* Varioram vs. GT3 - same dynamometer *

[Craig 930 RS]

My 3.6 runs pretty close to the GT3.....then the GT3 just takes off like a shot past 6,250:



Same dyno, same conditions. It is simply amazing what the actual RWHP is of a GT3. Porsche is so conservative with the published numbers. If the GT3 has a 15% drivetrain loss, this puts it at over 420 FWHP. My God. Nowhere even close to the claimed 380 FWHP!

[Craig 930 RS]

GT3 also puts out 29 lb ft more tq than the Varioram.

[mede8er]

So, will you be selling the V Ram anytime soon......

[jluetjen]

So, will you be selling the V Ram anytime soon......

Yeah -- for a CIS System!

NOT!

I wonder if Porsche quoted the HP the same way that Detroit used to quote Muscle-car HP, at about 1000 RPM below the peak HP engine speed....

[Mike Feinstein]

Dynojets are notoriously flattering. Do the same run on a Dynopack and you will get much more realistic (and less flattering) results. The Dynopack requires removal of rear wheels and use of special hubs which mount on the Dynopack. In my case, there was nearly a 40 hp difference between the two Dyno's. It's interesing that Porsche's published GT-3 numbers are about 40hp below your Dynojet results. There's a trend developing here...

[Craig 930 RS]

I must respectfully disagree. How is the Dynopack more accurate - only by virtue of the lower HP measurement?

Porsche ALWAYS underestimates its HP ratings - usually by quite a bit. So the 360+ RWHP reading of the GT3 doesn't surprise me -

[Jack Olsen]

I've seen a dyno sheet for a stock GT3. It was 320 hp at the wheels, which seems about right for the factory rating of 380 at the crank.

My guess would be you've got an optimistic dyno, there.

[Craig 930 RS]

Go to Rennlist and search for "GT3 dyno results" to see many similar readings from all different dyno locations.....

[KobaltBlau]

I tried but didn't find any on a dynapack

[Mike Feinstein]

My own experience and many comments from local tuners seem to indicate that Dynojets are not considered consistent and often provide flattering results. My car dyno'd 268 rwhp on a Dynojet and shortly after, 226 on a Dynopack. After pulling codes, it turns out the car was running in limp-home mode due to a bad injector and duty cycle anomolies. Had I relied on the Dynojet results only, I would have never known there was a problem. Once the work is done, I'll be happy to see 240 rwhp on the dynopack...which equates to about 282 crank hp....exactly as stated by the manufacturer. And even better, it could mean another 2+ seconds off my lap times! Bring on the back straight!

If you're having fun and are happy with your Dynojet results, than all is good.

[Craig 930 RS]

That is beyond strange. My experience, on the other hand, shows that the Dynojet is not only accurate - but can also provide comparable and repeatable dynojet to dynojet numbers.

Actually your 268 rwhp is very, very good.

So if you pick up 14 hp with the engine fixes, then you will have 282 dynojet HP?

Mine "only" did 280.5, with B&B headers, Flowmaster, 3.8 cams etc.
Maybe I need to check codes. On the other hand, I have the highest HP 3.6 ever tested on this Dynojet in this area.

The original post was to provide a comparison between two 3.6 engines and to show that they are fairly similar to that ethereal point where the GT3 just takes off like a rocket - and a Varioram is starting to head down -

[Joeaksa]

The German auto makers (and BMW bikes as well) are very conservative with their power ratings for one reason. The insurance people can get difficult when the power is above "their" limits, whatever that is.

BMW bikes for a long time had a 95 PS (hp) limit on some of their bikes. You could tweak the computer and get another 20 hp easily but they limited it for the insurance companies. Lots of factors need to be included when looking at why and what goes on over there...

JoeA

[Mike Feinstein]

Originally posted by Craig911
Actually your 268 rwhp is very, very good.

So if you pick up 14 hp with the engine fixes, then you will have 282 dynojet HP?

See, that's my point...I don't think the dynojet numbers were worth the paper they were printed on. So no, I don't think it's realistic that my nearly stock 3.6 will dyno 282 at the rear wheels as the Dynojet might falsely indicate. To the contrary, I think the low 240's as I hope to achieve on the Dynopack make a lot more sense.

