you may lose a couple. You get more HP cuz torque is greater at higher engine speeds. Headers and intakes can add a couple lb/ft as well.

The best way to add torque short of increasing displacement is to raise compression. This gives you a torque boost throughout the RPM range, but is a little on the expensive side!

Of course you could go forced induction. With a turbo, every lb of boost is good for about a 6% increase in torque, pretty much across the engine speed range.

As far as squeezing more torque out of the engine, it's gonna be tough. Given the SR20 has a square bore/stroke ratio, you can move the torque curve up the RPM range, but max torque will stay about the same.

well then i am hoping that JWT will do some test regarding a higher red line
130lb/ft @ 7400rpm? :D

Originally posted by manzano
yea, there are various types of dynos, but all use some method for measuring torque at a given RPM. That method may be hydraulic or roller timing, but Dynos only know torque and engine speed. It is impossible to measure HP without knowing engine speed, enough said on that topic.
<snip>
So once again, no machine can measure HP without knowing engine speed.


Enough said? Why? Because you might be wrong?

Tell you what......

One of my best friends worked on their software. He's a data acquisition programmer in the motorsports industry. Not the performance street car industry, but the honest-to-God, make your entire living from racing cars. I'll check and see if he knows exactly how it's done.

But I'll leave you with this......

Go back and read what Rob Cadle (a Garrett Engineer who was heavily involved with JWT's cam testing and is a brilliant engineer) wrote. Without the speed sensor hooked up, the Dynojet can give HP figures, but not torque. Just how does it do that?

Originally posted by manzano
As far as squeezing more torque out of the engine, it's gonna be tough. Given the SR20 has a square bore/stroke ratio, you can move the torque curve up the RPM range, but max torque will stay about the same

OK, it's official. You like to talking out of your ass.

You should learn more about what you're talking about before talking like you do.

I've seen Rob Cadle's dyno chart. I was there when he ran it. Not only was max torque very much improved, but the area under the curve was incredibly improved. BTW, it was also corrected for ambient conditions as he always does. I dare say Rob has more dyno time on his car than anyone else on this forum.

As for compression, it won't do that much. It's over rated. It's one of those things to do as long as you're in there, but there is so little gain, you don't go into the engine just to get compression. At least, if you're smart.

Cams will do a shitload more for you than compression ratio.

George,

Yes, cams will typically add more hp than compression. And it's always best to balance compression with the camshaft profile, if the funds are available. As for which mod adds the most torque and where, as you know, that varies with engine speed.

BTW, when I said some folks 'fudge' dyno numbers by plugging in bogus baro pressures and altitudes, I was NOT referring to JWT. JWT is a class act, and I respect and trust his knowledge, claims and products.

As far as cams adding torque throughout the engine operating range, I'd have to see the dyno chart. I have seen JWT pre-rocker charts, and their 260 deg cam is a strong torquer, but you can only squeeze so much from a 2 liter engine. You can move the torque curve up the RPM range, smooth a few valleys, but peak torque increase won't be substantial. An increase in compression is usually in order when switching to a hotter cam to boost torque at lower engine speeds which typically suffers, but does add power throughout the power band. And you get the added bonus of improved fuel economy. Once again I am generalizing.

If you believe i am blowing smoke, please provide me with concrete numbers to the contrary. I'm always open to new ideas, and will willingly admit to my errs. To say that 'so and so' confirms I am full of whatever really doesn't help anyone.

I've worked on engines of all types for 20+ years, and am partially deaf as a result of too many dyno runs.

As far as dynos and how they work, please check the following links:

http://www.howstuffworks.com/horsepower2.htm
http://rcboat.com/dynotech.htm
http://www.foxvalleykart.com/foxvalle/dyno1.htm

Originally posted by manzano
Yes, cams will typically add more hp than compression.


It's significant. One point of compression on a 200 bhp engine will add about 3-5 bhp.

Originally posted by manzano
And it's always best to balance compression with the camshaft profile, if the funds are available. As for which mod adds the most torque and where, as you know, that varies with engine speed.


How about area under the curve?

What are you driving at regarding balancing compression with cam profile?

Originally posted by manzano
As far as cams adding torque throughout the engine operating range, I'd have to see the dyno chart.


