Hp ratings for cars... new or old

Before '71 they were rated as "gross HP". This meant under controlled atmospheric conditions, at the flywheel w/o any accessories such as alt., water pump, etc.

'71+ and currently they are rated as "net HP". This is under controlled atmospheric conditions, with the forementioned accessories attached.

GT

Well, one thing is for sure, it's optimized and what the car puts out is often way less. It's the power at the wheels that matters. Also, those are just peak numbers, and those also really don't matter. I like to see torque curve.

GDTrumbo said:

Before '71 they were rated as "gross HP". This meant under controlled atmospheric conditions, at the flywheel w/o any accessories such as alt., water pump, etc.

'71+ and currently they are rated as "net HP". This is under controlled atmospheric conditions, with the forementioned accessories attached.

GT

Click to expand...

+1

Just wanted to add that in 2005, SAE required an independent observer to be present during the test. This made news at the time as some manufactures actually had to lower some hp ratings. Such as Mazda (RX8), Toyota (Camry), and a few others. I think the 350Z might have dropped too.

Some additional info here:

http://ateupwithmotor.com/terms-and...finitions/47-gross-versus-net-horsepower.html

SAE horsepower

[edit] SAE gross horsepower
Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headers) in lieu of the OEM exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.


[edit] SAE net horsepower
In the United States the term "bhp" fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net hp testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold. The change to net hp effectively deflated power ratings to assuage the auto insurance industry and environmental and safety lobbies.


[edit] SAE certified horsepower
In 2005, the SAE introduced a new test protocol for engine horsepower and torque.[12] The new protocol eliminates some of the flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified".

A few manufacturers such as Honda and Toyota switched to the new ratings immediately, with multi-directional results; the rated output of Cadillac's supercharged Northstar V8 jumped from 440 horsepower (330 kW) to 469 horsepower (350 kW) under the new tests, while the rating for Toyota's Camry 3.0 L 1MZ-FE V6 fell from 210 horsepower (160 kW) to 190 horsepower (140 kW). Much of the drop can be attributed to Toyota now rating engines on 87 octane, compared to Lexus which uses 91 octane. This is why the same 3.3 L 3MZ-FE V6 engine in the Lexus ES330 and Camry SE V6 did not show equal declines. The ES330 and Camry SE V6 were previously rated at 225 hp but the ES330 dropped to 218 hp while the Camry declined to 210 hp. The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette Z06. Certified power rose slightly from 500 horsepower (370 kW) to 505 horsepower (377 kW).


I have also seen it advertised as bhp


Brake horsepower (abbreviated bhp) is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components such as alternator, power steering pump, muffled exhaust system, etc. "Brake" refers to a device which was used to load an engine and hold it at a desired RPM. During testing, the output torque and rotational speed were measured to determine the "brake horsepower". Horsepower was originally measured and calculated by use of the indicator (a James Watt invention of the late 18th century), and later by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. The output delivered to the driving wheels is less than that obtainable at the engine's crankshaft.









source: Horsepower - Wikipedia, the free encyclopedia

Notchbck93 said:

[edit] SAE certified horsepower
In 2005, the SAE introduced a new test protocol for engine horsepower and torque.[12] The new protocol eliminates some of the flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified".

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This is what I was going to say. The Society of Automotive Engineers (SAE) dictates standards for engine output testing, but nobody actually has to follow them. Look for the SAE certification whenever you see a hp claim.

Ever since they did that in '05, I wondered what it would do to companies like Ford, that periodically UNDERRATE their power levels. A couple examples being the Terminators and 93 Cobras.

StreetDreamsGT said:

hmmm so then the next question is why would people underrate hp numbers?? I'd expect them to want to flaunt it, especially a performance car like ford's cobra...

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one story i heard was they didnt wanna get taxed or fined or something for having cars that were too powerful

StreetDreamsGT said:

hmmm so then the next question is why would people underrate hp numbers?? I'd expect them to want to flaunt it, especially a performance car like ford's cobra...

Click to expand...

Shaolin Crane said:

one story i heard was they didnt wanna get taxed or fined or something for having cars that were too powerful

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I've always heard its to keep auto insurance rates down. High HP numbers don't sell cars as much as a low cost of ownership sells cars.

StreetDreamsGT said:

hmmm so then the next question is why would people underrate hp numbers?? I'd expect them to want to flaunt it, especially a performance car like ford's cobra...

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i was watch muscle car and they said to keep insurance rates down.