4cyl vs 3cyl

[kuboman]

I stand corrected:ashamed:

 

[whistlepig]

Hummm... Then you must be assuming that the pistons, pins, rods, crank and bearings are of equal strength and quality. My guess would be that a smaller piston will be coupled with smaller components because the loads would be less. Kind of blows the argument. It all depends on what the manufacturer designs.

I wouldn't buy a tractor that had a single cylinder engine based on your assumptions.

 

[Rob-D]

I agree with you whistlepig, torque does NOT rule.

Tractors do work. HP is the rate of work per unit time. I can use a gearbox to divide or multiply torque. I can use a gearbox to divide or multiply rpm. I can NOT use a gearbox to divide / multiply horsepower. HP rules.

Yes and no. You need both, ever run an engine without torque? It sucks, you're constantly keeping the rpms up to make it go.
BMW made an engine once in a car called the 325e. It was about 125 hp but the torque band was great. I loved driving that car!

Rob

 

[SPYDERLK]

I am wondering what the advantages and disadvantages are to diesel engines making the same horsepower, but with one more or less cylinder. Is there a mileage or efficiency advantage to one? More or less torque? Please clue me in.

You are correct that more cylinders is not always better.

But the whole theme of this thread is what engines are "smoother".

And the short answer to that question (but not always the case) is the engine with more cylinders.

The bottom line is that the vibrations come from the "explosions" on the power stroke. There are very minute surges in the RPM of the crank for each one of these. Followed by a minute deceleration of RPM. The more frequent the explosions per revolution, the smaller these accels and decells are. Which minimizes felt vibration and harmonics. Especally at lower RPM or under deceleration. Everything is smoother at a higher RPM because of the momentum of the crank/flywheel.

Which is another thing I forgot to add earlier, using a heavier flywheel and heavier crank will also limit the vibrations due to the stored inertia in the mass. But it will also make it rev slower, but it's a tractor and fast reving engines aren't really what you want.

I didnt get your take on the theme, but otherwise I agree. Its amazing to think of the power developed during the power stroke. A 10 horse cylinder is actually giving close to 100HP during the power stroke to enable it to coast thru the other strokes while putting 10 hp to the output shaft.
larry

 

[LD1]

I guess I should have went back and re-read the first post. I could have swore he asked which engine was smoother running. But after over 50 posts, I guess I forgot:confused2: