New Mack's H.P rating ...flywheel or rear wheel?

[Lmackattack]

Where does Mack rate their engine H.P. at these days? If I recall they used to rate it at the wheels?

Where do other mfg rate the H.P at?

[theakerstwo]

Rated at the flywheel like always

[57 bcr]

I thought used to rate hp as bhp that meant "Brake Horse Power",while others used the flywheel hp rating . I used to hear it from the naysayers a lot!

[j_martell]

Brake horsepower is measured at the flywheel.

[GreenGiant2]

thought they always measured it @ the wheels

[57 bcr]

Alright then,I stand corrected. I argued with a couple guys (veteran drivers) years ago that told me Cummins rated their horsepower at the flywheel,while rated theirs at the wheel and that was why a 237 could kick a 290 Cummins' ass. I told them no, it was the amount of torque at low RPM that was responsible for that (and superior engineering)! Not to mention the was a better truck! This was some 35 years ago,when I wore a younger man's clothes! I really didn't care,I knew what I was going to buy when the time came around.

[theakerstwo]

Those cheap jap radios will tell you anything when your out on the road.Look at it this way, no engine manufactory would let the end user which is the truck builder rate their engine.The reason a 237 mack can out work a 290 and 335 cummins is because they have a low end torque rise that cummins did not have back then.With a 5 speed and max torque and HP at 1200 they was more than a 290 cummins.Cummins did try to duplicate the maxidyne with the NHCT 270 with a 5 speed but it was not what a 237 was.A maxidyne was very misunderstood by drivers and may be to this day but its how you drive it.Most guys wanted to keep the rpm up as hi as they could and would not let it pull down were it was working good.

[j hancock]

Back in the dark ages of high school, a science teacher once said that HP is for speed and torque is for getting work done.

He drank a lot of coffee. Always wondered what was in his coffee mug?

I would go with the 237 to get work done.

[staxx]

Back in the day it was common practice to turn a engine up before the owner took delivery of there new truck and this would get you real close to the hp rateing being at rear wheel hp. A little timing and fuel was all you needed. But from the factory all are rated at flywheel .

[Lmackattack]

Alright then,I stand corrected. I argued with a couple guys (veteran drivers) years ago that told me Cummins rated their horsepower at the flywheel,while rated theirs at the wheel and that was why a 237 could kick a 290 Cummins' ass. I told them no, it was the amount of torque at low RPM that was responsible for that (and superior engineering)! Not to mention the was a better truck! This was some 35 years ago,when I wore a younger man's clothes! I really didn't care,I knew what I was going to buy when the time came around.

I was told the same....and kinda the same example of why a 300 Mack would run with a 350 cummins....I was also told that Mack rated at the wheels because they made the whole truck and would test the H.P. loss thru the drivetrain and post the end H.P result at the rear wheel.

[MackMann85]

is and always has been at the flywheel. way too many variables to rate at rear wheel when you think about it. take several trucks with same HP rating, but different transmissions, oil weights, axles, etc, etc and the power at the wheels would vary....different friction values equal more or less parasitic driveline losses. Heck even the same HP rating can vary from engine to engine, there is usually a range the factory will let stuff go at (+/-2% or something like that). So two 500HP engines may actually have anywhere from 490-510HP.

[Lmackattack]

Ok flywheel it is.....thank you guys..

[theakerstwo]

That myth has been around since I have been working on trucks ,Like been said to many variables to take a measurement at the wheels.One thing that is not a mtth is what was said about a 237. If it was not for them we would not have the big horses we have now. They delievered the material that it took to invent the bigger engines.They made money for a lot of poor people.Ever one could not own a peterbilt.