Does anyone know a formula or off the top of their head what 324 rwhp equates to in terms of crank hp?
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rwhp vs crank hp
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Agreed, I read a car craft article a while back, they said average a manual eats about 18-20% of the power, while an auto eats upwards of 32-35% of power.sigpic
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Originally posted by ak- View PostYou did it backwards.
He was 324 wheel.Originally posted by 36bruaIsn't that what these forums are all about making stuff easier... OO no never mind this is r3v...
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I've read it's around 15% for manual and around 20% for auto.(autos are more variable though since newer ones are more efficient.
I would say 15% for a rear wheel drive manual BMW.
Lets take the e36 m3 for example.
They usually dyno 200-210WHP bone stock. (dynojet)
They are rated at 240HP by BMW.(CHP)
240 - 15% drivetrain loss = 205 WHP so the 15% works out perfectly for that example.
edit:
OP, using 15% you would have 324 x 1.15 = 372.6 crank HP.
Also, you have to consider that different dynos typically read higher and lower than others, some are at shops to be used for tuning only, not for bragging rights, so they don't change it from the factory settings which may be conservative. So I would ask the place that it got dyno'd at (or the dyno manufacturer if they don't know) because they would know how their reading correlate to crank HP better than anyone.Last edited by VinniE30; 01-07-2013, 03:22 PM.Zinno '89 <24v swap in progress>
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Originally posted by ja burna View Postyeah figures were using a Mustang dyno.. so I don't know if they read lower or higher
Look at this article on dynos and how much higher/lower different manufacturers' dynos can be.
Also see this thread: http://forums.bimmerforums.com/forum....php?t=1696183
And if comparing to a reading done on a different day or different place you have to consider how factors like temperature and altitude affect output.Zinno '89 <24v swap in progress>
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forget about calculating crank HP from a wheel dyno. it's totally pointless. not only does it change with ambient conditions, it changes with dynos, and the % is not linear - it changes for the same drivetrain based on how much power you put into it.
adding a magic 20% number, guessed from something you read on the internet (or pulled out of your ass, usually), to a wheel dyno result so you can brag about your mad HPs is one of the lamest bench racing excersizes there is. Chassis dynos are a tool used to tune an engine. That's all. The only comparisons should be cars done on the same dyno in the same conditions.
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