Transmission loss. RWHP
Discussion
Hey all,
Had my BMW on the rollers a few weeks back before carrying out any mods and it was making 195bhp at the flywheel and only 138RWHP, Is it me or is this a huge loss compaired with the general rule of thumb of 17%. This seems to be around 28% losses.
As you can see its from Austecs rollers which are accurate using the MAHA LPS3000 Unit, It just seems the losses are a bit high, or are the flywheel figures a bit high?
The car is a 323i.. Which book figure should be 170bhp. The only mod I have done is an enclosed induction kit, which I highly doubt will gain 25bhp!
I should add it was taken on a rolling road day where most people where saying there cars were reading under power.
The engine is suspect as its a 1995 car, yet it has a vanos engine cover, which wasn't being put in at the time, Also running hte M52 manifold which is restricted due to German tax laws to 170bhp. Yet it still made over.
Had my BMW on the rollers a few weeks back before carrying out any mods and it was making 195bhp at the flywheel and only 138RWHP, Is it me or is this a huge loss compaired with the general rule of thumb of 17%. This seems to be around 28% losses.
As you can see its from Austecs rollers which are accurate using the MAHA LPS3000 Unit, It just seems the losses are a bit high, or are the flywheel figures a bit high?
The car is a 323i.. Which book figure should be 170bhp. The only mod I have done is an enclosed induction kit, which I highly doubt will gain 25bhp!
I should add it was taken on a rolling road day where most people where saying there cars were reading under power.
The engine is suspect as its a 1995 car, yet it has a vanos engine cover, which wasn't being put in at the time, Also running hte M52 manifold which is restricted due to German tax laws to 170bhp. Yet it still made over.
Edited by TJW on Tuesday 11th November 01:19
Hardly the easy way to check! Not worth the effort !I dunno, those figures look about right. Take a look at:
http://www.pumaracing.co.uk/POWER3.htm
Taking your 138bhp measured and using the rule suggested for RWD cars (add 10bhp, divide by 0.88) gives 168hp - almost spot-on the book figure. Perhaps you actually came across a set of honest rollers!
http://www.pumaracing.co.uk/POWER3.htm
Taking your 138bhp measured and using the rule suggested for RWD cars (add 10bhp, divide by 0.88) gives 168hp - almost spot-on the book figure. Perhaps you actually came across a set of honest rollers!
Vixpy1 said:
Tim the 323i's generally do make over book, around the 180 to 185bp point. Your wheel fig is a bit low, your flywheel fig maybe a bit high, but not by much.
Hi, I was thinking of taking up to Surrey Rolling Road soon, I've added the M50 (unrestricted inlets) & Port&Polished TB with a larger butterfly. So hopefully see what It's making now. I had my E30 M3 on a MAHA rolling road and got some silly transmission losses of 68BHP with 190@wheels. I think it is the way the MAHA is. If doing a before and after it is worthwhile going hack to the same place.
A point worth noting is that the MAHA software seems to apply the correction to the calculated flywheel figure and not the measured wheel figures. Don't know why?
Steve
A point worth noting is that the MAHA software seems to apply the correction to the calculated flywheel figure and not the measured wheel figures. Don't know why?
Steve
TJW said:
Hey all,
Had my BMW on the rollers a few weeks back before carrying out any mods and it was making 195bhp at the flywheel and only 138RWHP, Is it me or is this a huge loss compaired with the general rule of thumb of 17%. This seems to be around 28% losses.
from my days of reading CCC et al, I thought RWHP was typically 20 - 25% less than flywheel.Had my BMW on the rollers a few weeks back before carrying out any mods and it was making 195bhp at the flywheel and only 138RWHP, Is it me or is this a huge loss compaired with the general rule of thumb of 17%. This seems to be around 28% losses.
What gear was your car tested in? If was tested in top gear, which is easier for the test in some respects, the power losses would have been higher because the tyre losses are higher at high speed.
Good figures, though.
just a thought. Nick
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