HP vs. Torque?

[LRamey]

Got my new head gasket in yesterday, and took her for a run this evening. From a stop to 1/4 mile I was at 85 mph. My rig weights 7600 lbs. So I went to a web site that has a 1/4 mile HP calculator and plugged in the figures. 432 hp!? How close are these things and now how do I figure the torque? I found a formula that states,

Torque = hp *5252/ rpm. Well I was close to 2400 rpm when I hit 85 in the qtr. so If my figures are right I'm around 945 lbs/torque.

Where are the flaws if any? Pick this apart for me please!

If this is all true then I'm very pleased to say the least.

Thanks,

Lonnie

 

[Don M]

your formula is corrrect for the conversion.

 

[JIM S.]

So my question is... . do you use the RPM for the calculation at top speed? or at peak HP? ??

Jim

 

[Joe G.]

Jim,



The way it works is that you have to measure maximum power generated at a particular RPM. You can make an estimate based on performance but there are a lot of other variables involved that make that estimate inaccurate. Torque is gross power. HP is a measure of work that can be done with that power. The dyno gurus could explain a lot better than that. Maybe Joe D. or one of the others will chime in.

 

[drees1]

Horsepower

To answer your question, use the rpm that you are running when you make your performance run. That would correspond to the torque required to perform the acceleration. Since the engine rises in speed, then transmission shifts, then speed drops and rises again, your figures will be an estimate. The first calculation has to assume constant HP input to get your weight up to speed in "X" amount of time over "X" distance. If you maintain a narrow rpm band during the run your calculation will be more accurate, and of course the rpm used to calculate the torque would be the rpm you actually ran. If you used any other rpm, it would be wrong in the torque calculation. Bottom line, the formulas you use are good estimates, and will bracket the engines ability, but due to actual conditions of variable rpm will not be exact. Using average rpms during your runs would be about as close as you could get to an estimate. Sounds like your motor is plenty healthy



Doug Rees

 

[LRamey]

Thanks guys for the replys.

I was flowing a fair amount of propane at the time and it sure feels good! My egt's were pegged past 1500 so had to back out a little.

Here in central Oregon no one has a dyno although there are a couple places that say they plan on having one by July. So I can't wait to get on one!

Lonnie

 

[LRamey]

Thanks guys for the replys.

I was flowing a fair amount of propane at the time and it sure feels good! My egt's were pegged past 1500 so had to back out a little. Its good to know I'm not too far off.

Here in central Oregon no one has a dyno although there are a couple places that say they plan on having one by July. So I can't wait to get on one!

Lonnie