I knew that, I believe in '71, they went from rating an engines horsepower from gross (crank), to net (rear wheel). Nowadays, in ads and such, where to manufacturers rate HP? Crank or rear wheel?

Net and rear wheel are two differnt things, actually. Net is still at the crank, but all the accessories are on the engine.

I think they still use net. Most of the time you hear people say some cars are under rated from the factory or over rated, so maybe they just make them up.

Tim.

actually i think (heard) that in 71 they began rating it with all of the SMOG-type equipment in place while before this they rated it without any power robbing accesories.

i think its still rated at the crank with all accesories in place, at least i think thats how most manufactures must do it or else there would be some montrous cars out there if the ratings were at the rear wheel.

im curious about this too. can somebody tell us for sure?

In the old days they might rate an engine at an rpm that was less than its peak. The L88 is a good example. It was rated 430hp at around 5000rpm but made over 500hp when measured above 6000rpm. They did this to lower the power ratings for insurance and NHRA class ratings. On the other hand, many of the performance engines were run with open headers to get there rated power. Makes sense when the hp wars were going on.

Originally posted by soccerguy045:
I knew that, I believe in '71, they went from rating an engines horsepower from gross (crank), to net (rear wheel). Nowadays, in ads and such, where to manufacturers rate HP? Crank or rear wheel? Net @ crank. Aircleaner, exhaust, waterpump installed. Alternator charging. 77 degree inlet air w/ 50 grains humidity.

Mike

Some cars lately have been significantly underated such as the LS1 which will actually RWHP almost or at the factory rated 305HP rating. Some cars come up a bit short. I'm sure insurance and things like that help make decisions like that and who will complain if it makes more than it is rated at. I had a bone stock (except for ECU) LS1 on the dyno and it made 400 HP with no accessories.

I thought todays SAE NET standard was this: at the end of the driveshaft with all accessories on. So basically everything except the rear end. I could be mistaken, but it makes sense to me.

Matt

Well I think it is the engines horsepower not the wheel hp, because if it was wheel hp they would say...WHP lol...

What I think...

http://www.cars.com/news/stories/102103_storyb_fp.jhtml