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HP diff between gas and diesel

I'm certain many others can and will answer better than me, but this is how I understand it:

Both gas and diesel provide the same horsepower. Difference is, diesel "normally" works at a lower speed, which creates less friction and less heat, which extends engine life. Also, diesel tends to generate more torque than gas. I ain't smart enough (yet!) to understand why, but this is why heavy equipment generally runs diesel engines.
 

Manufacturers often make the diesel version of a tractor a larger displacement than the gas version of the same model. As already said diesel horses make their power at lower RPMs with more torque rise.
 
There are also other things that can skew the difference between the two. Different cylinder heads, cams, timing, gas is dependent on a well tuned carb... These will all affect how the engines will run even if they have the same max horsepower.
 

A natural aspirated gasoline tractor engine with short cam timing will make slightly more HP at the same 1500-2300rpm power band . As the same engine in diesel with it’s typical short cam timing.
 
As I understand it, a diesel has 20% more real hp than a gas engine rated with same hp. Ed Will Oliver BC
 
Take for example a MH 444 gas vs a MH 444 diesel. With basically the same engine and rpm , the gas will develope a couple more hp. The gas will accelerate or rev up quicker than the diesel. The gas will lug down to a lower rpm but the diesel will pull more at the lower rpm and take longer to lug down with the same load. Comparing different gas vs diesel engines introduces a whole new set of variables, and with today's diesels, they generally perform better all around than a gas engine of the same power.
Ben
 
As I understand it, a diesel has 20% more real hp than a gas engine rated with same hp. Ed Will Oliver BC
 
50 horsepower is 50 horsepower. There is no difference. Horsepower is the rate of doing work ~ ft-lb/sec. 550 ft-lbs/sec = 1 horsepower
 
(quoted from post at 17:31:14 06/21/18) Is there any difference in power between a 50 hp gas and a 50hp diesel?
Click to expand...

Jerry has it correct, 50 hp is 50 hp is 50 hp, whether it be gasoline, diesel, or electric motor, its just a calculation.

so without knowing what your definition of "power" is the answer is no, kinda like which weights more...a ton of bricks or a ton of feathers?

There is also no such thing as something producing more "real hp" and how you get to 50 hp does not make any difference, short cam timing, different heads, etc etc etc....1 hp also equals 747 ish watts of power...

if you put your example into context i bet the brain trust can give you a better answer
 
Depends a lot on what engines you are referring to. Comparing same size and make tractor engines, actual power produced will be near equal. No one will ever be able to prove to me, however, that a "250hp Yamaha outboard" : or a 250hp 283 Chevy will pull what a 250hp Cummins diesel will. ( Cummins 855ci naturally aspirated mechanical engine)
 
(quoted from post at 20:05:42 06/21/18) As I understand it, a diesel has 20% more real hp than a gas engine rated with same hp. Ed Will Oliver BC
Click to expand...

Check your math. 1 HP is 1 HP no matter the source . Some people are also confusing torque rise with power .
 
(quoted from post at 23:01:01 06/21/18) Depends a lot on what engines you are referring to. Comparing same size and make tractor engines, actual power produced will be near equal. No one will ever be able to prove to me, however, that a "250hp Yamaha outboard" : or a 250hp 283 Chevy will pull what a 250hp Cummins diesel will. ( Cummins 855ci naturally aspirated mechanical engine)
Click to expand...

Put any of those engines on an alternator to generate electricity and all will produce the same amount of power .
Once again people are mixing up torque rise with power .
 
Having to identical tractors (MF135) but one with gas, and one with the diesel, same hp, but I can mow much thicker/heavier grass, weeds, etc with the diesel. I've mowed stuff with the diesel that would stop the gasser in its tracks.
 

Another source for the apparent discrepancy is another measure of "what horses?" are we talking about. IIRC, a few years ago some lawnmower/ lawn tractor manufacturers got their knuckles rapped for advertising their products' gross HP as appearing to be the net HP.
 
The difference in combustion speed between gasoline and diesel fuel has an effect on torque. Gasoline burns almost completely with a quick expansion of combustion gasses when the piston is at the top of the power stroke. Diesel fuel continues to burn and expand the whole time the piston is on the way down on the power stroke. This gives the gas engine quicker acceleration than diesel but the diesel has more torque from the longer burn time.
 
Plowing is another way to see the difference between gas and diesel. Gas you will know when the ground changes say from loose soil to hard pan. Diesel you will never feel it.
 
They will produce the same power on a dyno.

Of course, the Yamaha and Chevrolet engines are designed to produce such output only for a short period whereas, the Cummins is designed to do so continuously and at much lower RPM.

Dean
 
(quoted from post at 20:01:01 06/21/18) Depends a lot on what engines you are referring to. Comparing same size and make tractor engines, actual power produced will be near equal. No one will ever be able to prove to me, however, that a "250hp Yamaha outboard" : or a 250hp 283 Chevy will pull what a 250hp Cummins diesel will. ( Cummins 855ci naturally aspirated mechanical engine)
Click to expand...

