Diesel versus gas horsepower

[DK35vince]

The Diesel will generally do better on fuel and last longer. But they also cost more.
I have a 35 HP Kawasaki V-twin on my Zero turn and I have been impressed with its power.
I mow once per week, and in the spring/early summer our grass grows fast. On the smooth areas of our lawn we mow at full speed (13-14 MPH) with the zero turn with a 72" deck.
You can hear the engine sometimes is beginning to strain, but it does it.
I'm sure my 35 HP diesel tractor would also start to struggle if it were subjected to the same deck size, grass height and mowing speeds.

 

[4570Man]

If both engines were rated at the same low end RPM they should be equal. If you have a 75 hp gas rated at 6500 rpm and a 75 hp diesel rated at 1800 rpm the diesel is going to eat the gassers lunch. HP is a useless number. Toque is the name of the game.

 

[mike69440]

I have read that a lower hp diesel engine has virtually the same power as a higher hp gas engine. Is that true? What are major advantages of either? I know most large tractors are diesel, most zero turn mowers seem to be gas. I am looking at a 25 hp diesel compared to a 32 hp gas, both kubota. Thanks

ANS.
No HP is HP.

For the same hp a proper diesel will do far more work under varied load and RPM.

How can that be, Grasshopper?

Ans.

Area under a HP & Torque curve Vs. RPM is much greater Diesel vs. gas if both are deigned optimally

As a diesel encounters more load and slow down most diesels produce more torque and overcome that load, i.e. push through and just keep grunting.

A gas engine will slightly produce more torque, (Usually) but its torque rise may be 10 to 20%, if your lucky, not the +50% of the diesel.

Then at a RPM that is a much higher % of Peak HP RPM than a diesel, the gas engine looses torque.

Under a load, this means the gas engine stalls when it slows down.
Ask the question next time on Google.

 

[4570Man]

I'd buy the diesel one. It will last longer and burn drastically less fuel. What models are the mowers. They probably had to make the gasser 32 hp to get equivalent power as the diesel. My 25 hp Kohler is thirsty. I'd sure hate to be feeding the 32 hp one gas.

 

[MossRoad]

I have a little 25hp gas machine that will run circles around any 25hp diesel tractor of the same weight. Literally run circles around it. Around and around and around like a little yapping puppy. It can move vastly greater amounts of loose material from point A to point B in a much shorter time.

Now lets put a plow on them and drop it in the dirt. Ready, set, GO! I'll be sitting there spinning my tires while the diesel rips the earth apart and walks away.

So, its kind of a speed VS work comparison.

HP is HP and torque is torque.

Horsepower:
a unit of power equal to 550 foot-pounds per second (745.7 watts).

Torque:
a twisting force that tends to cause rotation.

Horsepower is the rate at which work is done (think time), while torque is the tendency of a force to rotate an object about an axis(think force).

A 25hp gas engine has the same horsepower as a 25hp diesel engine. They are the same. That's a fact. That doesn't mean they have the same ability to do work.

Start googling HP VS Torque and do some reading. Its very interesting. :thumbsup:

 

[4570Man]

I have a little 25hp gas machine that will run circles around any 25hp diesel tractor of the same weight. Literally run circles around it. Around and around and around like a little yapping puppy. It can move vastly greater amounts of loose material from point A to point B in a much shorter time. Now lets put a plow on them and drop it in the dirt. Ready, set, GO! I'll be sitting there spinning my tires while the diesel rips the earth apart and walks away. So, its kind of a speed VS work comparison. HP is HP and torque is torque. Horsepower: a unit of power equal to 550 foot-pounds per second (745.7 watts). Torque: a twisting force that tends to cause rotation. Horsepower is the rate at which work is done (think time), while torque is the tendency of a force to rotate an object about an axis(think force). A 25hp gas engine has the same horsepower as a 25hp diesel engine. They are the same. That's a fact. That doesn't mean they have the same ability to do work. Start googling HP VS Torque and do some reading. Its very interesting. :thumbsup:

Your gas tractor might drive circles around a diesel, but that isn't a very useful feature.

 

[pmsmechanic]

Several articles that explain things very well

Banks Power | Understanding Today's Diesel

Banks Power | Why Diesels Make So Much Torque

 

[MossRoad]

Your gas tractor might drive circles around a diesel, but that isn't a very useful feature.

Hauling 20 yards of moon dust across a ball diamond at twice the rate of a tractor with twice the bucket size is.

 

[4570Man]

Hauling 20 yards of moon dust across a ball diamond at twice the rate of a tractor with twice the bucket size is.

Is there even 20 yards of moon dust here on earth?

 

[MossRoad]

Is there even 20 yards of moon dust here on earth?

Most likely more...

Pieces of Moon in Antarctica