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

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

You drove all the way to SRR for a power run?!

...sorry, hijack over

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.

You drove all the way to SRR for a power run?!

 

...sorry, hijack over

Mate, I drove all the way down to Japfest to meet some members and noone spoke to anyone. I'm THAT outgoing

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.

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.

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)

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?

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.

Ahh that explains it

McGoo, TT6 @ 0.8bar - RWHP = 273.5 FWHP = 329.8 (20.58 % losses)

AndrewOW, Rebas Systems (Dyno Dynamics) - Auto @ 1bar, 314.6rwhp - 376.4fwhp - 16.41% loss. Is that right?!

SRR Dec 09 results..

Stock SZ 5spd - 215.1 FWHP, 173.8 RWHP (20.2% loss)

BPU RZ Auto @ 0.8bar - 354 FWHP, 294.2 RWHP (16.9% loss)

I'll see if I can find my SZ Auto results from May later..

Hmm the %age losses do seem a little odd. The Auto had less losses than the 5speed?

It would seem that the Auto has 16-19% losses and the manual has approx 21% losses.

Manual should have less loss (18%) than an auto (over 20%).

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

Manual should have less loss (18%) than an auto (over 20%).

Thats what I thought. I read manual as 16%ish and auto as 22%ish.

Strange that.

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.

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.

Can of worms but since every dyno operator (of the same Dyno brand) inputs different loss compensation parameters, why do we insist on focusing on flywheel HP? Why don't we just stick to RWHP and live with it?

because fwhp creates a higher number to share with friends

rwhp would defintely be a more accurate figure for most dynos

^Depends on the dyno

I had mine done at SRR a few years back, at the time it was running full decat and air filter, does it say on the graph for SRR what fly HP is as never noticed.

but,

SRR UK 6sp FWHP 404bhp

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.

because fwhp creates a higher number to share with friends

 

rwhp would defintely be a more accurate figure for most dynos

Manufacturers also always quote fly wheel hp. So I guess it makes it easier for comparisons as most people aren't familiar wheel hp figures.