3 Cylinder Life

john_bud · Feb 16, 2006

Guys,

There are many factors in how much torque and engine gets and where that torque is generated. A simple rule of thumb is the longer stroked engine will typically have more low end torque than an equally sized, but shorter stroked engine. Fewer number of cylinders does not automatically mean longer stroke. With Ag equipment, it should be true, but longer stroke engines cost more to manufacture, so ... well you get the point!

You should also look at the rated RPM (PTO RPM usually). An engine with a PTO rpm of 1414 will have more more low end torque than an equivalent Hp engine with a PTO rpm of 2700.

jb

Joe1 · Feb 17, 2006

One of the possible problems with a large displacement 2 cylinder engine is that while the stroke will be longer the bore will probably also be larger. All else being equal, purely from an emissions standpoint, it's more difficult for large bore engines to run as efficiently as small bore engines because of the time it takes for the fuel mixture to fill the cylinder and the fire to completely burn the fuel. This was particularly true for Chryler with their 440 cu. in. V-8 in the late 70's and contributed to it's demise. That's one reason you see V-10 engines (smaller bores than equivalent V-8's) in Dodge pick-ups (until recently) and in the Ford pick-ups, light trucks and gasoline motorhome applications. Manufacturers would rather build a V-8 than a V-10 because of fewer moving parts and assembly time, ergo a cheaper engine to manufacture but they are increasingly more difficult to get past the EPA.

Also, (again, all else being equal) a 2 cylinder engine will need a larger, heavier flywheel than a 3 or 4 cylinder engine to make it operate smoothly. A heavier flywheel means slower throttle response due to the time it takes to change the inertia of the recriprocating mass of the flywheel.

My gut feeling also is that a 2 cylinder engine might be harder to market than an equivalent displacement 3 or 4 cylinder engine. People think more is better.

jimmysisson · Feb 18, 2006

All well and good, but them old 2-cyl. Deeres would pull as well as anything in their day. And sound great doing it!
Jim

Joe1 · Feb 18, 2006

I saw an old JD 2 cylinder engine working on a farm in Pennsylvania. It was from the 1930's and was pulling a 4 wheel wagon. The owner said he had several and this one had over 10,000 hrs. It started right up after sitting all day and didn't smoke. He claimed to have 2 or 3 with at least tha many hours; all on original engines that had not been overhauled.

My comments pertained mostly to newer stuff.

As I understand it, Kubota is no longer marketing their 2 cyl BX line. Nothing wrong with it; it just wasn't a good seller and for something like $700.00 a 3 cyl with 3 (20%) more hp was available.

twinbird · Feb 18, 2006

Engine life is directly proportional to how long it takes to get a tablespoon of dirt in the engine. It can happen in 500 hrs or 5000 hrs.

IH3444 · Feb 18, 2006

Good post, I think you also get into the geomerty of the two cylinder, three cylinder, verse 4 cylinder engines with the same displacement. The less cylinders, more stroke, longer connecting rods need more, and more angle to swing, resulting in additional stress to the rod, thereby causing it to grow larger. Also the angle need to push the piston up, as well as carry the power energy down to the crank causes the cylinder to become more egg shape, figure 8 worn more rapidly. The rod is trying more so to push the piston into the side of the cylinder wall. My engine machinist friend who has done it all from small kohler engines, to large CAT V12 engine explains this to me when I visit him. He has had several of those JD 2 cylinder "Johnny Popper" lately on his large cylinder borer. They are big piston/cylinders, and all new parts are still available. I've like the 4 banger due to the smooth power, and a diesel delivers more than 90% of crank rotation on it's power stroke, making each power pulse on a 4 cylinder meld into the next. Good and smooth power. Short stroke, low piston speeds. The piston on a long stroke must accelerate, decelerate, stop, change direction in a very quick time. It's harder on the longer stroke engines. All in all I believe that the more cylinders, the better. Just my humble opinion, and listening to my engine machinist buddy for almost 25 years........ /forums/images/graemlins/smile.gif

MMM · Feb 19, 2006

( more cylinders, the better)

In tractors, the V8 was a dud. The I6 rules. I beleive it's true in the diesel passenger truck market also.

IH3444 · Feb 20, 2006

Really? I guess those CAT V12s, and V16s, (which are two V8s coupled together) were a waste of research, foundry time, manufacturing, and usage. Which V8 were you refering to. I have seen many an older Ford tractor at shows with the small 265cuin V8 shoe horned into them. One feller had adapted a 6ft Woods belly mower to it, and put on over sized turf tires. Just looking at that beautiful machine made me want to go out and cut grass on it all day. He also commented on how smooth, and almost vibration free it was. Ahhhh sweet! /forums/images/graemlins/grin.gif

Joe1 · Feb 20, 2006

Seems like most new large road diesels, i.e. tractor trailers, highway Buses, Diesel Pusher RV's are just about all inline sixes these days. Probably cheaper to manufacturer than a 12 or 16 with fewer moving parts and less overall weight. Nothing wrong with the V-12 or V-16, just "progress". Kind of like sex, it's all good, just some's better than others.

HGM · Feb 20, 2006

( ( more cylinders, the better)

In tractors, the V8 was a dud. The I6 rules. I beleive it's true in the diesel passenger truck market also.
)

Not sure exactly where you're going with this..... But I certainly wouldnt call the Ford Powerstroke a dud.. It's in a passenger truck, and by far the most popular diesel "passenger truck" on the market with 95% still on the road today(just read that recently)..

What makes it more popular than the torquey Cummins, is that it has more than one dimension. The Cummins is a great engine, and if I were looking soley for low/flat Tq band it would probably be my choice..Which brings me back to the topic.... The inline engines tend to produce more Tq per displacement than the V configurations because of the longer stroke(more push on the crank).. The V's tend to require more RPMs to produce the Tq, making for better all around driving.. I certainly dont mean to offend the Dodge guys out there..I like the sex reference, some perform the job better than others, but even the worst is pretty darn good at getting the job done..