Running a Diesel with no load and no water

[Circlotron]

I note that modern spark ignition engines have the facility that if they overheat they cut the fuel to one or more cylinders (probably walk through a pattern) to make you open the throttle further so that the dead cylinders ingest more air in an attempt to cool the engine and save it from catastrophic failure. Say you had a Diesel engine on a test stand with no load. Those things ingest a full load of air each cycle that would presumably add to the required cooling. Could the engine be operated without any cooling water, or perhaps with water circulating but no radiator? What if the intake air was minus 50 deg C like at the south pole? Remember, no load.

[PackardV8]

Yes, No, Maybe. The spark ignition engines reduce the heat load as much as they rely on air to cool the non-firing cylinders. So if one had a six-cylinder diesel and converted it to an eight-cycle poppin' johnny, where each cylinder skipped a turn receiving fuel and compression and there was no load, yes it would probably run a long time under those conditions.

However, what's the point, as it could do little useful work in that condition, other than getting the vehicle home in limp mode.

[mag2555]

VE on a spark ignited engine with the air Intake being throttled big time like at idle is at a flat out minimum, VE on a Diesel is at maximum for any rpm the motor can attain until the air systems sonic limit is reached, no?

It all depends on if the amount of heat the Diesel is producing from its level of hp being made is fully countered by the heat due to is mass it can reject off itself it would seem.

[peejay]

This is a lot of why Diesels run cool at idle in the first place.

I heard a story about a generator in some Siberian encampment that suffered a radiator failure, so they just bypassed the radiator. Ran all winter that way. I guess you can get away with a lot with -50 intake air.

[steve316]

Deutz has made air cooled diesel engine for a lot of different applications

[MadBill]

And their heaters, at least in the one I drove once, rely on engine oil as a heat source and suck...

[modok]

With a diesel the temp is more directly proportional to the load, quite logical.
It's more difficult to explain why on a spark ignition engine it really isn't.

[4vpc]

Quite possibly it would, modern diesels run very cool.
I remember one diesel I had for 10yrs, in all that time I heard the cooling fan cut in just once as I'd pulled a trailer with car on through some heavy traffic on a hot Summers day and pulled up. I also remember sitting in it one day in freezing temps with the engine running waiting for someone, the temp gauge went down and the heater started to blow a bit cooler.
They have electric heaters in the water circuits now, in my current one they look like glow plugs, it's got four in a chamber that the water gets pumped through.

[peejay]

With a diesel the temp is more directly proportional to the load, quite logical.
It's more difficult to explain why on a spark ignition engine it really isn't.

All the heat-generating friction, but running throttled at a set mixture ratio means there is no unburned air to cool and insulate the inside of the chamber. A Diesel will have an insulating layer of air around the combustible mix under all but the heaviest loads.

[strokersix]

With a diesel the temp is more directly proportional to the load, quite logical.
It's more difficult to explain why on a spark ignition engine it really isn't.

All the heat-generating friction, but running throttled at a set mixture ratio means there is no unburned air to cool and insulate the inside of the chamber. A Diesel will have an insulating layer of air around the combustible mix under all but the heaviest loads.

A throttled engine has to do a lot of pumping work at part load. This takes fuel and produces waste heat more so than an unthrottled diesel engine.

[Jagdpanzer]

Take a look at the difference in exhaust temperatures between an idling Diesel engine and an idling spark ignited Otto cycle engine.

[modok]

RIGHT!
AND spark ignition engine there can be a lot more exhaust gas dilution
Both from remaining in the chamber and being sucked up into the intake.