Oil & Fuel Diesel HP vs Gasoline HP

[DK45C_Dave]

There are a lot of factors in the big picture. However, in the example I gave, I tried to make the type of engine the only variable. The rated HP, weight, gears, tire size, etc of each machine are comparable, yet the capability of the machines is not similar at all. My question is whether diesel HP ratings are different than gasoline HP ratings. They are sure different between electric motors and gasoline engines.

 

[rockyridgefarm]

<font color="orange"> It is how the engine performs over its entire operating RPM range that tells the story...let's have them put a graphic on the hood showing both torque and hp over the operating range of engine rpm...
</font>

Well put, then more subcompact buyers will understand why they are getting more HP out of the same engines...

 

[MikePA]

<font color="blue"> My question is whether diesel HP ratings are different than gasoline HP ratings. </font>
No they are not. Here's the formula for horsepower.

a. Horsepower: The standard unit by which power is measured; one
horsepower is equivalent to 33,000 pounds lifted one foot in
one minute
HP = (Force (lbs.) X Distance (ft.)) / (33,000 (ft.lbs./min.) X Time (min.))

 

[higgy]

if they rate the engine properly then 1 hp is 1hp, just as a watt is a watt, but they don't talk about peak power, continious power of the power just before the thing self-destructs.

Lots of other things to concider as others have said. I have an old john deere pump motor, 1 hp hit and miss type. It is only one horse, but the flywheels on the thing weigh 100 or so pounds, I don't think that I would want to try and stop it.

The torque vs engine speed vs efficency curves should be avalible for any machine that you want to see. If they don't have it, vote with your feet.

my 0.02

Dane

 

[PineRidge]

<font color="blue"> There are a lot of factors in the big picture. However, in the example I gave, I tried to make the type of engine the only variable. The rated HP, weight, gears, tire size, etc of each machine are comparable, yet the capability of the machines is not similar at all. My question is whether diesel HP ratings are different than gasoline HP ratings. They are sure different between electric motors and gasoline engines.
</font>

Which weighs more a pound of feathers or a pound of lead? They look different but they both weigh the same. HP is still HP no matter how you dress it up. /forums/images/graemlins/grin.gif

 

[horse_guy]

There actually appears to be a difference in H.P. between a gasoline engine and a diesel engine. The H.P. rating on a gas engine is usually at maximum RPMs , where the diesel is at lower RPMs and they hold their power over a broader power curve than a gas engine which is in a narrow band and drops off quickly. Plus the RPM redline is usually a lot lower for a diesel engine than a gas engine. This all tends to give the diesel engine the edge and tends to make it appear to have more useable H.P.

 

[DK45C_Dave]

Just for giggles, here is another comparison. Lets say I have two identical Versatile tractors, each with Cummins 250BHP diesel engines. Now I take the engine out of one tractor and replace it with the 290BHP gasoline engine out of my Chevy pickup. If a HP is a HP, then the tractor with the Chevy engine should out pull the tracor with the Cummins.

 

[cowboydoc]

It wouldn't outpull because of the torque factor. Hp is hp but when you figure towing and pulling you have to figure in torque. In a gas engine you're going to have much more hp to make the same torque as a diesel engine. For example the gas V-10 can make 310 hp but only 425 lb ft of torque. The diesel makes 325 hp and a whopping 560 lb ft of torque. When you're talking pulling the diesel will win everytime. If you're talking speed and a drag race the V-10 is going to win. Take your example of the Versatile tractor. If you're talking about a drag race the 290 hp tractor would probably win but if you're talking about pulling the cummins will drag it all over the field.

 

[DK45C_Dave]

You are on to something here. The Chevy engine is 290HP with 275ft/lbs of torque and the Cummins is 250HP with 1100 ft/lbs of torque. So the torque is a measure of how much work the engine is capable of doing and the HP is a measure of how quickly the engine can perform the work as long as the work is within its torque curve!?

 

[Soundguy]

I think it was explained one thime that the small gas engines.. like the brigs riding lawmowers, etc.. ( not picking on brigs.. ) That that hp.. say 25 hp was the max generated hp by that engine, right before it detonated.. the usable hp, used int he throttle and rpm range that the mower was designed for is much less.

And as Bob pointed out... an old ford N can pull a 5' brush hog through moderate weeds, brush and grass, and pull itself up over obstacles that 1), the lawnmower would stall the engine /ruin the cutting deck..trying to cut and would spin the tires after hitting a 4" lip, instead of climbing over it.

Tractors are geared for lotsa torque. That's why a tractor can flip ove ron it's own axle if the tires are frozen to the ground... I doub't you will ever see a riding lawnmower do that.

Soundguy