RWH/Torq vs. Crank
Thread Starter
Pro
Joined: Jul 2004
Posts: 693
Likes: 0
From: Cumming Georgia
Who can tell me how to figure HP/Torque at crank?
Who can tell me what % to use in figuring estimates of horsepower and torque at the crank if you have dyno of both at rear wheels?
Thanks.
Thanks.
Last edited by rlee; May 7, 2008 at 11:08 AM.
Speedy
Joined: Mar 2007
Posts: 6,110
Likes: 931
From: Tn
2024 C8 of the Year Finalist - Modified
Our cars usually loose 15% by drivetrain loss so that means your rwhp is 85% of your engine hp, that is 400 x .85 = 340rwhp its not exact but pretty close. if you want engine hp from a dyno number take your dyno # and divide by .85, that is dynohp/ .85 = engine hp
the above is an assumption that your using a mustang dyno if its a dyno jet is a little less as far as % goes but same concept with multiplication and division. good luck bro
the above is an assumption that your using a mustang dyno if its a dyno jet is a little less as far as % goes but same concept with multiplication and division. good luck bro
Burning Brakes
Joined: Mar 2006
Posts: 946
Likes: 0
From: Midland, TX........ 550 RWHP/520 RWTQ (A6)
This is what I've seen (on average) after sorting thru tons of dyno sheets (some with the same engine on a flywheel dyno and then with a chasis dyno):
All Dynojet
MN6=12% drivetrain loss
A6=17% drivetrain loss
All Dynojet
MN6=12% drivetrain loss
A6=17% drivetrain loss
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
You have three wildly different responses now so you should see a trend by now...nobody knows!!! And the reason is because it isn't a percentage, it's a combination of constants and percentages with the constant losses being the predominate term. If you really want to use a percentage, Bushong572 is about dead on if you're talking a stock engine...but then again, we already know what a stock engine is making at the crank. If you want to know the HP/torque at the crank, remove the engine and put it on an engine dyno.
Last edited by glass slipper; May 7, 2008 at 11:52 PM.
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
After reading Dynojet 248 results on this Forum for 3+ years the LS2's seem to be 340-345 RWHP manual trans and 330-335RWHP for the automatics. Different Dynojet 248's give different results, some are notoriously high but the average is 340-345 for a stick LS2.
Very close to a 15% loss from Manufacturer stated Flywheel HP.
Then the eternal question of loss on a modded motor; Still aprx. 60HP OR do you use 15%? My modded '05 Dyno'd at 385 RWHP, does that mean I had 445 HP at the flywheel (60HP loss) or did I have 453HP (15% loss)? Personally I think the 60HP remains constant, not the 15% but thats IMHO.
Very close to a 15% loss from Manufacturer stated Flywheel HP.
Then the eternal question of loss on a modded motor; Still aprx. 60HP OR do you use 15%? My modded '05 Dyno'd at 385 RWHP, does that mean I had 445 HP at the flywheel (60HP loss) or did I have 453HP (15% loss)? Personally I think the 60HP remains constant, not the 15% but thats IMHO.
