Why Diesel engines only run at mediocre RPMs?

Answer 1

Because they'd blow themselves to pieces if they weren't limited. Diesel combustion is a far more violent process than the relatively 'soft' combustion process in a petrol engine. Despite all the trickery with high pressure injection and huge turbos to make them power competitive, a Diesel is an agricultural device, best suited to a 40 tonne truck or a tractor!

Answer 2

Diesel engines are high compression engines that produce more torque at lower revs than at higher revs.

As the power of an engine is determined by multiplying the torque of the engine by the RPM, and the torque of a naturally aspirated diesel engine drops as rev's increase (unlike petrol engines where the torque rises with revs) high revving diesel engines would have no power.

In order to combat this, most modern diesel engines are fitted with a turbocharger. This creates a high level of torque across a specific rev range, thereby making the diesel engine more practical at higher revs. But still, there is no point in revving a diesel engine above 4-5000 rpm as the torque produced would be so small that the engine would produce no power.

Answer 3

Now that you've read the nonsense....Diesel engines are timing limited. This is due to the fact that the ignition point is determined solely by compression. Even with direct injection, it's hard to build in much ignition advance. There simply isn't time to burn the fuel if the RPMs are too high. Think about what would happen to an Otto cycle (gasoline) engine if timing was retarded at high RPM.

Answer 4

What kind of diesel engine are you talking about,BMW have a diesel that will be in the US by next year that has more torque and horsepower that their most powerful gas engine.Also it was a diesel powered car that won the Le Mans 24hr this year,I own a Mercedes turbo diesel it revs to about 6000rpm I say about because at that RPM I am doing around 120 to 130 MPH or 180 to 220 KPH,so what was it you were asking about diesels.

Answer 5

I drive a semi and for the first reason is any higher rpm's in high gear and my fuel mileage woulg got to crap, considering I'm only getting 5.7 per gallon now. You would be hard pressed to find a truck that got anything above 7 mpg. Also when you are pulling load's close to our 80,000 pound limit, you need the power which is only available at lower rpm's. I have driven only two truck's in my 23 year's of over the road that has had over 1,000,000 mile's, try that on a high rpm car, lol.

Answer 6

they are high compression motors, this is to generate high torque at low rpms, not rpms. big truck desiels dont even have glow plugs, for the compression is so high it will start with no extra heat added

Answer 7

Because the pistons, connecting rods and crank are heavy and have too much inertia under high speed.