I've seen it. Flat as a billiard table from about 2-3k rpm to about 6 or 7k. It was the widest, flatest torque plot I've ever seen for a SR20DE. It's been over a year, so I don't remember it exactly.

Originally posted by manzano
To say that 'so and so' confirms I am full of whatever really doesn't help anyone.

Agreed. I'll see what I can do, but since I'm going out of town for a weekend of work the day after tomorrow, it might take a while.

I too am quite willing to admit if I stuffed my foot in my mouth.

Originally posted by manzano
As far as dynos and how they work, please check the following links

Yep. I'm quite aware of the relationship between rpm, torque and hp. The second link regarding the intertial dyno was interesting reading. It does make sense that it would still measure torque and convert to hp. What it doesn't explain is the Dynojet calculating hp w/o the speed sensor, but not torque. Of course, I'm relying on Rob being accurate (which he usually is, but isn't perfect).

.............. you know, sitting here pondering this in my head for about a half hour..................

I'm going to take a poke in the eye here. :biggrin2:

Help me work through this one......

On the interial dyno we are accelerating a mass. The mass happens to be a roller with the car stationary. We should be able to substitute and accelerate a car with the road stationary.

Therefore, all things being equal, if two cars of equal mass accelerate at an equal rate, the torque they exert on the ground should be the same, no? If so, I'm an idiot here for not thinking this damned thing through.

Shoot, I'm tired and not thinking this through very well at the moment. So..... I'm going to apologize here. All things going through my mind at the moment say you must logically be correct. So, I'd rather apologize and not necessarilly need to than to need to and not. :)

The thing about the Dynojet being able to display hp and not torque w/o the speed sensor hooked up is the confusing thing.

Originally posted by P10DET


So far JWT has not attempted it. All of their testing has been with stock redline.

Really!!!??? :confused:

JUN tests all their cams too much higher rpm. Including the cams for the SR20

It is very important for me because we are building a SR20 engine, which isn't supposed to redline before 9000 rpm. So if the JWT cams isn't build for these rpm's then I have to buy JUN cams......

Anybody have any experience with this??? :)

Originally posted by TeamNissan
It is very important for me because we are building a SR20 engine, which isn't supposed to redline before 9000 rpm.

How are you planning on keeping the rockers from flying off at 8k rpm?

Cams aren't the issue for higher rpm. It's the rest of the valvetrain.

Originally posted by P10DET


How are you planning on keeping the rockers from flying off at 8k rpm?

Cams aren't the issue for higher rpm. It's the rest of the valvetrain.

But isn't it importent that they are balanced for these high rpms???

Don't know the danish word for rockers, need a little help.... please explain what rockers is! :)

George,

Thanks for your graciousness. If I had a buck for every time I've been wrong, I'd be retired by now. Years ago, I worked in a shop with a couple of water brake dynos. Everyone there (including yours truly) thought the big number indicators reflected HP. Then, one day the repair guy came in, overheard one of us, and informed us that number was twist or torque. He was nice enough to share his knowledge of dynos with us, and I thanked him for it.

Like someone else mentioned, my P11 seems to hit fuel cut-off somewhere around 6700-6800 rpm, which seems odd as Infiniti lists 7000 as the max engine speed. I'm not sure why the redline was lowered. As I understand things, the roller rocker engines have a slightly more aggressive intake cam, the roller rockers (duh) and a lighter crank.

I wouldn't think the crank or rockers would be an issue at 7000, but maybe they eased up on the valve spring pressures a bit to reduce parasitic power loss at low RPMs. I bet JWT has checked the spring pressures, and could give you (anyone) the answer.

Increasing compression is a tough subject, and is dependent on a million things. First, you are right, nobody in his/her right mind would tear into a stock, proper functioning bottom end to increase compression. That wouldn't be cost-effective, and just doesn't make sense. And the favored method of increasing compression (over domed pistons, especially) is to reduce cylinder head combustion chambers, not changing pistons. (for street engines)

For those of us living at altitude, compression is more important as we lose torque throughout the engine speed range due to lower barometric pressures (which decrease cylinder pressures). If you live a mile high, you lose 15-20% of torque EVERYWHERE. Adding a full point of compression is no prob. Try that in Houston, and it's a different story!

