there is none, it all depends on many other engine components...this is why the auto is slower...the engine has the same hp, but it has to work harder to move more parts in an auto, therefore it takes away from the whp. there's MANY factors that play effect on Crank HP to WHP.
if you are losing that much hp, it's time to change the mtf or atf to synthetic and adjust the master cylinder for the clutch if you have one....105 whp from a 140 crank hp motor is 25% loss...that is huge...if you have an automatic, that is typical...you lose quite a bit thru the fluid and torque converter...my 15% quote is for manual trannies....
yes. it relates to the diff and how many gears, shafts, joints, and axles are in between the flyweel/clutch and the driveshaft. obviously a RWD car doesn't have as direct a link to the driveshaft that a FWD car has (from the flywheel to the tranny mainshaft, to the driveshafts in their transverse layout).
a nice discussion on the topic here from my friends at simple digital systems. they seem to think that the often quoted 20-25% is overblown and it is more on the order of 12.5%. When we dyno a teg you see 13% on the pure trailer queen race cars with 4 puck clutch discs, 2600-3000 lb pressure plates (stock is 1200 lb), racing diff with a beefier tranny mainshaft, racing synthetic gear oil versus typically 15% on street/weekend racer motors. The Nissan 300Zx's, RX7's, and Supras run 20%.:
Quote: The Nissan 300Zx's, RX7's, and Supras run 20%[/QUOTE]
from wat i have heard, its about 17%. i have a 240sx at 155hp. from wat i heard at 17% loss should mean:
155hp x 17% = 26.35 loss
155-26.35 = 128.65 rwhp
at 20% power loss:
155 x 20% = 31 loss
and from import tuner [which i know i shouldnt trust] says the base rwhp of a 240sx is about 128-130rwhp. so thats y im guessing 17% is more correct for these types of cars. but as from wat im told from my brother, "MD knows a lot" so im guessing i should juss shut up and guess your right.
I can only tell you what I've done and seen...not what I hear from other people....
compare apples to apples.
if the hp is rated in SAE Corrected whp then you at least have the standardized hp that takes into account the influence of ambient temp., humidity, and altitude. If you used raw hp or uncorrected hp then someone making 128 hp at sea level at 70 degrees F could have 120 hp in Denver at 85 degrees F FOR THE EXACT SAME CAR. And we also know that not all integras or cars of the same model BoNE STOCK have the same hp when they leave the factory. I have seen bone stock ITR's dyno at 155 to 165 SAE corrected whp. There can be that much variation depending on how the car was assembled, broken-in, and maintained. So if you are using a magazine's quote of the hp for your car, was it SAE corrected and is it fair to extrapolate another car even though it is the same model instead of using the one you dyno'd?
if you want to use 17% based on your assumptions, then I suggest to you that your facts are not based on sound empirical scientific method.