Rated engine power

[4x4ord]

How do manufacturers, presently, determine how to rate their engine's crankshaft horsepower? Is the cooling fan engaged and drawing air? Alternator charging? Power steering pump and A/C installed and working?

[twodownzero]

theoldwizard1 wrote:
In the US, all light duty vehicles are rated using the same testing procedures defined by the Society of Automotive Engineers. It is horsepower at the rear wheels with all accessories installed (A/C is likely turned off).

When you get to medium duty vehicles, I believe the horsepower is measured "at the crankshaft", but again with all accessories (probably not A/C).


The important thing is that it is done CONSISTENTLY across all manufacturers.

SAE Net Horsepower includes all accessories and emission controls, but is measured at the crankshaft.

https://en.wikipedia.org/wiki/Horsepower#SAE_net_power

[ShinerBock]

There is a lot more leniency in the SAE J1995 or J1349 test requirements than most think.

Attached is an old J1349 test standards. I have the current J1349 and J1995 standards, but cannot link them. However, not much has changed.

J1349 Test Standard

Pages 10-12 discusses what you are looking for.

J1349 requires most accessories while J1995 doesn't. However, that does not mean the manufacturers do not test with accessories on J1995. Some do when they know exactly what the engine is used for making them no different than J1349. They have to use J1995 because they are not building the complete vehicle.

[theoldwizard1]

In the US, all light duty vehicles are rated using the same testing procedures defined by the Society of Automotive Engineers. It is horsepower at the rear wheels with all accessories installed (A/C is likely turned off).

When you get to medium duty vehicles, I believe the horsepower is measured "at the crankshaft", but again with all accessories (probably not A/C).


The important thing is that it is done CONSISTENTLY across all manufacturers.