I'm sure you are familiar with Dan Paramore (dpr-racing.com). His Stage V and Stage VI heads for the SR20 can increase torque throughout the engine speed range (if you tell him that's what you want), with peak up a minimum 6-10 horses. He does this by cleaning up the ports and welding & reshaping the combustion chambers to increase compression. Of course, that's some serious bucks. And I'm of the mind that if you aren't racing professionally, don't pull a head if it ain't broke.

Bang-for-the-buck, you're right on target. Stick with headers, a cam, and maybe an intake, if you can find one that doesn't doesn't suck hot air, water, or both.

Originally posted by manzano
I'm sure you are familiar with Dan Paramore (dpr-racing.com). His Stage V and Stage VI heads for the SR20
George has/had :( the DPR Stage VI head on his built up SE-R.

G-Forces,

Cool, sorry, I'm kinda new here, and didn't know. :confused:

George, I'd like to hear what your impressions are of the Stage VI head work. And did they install oversize valves? Did you tell them you were interested in peak HP, or drivability? I apologize if this is a rehash of an old thread.

Thx for your time...

Originally posted by manzano
George, I'd like to hear what your impressions are of the Stage VI head work. And did they install oversize valves? Did you tell them you were interested in peak HP, or drivability? I apologize if this is a rehash of an old thread.


I cannot tell you about the head by itself. It was part of a total psycho NA engine build. Basically I built the same engine as Mike Kojima's Project SE-R engine. I didn't do a couple of minor things he did, but I did a couple of other minor things. Other than the high-port/low-port difference, the two are 98% identical.

I did not install the oversize valves. Dan wasn't too sure about being able to use them at the time (3 years ago). He didn't do them for the guy who built one after me either. The next one after that he figured it out. Personally, from all that I've heard talking with other talented head builders, it would be a waste. As it stands, the Stage VI valves are a bit shrouded. Personally, I wouldn't do another DPR head. The cloverleaf combustion chamber is cool, and since I have it already (well, it needs to be repaired), I'll keep it. I know a couple of other people I'd be more likely to have build my head today.

As for what I told him, I just told him to copy Mike Kojima's head. At the time, I think mine was the second SR20DE head he built.

Today the engine is a total write-off. Turns out there was 0.020" and 0.040" steel shot throughout the head. There are two theories where it came from, but I won't address them here. Basically, the head is repairable with align boring. I have someone who is going to improve it as well. Should flow better.

The steel shot took out the crank, bearings, pistons (they are reuseble, but when spending that kind of money, why bother?). The oil pump was TOTALLY hosed up. The cams were such a mess you would never believe it. The HVLAs were so jammed with shot that they wouldn't even compress.

The only things even remotely reuseable are the block itself, although it migh need to be resleeved, the rods, and, well..... nothing else. Those parts would all need to be ultrasonically cleaned before use however.

Life's a bitch.

Originally posted by manzano
Years ago, I worked in a shop with a couple of water brake dynos. Everyone there (including yours truly) thought the big number indicators reflected HP. Then, one day the repair guy came in, overheard one of us, and informed us that number was twist or torque. He was nice enough to share his knowledge of dynos with us, and I thanked him for it.

I was quite aware of this before.

Originally posted by manzano
I'm not sure why the redline was lowered. As I understand things, the roller rocker engines have a slightly more aggressive intake cam, the roller rockers (duh) and a lighter crank.

I would guess it was lowered because of increased valvetrain harmonics. The heavier weight (making an assumption here) of the roller rockers would increase the harmonics.

Originally posted by manzano
I wouldn't think the crank or rockers would be an issue at 7000, but maybe they eased up on the valve spring pressures a bit to reduce parasitic power loss at low RPMs.

The crank is not an issue, but indeed the rockers are. First, and once again, the issue with the SR20 vavletrain is harmonics. This causes the valves to float at high rpm and this in turn causes the rockers to fly off above 8000 rpm.

Originally posted by manzano
I bet JWT has checked the spring pressures, and could give you (anyone) the answer.

