My Dyno session

[JonnyX]

It's a bit specious to claim that the wheel power is wrong but that the flywheel figure is correct. You
can only really measure the power at the wheels. The flywheel figure is always a calculated figure,
not a measured one. I think FATS style tests tell you a lot more about the performance of your
car to be honest.

[s4woody]

just so everybody is clear on this..IT WAS MY OLD CAR...now QST's dyno does give strange reading thats for sure..@jeffW i took my car to surrey Rolling road and met you there..it was running with poor lambda.s but reached a figure of about 252bhp at the wheels and 522nm if i remember correctly..
when kim fitted the milltek system he took it out and it peaked at 20psi twice out of 3 runs..he said that is about 1.2-1.3bar..
steve couldnt drive the car cos he has a heavy rite foot and it kept over boosting ??
MRC have (tweaked) the map and now it seems ok..
steve has all the past dyno read out,s so he can compare..

[jeffw]

Woody, I know we met at Surrey RR....that was my point really. 252BHP at the wheels with a dodgy Lamda was very good and makes the new QST figure even more suspect.

[GrahamS4]

I don't think there can be driver fault for a car overboosting. Is that what you are saying - not really sure? It's either mapped right ior it wasn't. IF you had to drive it a certain way for it not to overboost then there was a problem.

I thought 1.2 bar (which is what my map peaks at) was about 17psi.

From what I have read, MAHA dynos tend to give odd wheel BHP readings, but are reagard in general (no sure about QST's) as giving a reasonable flywheel figure. Doesn't make sense to me but this is what I read.

I think to make any usefull comparison the car has to go back to Surrey Rolling Road or at least another Dyno Dynamics dyno.

[DavidT]

20 psi is almost 1.4 bar. What rpms was that ? its an awful lot of boost for K03's

[jeffw]

I'm no expert on MAHA rolling roads specifically but it appears that the problems are specific to QSTs RR.

[dodgydave]

I'm no expert on MAHA rolling roads specifically but it appears that the problems are specific to QSTs RR.

MAHA are normally very precise and tent to show less than other RRs. I think QSTs RR must be wrongly calibrated.

[jimbogrey]

I had my car dyno'd at QST when my turbos were replaced and although I have unfortunately lost the plot (literally not metaphorically) i remember that my wheel bhp was 265 and crank was 349. so it seems the calibration may have been changed.

Jimbo

[s4woody]

you also posted 3 times...graham i never had any issue,s with the overboost underboost of any type of boost..my point about the driving style was that steve says he,s got a heavy rite foot..so if he's planting the throttle everywhere even in high gears then summits gotta say enuf's enuf..
its been a while since ive seen my old boost gauge and it did read a peak of 20psi on occasions..everytime i reset the throttle body it would read 20psi then settle into 15-20 psi..

[SLC Detailing]

Well looks like i will get down to Surrey rolling road and get another opinion. What boost should a remapped S4 be running then?

[GrahamS4]

Speaking for my own car, peaks at 1.2bar, dropping to 0.8 at the redline.

[SLC Detailing]

How much is that in regards to PSI? Also whats the conversion rate of changing NM to ib/ft

[davs4]

How much is that in regards to PSI? Also whats the conversion rate of changing NM to ib/ft

Try this link for PSI - BAR
http://www.centauro-owners.com/articles/psibar.html
1 Lb-Ft = 1.35582 Nm
HTH

[DavidT]

Speaking for my own car, peaks at 1.2bar, dropping to 0.8 at the redline.

Sounds high at the redline Graham, I'd expect it to be 10psi or less ?

[GrahamS4]

Speaking for my own car, peaks at 1.2bar, dropping to 0.8 at the redline.

Sounds high at the redline Graham, I'd expect it to be 10psi or less ?

You are probably correct. My plots only show to about 6500rpm, at which boost is about 0.8bar. Given how sharp the curve is falling, but 7100rpm or wherever the redline is it's most likely fallen some more.