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Stock or BPU RWHP at SRR? What are your figures?


Scott
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Having an interesting discussion regarding transmission losses in another thread. Just looking to collect some input from the guys who have had a run at the same dyno. I know that SRR is the most popular so I have written that in the heading but any input would be appreciated, just please write the RR next to your HP.

 

Looking for RWHP figures and FWHP figures if you have them, RWHP being the most important for now.

 

Could you also put whether you are Auto Or manual.

 

Scott - SRR - 350rwhp - 420fwhp - Manual

 

Something like that.

 

Thanks folks

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Just thinking about it, the reason I have asked for BPU and Stock is that the power will be fairly similar for a comparison in losses. Would appreciate guys with singles too as if I can get a manual RWHP and auto RWHP that are close, I can do the same calculation. The chances of getting them similar might be slim though.

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Scott, Gaz done this brilliant article of the SRR day we had a few months ago

 

http://www.mkivsupra.net/vbb/showthread.php?t=204366&highlight=Surrey+Rolling+Road+Day

 

Sorry I don't have the details on me but mine ran 352BHP (0.8 Bar), the only modification which had been done on my car was both cats had been removed and Paul put in a RR along with the decats, it also had a full service carried out. Mine is a Auto TT with 100k on the clock.

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Cheers mate, the figures quoted are all FWHP though, really need RWHP figures AND FWHP figures to do the comparison.

 

Alex M's seems to be the closest comparison for what we are after.

 

Edit:

 

Picked out 2 that might be useful

 

Supra Plant – Supra TT auto – 334.2bhp (stock)

Alex M – Supra 5-speed N/A – 215.1bhp

 

 

I think the auto transmission losses are estimated to be 20%. If that is the case, and you think it should be 30%, that would make the car actually producing 371.3hp. Same with the 5spd. I think it is taken as 15%, increase that to 25% and you get 239hp. The latter wouldn't be THAT unbelievable but 371hp from a bone stock TT is just too much.

Edited by Scott (see edit history)
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Are you after drag coefficients & losses? That won't an exact science as all driveline components play a part in that ratio (diff drive ratio, gearbox, wheel weight, tyre weight, flywheel, etc).

 

For what it's worth, my old car with a 6spd (same dyno, same shoot, similar atmospherics)

 

BPU - 359rwhp, 429fwhp (19.5% loss)

Single - 460rwhp, 545fwhp (18.5% loss)

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Are you after drag coefficients & losses? That won't an exact science as all driveline components play a part in that ratio (diff drive ratio, gearbox, wheel weight, tyre weight, flywheel, etc).

 

For what it's worth, my old car (same dyno, same shoot, similar atmospherics)

 

BPU - 359rwhp, 429fwhp (19.5% loss)

Single - 460rwhp, 545fwhp (18.5% loss)

 

No bud, it is to do with transmission losses as per Gman's thread.

 

Is it not very strange that the %age of loss changed? Surely it should have been the same with the same drivetrain? Would that have been down to something like the flywheel/clutch?

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No bud, it is to do with transmission losses as per Gman's thread.

 

Is it not very strange that the %age of loss changed? Surely it should have been the same with the same drivetrain? Would that have been down to something like the flywheel/clutch?

 

Difficult one to answer as there are so many variables. Dynos measure drag rate in various ways, and in that the results vary considerably dependant on the dyno, it's operator and it's shootout configuration.

 

For the results I posted: It's not an exact science (e.g. different rear tyre's were fitted between runs - BPU was on new tyres, single on old worn out ones, it's only going to be a couple of ib's or so or rubber, but with such a huge rotational mass that will make a big difference to final drive torque). 1-2% difference would be within acceptable variation on the same dyno, etc.

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So really, you'd be better off taking your car to several rolling roads, getting an average and going from there?

 

To be honest I think you could go to dyno's till the cows came home and struggle to find 2 the same. I think you could average out the RWHP figures to get a reasonably accurate power of the car, it seems the FWHP figures really are just pie in the sky.

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Or at least to the ones that have been used by many members, SRR, G-Force, and Thor's dyna pak come to mind.

 

My figures from a few years ago (stock boost with cats in)

 

RR Figure - 265 RWHP - 323 FWHP (1% loss variation). 18 % loss figure.

Hub figure - 306 RWHP - Fly and loss, no idea.

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To be honest I think you could go to dyno's till the cows came home and struggle to find 2 the same.

 

Even the same dyno will give different readings on different days, ive seen a change of 30bhp on srr the day after with no change to anything except a cooler engine.

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