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Having had the use of diesel cars, trucks, farm tractors, and marine engines, in my experience the operators / engineers invariably say that the engines run smoother after a full load run when they have been lightly loaded for a period. Does this clear out of soot have a similar effect as a fuel additive. I make a point of accelerating up a steep hill or motorway slip road if I have been pottering around for a few days and have produced some spectacular smoke, my current car (2.0 tdci) doesnt smoke given this treatment, modern technology?
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Certainly, running your car hard can help clean out the fuel injectors. They are basically forcing fuel under higher pressure through a nozzle to start the combustion process (from a basic viewpoint).
The combustion process naturally leaves particles or the soot in the valves and on the internals of the engine as it gets into the oil etc. The additives help break this down and burn off in the oil. If you ever noticed, diesel oil gets very black very quickly. Using V-Power diesel in my new car has kept it pretty dam clean for quite a few thousand miles. The soot in your oil really isn't ideal and once it gets inside the turbo and on the bearings after a period of time it can reduce lubricity and heat dissipation and can generally retard the function of the mechanics in a way that could eventually lead to failure.
Valves still get clogged up and thrashing it can help remove his build up even without additives.
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Thats not to say go round driving like a crazy madman. Make sure you have done at least 15miles of normally / gentle driving and then get up to 4.5k revs in first and 2nd with positive acceleration and that should be sufficient to blast fuel through the injection system.
Once or twice a week seems fairly sufficient and as you say going up a steep hill especially with more than 2 people in the car is a pretty heavy load to move. Wouldn't want to do it too often though as it puts strain on the turbo and its not really a good idea to rev higher than when max power is reached. Going past max power puts extra strain on the engine as it runs out of air intake from the turbo and struggles / basically runs out of steam. At this point of running past max power your engine's power usually tails off rather quickly and changing gear at this point puts a lot of stress on the engine and probably gearbox going from little torque and power to the exact opposite.
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I like to think I have some mecanical sympathy, "Full load" and "Italian tune up" are totaly different in my opinion.
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>>They are basically forcing fuel under higher pressure through a nozzle to start the combustion process
No - the fuel injection pressure remains unchanged, in general terms, only the duration of injection changes. There are some CR systems which can vary the pressure, but it isn't a large effect.
>>If you ever noticed, diesel oil gets very black very quickly.
The colour of oil has *nothing* to do with its ability to lubricate your engine. Soot is relatively benign, and isn't a problem.
>>it can reduce lubricity
Really?
>>Valves still get clogged up
There are some engine where this happens, but in general, this is rare
>>Wouldn't want to do it too often though as it puts strain on the turbo
As long as the turbo gets a chance to cool off, and it's lubrication system is well designed - i.e., there's plenty of flow, there's no problem. Ignoring wastegate operation, a turbo always simply balances energy lost in the compressor with energy gained in the turbine.
>>Going past max power puts extra strain on the engine as it runs out of air intake from the turbo and struggles
No, the stress comes from the extra inertial loads of moving the pistons up and down, which increases with speed squared. Yes, the airflow does reach a limiting value, but this just prevent the engine producing more power, the lack of extra airflow doesn't actually stress anything.
>>changing gear at this point puts a lot of stress...
Depends how skillfully you do it
Number_Cruncher
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I think it's more to do with cylinder bore glazing. Industrial engines are designed to work at full load most of the time. Idling for long periods tends to glaze and polish the bores, and eventually this leads to loss of compression and heavy oil consumption. Full load running before shutting down helps to prevent glazing.
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You can still get this with excess idling of engines in cars - i ensured that i didnt idle too often and ran the breaks in gently to prevent glazing. If you are running at full load its very important to idle after for a realistic period depending on the engine.
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