Acceleration Testing

[Lawrence Coppari]

Is anyone out there interested in doing some acceleration testing? The test I am thinking of is one where you accelerate the car from 4K rpm to 6K rpm in third gear. Your result should be the average of both directions on the same strip of highway. To make results comparable you should indicate the temperature and altitude at your location. Indicate whether you car is a turbo or not. Lastly, the size of the wheel/tire combo is crucial. Here are my results for full boost acceleration.

Tire Size 225/60-16 Time = 5.06 seconds

Tire Size 225/45-16 Time = 4.20 seconds

Altitude: 1200 feet above sea level
Temperature: 67-68 degrees F

[This message has been edited by Lawrence Coppari (edited 08-20-2000).]

[Goku]

you forgot yourself to specify your car. N/A or Turbo =)

[1.2gees]

Originally posted by Lawrence Coppari:
Here are my results for full boostacceleration.

Tire Size 225/60-16 5.06 seconds

Tire Size 225/45-16 4.20 seconds

Altitude: 1200 feet above sea level
Temperature: 67-68 degrees F

I think that kinda helps clearify...
Ahmet



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It's all the driver...

[todd951]

Yeah, I don't know many 944na drivers that run around talking about their cars' boost

[This message has been edited by todd951 (edited 08-20-2000).]

[Lawrence Coppari]

Not sure I understand what is not clear. Test from 4K to 6K was done in 3rd gear. Since time is wasted getting the turbo spooled up, you floor it at around 3K, then start watch as you accelerate past 4K because it has fully spooled up by then. Naturally, an NA car does not suffer the lag.
The acceleration test is done when you reach 6K. You stop the clock as the tach passes 6K and note how many seconds elapsed. This is a standard test.

My tests were done with two sizes of tires. The big ones make the car less fast in the rpm range tested.

[Dave's 944]

Yes but your bigger tires would give you a higher final drive ration (lower numeric) so the delta speed between 3 and 6 grand on the tach would be greater.

[Lawrence Coppari]

I know. The larger tires make a difference in the elapsed time because you're going faster to start with and go faster in the end.

Reason why I used two different tire sizes is to demonstrate just that point and also to get an idea of how fast other cars are. I wanted mine with the smaller tires to be more like what everyone else has. I should not have done two tests because is seems to confuse everyone. I should have only provided results with the 245/45-16 of 4.20 seconds.

[Dave's 944]

Yeah, i understand what your saying and i think its cool that you did two test. Just curiouse what whas your speed at 6k with the 225/60, and what was your speed at 6k with the 225/45, Does the speedo read the same speed. I imagine it would because the sensor is on the tranny. Just wonderin how much going to the smaller tire sets of the old speedo. I'll run my test out tonight and well see what an 87 NA can to. THen i'll put my new bosche 4+ in and try it again. see if i can get some improvement.

[Dave's 944]

OK heres my numbers. It was early morning so where looking a about 57 degrees, elevation 4090 ft. Its a bone stock 87 NA running 215/60 15.

8.14 secs

Reading the above post though i think i did the test wrong. i was holding it at 4 grand then starting the timer right after i floored it. instead of flooring it a 3 grand and starting the timer as it swung past 4 grand. But its a NA car so that shouldnt make a hug difference. but i'll run some more test tonight and see how it goes.

[Goku]

OK my numbers...very disappointing. I am wondering if I have some problem I don't know about with me car =(. 88' 951 almost completly stock.

Front tires = 205/55 ZR16
Back tires = 225/50 ZR16

4k - 6k = 9.8 seconds

I did accelorate fomr 3k then started the timer at 4k .....it was around 90° and around 3500 ft. This really concerns me. Any info would be great.

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Goku Super Saiyan MCSE
88' 951
reluctantly crouched at the starting line...

[todd951]

What was your boost gauge doing? If you're not getting much boost then there's something wrong with the turbo or the wastegate, or possibly the boost control electronics.

[Goku]

my boost was reading at about 1.5psi I believe. Maybe a little low/higher. Um when you guys shift does your gage for boost jump around a lot when you put the clutch in?

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Goku Super Saiyan MCSE
88' 951
reluctantly crouched at the starting line...

[1.2gees]

I LOVE YOUR NEW SIGNATURE!

CAKE RULES!!!

Umm, right sorry...

Anyway, seems like a very bad case of the "turbo lag"...

I'm sure there's something wrong with it, so far I'm the winner, if you let me be in neutral, cause I can't really use any other gear at this time...
Ahmet

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It's all the driver...

[Dave951]

Goku, the boost jumping like that when you shift is normal. It happens because when you shift, you let up on the gas temporarily. This causes a vacuum in your intake which causes the gauge to dip very quickly. Also, your boost gauge measures in bars. 1 bar is about 1 atmosphere which is 14.7 PSI. It measures absolute pressure though, so when it is reading "1", your intake is at atmospheric pressure. Only when it goes above one is your pressure being "boosted". Your time does seem really slow, but my car won't even get to third gear(I'm doing a clutch job). I would check vacuum lines and make sure all hose clamps on the intake are tight. Good luck.

-Dave

[Goku]

Also. What do you guys think about this tire size? Kinda weird or what? They came with the car a few months ago

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Goku Super Saiyan MCSE
88' 951
reluctantly crouched at the starting line...

[hoff944]

Engines pumping and thumping in time.
The green light flashes, the flags go up.
Churning and burning, they yearn for the cup.
They deftly maneuver and muscle for rank,
Fuel burning fast on an empty tank.
Reckless and wild, they pour through the turns.
Their prowess is potent and secretly stearn.
As they speed through the finish, the flags go down.
The fans get up and they get out of town.
The arena is empty except for one man,
Still driving and striving as fast as he can.
The sun has gone down and the moon has come up,
And long ago somebody left with the cup.
But he's driving and striving and hugging the turns.
And thinking of someone for whom he still burns.

Sorry......I had to do it.



[This message has been edited by hoff944 (edited 08-25-2000).]

[1.2gees]

Yeah Hoff, YOU RULE!!!

Cake is THE *****, I hate listenning to music when I'm driving as fast as I can through a turn, at the auto-x, or whatever, but if I ever play music while driving hard, it would HAVE TO include CAKE!!!

GOKU, that tire size sounds good, in any case, it should NOT give you that bad acceleration times... I mean, you're on full boost by than, and I with something like 70+hp less than what you got... I should be way behind you, but I'm quite positive it's MUCH less than that, but I shall find out for sure when I get the car back on the road (about a week from now)...
Ahmet

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It's all the driver...

[hoff944]

Dare I start a 944 music topic in the forum?

[Goku]

Well I am taking my car to a machanic tomorrow or the next day and getting all my belts changed and my turbo checked out. How much should a full belt change and service and checking out my turbo cost? Thanks

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Goku Super Saiyan MCSE
88' 951
Tonight I feel ambitious and so does my foot as it sinks on the pedal I press it to the floor...

[This message has been edited by Goku (edited 08-27-2000).]

[hoff944]

Well a belt job runs about $450 at the Porsche shop where I have mine done.