Horsepower conversion, at wheels vs. at crank, what's the ratio?
07-13-2001, 08:19 AM
#2
Depends on the dyno and FWD vs AWD etc. There is no standard.
<center><img src="http://www.giacusa.com/images.dir/ttk04.jpg"></center><p>But for most FWD on a mustang dyno it is 1.15
For example the 180TT FWD with K04 pulled:
222.9hp and
247.9 ft/lbs torque.
The correction factor for this setup was 1.15 so the numbers at the crank come out to:
256hp and
285 ft/lbs torque.
Not sure if this answered your question.
I believe the APR dyno that bolts to the hub of each wheel has a different factor.<ul><li><a href="http://www.giacusa.com/tt.htm">http://www.giacusa.com/tt.htm</a</li></ul>
For example the 180TT FWD with K04 pulled:
222.9hp and
247.9 ft/lbs torque.
The correction factor for this setup was 1.15 so the numbers at the crank come out to:
256hp and
285 ft/lbs torque.
Not sure if this answered your question.
I believe the APR dyno that bolts to the hub of each wheel has a different factor.<ul><li><a href="http://www.giacusa.com/tt.htm">http://www.giacusa.com/tt.htm</a</li></ul>
07-13-2001, 08:31 AM
#5
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Driveline efficiency and tires have effects. It's also difficult to quantify.
It varies from vehicle to vehicle, but 15%, as Jenner said is a fair estimate for FWD. quattro is much more difficult to figure. Because there are additional driveline losses, 15% might be low.
Best use of chassis dyno numbers is to compare before-after changes, not to claim flywheel horsepower gains. A 5% increase noted at the wheels should be about the same PERCENT increase at the flywheel.
My $.02
Best use of chassis dyno numbers is to compare before-after changes, not to claim flywheel horsepower gains. A 5% increase noted at the wheels should be about the same PERCENT increase at the flywheel.
My $.02
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07-13-2001, 08:47 AM
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capture.dat is fine, if you feel industrious add block #204
Start by holding at a nice low rpm, like 720 or so. Easiest done by slowing & holding a crawling cruise rather than by starting from stop. No clutching please.
07-13-2001, 10:07 AM
#9
I use 117% value...why.....
in a dyno test of several 225TTs all of which were chipped with performance exhausts except one...that one was the datum used....knowing that Audi (or any German car manufacture of vehicles built in Germany) must release engines that are at the equal to or higher of the advertised HP I took the dyno (to the wheels) number and factored in the advertised HP and came up with 117%-118%. When applying to the rest of the TTs the resultant look reasonable and generally close to what the chip manufacturers were claiming. Not the most scientific method but the approach had a certain amount of validity.
07-13-2001, 12:06 PM
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That sounds very reasonable, for that particular dyno anyhow.
So for a 24 hp (or ft-lb) increase shown at the wheels, there would be 28 more at the flywheel.
Thanks for the info, Michael.
Thanks for the info, Michael.
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