Rolling Road Day at QST

[BRETTCOLLINS]

sounds like fun, would like to see my car on a different set of rollers.

[bjacks]

sounds like fun, would like to see my car on a different set of rollers.

Probably best you didn't, none of the other S4's made what they should do

[sitas3]

I lost loads more than you Simon.

Corrected Power 419.3
Engine Power 431
Wheel Power 206
Drag Power 225
Max Power at 6960RPM
Torque 531.3

Intake temp 9.6C
Ambient temp 9.4C

I think we'd best be ignoring losses as 2 identical cars (on same sized tyres, suspension etc etc) cannot differ that much.

yes I agree Ben - something can't be right here surely. How can you only get 50% of your power output at the wheels! I thought the average for 4 wheel drive cars was about 30%?

[djb1]

Its Doug(couldn't remember my password at work)

There is definitely something wrong with your RR measurements. On Audi 4WD Cars you should get 25% to 30% losses.

I do not beleive that you are only putting out 206bhp and 246bhp at the wheels. That is the measured value. The losses should be measured and added to that - that is why the flywheel figures can vary a bit - as it has 2 measured errors.

[bjacks]

Bit odd I know. TBH, something I really have no idea about, perhaps Prawn knows, or can ask Kim.

On another note, how does the corrected power figure work? IIRC, it usually is more than the actual power is it not?

[DuncS3]

I have run my car on AMDs rollers before and it had a figure of over 50% losses - and this varied greatly between other S3s on the day with the same wheel sizes etc - some were like 30+%

Unless I have the wrong end of the stick and am talking about something different?

Dunc

[Prawn]

perhaps Prawn knows, or can ask Kim

Funnily enough something I have been looking at.
Mainly due to my 'power at the wheels' figure being 0.5BHP higher than Johns , got to get
him on something !
Unless you use an engine Dyno you will always be getting a best guess at Flywheel Power as all Chassis Dyno's (Rolling Roads) read wheel power. What I do know is that the corrected power is calculated by one of several methods, DIN 70020, SAEJ1349, EEC, ECE, ISO, or some other? Depending on which correction factor is used, the results vary, according to conditions. For e.g. DIN 70020 standard often results in "larger" figures than other commonly used formulas. Non of them are actually wrong as such - just different standards. Kims MAHA uses DIN70020, as do most other UK tuners from what I have seen.
The only real measure is Wheel Power, however I am not sure how this is measured or represented in the plots, I will ask Kim if he knows or can find out.

My wheel figures on Saturday where 300.9BHP with a corrected O/P of 477.1BHP which would work out at approx 37% losses.

[djb1]

Do your plots not show the plot of power at the wheels along with a plot of losses, corrected value, torque and boost?

I have one of mine, on the maha, from a couple of weeks ago - how to I post a picture in here!

37% sounds too high - that is a lot of heat to dissipate in your gearbox and diffs.

[djb1]

plot:

[bjacks]

[/quote]

My wheel figures on Saturday where 300.9BHP with a corrected O/P of 477.1BHP which would work out at approx 37% losses.[/quote]

My wheel power was only 206BHP, with losses equating to the power of a standard S3 (225)

That must be total BS. My old S3 had more wheel power than that

[sitas3]

Doug, yes the QST plots do show Wheel Power (it is a blue line) along with drag power but I don't have a scanner here at the mo so I can't upload it.

[ChrisG]

my wheel power was 77, corrected 171 , isn't that about 55% loss !!

[S4driver]

sounds like fun, would like to see my car on a different set of rollers.

Probably best you didn't, none of the other S4's made what they should do

[Scotty]

My wheel figures on Saturday where 300.9BHP with a corrected O/P of 477.1BHP which would work out at approx 37% losses.[/quote]

My wheel power was only 206BHP, with losses equating to the power of a standard S3 (225)

That must be total BS. My old S3 had more wheel power than that [/quote]

A soft tyre, dodgy tracking (errrrmmm!) etc will cause additional losses on top of the normal drivetrain etc.

I've seen up to 55% loss on TT rr days!

[bjacks]

Kim did say my tracking was shot, but then he also said Simons was