Lord Popgun
Road warrior
Ferret,
Don't forget to divide by the constant 5252---torque x rpm divided by 5252
Don't forget to divide by the constant 5252---torque x rpm divided by 5252
Horsepower vs. Torque ?
- Thread starter Rebel73_imp
- Start date
gossman_imp
Been there
rboe
Road warrior
We can really muddy the waters by looking at hp ratings of common electric motors; like vacuums (floor models as well as shop vacs), drills, saws etc. They can be highly "optimistic".
ChipBeck_imp
Road warrior
Mickey,The ferret_imp said:
Yes you will understand it. Although I don't have time this morning due to prior obligations there are readily understandable reasons for this that are quite easily understood and I'll help you form a mental picture. When I write it up I promise you will understand precisely why this is happening and why torque and horsepower curves do not directly correspond. To be continued when I have a bit more time.
Chip
LOLThe ferret_imp said:
Mickey,
Have you ever run a 100 yard dash in school. Think of it this way. To get off the line requires a lot of torque to your muscles, half way through the race your muscles tend to level out with still a fair amount of torque, toward the end of the race your torque decreases ( almost floating on air) as your speed increases.
http://3ln.org/articles/horsepower-vs-torque
Interesting read Mickey Diesel vs Gas vs Electric
What he said.metallyguitarded_imp said:
DGShannon_imp
Been there
With multiple threads now going on this subject, we have talked and explained it to death. Except for one little item regarding the "relationship" you were looking for. On ANY dyno chart, for ANY engine, notice that the two torque and horsepower lines will ALWAYS cross over each other at exactly 5,252 RPM.The ferret_imp said:
Given all the other postings and info, I am sure that you see now why the torque line and the horsepower line won't "mirror each other", but the formula behind their "relationship" dictates that they MUST ALWAYS cross at that specific RPM.
Before (blue lines) or after (red lines) mods, both lines will shift, but they must still always cross each other at the 5,252 point.
thessler3_imp
Running like a top
As a retired scientist, let me add my two cents:
Dyno's do not directly measure horsepower, they measure torque in foot pounds. Horsepower is then CALCULATED and displayed by the century old formula below:
Horsepower = torque (in Ft Lbs) * RPM / 5252
On any dyno chart, horsepower will ALWAYS equal torque at 5252 RPM and the two curves will cross, with horsepower usually exceeding torque beyond 5252 RPM. Bad news for Harleys and other cruisers that top out at 5200 RPM. Their horsepower can never exceed their torque numbers.
If you see any dyno charts that do not cross at 5252 RPM, they are bogus. You can look up where the 5252 number comes from on the web. It is a "units" conversion factor.
Looking at the formula again, you can make bigger horsepower numbers by increasing either torque or RPM above 5252 RPM. That is why GP racers are turning close to 20,000 RPM. Friction losses reduce torque, so there are limits in practicality.
One Very Important point - gearing: Gearing multiplies torque. The "lower" the overall gear ratio, the more torque applied to the rear wheel. Engines that can turn high RPM can be geared lower and apply monstrous torque at the rear wheel. That is why small displacement, high-revving motorcycles can out accelerate big-block low revving bikes. Soichiro Honda figured this out in the 1950's. He obviously got an A in physics class.
I have seen many quick Harleys at the drags, but they usually get overtaken by high-revving bikes when the tires finally hook up and the revs get higher. Don't think I am a Harley hater, I have owned 4 of them and their low-revving power characteristics please many people.
BTW - Kevin Cameron is a class act. As busy as he is, he always responds to my emails.
Dyno's do not directly measure horsepower, they measure torque in foot pounds. Horsepower is then CALCULATED and displayed by the century old formula below:
Horsepower = torque (in Ft Lbs) * RPM / 5252
On any dyno chart, horsepower will ALWAYS equal torque at 5252 RPM and the two curves will cross, with horsepower usually exceeding torque beyond 5252 RPM. Bad news for Harleys and other cruisers that top out at 5200 RPM. Their horsepower can never exceed their torque numbers.
If you see any dyno charts that do not cross at 5252 RPM, they are bogus. You can look up where the 5252 number comes from on the web. It is a "units" conversion factor.
Looking at the formula again, you can make bigger horsepower numbers by increasing either torque or RPM above 5252 RPM. That is why GP racers are turning close to 20,000 RPM. Friction losses reduce torque, so there are limits in practicality.
One Very Important point - gearing: Gearing multiplies torque. The "lower" the overall gear ratio, the more torque applied to the rear wheel. Engines that can turn high RPM can be geared lower and apply monstrous torque at the rear wheel. That is why small displacement, high-revving motorcycles can out accelerate big-block low revving bikes. Soichiro Honda figured this out in the 1950's. He obviously got an A in physics class.
I have seen many quick Harleys at the drags, but they usually get overtaken by high-revving bikes when the tires finally hook up and the revs get higher. Don't think I am a Harley hater, I have owned 4 of them and their low-revving power characteristics please many people.
BTW - Kevin Cameron is a class act. As busy as he is, he always responds to my emails.