Not intending to throw stones here, just offering some comments based on my admittedly limited experience. Even if the dynojets we used were identical, you are obviously making some serious hp. The first clue that I had a fuel injector duty cycle issue was when my mechanic noticed a left-side exhaust flame as I downshifted coming into turn 1 at Road Atlanta. Dyno-ing and pulling codes confirmed it. Actually....I asked him if he could make flames come out of both pipes , but I don't think that's what he'll do!

[Craig 930 RS]

Again....use the numbers at least for comparison's sake. Whether you use a dynojet, dynapack or dynamite....

I still don't see how the dynojet numbers - while apparently higher - makes it any more 'inaccurate' than a dynapack.

[Jack Olsen]

Originally posted by Joeaksa
The German auto makers (and BMW bikes as well) are very conservative with their power ratings for one reason. The insurance people can get difficult when the power is above "their" limits, whatever that is.

I don't believe that's been the case for a long time, now. If a stock GT3 was putting out 420 hp at the crank, you can bet Porsche would be publishing that number. No one who buys a GT3 is worried about insurance rates, and the small market for those kinds of street cars is very competitive. No manufacturer is going to sandbag when its buyers are comparing the numbers on such high-margin vehicles.

If you do a search on this site, or across the internet, you'll see that stock 911 motors generally put out only very slightly better-than-published numbers (and that's with the somewhat-dubious 15% drivetrain loss figure). This makes perfect sense, as the factory has to consider that there will be some variation in performance off the factory line. But that variation is small --maybe 10 hp at the outside.

My .02.

As Craig points out, though. side-by-side with the GT3, his motor is kicking ass.

[Craig 930 RS]

I'd venture the best one can hope for on a dyno is:


Back to back testing - with changes made on the same day

If comparing different cars, make sure they are on the same dyno in similar conditions

I've even found that if a dyno has not been run that day, the dyno can read low because the mechanical portions of the machine itself are not 'warmed up'

Hey thanks for the nice words about the engine. Now I need to change the appearance & outward function to match the drivetrain - and get rid of the urethane bushings I installed in 1999. They are binding like crazy -

[Craig 930 RS]

FWIW -

While on Rennlist, I came across this Dynapack 993 Varioram dyno chart - a stock engine:



Again - FWIW - the same readings as on a Dynojet

[Craig 930 RS]

Dynojet stock 993 Varioram

[ZAMIRZ]

Originally posted by JackOlsen
I don't believe that's been the case for a long time, now. If a stock GT3 was putting out 420 hp at the crank, you can bet Porsche would be publishing that number. No one who buys a GT3 is worried about insurance rates, and the small market for those kinds of street cars is very competitive. No manufacturer is going to sandbag when its buyers are comparing the numbers on such high-margin vehicles.

If you do a search on this site, or across the internet, you'll see that stock 911 motors generally put out only very slightly better-than-published numbers (and that's with the somewhat-dubious 15% drivetrain loss figure). This makes perfect sense, as the factory has to consider that there will be some variation in performance off the factory line. But that variation is small --maybe 10 hp at the outside.

My .02.

As Craig points out, though. side-by-side with the GT3, his motor is kicking ass.

Jack, the reason the GT3 is underrated from the factory is because they don't want it to appear to have the same or near the same horsepower as the turbo which is significantly more expensive. It's also the same reason GM would always underrate the LS1 Camaro SS, because they didn't want it to get into Corvette territory.

[MuffinMan]

We had a dyno day in March, and used a dynapack dynamometer as our tool of reference. We scanned all of our dyno sheets and posted them, along with pics from the day. You can see the sheets here .

The cars:

Slow White: 2.0L 4 cylinder 914
Tubbo: 1994 911 3.6 Turbo
Pesky: high compression 3.2 in a 914
Terrible Pumpkin: 1997 3.6 varioram (conversion)
Hippy White: Stock 97 993 (non-functioning varioram)
White Rice: Stock '95 993
Mr. Softee: SC stroked from 3.0 to 3.2

If you want more details on the cars, read the story .