A Poll of a Pull

[MikeW]

I recently installed one of Jake's turbo kits in my 1991 318i (M42T) and didn't feel the need to dyno it but was curious how it stacked up against my M3 and WRX, and other cars for that matter. So I used a track App I like to conduct a series of controlled pulls on the highway, put a stop watch to the video output, and this was born:



More detail about the process is provided in my post in Jake's thread at the M42 board http://www.r3vlimited.com/board/show...259174&page=31

As I mention in the original post, the reason the M42T starts to fall behind after the 60-70 interval is that I went up to 4th to avoid putting too much stress on my old engine. Keep in mind that this build cost me a total of $2,300.

Any thoughts on its usefulness? It only takes a few hours to do the comparison and the cost of gas money.

[ELVA164]

Looks like you need a bigger turbo.

[MikeW]

I edited with an explanation of the GAP. Funny how it came back home after she got up to 70 starting point.

[MikeW]

What I am really wondering about is whether given the fact you can sort of extrapolate HP from vehicle weight, final gear ratio, and tire radius - could this method serve as a poor mans dyno?

[Mr. Tasty]

What I am really wondering about is whether given the fact you can sort of extrapolate HP from vehicle weight, final gear ratio, and tire radius - could this method serve as a poor mans dyno?

theoretical numbers

[MikeW]

It's all theoretical at some point. But "if the line fits you must acquit." I mean, if we trust that the M3 power output numbers are correct, than extrapolating the power of the M42T will be reasonably accurate based on the line fitness in this case.

[slammin.e28]

HP is a theoretical number anyways.

Looks like it gives you a good comparison either way.

[nando]

HP is a theoretical number anyways.

Looks like it gives you a good comparison either way.

no, it isn't. it's a measure of how quickly the motor can do work, ie, accelerate a car. it's as real as your broken M20 timing belts. ;)

[slammin.e28]

no, it isn't. it's a measure of how quickly the motor can do work, ie, accelerate a car. it's as real as your broken M20 timing belts. ;)

....but it's calculated, using torque. (TQ/rpm)/5252 = hp

Torque you can measure.

HP is as real as my broken timing chains.... ::p

[nando]

torque can be calculated as well. and you can measure power too - by how quickly an object accelerates. ;)

[slammin.e28]

......but can OPs method be used to calculate torque/hp....accurately?

[nando]

probably not! I can't even tell what I'm looking at, lol

[MikeW]

You can calculate average torque for each interval, but that's lots more work and not as fun. It also doesn't stress the point that an M42T can challenge an M3 with just a cheap bolt on!


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[MikeW]

......but can OPs method be used to calculate torque/hp....accurately?

Yes, if the curve fits than you can easily extrapolate power for the portion that fits, and it will be pretty darn close to reality.


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[MikeW]

But really, usefulness aside, I thinks it's just cool that when you slap a cheap turbo on an e30 m42 it basically keeps up with a an E36 M3 up to 60 or 70.




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