1981 HP Question
Thread Starter
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
1981 HP Question
The L81 motor was 190 HP at 4100 RPM. Is this rated at the crank or rear wheels. If this is the crank then the rear wheel HP had to be around 120 HP.
Am I correct or am I on something?
I just dynoed my car Last September and its now 290 RWHP. Was it that much of a dog?
Am I correct or am I on something?
I just dynoed my car Last September and its now 290 RWHP. Was it that much of a dog?
Le Mans Master
Joined: Dec 2004
Posts: 5,230
Likes: 418
The L81 motor was 190 HP at 4100 RPM. Is this rated at the crank or rear wheels. If this is the crank then the rear wheel HP had to be around 120 HP.
Am I correct or am I on something?
I just dynoed my car Last September and its now 290 RWHP. Was it that much of a dog?
Am I correct or am I on something?
I just dynoed my car Last September and its now 290 RWHP. Was it that much of a dog?
Race Director
Joined: Jul 2004
Posts: 12,696
Likes: 329
From: Scottsdale Arizona
I don't think it was at the crank. I think it was 190 HP at the rear wheels (net). The change to net HP occured in the early 70s (I think). That and the change to unleaded fuel and emission controls were the reasons for the steady decline in HP.
Drifting
Joined: Aug 2007
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Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Net HP is not at the rear wheels. It is with all the acc. hooked up and run like it is in the car with manifolds. The old way was just the crank HP without all the acc. Rear wheel HP was never advertised or never really used until the newer cars came around.
So yes the 190 HP Vette was a real dog as far as performance. I actually drove one in about 82 and the V6 Citation I had then was actually faster.
So yes the 190 HP Vette was a real dog as far as performance. I actually drove one in about 82 and the V6 Citation I had then was actually faster.
Le Mans Master
Joined: Dec 2004
Posts: 5,230
Likes: 418
I can not believe that people are out there who believe that any HP rating would be at the rear wheels. There are simply too many variables for the OEM to confirm. An engine system in a dyno room is much easier to control with respect to everything from fuel to ambient temperature. All HP ratings (net or gross) are engine only. The gross ratings from pre-72 included exhaust headers and no accessories. It also does not include the effect of the package environment, like access to airflow, engine heat from the radiator, cooling strategy, etc. Net HP takes all that into consideration.
RWHP is ideal for individual cars though and can give one an indication of how fast and efficient that one car can be.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
You should also note that the rated HP was specified at 4100 rpm. It's not that the engine's max HP occurred at 4100 rpm...it's just that the engine generated that much HP at that point on the curve. If you revved it higher, it would make more power. But, rated HP was a 'killer' for insurance rates, so GM de-rated engine power so their customers wouldn't get "soaked" by the insurance industry.
Check the engine power specs on Corvettes from 1972 through 1991. Specified power points are as low as 4000 rpm...all in an effort to "beat the system". Even though those engines weren't as powerful as in earlier years, they would make more power than was spec'd.
Check the engine power specs on Corvettes from 1972 through 1991. Specified power points are as low as 4000 rpm...all in an effort to "beat the system". Even though those engines weren't as powerful as in earlier years, they would make more power than was spec'd.
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
You should also note that the rated HP was specified at 4100 rpm. It's not that the engine's max HP occurred at 4100 rpm...it's just that the engine generated that much HP at that point on the curve. If you revved it higher, it would make more power. But, rated HP was a 'killer' for insurance rates, so GM de-rated engine power so their customers wouldn't get "soaked" by the insurance industry.
Check the engine power specs on Corvettes from 1972 through 1991. Specified power points are as low as 4000 rpm...all in an effort to "beat the system". Even though those engines weren't as powerful as in earlier years, they would make more power than was spec'd.
Check the engine power specs on Corvettes from 1972 through 1991. Specified power points are as low as 4000 rpm...all in an effort to "beat the system". Even though those engines weren't as powerful as in earlier years, they would make more power than was spec'd.
Burning Brakes
Joined: Jan 2009
Posts: 1,224
Likes: 1
From: Clarksville Indiana
does anybody know how desk top dyno results compare to factory ratings when you input stock specs? just curious, wondering if you can say factory says it was xxx but it realy was xxx ?