Old HP ratings vs new

[shroomjohn]

Its been talked about before how HP ratings were calculated differently "back in the day". I was just curious how they were calculated compared to now? I mean if a camaro in 69 had 375 horse what would that make today,what would ours make then, also are the torque ratings measured differently? Just curious THanks

[MONTANACARGUY]

''Back in the day'' horsepower and torque ratings were measured in SAE( society of automobile engineers)gross.meaning the power was calculated at the flywheel. Currrently, we measure SAE net ratings that account for the losses that occur from the transmission and driveline.If the two numbers are the same the net rated vehicle has more horsepower.

[76z28]

eh i tend to disagree with that
most cars are rated at 426 horse and are dynoing at 350
back then it was the same way

[SlingShot]

Originally Posted by 76z28

eh i tend to disagree with that
most cars are rated at 426 horse and are dynoing at 350
back then it was the same way

Agree ... The LS3 426 Hp is gross at the crank aka flywheel ...

[THE EVIL TW1N]

Originally Posted by MONTANACARGUY

''Back in the day'' horsepower and torque ratings were measured in SAE( society of automobile engineers)gross.meaning the power was calculated at the flywheel. Currrently, we measure SAE net ratings that account for the losses that occur from the transmission and driveline.If the two numbers are the same the net rated vehicle has more horsepower.

back in the day, the engine was dyno'ed with longtubes and without all the accessories, including water pump.

[Number 3]

They are not the same. Old numbers were measured not calculated at the flywheel as they are today but back the they had no accessories. So no ac compressor no alternator no power steering pump.

Today's engines are measured as they would be installed in the car,

the V6 in your Camaro is making nearly the same hp as the old V8s

[Thrillz]

Originally Posted by Number 3

They are not the same. Old numbers were measured not calculated at the flywheel as they are today but back the they had no accessories. So no ac compressor no alternator no power steering pump.

Today's engines are measured as they would be installed in the car,

the V6 in your Camaro is making nearly the same hp as the old V8s

I get the comment after i tell people at work aw you got the V6 that sucks i laugh every time. I then tell them it has 270ish ft tq 305 hp they are like wtf. Its my daily driver 300 hp is enough to get to work. I dont go to the track and i do not street race so 425 would be not of much use to me. I do love the grunt of the V8 though its awesome. For what you get this car is a steal imo.

[shroomjohn]

They are not the same. Old numbers were measured not calculated at the flywheel as they are today but back the they had no accessories. So no ac compressor no alternator no power steering pump.

Today's engines are measured as they would be installed in the car,

the V6 in your Camaro is making nearly the same hp as the old V8s

Huh thats pretty interesting it was done before the accessories or luxuries back then were on. I wonder w all the increase in tech if the loss due to having an auto for instance has been consistent I think its around 15% now but I could be wrong

[THE EVIL TW1N]

Originally Posted by shroomjohn

Huh thats pretty interesting it was done before the accessories or luxuries back then were on. I wonder w all the increase in tech if the loss due to having an auto for instance has been consistent I think its around 15% now but I could be wrong

auto's nowaday's are about as efficient as the smaller/weaker transmissions of yesteryear, and much more efficient than the stronger automatics of the past.

[1camaro70]

in 1970 my camaro was rated at 200HP, in 1971 the same engine was 155HP.

[rayhawk]

Originally Posted by shroomjohn

Huh thats pretty interesting it was done before the accessories or luxuries back then were on. I wonder w all the increase in tech if the loss due to having an auto for instance has been consistent I think its around 15% now but I could be wrong

The power lost through the transmission was never taken into account back then or today, so it has no effect on factory hp ratings. Factory hp ratings have always been measured at the flywheel on an engine dyno.

[CLEAN]

Stolen from the internet....

Before 1972, most American engines were rated under the methodology laid out in Society of American Engineers (SAE) standards J245 and J1995, which calculated the output of a 'bare' engine on a test stand with no accessories, optimal ignition timing, free-flowing exhaust headers (no mufflers), with a correction factor for standard atmospheric conditions.

Starting in 1971, manufacturers began to lower compression ratios and de-tune their engines to prepare for the advent of unleaded gasoline. Both the early emission-control systems (air-injection pumps, exhaust gas recirculation) and the reduced compression ratios made engines perceptibly less powerful, whether those losses were reflected in the gross power ratings or not.

Faced with this reality, along with the pressures of the safety and environmental lobby, domestic manufacturers decided it was time to abandon the gross rating system. In its place they adopted the SAE net rating methodology, described by SAE standard J1349. "Net" horsepower ratings are still made with the engine on a test stand, but with stock ignition timing, carburetion, exhaust, and accessories -- in short, a closer approximation of how much power an engine produces as actually installed in the car. (SAE net horespower does NOT, contrary to some assumptions, measure horsepower at the drive wheels; both gross and net ratings are at the flywheel, and don't reflect power losses in the drivetrain.)

[Stefan@D2AUTOSPORT]

All that matters to me is how much of that power is hitting the street.