In the 60's and 70's the horsepower was for exapmle a 454 LS-6 had 450 Gross H.P. what was the net? Today we have the LS1 with 345 Net Horsepower what would be the gross to compare with back then?
Posted by Mike2001SS (Member # 2088) on :
quote:Originally posted by 2002 SLP SS: In the 60's and 70's the horsepower was for exapmle a 454 LS-6 had 450 Gross H.P. what was the net? Today we have the LS1 with 345 Net Horsepower what would be the gross to compare with back then?
Well the net on those back then would be less than the net on the new LS1's not only did they come up with gross H.P. in different ways but the drive trains were less efficiant and they lost more from everything on the motor and the drive train before it got to the wheels. Some engines were put on a engine dyno with no plulleys turning anything not even the water pump was turning and no exaust hooked to the motor. For example a 428 Super Cobra Jet 435 H.P. in the 60's dynoed 295 at the wheels.. On average a good rule of thumb today is you lose 15% for a M6 car and maybe 18% for a A4 car some say less than that but that is close. Cars back then lost more and they went about getting gross different also. They were selling gross H.P. back then and they used all the tricks to get the most to show up. Then came a time they started underrateing the HP for insurance and government regulations Posted by sscamaro (Member # 1330) on :
I have heard some where that you devide your flywheel hp by .75 and that would be the gross hp. So if you had 400 net hp at the flywheel, you would have 533 gross hp.
Posted by MCKNBRD (Member # 2238) on :
Gross HP= engine output with NO accessories...no water pump, alternator, P/S, A/C or anything attached...its what the enigne is capable of doing.
Net HP= crank output in the configuration it will be in in the car...with all accessories attached, even if they're not turning (ie: A/C compressor).
Basically, what we consider 'crank HP' is the old 'net HP' term. As far as driveline losses, I've heard 8-10% for a modern manual transmission, with the same loss for an auto, if the TC is locked up. 12-15% if the TC isn't locked.
Byrdman
Posted by SSHEETS (Member # 1989) on :
quote:Originally posted by MCKNBRD: Gross HP= engine output with NO accessories...no water pump, alternator, P/S, A/C or anything attached...its what the enigne is capable of doing.
Net HP= crank output in the configuration it will be in in the car...with all accessories attached, even if they're not turning (ie: A/C compressor).
Basically, what we consider 'crank HP' is the old 'net HP' term. As far as driveline losses, I've heard 8-10% for a modern manual transmission, with the same loss for an auto, if the TC is locked up. 12-15% if the TC isn't locked.
Byrdman
Ditto, except I've heard 12%-18% drive train loss. So you take your rwhp and dived by .85 (for a 15% loss) and that'll give you a theoretical Net. The only way to get gross that I know of is with an engine dyno.
Posted by MCKNBRD (Member # 2238) on :
quote:Originally posted by SSHEETS: Ditto, except I've heard 12%-18% drive train loss. So you take your rwhp and dived by .85 (for a 15% loss) and that'll give you a theoretical Net. The only way to get gross that I know of is with an engine dyno.
I think those numbers are outdated, but I've heard the same thing. I like the idea of going with about 8%, as it artificially inflates the crank HP numbers, and no one ever calls you on it anyway!
And you are correct, gross is engine dyno with a stripped engine...
Byrdman
Posted by Mike2001SS (Member # 2088) on :
I can tell you the Nascar crews would kill to get below 11% loss 15% I think is more close.
Posted by JeffY (Member # 120) on :
quote:Originally posted by sscamaro: I have heard some where that you devide your flywheel hp by .75 and that would be the gross hp. So if you had 400 net hp at the flywheel, you would have 533 gross hp.
Not even close.
Posted by JeffY (Member # 120) on :
The only way to tell is from dyno testing before and after. So much depends on emission controls, engine management schemes, PCM, ECM, set-ups, electronic vs. hydraulic controls, drivaeablity set-ups, limited slip transmissions, fuel economy concerns. NASCAR vehicles want no-slip, bang it home, lock ups; consumers want good fuel economy, comfy rides. The F-car trannies are really very good and very low on drive loss. We ahd some GM testing and saw the actual numbers and they were much lower than any one thought. The end result was that all of those owners that thought they had 400HP at the flywheel had a lot closer to 350.
Posted by Mike2001SS (Member # 2088) on :
Thats true Jeffy
Posted by Brian's 01 SS (Member # 1499) on :
Ok, so if I dyno 409 at the rear wheels (this is on the same dyno I pulled 327 stock with lid and y-pipe), do I 409/.85 (for 15% loss mn6) and get 481 hp? That seems like alot of pony's. But if its in the ball park, I'll take it!!!
Posted by Mike2001SS (Member # 2088) on :
That would not be much off Brian should be within 10 hp anyway
Posted by 2002 SLP SS (Member # 1893) on :
Jeff read your reply thanks but,(sorry I went to public school) what would be the Gross horsepower of out SS? advertised is 345 with airbox so if SLP dyno tested or GM tested these cars what would be equal to groos Horsepower!
Posted by MCKNBRD (Member # 2238) on :
quote:Originally posted by 2002 SLP SS: Jeff read your reply thanks but,(sorry I went to public school) what would be the Gross horsepower of out SS? advertised is 345 with airbox so if SLP dyno tested or GM tested these cars what would be equal to groos Horsepower!
I doubt they did any specific testing on the SLP package, without it being a real-world (ie: net) HP reading. If you stripped the LS1 down, and you're looking at 345 as a realistic number at the crank, you'd probably get about 360-365, at best. Today's accessories are incredibly low drag compared to the 'good old days'.
That said, if you tried whipping out gross vs net vs crank vs wheel hp numbers at a car show, you'd probably spend more time explaining the differences than looking at the cars there.
JMHO, of course...and SLP could very well have stripped an LS1 down to bare-bones to see what the base powerplant did, but I doubt we'd ever get those numbers..something about GM under-rating their engines...
Byrdman
Posted by SSHEETS (Member # 1989) on :
quote:Originally posted by MCKNBRD:
That said, if you tried whipping out gross vs net vs crank vs wheel hp numbers at a car show, you'd probably spend more time explaining the differences than looking at the cars there.
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