Does anyone know what the formula is for working out flywheel bhp from RWHP ? At the RR day I was told my RWHP was 250 BHP and at the flywheel the approximate figure was 330 BHP. As mine is an auto they couldn't get a definate flywheel figure. Their estimate seemed a bit high to me - any thoughts ?

Differnet people give different figures, but I tend to go with 15% less for Manual, 20% for auto.

 

That would mean about 315hp @ flywheel for yours.

Differnet people give different figures, but I tend to go with 15% less for Manual, 20% for auto.

 

That would mean about 315hp @ flywheel for yours.

 

When mine was last on the RR, she came out with 340 at the rear wheels and they told me 419 at the fly. Fook knows how they worked that out. I have a manual and yet that figure is over 20%. IMO, he's way out with his estimation.

When mine was last on the RR, she came out with 340 at the rear wheels and they told me 419 at the fly. Fook knows how they worked that out. I have a manual and yet that figure is over 20%. IMO, he's way out with his estimation.

 

I think they over-estimate to make us feel good !!! :)

The guy told me that for autos they say 300rwhp is around 400fwhp. So my 288rwhp comes out around 385fwhp. I think that's way too much loss as they're assuming 25%!

 

On the other hand, the manuals were given fwhp figures, rather than rwhp and their conversion was assuming a loss of 20%, which is also probably too high for a manual.

 

As someone said on another thread, SRR's dyno is thought to give very conservative rwhp figures, so maybe they bump up the power loss to compensate? :confused:

 

Most of the rwhp figures we got did seem to be at the low end of what you'd expect though. :nono:

The guy told me that for autos they say 300rwhp is around 400fwhp. So my 288rwhp comes out around 385fwhp. I think that's way too much loss as they're assuming 25%!

 

On the other hand, the manuals were given fwhp figures, rather than rwhp and their conversion was assuming a loss of 20%, which is also probably too high for a manual.

It is a bit frustrating, I think I would rather just have the RWHP figures.

As someone said on another thread, SRR's dyno is thought to give very conservative rwhp figures, so maybe they bump up the power loss to compensate? :confused:

 

Most of the rwhp figures we got did seem to be at the low end of what you'd expect though. :nono:

I got 284 and was expecting 300 at the fly :rolleyes:

spoke to several transmission/drivertrain experts and all say drivetrain loss can not be represented as a static percentage.

Drivetrain loss is a static figure and depends on the type of transmission/differential/wheels and number of links/bearings before the power is actually put to the ground.

 

for a Manual Zed (both NA and TT) the loss is approx. 33kW/ 44hp and for a stock TT this would be approx. 15% of the total fwhp, but for a zed that puts out 550 rwhp the percentage loss has dropped to 9%.

For a stock NA it's closer to 19%

spoke to several transmission/drivertrain experts and all say drivetrain loss can not be represented as a static percentage.

Drivetrain loss is a static figure and depends on the type of transmission/differential/wheels and number of links/bearings before the power is actually put to the ground.

 

for a Manual Zed (both NA and TT) the loss is approx. 33kW/ 44hp and for a stock TT this would be approx. 15% of the total fwhp, but for a zed that puts out 550 rwhp the percentage loss has dropped to 7%.

For a stock NA it's closer to 19%

 

 

:bow: always amazes me that you know everything!!!

spoke to several transmission/drivertrain experts and all say drivetrain loss can not be represented as a static percentage.

Drivetrain loss is a static figure and depends on the type of transmission/differential/wheels and number of links/bearings before the power is actually put to the ground.

 

for a Manual Zed (both NA and TT) the loss is approx. 33kW/ 44hp and for a stock TT this would be approx. 15% of the total fwhp, but for a zed that puts out 550 rwhp the percentage loss has dropped to 7%.

For a stock NA it's closer to 19%

Makes sense. I think it would be better to quote rwhp for both manuals and autos as that's what matters, rather than some estimated fwhp figure.

 

I still think that the rwhp figures were a little conservative. Mine at 288rwhp was the highest, followed by JonJon's manual at around 280 and another at around the same (not sure who as it was before I got there, I think). There were a few TTs down at around 200rwhp too, so it suggests to me that the figures given were a little on the low side.