Indeed. That is where the information comes from regarding the valvetrain harmonics. I'm not sure how much I'm allowed to share, but I know in general terms what they discovered and how they came up with the info. I can say that the engineering that went into their cams and springs is on the same order of engineering that goes into F1 and Champ Car engines. This is no exaggeration either.

Originally posted by manzano
Bang-for-the-buck, you're right on target.

Yep. Bang-for-the-buck, the DPR heads suck wind. I'm not dissing DPR. All wacko head work does. They are more for someone who is crazy (like me) and wants to build an all-out NA engine.

Originally posted by manzano
Stick with headers, a cam, and maybe an intake, if you can find one that doesn't doesn't suck hot air, water, or both.

You pretty much don't have to worry about an intake under the hood. A number of folks have instrumented their cars and found the temps at the intake to be essentially at ambient once the car is at street speeds.

Regarding the Dynojet dyno, I think I may have been right in the first place. I have to do some more research, but I think I have it.

Where T = torque, I = rotational inertia, and a = angular acceleration,

T=Ia

(a should be a lower case alpha, but I don't know this digithead stuff enough to reproduce it here, so I'll settle for a lower case a in italics)

Since I for the drum is known, and a is measured with data acquisition, T can be readily calculated. So far so good. The question is how we get to hp.

Well, since hp=TxN/5252 (where N = rpm), we simply plug in the figures for T and N. T was calculated as above. RPM is the rpm of the drum (not the engine of the car spinning the drum through the drivetrain). Therefore, since we know N and T at the drum through data acquisition, we can calculate the hp at the drum as well as the torque. Pretty clever, don't you think?

So, now we know the torque (and thus hp) being applied to the drum. What we cannot do is relate the torque and hp at the drum (and thus the wheels) to the rpm of the engine. So, we need to also collect the engine rpm data to plot the torque and hp as a function of engine rpm rather than the drum rpm.

So, there you are. My take on this after pondering for a day. I'm open for shooting holes in this and I'll be copying this to the SE-R Mailing List as well. I think this theory will hold up, but we'll see. If not, I'm sure we'll come away with additional insight.

Thanks for the head's up.

As for the steel shot, haven't those guys heard of walnut shells? I don't think I've ever left anything in an engine, but I did neglect to use Loctite on the flywheel bolts one time. Thankfully, it was the engine in my car.

I think I'll go where nobody has gone before (that I know of) , and get a Crower stroker kit, somewhere between 2.2 and 2.3 liter displacement.

I know some folks rant on about how you shouldn't mess with the bore/stroke ratio of an engine, but I don't think that will be an issue. That, along with a JWT cam, should be good for some good, streetable torque and hp. The funds are there, I am waiting on the warranty to run out.

Does anyone know if the JWT SE-R motor mounts fit a 2000 G20t?

Cheers

Do you get valve float about 7k in the SR20?

Originally posted by manzano
As for the steel shot, haven't those guys heard of walnut shells?


For the record, I did not accuse DPR of leaving the shot in the head.

Originally posted by manzano
I think I'll go where nobody has gone before (that I know of) , and get a Crower stroker kit, somewhere between 2.2 and 2.3 liter displacement.

Unless you build it tomorrow, you won't be going where no one has been before. :right:

Originally posted by manzano
Does anyone know if the JWT SE-R motor mounts fit a 2000 G20t?


That I cannot help you with.

Originally posted by A380Driver
Do you get valve float about 7k in the SR20?

I don't have information that detailed, but I think that is true. It's pretty slight though and not enough to throw the rockers.

The reason I know there is some very minor valve float going on is that the JWT valve springs by themselves will gain you a couple of hp.

Re: shot - I consciously did not ask you to finger anyone - that is your business.

As for the stroker, I don't mind being second. I can grind the block if I find any interference there, but it will be nice for someone else to discover other issues such as oil pan clearance, etc. I'm not looking for mega HP numbers, just 'bout 150 hp and 150 lb/ft torque at the (drive) :D wheels.

Life does suck sometimes, but it's part of the game.

George,

Regarding that dyno thingy that won't die, the roller rpm has no correlation to engine speed. If a dyno is reporting HP without monitoring engine speed, it would be assuming a fixed drive ratio and outside tire circumference.

