Diesel vs gasoline

[DavidBarkey]

One other thing to remember . When that was built and marketed manly to farmers . The price of "off road " diesel was substantially less than it is now . I have a farmer customer that has one , a little bigger than that one with the 3 pt hitch rear & centre pto . He uses it for cutting grass and pulling small road trailers around the farm . It has over 2000 hrs on it . Still runns like new . Other than standard maintenance , he has only had to do miner stuff like hydraulic hoses , belts ect. and rebuild the deck spindles and gear box . I did that last summer . I think the thing is like 10-12 years old .

[Eugen]

Interesting discussion, maybe we should open a thread on this. I did some searches and looked at the specs of a few published Kubota and Kohler diesel engines. Seems to me that if we compare with the Kohler K series, in particular K301 and K321, a modern Kohler diesel engine of similar size will produce similar torque with an old Kohler gas engine with 2HP more.

Example 1: Kohler LDW492, 11.5HP and 20.6 lb-ft gross torque, that would be 1.79 lb-ft per HP
https://kohlerpower.com/en/engines/product/ldw492

vs K321, 14HP and 20.5 lb-ft gross torque, that would be 1.46 lb-ft per HP

Note: peak torque would be more for both, but I could not find those values for the diesel engines.

Example 2: Kohler KDW702 15.4HP and 25.1 lb-ft gross torque, that would be 1.63 lb-ft per HP
https://kohlerpower.com/en/engines/product/kdw702

vs K341, 16HP and 23.5 lb-ft gross torque, that would be 1.59 lb-ft per HP.

@propane1 , that Shibaura engine seems to show 36 lb-ft peak torque. That would probably be matched by an 18HP gas engine? Found the M18 Kohler apparently produces 39 lb-ft at 2600 RPM peak torque.

I'm not trying to prove anything, I was just curious how big the difference is.

[propane1]

That could be true Eugen, the gas kohler engine having the same or more amount of torque, But the shibaura engine has its peak torque at a much lower rpm. How much torque the shibaura looses by the time it gets to 2700 rpm to make full hp is a question.

Noel

[Eugen]

Plus I think that 39 lb-ft torque for the Kohler M18 is wrong. Does your son have the Shibaura engine in the Ford?

[propane1]

Yes, that’s where I got the info Eugen. Actually the whole tractor is made by shibaura. Just painted Ford colours.

Noel

[MattA]

That could be true Eugen, the gas kohler engine having the same or more amount of torque, But the shibaura engine has its peak torque at a much lower rpm. How much torque the shibaura looses by the time it gets to 2700 rpm to make full hp is a question.

Noel

Horsepower = (Torque × RPM) ÷ 5252.
Rearranged...
Torque = (Horsepower × 5252) / RPM.
Shibaura torque = (16HP × 5252) / 2700rpm = 31.12ft-bs.
Hopefully I did that right... the hardest part was spelling shibaura

[MattA]

I recall reading on the forum that someone with a 4020 onan and a 4023 vanguard said the vanguard would mow his lawn with 1/3 less gas.

The latest fuel injected lawn mowers are supposed to be 25% more efficient than today's carburetor lawn mowers plus they start right away.

[propane1]

That could be true Eugen, the gas kohler engine having the same or more amount of torque, But the shibaura engine has its peak torque at a much lower rpm. How much torque the shibaura looses by the time it gets to 2700 rpm to make full hp is a question.

Noel

Horsepower = (Torque × RPM) ÷ 5252.
Rearranged...
Torque = (Horsepower × 5252) / RPM.
Shibaura torque = (16HP × 5252) / 2700rpm = 31.12ft-bs.
Hopefully I did that right... the hardest part was spelling shibaura

Interesting calculations. Boy you fellas know how to figure stuff out.

Noel

[Gordy]

I recall reading on the forum that someone with a 4020 onan and a 4023 vanguard said the vanguard would mow his lawn with 1/3 less gas.

The latest fuel injected lawn mowers are supposed to be 25% more efficient than today's carburetor lawn mowers plus they start right away.

There is a lot to consider when making these comparisons like displacement and compression ratios. Like the old GM 350ci gas to diesel conversions If memory is correct they were in the 15 or 16 to 1 compression ratio range, while I have seen other diesels as high as 21 to 1 compression ratios.

It has been said many times the Onan's were a successful design from the 1930's (when gas was cheap) that lasted with only small changes till the EPA changed the rules on emissions and how HP was calculated. The old Onan's and Kohler's were known as torque monsters compared to modern engines, this is due to the larger diameter of the pistons. As an example I was looking to replace a 14hp Kohler, as I recall with a Vanguard to get the same torque as the Kohler the #'s lined up between the VG 18 and 20hp engines. For the greens keepers the torque #'s are not that important, but for us with snow blowing and occasional brush hogging in tall grass it matters.


Gordy

[Eugen]

I don't trust the numbers posted by people on the web very much, like the 39 lb-ft torque for the Kohler, I'm sure that's wrong. I would trust more numbers either published in manufacturer literature, or on their website. Even those number published by the manufacturer are probably somewhat ideal. For me it's better to take it with a little grain of salt.

Of course everyone would rather have a diesel engine in their tractor, and I think your son will be very happy with that diesel tractor @propane1 . Is that a considered a compact tractor?

As for me, it would be nice to get a diesel engine, but it would have to be at a good price. Most sell for a lot of $$ around here. My point earlier in this thread was that it's hard to beat a Kohler 1-cyl engine if you take into consideration the bigger picture, that is, easy and cheap parts, reliability, power.

But since a diesel engine will cost less in fuel, do you make up enough savings in 10 years to buy a full rebuild kit? I think it also matters how much the tractor gets used. Someone with a lawn care or snow blowing business will go through a lot of fuel in 10 years, much more than me.

Please don't get upset Noel, we are just discussing. The best engine for everyone is the one they decide. I don't decide what's best for you, or for Dave.


@DavidBarkey is your diesel engine going to be deployed? It would be nice to get some first hand experience from you.