Gas vs Diesel Hp vs Torque

[workinallthetime]

Someone wrote in wanting us tractor guys to explain about horsepower and it got way out off track so I thought I would start this one.

I say if you working use a diesel and playing use gas burner. I justify my claims by cost of a diesel engine both up front and throughout its life, the diesel will last longer but maintenance is more expensive than a gas engine. I am talking about trucks here which pull your tractors around. If you dont need to pull over 10k then I dont see the need in buying a diesel, however if you do pull 10k and up buy a diesel or buy a pull truck built to pull.
I see no comparison in a 23 hp briggs engine (gas) and a 23 hp kubota diesel. both have 23 hp but one looks like it belongs on a lawnboy. I have owned a MF 175, JD 301a, and now a kubota bx23. My next puchase will be a kubota zd321 then maybe a larger 34-45 hp tlb.

bend to fit paint to match

 

[Doc_Bob]

What is the question?
Bob

 

[workinallthetime]

whats more important hp or torque
which is better gas or diesel

 

[art]

It takes torque to move things, so give me torque!

 

[MossRoad]

I have a 25HP Kohler gas engine in my little PT425. I'll bet your BX23 will pull me around all day. But I bet my PT425 will move a 20 yard pile of mulch or gravel 100 yards in half the time it takes your BX23 with less lawn damage.

Each tool has its use.

 

[GaryCrowell]

These torque vs. HP questions come up quite a bit and they always generate a bunch of misleading answers. You can't have "torque vs. HP", torque is a component of horsepower. Horsepower is essentially the rate at which torque is applied. The physics equation to calculate horsepower is: HP=torque x RPM/5252. In the end, horsepower is what counts, everything else is done through gear ratios. Go to a heavy equipment dealer and spec out a bulldozer, no where will you find the engine's torque mentioned unless you look in the maintenance manuals. The dozers are always catagorized by horsepower. Horsepower is what does work. Look at the gas turbine engine in a M1 abrams tank, it's pretty small and doesn't put out much torque, but it spins at about 13000 rpm's so it's got about 1500 HP and it gets that 30+ ton tank moving pretty well.

Compare your two 23 HP engines, the one in the lawnmower has the capacity to do as much work as the much bigger diesel in the tractor, that's just a physical fact. You could switch the lawnmower engine into the tractor and, for a few minutes anyway, it would do the same thing as the tractor's original motor. However, it certainly wouldn't be optimal for several reasons. First, you'd have a much more unforgiving power band. In order for the small gas engine to make the 23 horsepower it has to run at a high RPM, vary that RPM by more than a few hundred and now it's not putting out 23 HP. In other words, it's got a very peaky powerband and if it's not kept at the top of it's powerband through gearing then it won't put out the horsepower you need to do the job, certainly not optimal for a tractor because you'd be shifting gears all the time to try and keep it moving. A diesel engine that puts out more torque will produce the same horsepower at a slower engine speed and the horsepower band will be much flatter than the small gas motor. The flatter horsepower band is much more user friendly from an operator's perspective. Second is obviously longevity, a small gas engine running at peak RPM's all day just isn't going to last very long, it's not built for that.

I don't know that I've explained it very well, but maybe it'll help to put to rest the "HP vs. torque" argument. Argueing HP vs. torque is a lot like asking whether you like oranges or fruit better, one has a component of the other. When trying to find an answer you first have to ask a reasonable question, and HP vs torque is misleading from the start, that's why you have these long winded posts that you get from that question.

 

[Egon]

Lets not confuse the question with practicality!

 

[Oleozz]

For me at least, you explained it very well and what you are saying makes sense.

I don't know that I've explained it very well, but maybe it'll help to put to rest the "HP vs. torque" argument. Argueing HP vs. torque is a lot like asking whether you like oranges or fruit better, one has a component of the other. When trying to find an answer you first have to ask a reasonable question, and HP vs torque is misleading from the start, that's why you have these long winded posts that you get from that question.[/quote]

 

[john_bud]

I have a 25HP Kohler gas engine in my little PT425. I'll bet your BX23 will pull me around all day. But I bet my PT425 will move a 20 yard pile of mulch or gravel 100 yards in half the time it takes your BX23 with less lawn damage.

Each tool has its use.

Each tool has its use! Too true.



Still, give me big gobs of torque down low, peaking at 1400 rpm and dropping less than 5% thru 3000 rpm . That's where I want my 10,000 pound equipment to operate. I'd also like huge piles of rapidly increasing HP from 3000 to 7500 rpm in a 2600 pound '33 Ford Vicky. Heck, if you can give me both all in one reliable engine --> I'd take that too!!

jb

 

[Doc_Bob]

whats more important hp or torque
which is better gas or diesel

Torque and diesel, if price no object.
Bob