As Jerry/MT has posted correctly, HP has a definition and can be applied across the board to all engines. Yes, indeed a 250 HP Yamaha or 250 HP Chevy can pull the same load at the same speed up the same hills as a 250 HP Cummins. There are differences, the Cummins will certainly give a longer service life and as such would be a better choice for the service you imply.

Since the Yamaha and Chevy would develop 250 HP at a higher RPM, a proper transmission/gearing would be required to demonstrate the ability to pull on par will the Cummins.

There are high speed engines used in heavy load aplications. For example, consider the Honeywell AGT 1500 (google for details) used to power the Abrams M1 Tank. Typically, the specs for this engine are given as 1500 HP, 2750 Ft-Lbs torque at 3000 RPM. However, this is taken after a 10:1 reduction gearbox packaged into the engine. The numbers ahead of the gearbox would be; 1500 HP, 275 Ft-Lbs at 30,000 RPM. HP is HP however, gearing must used to match the engine/power to the application.
 
There in lies my point. The 250hp
Chevy and a 250hp Cummins, both with
1 to 1 direct drive transmission,
will result in vastly different
outcomes. Horsepower is supposed to
be a statistic at the flywheel. Not
as a result of gearing and
transmissions. When in vocational
school, I also was told the
mathematical formula that was
supposed to be used as to calculate
horsepower. I stand by my statement.
This day and time, seems that
horsepower ratings are based on
whatever formula the builder wants to
use.
 
The 250hp Chevy and a 250hp Cummins, both with 1 to 1 direct drive transmission, will result in vastly different outcomes.
Click to expand...

Yes, they will. At the RPM at which each respective engine develops 250HP, a vehicle with 1:1 gearing the Chevy engine will be going over twice as fast as the Cummins assuming equal diameter tires.
 
(quoted from post at 17:31:14 06/21/18) Is there any difference in power between a 50 hp gas and a 50hp diesel?
Click to expand...

Main difference is the rpm the 50 HP is obtained at.

With a diesel you will typically reach peak HP at a lower more useable rpm than the gas engine.

For example if the gas engine reaches its 50 HP at 4000 rpm and the diesel does it at 2000 rpm assuming both tractors have the same gearing and tire size the diesel will deliver more pulling power coming off idle and accelerating up to operating speed.
 
(quoted from post at 07:22:08 06/22/18) "There in lies my point. The 250hp
Chevy and a 250hp Cummins, both with
1 to 1 direct drive transmission,
will result in vastly different
outcomes."

- Yes indeed the outcomes would be much different. Running without a transmission would have only the rear end reduction. This would be an improper application and none of the engines would be effective to it's potential.

"Horsepower is supposed to
be a statistic at the flywheel. Not
as a result of gearing and
transmissions. When in vocational
school, I also was told the
mathematical formula that was
supposed to be used as to calculate
horsepower. I stand by my statement.
This day and time, seems that
horsepower ratings are based on
whatever formula the builder wants to
use."

- The formula is: HP = Torque x RPM / 5252. It is the result of the engine output and does not change with gearing. Included in my post was the AGT 1500 HP after the 10:1 reduction and the HP ahead of the 10:1 reduction, i.e. at the engine output shaft. The gear reduction increases the torque and reduces the RPM however, HP remains the same. For the formula, the RPM is the RPM of the shaft where the torque is measured.
Click to expand...
 
I am certainly no expert on HP, but it seems 2 things are getting confused. Seems it comes down to the age old question. What is heavier....15 pounds of lead, or 15 pounds of cotton?
 
(quoted from post at 09:56:52 06/22/18) I am certainly no expert on HP, but it seems 2 things are getting confused. Seems it comes down to the age old question. What is heavier....15 pounds of lead, or 15 pounds of cotton?
Click to expand...

Greg, looks like your response has already been given:

so without knowing what your definition of "power" is the answer is no, kinda like which weights more...a ton of bricks or a ton of feathers?
 
I have two Oliver 1550 tractors one gas one diesel both motors are in good running condition and the tractors are about identical supposed to be the same HP.Pulling a NH 851 round baler,both will pull it OK but
the diesel definitely pulls it easier than the gas.I run both over 2/3rds throttle when baling BTW.
 
(quoted from post at 11:11:18 06/22/18)
(quoted from post at 17:31:14 06/21/18) Is there any difference in power between a 50 hp gas and a 50hp diesel?
Click to expand...

Main difference is the rpm the 50 HP is obtained at.

With a diesel you will typically reach peak HP at a lower more useable rpm than the gas engine.

For example if the gas engine reaches its 50 HP at 4000 rpm and the diesel does it at 2000 rpm assuming both tractors have the same gearing and tire size the diesel will deliver more pulling power coming off idle and accelerating up to operating speed.
Click to expand...

Please explain tractors that were available with gasoline or Diesel engines . The 4020 JD for example made the same power at the same rpm.
 
