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So what's the difference between the GM rating of 405 HP for the Z06 and what the dynos measure in rwhp? I mean why the 405 number from GM is so higher that what the dynos measure? is rwhp different than the measurement used by the cars manufacturers?

If you install some mod that the dyno shows a gain of lets say 20 rwhp, does this mean that your Z06 now becomes 425 HP? :-?
 

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You lose horsepower through the drivetrain, so the actual RWHP will be less than than the actual rated HP. Normally it's about a 13% drivetrain loss which is why most Z's will dyno at around 360.
 

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Yup, it takes power to spin all the gears and such in the drivetrain, not to mention losses that occurs from all those gears spinning in oil, creating heat. Voila'! You have a factory HP rating, which is the "crank" HP, and then you have what it's actually putting to the ground after all those losses. That's why 405 "crank" hp = ~360whp. :guiness:
 

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All auto manufactures like to list the Horsepower rating at the crankshaft because this will yield a higher number. But as others have already stated, the driveline reduces this number by the time the power gets to the rear wheels.

This is also why horsepower rating from the 60's seemed so much higher than todays cars. Most didn't have emissions or air conditioning of which are included in crank shaft horsepower ratings for today's cars.
 

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Before 1969, I believe it was, horse power ratings were also based on an "unloaded" engine. It didn't have loads like water pumps or alternators. In many cases it can make about a 40 to 50 horse power different. If you ever noticed the dyno runs of the 427 CI - 435 horse, they come out to about 335 to 340 rwhp or some where around 385 crank horse power.



Resist said:
All auto manufactures like to list the Horsepower rating at the crankshaft because this will yield a higher number. But as others have already stated, the driveline reduces this number by the time the power gets to the rear wheels.

This is also why horsepower rating from the 60's seemed so much higher than todays cars. Most didn't have emissions or air conditioning of which are included in crank shaft horsepower ratings for today's cars.
 

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The drivetrain loss can always be slightly different between an auto and a manual 13% vs 17% I think is what i was told.
 

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2001Z06 said:
Before 1969, I believe it was, horse power ratings were also based on an "unloaded" engine. It didn't have loads like water pumps or alternators. In many cases it can make about a 40 to 50 horse power different. If you ever noticed the dyno runs of the 427 CI - 435 horse, they come out to about 335 to 340 rwhp or some where around 385 crank horse power.

I may be wrong, but I think the big block factory racers from chevy, ford, and mopar from the mid '60's to the early '70's probably all dyno'd out with more RWHP and torque than the C5 and C6 Z06. If memory serves, the L88, ZL1 and the LS7 454 were reportedly somewhere north of 550 at the flywheel but were never advertised as such due to insurance and/or never reached the general public. I had a '66 427/425 that-I'm sure-with todays tires would beat my Z06 in straight line acceleration.
 

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fcar said:
I may be wrong, but I think the big block factory racers from chevy, ford, and mopar from the mid '60's to the early '70's probably all dyno'd out with more RWHP and torque than the C5 and C6 Z06. If memory serves, the L88, ZL1 and the LS7 454 were reportedly somewhere north of 550 at the flywheel but were never advertised as such due to insurance and/or never reached the general public. I had a '66 427/425 that-I'm sure-with todays tires would beat my Z06 in straight line acceleration.
They just rated some of those old engines at a lower rpm like 5200 instead of the 6500 they made peak power at.
 

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Factory racers are certainly not stock production. ZL1 was an extremely limited production number and really doesn't fall into the category of standard production. The stock L88s and LS7s were in the 435 to 450 range but those were unloaded numbers. Yes, they could easily be modified with a nice cam, tunnel ram and dual double pumper carbs to make wild numbers. My L88 had a huge cam with tunnel ram and dual 750 double pumpers and produced some where in the 600 or so horse power range, but that was not even close to stock. And no, my C5 Z06 could not come close to it in 1/4 but my Z06 would kill it on the road course hands down.

I have seen stock 427 / 435hp vettes put down 340 to 345 rwhp. I also saw a stock 454 LS7 put down in the 350 rwhp range, same dyno, same day and same operator. The owners were rather dissappointed when it was explained to them why the rwhp numbers were so much lower than the 435 label that was on the engine.

fcar said:
I may be wrong, but I think the big block factory racers from chevy, ford, and mopar from the mid '60's to the early '70's probably all dyno'd out with more RWHP and torque than the C5 and C6 Z06. If memory serves, the L88, ZL1 and the LS7 454 were reportedly somewhere north of 550 at the flywheel but were never advertised as such due to insurance and/or never reached the general public. I had a '66 427/425 that-I'm sure-with todays tires would beat my Z06 in straight line acceleration.
 

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That would be 1971.
The '71 LS5 was rated at 365 hp, in '72 rated at 270 hp.
 

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2001Z06 said:
Factory racers are certainly not stock production. ZL1 was an extremely limited production number and really doesn't fall into the category of standard production. The stock L88s and LS7s were in the 435 to 450 range but those were unloaded numbers. Yes, they could easily be modified with a nice cam, tunnel ram and dual double pumper carbs to make wild numbers. My L88 had a huge cam with tunnel ram and dual 750 double pumpers and produced some where in the 600 or so horse power range, but that was not even close to stock. And no, my C5 Z06 could not come close to it in 1/4 but my Z06 would kill it on the road course hands down.

I have seen stock 427 / 435hp vettes put down 340 to 345 rwhp. I also saw a stock 454 LS7 put down in the 350 rwhp range, same dyno, same day and same operator. The owners were rather dissappointed when it was explained to them why the rwhp numbers were so much lower than the 435 label that was on the engine.
This man is right on the money, listen to him. There were very, very, few stock cars to come out of the muscle car era that are as fast as todays Z with a few exceptions (426 hemi, aluminum 427 COPO cars...).

The old school ratings were gross with no accessories hooked up to the motor, and quite often open headers. Todays ratings are net at the crank and are a more accurate representation. But what the thread poster says is correct, to be even more accurate it would be great to have a RWHP rating from the factory...Actually my '99T/A was under rated from the factory and made close to the flywheel ratings at the tire.

A '67 427/435 dynoed 330 RWHP on the same dyno that my T/A made 328 RWHP (mine is modded). My T/A ran high 12s @ 110-111 .

I watched a great TV show not to long ago where they drag raced some factory stock old school muscle cars (AMX, Boss 429, LS6 Chevelle...and about 6 or 7 others..) None of them busted into the 12s and none of them trapped more than 108.
 

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I watched a great TV show not to long ago where they drag raced some factory stock old school muscle cars (AMX, Boss 429, LS6 Chevelle...and about 6 or 7 others..) None of them busted into the 12s and none of them trapped more than 108.[/QUOTE]

Dream car garage baby :thumb: I thought some of those car would be faster than they were. Oh well. They were still bad ass cars.
 
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