Horsepower vs. Torque ?

[Lord Popgun]

Ferret,

Don't forget to divide by the constant 5252---torque x rpm divided by 5252

[gossman_imp]

[rboe]

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]

Lol MG

Steve.. What I don't understand is if there is this symbiotic relationship between torque and hp expressed in the formula

Torque x rpm = HP,

Why don't the lines on dyno charts reflect this relationship and mirror each other? ..why would the lines be any different. Why does it not show a corresponding dip in horsepower where it shows a dip in torque? Why would there be a dip in torque when rpm is increasing. One chart is going up in the same spot the other chart is going down and vice versa.

Do you see what I am saying?

As far as carbs and cams and valves go, they are the same ones in the motor when you start the dyno runs as when you end the dyno runs, and they are made of metal so they don't radically alter shape ( lift duration etc) from 2000-6000 rpms where the dip in torque shows up on the dyno chart of 600s I posted.

I will probably never understand this so the explanation is moot I suppose. it just doesn't make any sense to me.

With my last breaths I will probably still be saying torque makes you go and hp makes you go fast lol

Mickey,

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

[CIP57_imp]

Lol MG

Steve.. What I don't understand is if there is this symbiotic relationship between torque and hp expressed in the formula

Torque x rpm = HP,

Why don't the lines on dyno charts reflect this relationship and mirror each other? ..why would the lines be any different. Why does it not show a corresponding dip in horsepower where it shows a dip in torque? Why would there be a dip in torque when rpm is increasing. One chart is going up in the same spot the other chart is going down and vice versa.

Do you see what I am saying?

As far as carbs and cams and valves go, they are the same ones in the motor when you start the dyno runs as when you end the dyno runs, and they are made of metal so they don't radically alter shape ( lift duration etc) from 2000-6000 rpms where the dip in torque shows up on the dyno chart of 600s I posted.

I will probably never understand this so the explanation is moot I suppose. it just doesn't make any sense to me.

With my last breaths I will probably still be saying torque makes you go and hp makes you go fast lol

LOL

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

[Cormanus]

I have decided I don't want to know about horsepower and torque and rpm and acceleration, about tractors or pulleys or marine engines. I do not like them Sam I Am. I will not learn this on a boat. I will not learn this on a goat. I will not, cannot on a plane. All this talk drives me insane. I do not like them Sam I am.

What he said.

[DGShannon_imp]

Lol MG

Steve.. What I don't understand is if there is this symbiotic relationship between torque and hp expressed in the formula

Torque x rpm = HP,

Why don't the lines on dyno charts reflect this relationship and mirror each other? ..why would the lines be any different. Why does it not show a corresponding dip in horsepower where it shows a dip in torque? Why would there be a dip in torque when rpm is increasing. One chart is going up in the same spot the other chart is going down and vice versa.

Do you see what I am saying?

As far as carbs and cams and valves go, they are the same ones in the motor when you start the dyno runs as when you end the dyno runs, and they are made of metal so they don't radically alter shape ( lift duration etc) from 2000-6000 rpms where the dip in torque shows up on the dyno chart of 600s I posted.

I will probably never understand this so the explanation is moot I suppose. it just doesn't make any sense to me.

With my last breaths I will probably still be saying torque makes you go and hp makes you go fast lol

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.

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]

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.