Hi
A technical question on diesels in general.
With a petrol engine efficiency can be raised by having the coolest possible air coming in (heavier, more dense charge), and having the exhaust temperature as high as possible - without melting anything of course. Generally speaking this gives an indicated water temperature of 90-100 degress with a pressurised system.
Now I know diesel engines naturally run cooler. The 2.0HDi turbo-diesel in my Berlingo Multispace runs at 80 degrees, and never goes above this.
Is there anything to be gained by blanking off part of the radiator to raise the water temperature, or is there no benefit on a diesel?
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>>Now I know diesel engines naturally run cooler. The 2.0HDi turbo-diesel in my Berlingo Multispace runs at 80 degrees, and never goes above this.
Is there anything to be gained by blanking off part of the radiator to raise the water temperature, or is there no benefit on a diesel?
No benefit on either unless the thermostat is stuck open
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Steve
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Worked with mainly large Diesel plant all my working life could be wrong here but in my Thermodynamics class in collage. Diesels are Heat engines I always thought they run hoter or produced more heat
Same goes for Diesels as regards the Charge air or inlet air as cool as posible thats why we have intercoolers on TD's
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Sparkyfrog
What's needed is a cool air inlet, to maximise density, high combustion temperature, but as cool an ehaust as possible, or you're throwing heat energy away down the exhaust - and this applies to both petrol and diesel engines. The high exhaust temperature is one reason vehicle engines have pretty poor overall efficiency. Turbochargers recover some of this energy.
The cooling system is yet another energy loss from the engine, but as you say necessary to prevents the components from melting. Coolant temerature is usually controlled around the 80 - 90 mark for purely practical reasons - boiling point of water. Diesels don't inherently run cooler - the coolant temperature is set by the characteristics of the cooling system. Many years ago I read an article about the US army experimenting with running piston engines without cooling systems, using some pretty expensive internal components. This was designed to hide the heat signature from enemy IR systems, but the reduced heat loss gave efficiency benefits. I don't believe it ever got into service, and I think efforts have gone in to recuperative gas turbines - again recyling the waste heat from the exhaust to improve eficiency.
JS
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There was an experiment several years ago using an entirely ceramic engine. That had no coolant system as the ceramics were quite happy at over 500 degrees C. Thermal efficiency was superb and the 500 cc experimental unit produced a measured 120 bhp on a dyno. It had an inherent problem though - lubricants don't like those sort of temperatures for long!
For those interested in the technical, find any article covering the Carnot cycle or the Stirling cycle/engine. Makes interesting reading on why internal combustion engines are not that efficient.
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Oh, and blanking the radiator won't incease the running temperature - only changing the thermostat will do that. Blank the radiator and the thermostat will compensate by allowing greater water flow to maintain the set temperature. Temperature will only increase when the demand on the radiator exceeds its capability to dispose of the heat, at which point the system is uncontrolled and will boil up.
JS
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Probably an indication that the engine is relatively unstressed and in a temperate UK.
We have the same car but with the 1.9IDI unit and that runs around 85/90 in GB. In France last summer it often went up to over 100, particularly on long hot climbs. At that point the fan audibly cut in and the temp fell back again. Susoect yours would be the same if worked harder!!
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How accurate is the temperature gauge you are using? If it is a standard dashboard gauge then this could mean anything. If you ever remove the thermostat the temperature should be stamped on it somewhere.
My father whilst working for Westlands in WW11 said they tried to get the 2 Merlin engines in the Welkin (looks like a bigger version of the Whirlwind fighter)high altitude fighter to run on 100% Glycol in order to run the cooling system over 212F which gave better performance. However they gave up the idea as they could never stop the system leaking. I think the plane also had a 80 gallon tank of liquid oxygen to improve high altitude performance when required!
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I used to worry about the temperatures shown in my Fiat-it had degress shown on the dial;thenI remembered my Fiesta just had blue,white and red-much better.
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