Rated engine power
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 ...
Forum Discussion
If there is anyone interested in knowing their engine's peak crankshaft horsepower and you don't mind a bit of screwing around, you could provide me with the following data and I would be able to calculate it for you.
I would need an accurate combined weight of your truck and trailer.
You would need to know the speed your truck travels in the most straight through gear of your transmission at rated engine speed.
I would need a measurement of the time it takes on a level stretch of highway for your unit to slow from 2 mph over that travel speed at rated rpm to 2 mph slower while coasting in neutral.
I would need the time required to accelerate from 2 mph slower than rated travel speed to 2 mph faster.
(So for an f350 Powerstroke with 3.55 gears and 20 inch rims you yould would get going 75 mph and shift to neutral. Start your stop watch when the truck slows to 71 mph and stop it at 69 mph. Record that time value. Then select 4th gear and with the skinny pedal matted record the time required to accelerate on level ground from 69 mph back to 71 mph. To increase your accuracy it would be beneficial to perform these tests going one way on the road then turning around and performing them the opposite direction over the same stretch of road. Then average the results).
If the measurements taken are accurate the calculated hp will be very accurate as well.
I would need an accurate combined weight of your truck and trailer.
You would need to know the speed your truck travels in the most straight through gear of your transmission at rated engine speed.
I would need a measurement of the time it takes on a level stretch of highway for your unit to slow from 2 mph over that travel speed at rated rpm to 2 mph slower while coasting in neutral.
I would need the time required to accelerate from 2 mph slower than rated travel speed to 2 mph faster.
(So for an f350 Powerstroke with 3.55 gears and 20 inch rims you yould would get going 75 mph and shift to neutral. Start your stop watch when the truck slows to 71 mph and stop it at 69 mph. Record that time value. Then select 4th gear and with the skinny pedal matted record the time required to accelerate on level ground from 69 mph back to 71 mph. To increase your accuracy it would be beneficial to perform these tests going one way on the road then turning around and performing them the opposite direction over the same stretch of road. Then average the results).
If the measurements taken are accurate the calculated hp will be very accurate as well.
