Re-engine a 425?

Abitnutz · Jun 30, 2004

Ok, this is all hypothetical. The engine in the PT-425 is a 25 hp Kohler Command Pro right? Kohler makes, from what I can determine, a liquid cooled version of this engine called the Aegis. This engine appears to be identical to the Command Pro except that it is liquid cooled. The bore is slightly smaller, I’m sure to handle the water jacket. The dimensions of the two engines are very close. Is there any reason why putting one of these in a PT-425 would be just too costly or difficult to be practical? I checked and the cost of the two engines is also very close. Below are the specs for both engines. It’s interesting that the LC engine has a bit more torque at a lower RPM but a lower compression ratio. Please comment…perhaps Power-Trac is listening

Liquid Cooled
MODEL LH685
MAX. POWER @ 3600 RPM
hp (kW) 25 (18.6)
DISPLACEMENT cu. in. (cc) 41.1 (674)
BORE in. (mm) 3.15 (80)
STROKE in. (mm) 2.64 (67)
PEAK TORQUE @ MAXIMUM lbs. ft. (Nm) 40.1 (NA) @ 2200
COMPRESSION RATIO 8.5:1
DRY WEIGHT lbs. (kg) 114 (51.7)
OIL CAPACITY U.S. quarts (liters) 2 (1.9)
LUBRICATION Full pressure w/full-flow filter
*DIMENSIONS
L x W x H 17.0 x 18.1 x 26

Air Cooled
MODEL CH730
MAX. POWER @ 3600 RPM
hp (kW) 25 (18.6)
DISPLACEMENT cu. in. (cc) 44.0 (725)
BORE in. (mm) 3.27 (83)
STROKE in. (mm) 2.64 (67)
PEAK TORQUE @ MAXIMUM lbs. ft. (Nm) 39.9 (54.1) @ 2800
COMPRESSION RATIO 9.0:1
DRY WEIGHT lbs. (kg) 94 (43)
OIL CAPACITY U.S. quarts (liters) 2 (1.9)
LUBRICATION Full pressure w/full-flow filter
*DIMENSIONS
L x W x H 13.8 x 17.7 x 26.5

smartguyz · Jun 30, 2004

Very interesting notion. I note that it IS several inches longer. How is the water cooling accomplished? Is there a radiator and water pump? How about a thermostat?

-Rob /forums/images/graemlins/grin.gif

MossRoad · Jun 30, 2004

3" is alot longer in that little engine compartment. Then you need to find a place for the radiator. On my PT425, there are pumps on both ends of the engines, so the crankshaft is capable of having mounts on both ends. The newer models have the pumps only on one end of the engine. The only other concern I would have is what is the diameter and length of the shaft coming out of the engine? Is it long enough to except the lovejoy(?) connection and will it except a pump mount?

FOURTEEN · Jul 1, 2004

/forums/images/graemlins/shocked.gif OK, maybe you could, but WHY???? /forums/images/graemlins/shocked.gif

/forums/images/graemlins/confused.gif After all that work and expense, where is the advantage???? /forums/images/graemlins/confused.gif

A Kohler 745 is the same L & W, but taller, and has 28 HP!! However, HP is not the limiting factor. My PT-425 never stalls out, bogs down, or shows any other signs of overloading the engine. At some point the hydraulics just won't do any more!

/forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

tracdoc · Jul 1, 2004

I was wondering the same thing about liquid vs air cooled powerplants. During my visit to Tazewell earlier this week, I had a wonderful service session with Terry. Quite simply, Power Trac's philosophy is that liquid cooled powerplants add layers of complexity to the unit--water pumps, radiators, hoses, belts, thermostats, etc., which they feel are better avoided in the normal working environment for these machines.

Abitnutz · Jul 1, 2004

There are several good reasons I think to use the LC variant of this engine. There is a 28hp version of the air cooled engine but they had to use electronic fuel injection to gain that 3hp. Talk about increased complexity…wow. Anyway, I think a good case can be made that an LC engine is more desirable under most circumstances. They have lower oil temperature, lower oil consumption and have far more consistent overall engine temperature which results in longer engine life. This engine also develops more torque at 600 lower RPM and at a half point lower compression. It gets better fuel mileage and is quieter. It’s true I would have to consider the increased maintenance of a cooling system but to me it would be worth it. There is almost no difference in cost between these two engines. If they were to offer me a choice between two PT-425’s, one with a 25hp liquid cooled engine and the other with a 25hp air cooled engine. I would have to choose the LC model and pay an extra $200.00. Would I rather have a diesel? You bet! That would be almost irresistible! But the maintenance on those is higher and the cost of the engine would be much greater. Power-Trac would also have a much greater job of re-engineering to do. I guess I saw the LC variation of this engine that already lives in the PT-425 and thought what if? And wondered how little it would take to do it. I’m posting a picture if the 2 engines. I can’t address the issues about specific shaft length and diameters but as you can see from the pictures, these two engines are just about identical except for the radiator....Just a thought.

