What characteristics make the diesel engine especially durable

Factual Questions
1

When compared with the standard internal combustion gasoline engine, the diesel engine is generally regarded as a solid workhorse of a contraption, less fragile and with less maintenance involved and more suited in particular to long hauls of nonstop activity.

Reciprocally, other characteristics are attributed to the gasoline engine: no one is entering a diesel vehicle into compettiion at the Indy 500.

Is it because a diesel engine is operated (generally) in a narrower range of engine RPMs?

Why doesn’t the spectacularly higher compression ratiio in a diesel engine’s combustion chamber result in more wear and tear?

Is it the fuel itself, somehow? That is, if, hypothetically speaking, you could invent Additive X which would prevent gasoline from doing a spontaneous and explosively destructive combustion at diesel-engine compression ratios, so that you could spritz a mist of gasoline air-fuel mixture into a diesel engine instead of its usual diesel-fuel diet, would the heat or energy or other characteristics of gasoline produce more wear and tear nonetheless?

Is it, umm, bullshit? Are there simply economic reasons to bother to develop stolid solid reliable engines built to last for the long haul mostly as diesels, and given a sufficient shift in the affordability & availability of diesel fuel, “workhorse” gasoline engines could be built, easily enough?

Is it the act of acceleration, the very strength of gasoline engines becoming their weakness, that they can built up rotational speed against resistance more quickly but that doing to wears out parts, whereas accelerating more slowly through a more narrow band of RPMs and using more gears to convert that into speed = less wear and tear? If so, once again, could a gasoline engine, if deployed in the same manner, deliver the same reliability and durability?

2

Part of it is that they operate at lower speeds. Diesels have more low-end torque and can be geared higher. I can idle in fifth gear in my truck. Lower engine speeds obviously mean less wear.

The parts (especially the pistons) are a bit sturdier to handle the compression ratio. They’re a bit overbuilt for it so that makes them last longer as well.

And diesel engines aren’t completely absent from racing. Mercedes uses them in sports car racing. It’s pretty atypical though. The gasoline engine’s ability to rev higher typically means more power in addition to being lighter.

3

Diesels run at lower RPMs so it may be that if you compare total number of revolutions over their lifetime there is not as much difference as you may think. Diesels are also heavier for the same power output

I think you are missing something here. Diesel fuel is gradually injected into the cylinder and the air is already in there. There is no injection of fuel-air mixture and high flammability is a desirable characteristic. There is no problem with knocking because of the way the fuel is injected into the cylinder. One reason gasoline is not suited for diesel motors is that diesel fuel is more lubricating and lubricates the injectors while the same injectors would be destroyed by the lack of lubrication if using gasoline. Having said that there are different diesel motors which are designed for different fuels and I would think you can burn pretty much anything which will ignite.

4

Also the internal parts are much more robust to take the strain of 22:1 compression ratios, the cranks, rods, pistons, bearing surface size, there is a world of difference in a 400 HP gas engine and a 400 HP Diesel engine.

Making 400 HP at 2000 RPM and at 6000 RPM like a car is way different. An 40o HP aircraft pistion engine has a lot more in common with a diesel than an auto engine. the make the 400 HP at about 2500 RPM.

Much larger cranks, longer stroke, more support for the crank, cam design is way different, etc…

Fast acceleration = light weight, short stroke, cam profiles and RPMS to bring it all together in a reliable package.

5

However the Audi R10 has won Le Mans for the last 3 years.

6

It’s actually Audi and Peugeot. They took the top 6 spots at the 24 Hours of LeMans this year. These cars have a diesel hybrid, the fuel is a diesel/alcohol mix. The engines run up to 8,000 rpms and blow away gasoline powered cars in the torque department. Diesel engined cars have competed at Indianapolis but not since the late 1920’s.

7

Seat (the Spanish arm of Volkswagen) is running some diesels in the WTCC.

8

If you want to wash oil off something, gasoline does a very good job (dangerous, not recommended, but effective). One of the problems with gasoline engines is that the walls of the cylinders get a slight washdown with gasoline every stroke,
breaking down to some degree the thin film of oil that protects them from wear.

Contrastingly, diesel is a much heavier grade of oil than gasoline and is quite lubricating.

9

I’ve heard talk about the amount of time they spend on track instead of in the pits refuelling. I didn’t think that at such high revs there would be an appreciable difference, but wikipedia says there is.

10

Isn’t part of the reliability for diesels just that they’re simpler, not having to deal with spark plugs/distributors/timing and related things that can break?

11

They aren’t automatically more reliable, as GM found out in the 1980s.

[QUOTE]
The Oldsmobile 5.7 liter engines experienced a wide gamut of malfunctions. One of the common failures was with crankshaft bearings. This was frequently attributed to owners and maintainers running the engines on SG rated oil (intended for gasoline engines), versus CD oil (intended for Diesel engines).

12

There is a new type of engine that supposedly offers the best of both worlds: the Homogeneous Charge Compression Ignition (HCCI) engine. Of course, it has its own set of disadvantages, but it does have some intriguing possibilities.

13

I believe that most of the problem is that Oldsmobile took a gas 350 short block and modified it to become a diesel motor. As pointed out in many of the posts here, a diesel requires a stronger block and crank system. GM gambled on saving a few bucks and lost.

Another advantage to diesels is that they can be made in very large displacements. The largest I could find is the Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine. It is used in cargo/container ships.
Stats.
14 cylinder version
Total engine weight: 2300 tons (The crankshaft alone weighs 300 tons.)
Length: 89 feet
Height: 44 feet
Maximum power: 108,920 hp at 102 rpm
Maximum torque: 5,608,312 lb/ft at 102rpm

from…http://people.bath.ac.uk/ccsshb/12cyl/

Note the 102 rpm, that’s about 1/6th. of a gas engine’s idle speed.

14

In a well designed, tuned, and warmed-up diesel, the injected fuel burns before it impinges on the cylinder walls, or piston top for that matter. Getting this right is one of the reasons that modern diesels burn so much cleaner than older designs.