Acceleration test!
 

I remember when we posted our 70-100 figures a few months ago... I used to do 0-60 runs to see how the car was doing after mods/etc, but the results of this or similar test will not only introduce many variables (launch technique, tires, lsd, road conditions/grip, etc.) but also be much harder on the entire drivetrain.
Anyway, so the 70-100 tests we did were done as follows: cruize @60 in 3rd, floor it and start timer @70, stop timer @100. About 8 months ago in similar weather I ran an avarage of 3.9 secs with a 200lbs passanger some gas and a little luggage. Today I did two runs and avaraged about 3.8 with the same amount of weight, I've rebuilt the engine but no other 'mods' were installed. I do believe today I have a muffler and I ran open exaust at the time.

Currently the car has a 3 inch exaust turbo back with one straight through muffler, an intake, wires/plugs and coil, a little headwork, headerwrap, unregulated boost and 993tt blow off valve as well as chips. Slight boost leak.

I'd like to see how your cars compare.
Ahmet

Ahmet, what size wheels and tires are you using? I do the tests with 225/60-16 tires that are about 7.1% larger than the 225/50-16. If the 225/60-16 gives the correct speed, then 70-100 with 225/50-16 on my car is only 65 - 93. The difference in KE between 70 - 100 and 65 - 93 is about 13%, and that change when divided by time gives power. Then there is the shorter moment arm with the smaller tires that also drops acceleration times.

Lawrence, I'd like to thank you again for this concept of performance testing!

I'm using stock rolling diameter tires, so your calculations should be correct. It'd be interesting to compare calculated estimates and #s from a similar test with stock size tires, are your track tires closer to factory spec rolling diameter? BTW, my results for 3rd and 4th gear test of this speed range are no more than .1 sec apart, but I think that's because I make more boost in 4th.

BTW, when are you going to vir next?
Ahmet

Hi Ahmet,

Don't know when I'll be going to VIR but I hope this spring. I'll probably do 6 events at Road Atlanta this year; 3 with BMW and 3 with PCA. I need to get signed up for one at VIR. I am not familiar with that track but everyone I know really likes it. I need to learn it. I just need to find an event.

My track tires are 245/45-16 rear and 225/50-16 front. After I did some mods last winter, I rechecked it with the large street tires. The last set of mods dropped the time from 4.50 seconds to 4.15 seconds, 70 - 100. This was 3rd gear, big tires, 1/2 tank fuel and just myself in car. Did not try it in 4th. Temp was 50 F. If you ratio it out based on KE and tire diameter, I would get 4.15 * .87 * .93 = 3.4 seconds. The .87 is the 13% less KE and the .93 represents the 7% torque/force difference.

When I get around to doing it, it'll be in the 3's with the small tires. I have some oil leaks to tend to now but will do the test. I have never gotten this thing to stop leaking oil. It is leaking where you put the oil in the engine and there also is a leak along the head gasket. I'll just have to live with the head gasket leak because I don't feel like taking the head off again. I installed a PowerHaus head/intake several years ago.

There's a DE on the 12th of next month if I remember correctly (@VIR), also time trials. I could look up a link if you want.

Mine keeps blowing oil pan gaskets, but I might have a bent oil pan, it now looks like (!!!) so hopefully that'll be the last of it. The rest of the seals are moist, which I don't care about as long as they don't leak enough to get on the ground overnight. That's too bad about the headgasket, I would probably turn up the boost and wait until it blows! :)

Anyway, what kind of modifications are you running and what made the biggest differance for you? I'm thinking about doing some other things to the engine soon, but would like to avoid getting another turbo. I'm thinking a MAP kit, along with some weight savings, and fixing the small boost leaks could let me do a low 3 sec pass? Don't know if I'll shell out the money to do that, we shall see...
Ahmet

Ahmet..

If the stock turbo S times are as follows....

0-30 = 2.0;
0-40 = 3.0;
0-50 = 4.1;
0-60 = 5.5;
0-80 = 8.8;
0-100 = 13.6;
0-120 = 22.1
with a quarter mile time of 13.9 at 101 mph.

It would give the S a time of 4.8 seconds to get it from 80 mph to 100 mph. So if you are times are right. Your numbers are quite impressive.

I have all PH mods that include:
Extrude honed intake
Ported/polished head
Head gasket
K27DR turbo
3 bar fuel pressure
Oversized pre/post intercooler tubes
Reamed out throttle body with bigger butterfly (not PH)
MAF system and chips and cone K&N
1.1 bar boost

The K27 and MAF were done together along with 1.0 bar boost. That made the biggest difference. When at 4.5 seconds (everything except boost tubes, 1.1 bar and throttle body ream job), I changed to larger boost tubes and reamed throttle body. The time dropped from 4.5 to 4.33 seconds. Then I installed the 1.1 bar metering jet which dropped it to 4.15 seconds. All tests were done at 50 F, which is important to turbos. There was a change when I installed the intake/head but I cannot recall the improvement.

According to PH, I should be getting nearly 400 hp out of it. I don't think they are far from wrong because I have a supercharged SLK32 AMG roadster. It has 349 hp with 332 ft-lbf torque. It does the 70-100 in 4.74 seconds, true speed. It weighs 3268 pounds. Ratio and proportioning the weight and time and HP puts my 944 at nearly 400.

Do you have the times for a stock turbo non s? I would like to know the stock and see what I run.

I had this problem on a 931 there was a small scar in the head, right near an oil passage. Kind of like a scratch...which caused oil to come out the head gasket. Could fill it in with some jbweld but my experience with JB weld in other applications has not been good. Not sure if that's your head gasket problem.

Thanks, AMC931turbo. When I do a bunch of maintenance this winter, I'll clean the area and put something in the crack between the head and block. I'm thinking about a sealer that MB recommends for its oil wetted gaskets. It's like the Permatex sealant but is considerably stronger. The technicians at the local Porsche, MB, BMW, Audi dealer recommended it.

I'm not about to remove the head again. If I have to, I'll just live with it.