Abitnutz · Jul 1, 2004

2nd picture

toolz_not_toyz · Jul 2, 2004

I second that motion, of course. I would go with liquid cooled over air cooled for the exact reasons that Abitnutz mentioned. An LC doesn't add much more complexity to the setup: radiator, pump, hoses, fan. Big deal. This is really PT saying "We don't feel like doing it" for some reason or another.

Would PT have to reconfigure the engine compartment? Yes. But how many times have they done that now over the past three years?? Should be a breeze. Of course, by the way things have been headed with their evolving engine compartment design they'd probably mount the radiator at the front, behind the seat, where it wouldn't get any airflow and they'd relocate the gas tank under the seat so the operator could either blow up directly or indirectly if the fuel hose gets snapped off at the pivot point. /forums/images/graemlins/mad.gif

I already have an air-cooled Kohler in my JD lawn tractor. And I don't think it's a particularly great application. The PT needs something better when it carries a base price of $9500.

I've been quiet lately since I've been working on my other projects. But I sure hope PT makes some serious advances in their design between now and the time that I consider a PT 425. They need to address:

1) Gas tank location (it sure as heck shouldn't be attached to the engine compartement lid, nor should it live next to the exhaust).

2) Weak pivot pins (unless people have been overloading their PTs, this is a pretty good design flaw).

3) More powerful engine or at least some engine choices.

4) The ability to add removable weights as low to the ground as possible.

And all that other stuff that fourteen wrote about in his recent pros and cons thread. /forums/images/graemlins/wink.gif

MossRoad · Jul 2, 2004

They have several engine choices and sizes of machines.

As far as I can tell, none of their diesels are liquid cooled, they are oil cooled.

My engine has plenty of power for the size of the unit.

If they add weights to it, we will just abuse it more. Add weight, lift more, add more weights, lift even more, again and again until it snaps. /forums/images/graemlins/laugh.gif

The pivot pin problem hasn't bit me yet and I'm not sure it will until I start using a mini-hoe. I like my plastic gas tank on my older model. However, I like the layout of the engine compartment on the new models better. They keep evolving. I like that. /forums/images/graemlins/wink.gif

We also need to size a machine to the job. A small machine, while seemingly very powerful, will wear out and/or break when subjected to heavy loads over a period of time faster than a larger machine. That's why Power Trac offers so many different sized machines. We all want the most bang for our buck, but we have to be realistic as to what a machine of any size can do without subjecting it to a daily beating.

Again, I will stress that everyone should research these machines vary carefully before they buy them. They are not for everyone and if you do not enjoy mechanical work, when they break(and all machines break eventually), you will not be happy. It is a known factor. The warranty is a known factor, too. So is the absence of local dealer support. You have to be willing to accept this product on Power Trac's terms. That's the way they do business. We know this going into the deal. /forums/images/graemlins/crazy.gif

smartguyz · Jul 2, 2004

Wow, this thread is getting just a wee bit heated. However, I will wade in...

( I second that motion, of course. I would go with liquid cooled over air cooled for the exact reasons that Abitnutz mentioned. An LC doesn't add much more complexity to the setup: radiator, pump, hoses, fan. Big deal. This is really PT saying "We don't feel like doing it" for some reason or another. )

I used to think I wanted a liquid-cooled engine. It does allow the engine to have tighter tolerances because of the better control of temperature variation, etc. However, I have several liquid-cooled engines (in my cars/trucks), and I realize I don't really like it that much from a maintenance point-of-view - hoses to break and replace, coolant to recycle and replace, thermostats to go haywire, water pump leaking (!) and overall, more maintenance. On the other hand, assuming we keep the cooling fins cool, run the machine with reasonable limits (e.g. if it gets really hot outside, you might need to stop work and cool-down every so often - probably goes for both the tractor and ME /forums/images/graemlins/smile.gif) I appreciate the simplicity of the air-cooled designed. No, I'm not trying to be obstinant or insist my machine is more-wonderful - I just like the simplicity of having less stuff to maintain and break. I realize that my 20-year Snapper riding mower has an air-cooled engine, and still runs like a top. Never leaked, because there was nothing to leak!

( I already have an air-cooled Kohler in my JD lawn tractor. And I don't think it's a particularly great application. The PT needs something better when it carries a base price of $9500. )

I don't see that more complexity is really that much better unless something significant of value comes along for the ride. I'm not sure what tangible benefits a liquid-cooled engine would buy me in the 425-class machine. I would be happy to hear other opinions. I'm not being dogmatic here.

)
2) Weak pivot pins (unless people have been overloading their PTs, this is a pretty good design flaw).

)

I haven't had any problems here. Didn't know they were 'weak'. What exactly is the problem?

-Rob /forums/images/graemlins/grin.gif