How many Engine HP needed for 500rwhp?

[Michael_]

Just curious how many Engine HP will be needed for 500rwhp.
Related to b Bodies with 440 or 426 with a 727 Automatic Transmission Setup. Maybe with GV Overdrive.

What do you think?

 

[44070dart]

You lose about 20% through auto trans drive line.

 

[Kern Dog]

Everything after the flywheel costs power from the transmission, the drive shaft to the axle and tires. A manual trans with a small diameter driveshaft and a 7 1/4 axle and 14 inch stock tires soaks up the least.
The 727 is a great transmission but it eats a LOT of power to operate. The Dana is durable but the heavy parts take power to spin the gears. It used to be figured that drivetrain losses on automatics were over 20%. The GV eats power as well.

 

[NOSTRT980]

I would think 625 to 650hp at motor. a guess only

 

[Michael_]

Thanks for the quick answers
So i think 650 or better 700hp and one would be at the safe side, right?

 

[BSB67]

if 20% loss, 625.

 

[Michael_]

if 20% loss, 625.

Yes but maybe its a bit more. So a few extra hp wont hurt i guess.

 

[Brandy]

Is there a specific reason for wanting 500hp at the rear wheels?

 

[Michael_]

From my personal experience i think 500hp are just right for me. Of course it does not have to be 500,00hp.

 

[1967coronet440]

I have an engine/trans combo up for sale that I guarantee will make 500+ at the wheels.

 

[Stroker68]

Everything after the flywheel costs power from the transmission, the drive shaft to the axle and tires. A manual trans with a small diameter driveshaft and a 7 1/4 axle and 14 inch stock tires soaks up the least.
The 727 is a great transmission but it eats a LOT of power to operate. The Dana is durable but the heavy parts take power to spin the gears. It used to be figured that drivetrain losses on automatics were over 20%. The GV eats power as well.

Agree. Bout 20% for auto. Less on manual.

 

[70sixpkrt]

When I had my motor on an engine dyno about 12 years ago it pulled 499hp at the crank. A few years later, I put the car on a chassis dyno. It came back at 398hp at the rear wheels. So 100hp equals 20% and mine is a 4 speed. If I leaned it out, I would of picked up a couple more hp.

 

[Kern Dog]

It is hard to imagine that a transmission, drive shaft, rear axle and tires could eat that much power. A slant six of the mid 70s couldn't even turn the rear tires with that kind of parasitic loss.

 

[cryplydog]

The biggest loss is going thru the differential.

 

[Kern Dog]

The biggest loss is going thru the differential.

That would be interesting to prove. I can see why though with all of the rotational mass of the gears, differential, axle shafts, drums, wheels and tires.

 

[cryplydog]

It occurs at the ring/pinion and I think there is a mathematical equation for the 90* directional change. There have been published articals on this question but the convertor/auto trans is prob. a major player also.

 

[BSB67]

Which style of RWHP dyno will matter. It's pretty well established that typically the DynoJet will generate hp results higher than a Mustang dyno. But if you use an equally happy engine dyno, it probably won't matter from a % loss standpoint.

 

[ksurfer2]

This is what I never understood about parasitic loss through the drivetrain...Lets assume you start with an engine setup that makes 400hp at the flywheel and assuming 20% drive train loss, you should expect to see 333hp at the wheels. A 67hp loss. Now, you start to mod the motor and when you are done, you are making 550hp at the flywheel. Still assuming the 20% loss, you are now making 458hp at the wheels. a loss of 93hp. Since no other changes were made to the drive train, the power loss should have remained constant at 67hp. Parasitic loss of hp through a torqueflite with a specific torque converter and dana 60 with a given set of gears should be constant regardless of the hp the engine is making. Correct?

 

[33 IMP]

I never understood that either. The only explanation i could think of, was that it probably made 333hp at 4500rpm, and probably makes 550 at 6500rpm. Parasitic loses are bound to go up.
What puzzles me... n.a. 450hp, 6000rpm verses turboed 900 hp at 6000 rpm. What did parasitic loss do?

 

[Stroker68]

This is what I never understood about parasitic loss through the drivetrain...Lets assume you start with an engine setup that makes 400hp at the flywheel and assuming 20% drive train loss, you should expect to see 333hp at the wheels. A 67hp loss. Now, you start to mod the motor and when you are done, you are making 550hp at the flywheel. Still assuming the 20% loss, you are now making 458hp at the wheels. a loss of 93hp. Since no other changes were made to the drive train, the power loss should have remained constant at 67hp. Parasitic loss of hp through a torqueflite with a specific torque converter and dana 60 with a given set of gears should be constant regardless of the hp the engine is making. Correct?

Never understood the exponential part of it either. Always seemed like a canned estimated hp loss statist. Good point.