To all the people who have had their S2s dyno tested

[Mihnea]

Hi all,


I have one question for all of you, regarding the results your cars have gotten. This is no matter if your car was dynoed last monday, last year or 3 years ago actually.

I need to know the wheel HP you guys have gotten measured, as well as the calculated flywheel HP.

This is because it seems to me I've noticed that driveline losses on most of the cars that got tested last Monday were around 50-60 BHP, whatever the engine type, flywheel power and so on.

That will help me try to work on the theory that driveline losses can't be expressed as a percentage relative to flywheel power but rather as a fixed number that can be applied to about all wHP numbers for a similar car/driveline.

So could you please state here the following information:

Engine type
Mods
crank/flywheel HP (calculated)
wheel HP (measured)
wheel/tyre sizes
ambient conditions for the test.


Thanks a bunch!


Mihnea, still trying to overcome jet lag :wacked:

[Mark Halligan]

Mihnea,

I can't find Mondays sheet, did I give it to you?

If not it's at Gregs, probably. You have a copy of my last one from August.

Cheers,

Mark.

[Mihnea]

lol Mark, just looked in my laptop case and it's in there as well as one of Lee's dyno plots too... will give it back to you next time


So we have Mark with:

S2 ABY
Garrett/KKK hybrid T04E 57 trim cold side
flywheel HP: 326.8 HP at 6200 RPM
wheel HP: 224.8 HP :wacked:

losses: 97.5 HP :wacked:


Cheers,


Mihnea

[Glen Chamberlain]

ABY
RS2 Turbo MAP. With K&N filter
Flywheel: 325 BHP = 239 KW
Wheels: 282 BHP = 207 KW
205/55/16's
Not sure on ambient temp though?

This was based on the 1st out of the 6 runs i mailed you.

This was done with the fans on only when the run was being done. The fans were then switch on permanantly and the heater on full to try and cool things down. This changed things from run 1 which was 325 @ flywheel with 466nm to run 6 which was 332 @ flywheel with 475 nm. One peak run to 337 @ wheels on run 3 but a bit of a flooke i think!

Hope it helps?

[Mark Halligan]

Mihnea,

I just dug out the one from July (not Augustops: ) and the

Flywheel Bhp was 393.4

Bhp at wheels 301.2

with 83.9 Bhp transmission loss

Mark.

[sal_s2]

s2 aby

rs2 turbo and manifold

power at flywheel 296@5771
power at wheels 243
power loss 49.2

torque 292 lb ft @ 4675

min temp 15degC
max temp 20

wheels/tyres 8x17/235-40-17

[Lee]

That's high losses! It is possible to get artificially high loss figures if the rolling road wheelbase is incorrectly set. I know some rolling road operators do this to fudge their figures at the flyweel. Power at the road is near correct but if the losses are predicted to be high then so is the flywheel figure derived from that.

I would expect losses to be more of a function of revs predominantly. Obviously there is increased friction in the big ends and gear teeth meching and more end loads in the gearbox due to the helical gears (there's a good reson for straight cut boxes!!). Big tyres don't help alot but they are worth if for the increased cornering power.

The TT guys show big losses on some rolling roads with the Haldex diff system. During the runs on some rolling roads the Haldex is so busy shifting power around to the various wheels that it actually loses a lot of power to heat.

Mihnea, it would be great to see the effect of power on drivetrain losses. Lets hope you get a good enough sample to derive an empirical correlation. Have you got any data for those 600+PS beasts in Europe? I guess they may be using different clearances in the engines but it would be useful data. Do you think much is lost on the Torsen centre diff shifting torque front to rear on the rolling road? I doubt it myself.

Lee

[Lee]

Mark, hows your gearbox? Your losses seem consistently high!!

[audiman]

252 at wheels
305 at flywheel

ambient was about 8degs
standard wheels etc.
K26/27 turbo
RS2 bits
You know the score

[Mihnea]

Lee, this is still somewhat weird that my friend with the S4 running RS2 bits got 352 crank and 299.8 at the wheels, Paul N with his ABY got about 170 in stock form at the wheels (about 230 crank) and about 220 or 230 at the wheels with the homefry for 280 at the crank, all those figures tend to get me thinking of the driveline loss being a more or less constant instead of a variable.

Let's put it that way, if you have 25% losses, on a coupe quattro with a KV engine (136 crank HP) you'd have about 102 HP at the wheels or about 34 HP "eaten" by the driveline. Now if you throw a highly and unreasonably modified 20vt in it with say 1000 HP, your tranny/driveshafts/wheels/tyres combo would be eating 250 fricking HP, that just doesn't make sense to me, or does it?

I know frictional losses increase with heat and that a 1000 HP engine generates more heat than a 136 HP one, but can one just generalize and say that the driveline losses are a 25% constant?

I'd say no...


cheers,


Mihnea


PS: still got an email to send you Lee, thanks for your patience!

[Mihnea]

Originally posted by audiman
252 at wheels
305 at flywheel

ambient was about 8degs
standard wheels etc.
K26/27 turbo
RS2 bits
You know the score

Tom, when we were done with Greg's car (okay, that was later than yours), ambient temps in the workshop were 17 degs C.


Cheers,

Mihnea

[Mark Halligan]

Lee,

it causes me no problems, and it's not overly noisy (did you hear anything the other day?), not sure why its doing it, I am using Redline oil in it, but I doubt thats the cause.
I am going to try to dig out the original AMD sheet from 2000 and post the figures from that too, I'll do it tomorrow.

Cheers,

Mark.

[audiman]

Ah yes Mihnea! Those power figures are my best, but that was the temp from the first run in the morning. I had a thermometer in my coat pocket for measuring this!

[Lee]

G-Force have an inertia dyno which is mean to be 0.1% accurate at the wheels. They build racing racing cars, specifically Porsches (GT1s, 935s, etc) and the have derived some software to calculate power losses for various transmission and engine configuratioms. THeir derivation had proved accurate on many race cars and some silly power Skylines and Cosworths I believe. Stock RS4s were putting out a derived 380bhp at the flywheel which is spot on. Maybe we should have a rolling road session there so Mihnea can find out how its done! They estimated the losses on my S2 to be 42 BHP although I have also had it measures at 81bhp on mine by someone who has a bit of a reputation for being anle to cook the figures so I am told. Explains some of my power figures though!!

@Mihnea, I suspect that frictional losses are more a function of Torque than power too. Just a thought!

@Mark, I hears nothing out of the ordinary other than the RRAAAAAPPPP of you mental wastgate pipe!! Your gearbox sounded fine. Would be nice to see another figure if you have one.

Lee

[Lee]

Now that I've sourced some wicked Millers 10W60 oil I now know where to buy the Millers 80W140 gearbox oil. Am just waiting for the quotation. It's meant to be a really good motorsport synchro oil.