Horsepower formula
Thread Starter
Racer
Joined: Jul 2004
Posts: 282
Likes: 2
From: Wappingers Falls NY
Horsepower formula
what is the formula for calculating horsepower at the flywheel if i know the horsepower at the rear wheels ?? i know you multiply by.0** ??
http://img.photobucket.com/albums/v6...ic23w/scan.jpg
http://img.photobucket.com/albums/v6...ic23w/scan.jpg
Safety Car
Joined: Oct 2000
Posts: 4,949
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From: Monticello MN
Originally Posted by Patches
Over the years I've seen a 13-15% loss used on the MN6/M12 while 15-18% is applied to the A4. So, for a 305 rwhp MN6 C5 with a 13% loss applied:
305/.87 = 350.57 fwhp
305/.87 = 350.57 fwhp
I've been told 15% for an M6 and 18-20% for an A4 from some pretty reputable tuners. Don't know how accurate that is, though. I would think, for example, that a 2.73 rear would dyno higher than a 3.15. Logic would say that the A4 has more drivetrain loss than an M6, but exactly how much, seems open to some conjecture. In the final analysis, it probably doesn't really mean much, except for bragging rights. It's in, as they say, where the rubber hits the road.
Ed
Melting Slicks
Joined: Jul 2004
Posts: 3,353
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From: Richmond Hill Ontario
Originally Posted by C5XTASY
I've been told 15% for an M6 and 18-20% for an A4 from some pretty reputable tuners. Don't know how accurate that is, though. I would think, for example, that a 2.73 rear would dyno higher than a 3.15. Logic would say that the A4 has more drivetrain loss than an M6, but exactly how much, seems open to some conjecture. In the final analysis, it probably doesn't really mean much, except for bragging rights. It's in, as they say, where the rubber hits the road.
Ed
Ed
Supporting Tuner
Joined: Sep 2004
Posts: 51,896
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From: ================== Houston, Texas www.englandgreen.com ================== Necessary Evil™ __________
CI 6-7-8-9-10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14
I agree. I'm only interested in rear wheel horsepower and rear wheel torque. I can't use the power at the crank - only at the tyres 
EG
EG
Melting Slicks
Joined: May 2005
Posts: 3,394
Likes: 12
From: Leon Iowa
St. Jude Donor '06-'07-'08-'09
Originally Posted by Awsum98
what is the formula for calculating horsepower at the flywheel if i know the horsepower at the rear wheels ?? i know you multiply by.0** ??
http://img.photobucket.com/albums/v6...ic23w/scan.jpg
http://img.photobucket.com/albums/v6...ic23w/scan.jpg
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Safety Car
Joined: Sep 2003
Posts: 3,558
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From: Cape Coral FL
Originally Posted by Rock'en Silver 02
the correct number is 17%. thats from my dyno/tuner guy
Team Owner
Joined: May 2004
Posts: 26,345
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From: SoCal
Originally Posted by BIGMAC
I am told that on an A4, 3.42 gears and a 2600 stall converter will increase the driveline loss to 18-20% vs. 13-15% with stock 2.73 gears and 1400 stall. Can anyone confirm?
I can only confirm that your car will be MUCH FASTER
DH
Racer
Joined: Apr 2004
Posts: 387
Likes: 0
From: Rollin' Worldwide from OH10 Ohio
I usually tend to stay out of these hottly contested debates, but I will say this: You are all pretty much in the ball park, and are fairly well informed. Typically we see in manual trans, vehicles approx 10-15% loss and 15-25% loss in automatics.
You can get really close, but for those of us who are sticklers- next time your engine is out, have it "easy" dyno'ed and then when installed, take your car to a chassis dyno and you'll know exact loss.
The last thing I will say between the Mustang Dyno and Dynojet( "Mine's Better Than Your's" ) argument that will go on till eternity- we use a Dynojet, but- have had the same vette on a MDyno, with an extremely qualifed operator and have acheived results to within 1hp.
You can get really close, but for those of us who are sticklers- next time your engine is out, have it "easy" dyno'ed and then when installed, take your car to a chassis dyno and you'll know exact loss.
The last thing I will say between the Mustang Dyno and Dynojet( "Mine's Better Than Your's" ) argument that will go on till eternity- we use a Dynojet, but- have had the same vette on a MDyno, with an extremely qualifed operator and have acheived results to within 1hp.
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
Originally Posted by Rock'en Silver 02
the correct number is 17%. thats from my dyno/tuner guy