If you could input drive ratio (for whatever gear you use for the pull) and tire size for each different car, yes, the dyno could calculate HP without engine speed input, no problem.

Without that info fed into the dyno, it would be a 'one size fits all' ratio, which would not be accurate.

To illustrate, get two identically prepared rear-drive (for simplicity sake) cars and outfit one with a 2.06 rear-end ratio, the other with 4.11 gears.

Now, do a dyno pull for both, 2nd gear, no engine speed input. Without knowing engine speed, the car with the 4.11 gear is gonna kick the others' tail. The 4.11 jumps off the rollers, while the taller geared heap takes forever to make the pull.

Hook up the engine speed, and you'll see that both vehicles have identical torque curves.

That's the best example I can think of

Cheers

Originally posted by manzano
Regarding that dyno thingy that won't die, the roller rpm has no correlation to engine speed. If a dyno is reporting HP without monitoring engine speed, it would be assuming a fixed drive ratio and outside tire circumference.

Nope. This is 100% incorrect. That I'm quite sure of. If you look at the second link you provided, you will find they used an inertial dyno hooked up directly to the engine. The rpm being measured is in essence the rpm of the drum (since it's hooked directly to the engine).

Originally posted by manzano
Hook up the engine speed, and you'll see that both vehicles have identical torque curves.

Nope. Not even close. Now you are assuming that the Dynojet measures engine torque. It does not. It measures torque to the wheels and with different gear ratios comes different torque multiplications.

George,

We've been referring to roller dynamometers, which have no relationship between engine speed and roller speed.

Here's THE link: http://www.idavette.net/hib/dynojet/index.htm

After reading all the info, uh, I can with certainty say

I was wrong about a couple of things.

I was oversimplifying, and underestimated the ingenuity of Dynojets. Dynojets can indeed measure hp, but do require engine speed input to factor out gear ratios.

If I knew how, I'd insert one of the 'poke myself in the eye' thingys.

anyway, read away. It's good stuff....

cheers

So, in closing....

The Dynojet brand of dynamometer can determine the current horsepower of a vehicle without knowing its engine speed based on, uh, here it is from Dynojet:

*** Start ****
During manufacturing, Dynojet Research figures the mass equivalent of each pair of drums to four places and bearing drag to five places. Those proprietary figures are figured into the computation the dyno computer makes. If the mass equivalent of the drums is known, the drum bearing drag is known and the rate at which a vehicle’s drive wheels accelerate the drums is accurately measured; then the "thrust force," in pounds, at the rear wheels can be computed with a high degree of accuracy.
*** End ***

So you run your car on the dyno at a steady engine speed, and it says: '150' HP.

What the Dynojet doesn't know is if the car on the dyno making 150 horses is an 8 cylinder loafing at 2000 rpm's or a 2 liter 4 cyl screaming at 7000 rpm's.

So it uses engine speed to factor out gearing. In other words, it can calculate torque at the wheels by comparing roller speed to engine speed. One little calculation to factor out gearing, and it knows wheel torque.

So now it can plot the points for HP and torque, and draw the nice little curves.

Hope I got it right this time. Crow tastes like crap. :bloatted:

Manz

Oops,

Sorry for the extra 't'

Originally posted by manzano
So you run your car on the dyno at a steady engine speed, and it says: '150' HP.

Actually, on a Dynoject, you don't run at a steady engine speed, but rather run it up through the rev range.

Originally posted by manzano
So it uses engine speed to factor out gearing. In other words, it can calculate torque at the wheels by comparing roller speed to engine speed. One little calculation to factor out gearing, and it knows wheel torque.

Oh so close. Someone sent me a private e-mail from another list that I think hit the nail on the head. While T at the drum can be determined, and hp at the drum can be determined......

HP at the drum is the same as hp at the wheels. But, the rpm of the wheels is different from the rpm of the drum. So..... the speed sensor actually figures out the rpm of the wheels and calculates torque at the wheel. Whew. What an exercise. I'm a geek. No doubt.

Originally posted by manzano
Crow tastes like crap. :bloatted:

It goes down better with Shiner Bock. Trust me (it would be rude at this point to ask me how I know). ;)

If you can't get Shiner Bock, you'll just have to make do with some inferior beer. :D