(quoted from post at 08:02:11 06/22/18) The difference in combustion speed between gasoline and diesel fuel has an effect on torque. Gasoline burns almost completely with a quick expansion of combustion gasses when the piston is at the top of the power stroke. Diesel fuel continues to burn and expand the whole time the piston is on the way down on the power stroke. This gives the gas engine quicker acceleration than diesel but the diesel has more torque from the longer burn time.
Click to expand...

Have a look at the attached article regarding flame speed of various fuels in laminar vs turbulent combustion .
The diesel “knocks” due to the rapid flame speed .
To improve the mechanical efficiency of the reciprocating ICE . The less combustion chamber pressure BTDC the better . And the closer to ATDC that combustion completely occurs and combustion chamber pressure peaks due to heating of the gasses, the better.
Combustion occurring with the piston halfway down the cylinder borie vs when combustion occurs during the first 10-20 greees of crankshaft rotation is very inefficient. More heat lost out through the cooling system , the crank angle is less efficient and there is less degrees of rotation for the pressure on the piston to exert force on the crank.
https://www.sciencedirect.com/topics/chemistry/flame-speed
 
bumblebee 4020 ratings are the same at 2200 rpm but diesel goes up a little at lower rpm. This is according to Nebraska test. This may be due to the diesel having 404 and gas 362 CI. First one is diesel second is gas. Lynn
a271341.jpg

a271342.jpg
 
(quoted from post at 20:04:14 06/22/18)
(quoted from post at 11:11:18 06/22/18)
(quoted from post at 17:31:14 06/21/18) Is there any difference in power between a 50 hp gas and a 50hp diesel?
Click to expand...

Main difference is the rpm the 50 HP is obtained at.

With a diesel you will typically reach peak HP at a lower more useable rpm than the gas engine.

For example if the gas engine reaches its 50 HP at 4000 rpm and the diesel does it at 2000 rpm assuming both tractors have the same gearing and tire size the diesel will deliver more pulling power coming off idle and accelerating up to operating speed.
Click to expand...

Please explain tractors that were available with gasoline or Diesel engines . The 4020 JD for example made the same power at the same rpm.
Click to expand...

You can de-rate any engine to produce a lower than potential chosen HP.
At times this has merit as the longevity is increased.
Unfortunately running an engine at such a reduced efficiency will cost you dearly in fuel consumption.

Gas engines typically reach peak HP at higher rpm than diesel engines so all you are doing is holding it back from it's potential and wasting fuel.

The 8.1 Vortec in my dually for example makes about 150 HP at 2000 rpm by the time it reaches 4000 rpm it peaks around 340 HP properly geared and utilized it makes a lot more sense to use the power it can dependably make instead of governing it at 150 HP.

Limiting factor on a tractor is being able to use the same transmission and gearing for gas or diesel and still maintain a 540 or 1000 rpm at the PTO.
 
(quoted from post at 23:51:44 06/22/18)
(quoted from post at 20:04:14 06/22/18)
(quoted from post at 11:11:18 06/22/18)
(quoted from post at 17:31:14 06/21/18) Is there any difference in power between a 50 hp gas and a 50hp diesel?
Click to expand...

Main difference is the rpm the 50 HP is obtained at.

With a diesel you will typically reach peak HP at a lower more useable rpm than the gas engine.

For example if the gas engine reaches its 50 HP at 4000 rpm and the diesel does it at 2000 rpm assuming both tractors have the same gearing and tire size the diesel will deliver more pulling power coming off idle and accelerating up to operating speed.
Click to expand...

Please explain tractors that were available with gasoline or Diesel engines . The 4020 JD for example made the same power at the same rpm.
Click to expand...

You can de-rate any engine to produce a lower than potential chosen HP.
At times this has merit as the longevity is increased.
Unfortunately running an engine at such a reduced efficiency will cost you dearly in fuel consumption.

Gas engines typically reach peak HP at higher rpm than diesel engines so all you are doing is holding it back from it's potential and wasting fuel.

The 8.1 Vortec in my dually for example makes about 150 HP at 2000 rpm by the time it reaches 4000 rpm it peaks around 340 HP properly geared and utilized it makes a lot more sense to use the power it can dependably make instead of governing it at 150 HP.

Limiting factor on a tractor is being able to use the same transmission and gearing for gas or diesel and still maintain a 540 or 1000 rpm at the PTO.
Click to expand...

Run the same cam lift and duration in a natural aspirated gasser and a natural aspirated Diesel . The gasser will have identical torque and HP curve shapes . With the gasser having a slight advantage in torque and power .
 
All things the same, the diesel will always come out on top with TORQUE, the gas will have more HP. The Allis Chalmers D19 is a good example. The turbo diesel produced 66hp, the gasoline produced 71hp on the Nebraska tests.
The difference is due to burn time. All of the gasoline is burned in one quick burn. The diesel burn time is longer due to the burn lasting until fuel cutoff by the pump. This longer burn time pushes the piston down nearly the entire stroke whereas a gas engine burn is comparable to only a hammer hit.
 
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