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MG MGF Technical - Question - HGF - why don't engines use solely oil?

Why don't engines use oil for both lubication and cooling - i.e. no seperate water cooling system?
Is it because oil is too viscous? too expensive? contamination?
On the plus side it would heat up quicker, less thermal stresses on the engine due to oil / water temp.
At least you wouldn't get the mayo effect when HGF occurs!
Thoughts?
Phil M

>Is it because oil is too viscous

very costly in bhp to pump round oil

also oil is not very good at absorbing heat, so it would be difficult to keep the temp stable

>less thermal stresses on the engine due to oil / water temp

What are these stresses you are talking about?
Will

Actually oil is used in some engines - the new BMW Boxer engines use engine oil as a cooling aid to the cylinder heads although the barrels are still air cooled.

And they still kick out 100 plus bhp - not bad for a 1.2 litre engine.

Ted
Ted Newman

In the two wheeled world weight is everything - but it doesn't make the oil good at that job, just better than nowt, and good enough for the weight/reduction in complexity.
Will

Will

May I respectfully suggest that you study the BMW boxer engine a little more than you obviously have.

It is not weight or complexity reduction that BMW are trying to achieve - if it was they would have gone down the fully watercooled route as most Japanese manufacturers have - in fact they wanted to keep the tradional Boxer engine but needed to find away of getting extra cooling to the cylinder heads and after much research (and BMW what ever people may think of them do a lot of research) decided that oil cooling was the best option.

Incidently oil cooling is also used a lot in other industries so it can not be that bad!

Ted
Ted Newman

about 2 wheels, oil cooling was used in the past by Suzuki in their hyper-sports GSXR, but they finally gave up and went for the classic H2O route, mainly because of the better heat absorbing capacity of water, despite of its weight (approx 20% more than oil) and other disadvantages.
Viscosities of oil for a cooling circuit and oil for a lubricating circuit aren't equal... I'd say the goals are somehow opposed.
Fabrice

some small points of order:
1- BMW bikes had an oil radiator since 1977 with the R90S. Then the R100RS and the R100 G/S, all before the "new" R generation, so hardly any new setup.
Suzuki SACS (again oil cooling) was inspired by some WWII plane engines, so much older news there.
2- Most modern Turbodiesel rely on a oil jet spraying the inside of pistons to cool them, so oil IS commonly used to cool the engine. Also the K has some sort of oil cooling for the top of the head.
3- the oil thermal behaviour is generally insufficient to fully cool a modern engine: you either have direct air cooling (as on many bikes and old Porsches) or cool the oil with the water.
SEOT
Picquart martin

The oil rads on the older type Boxers was to cool the lubricating oil - the engine including the cylinder head was air cooled.

The new generation Boxer uses oil to cool the cylinder head as well as lubrication - and yes they have oil cooling rads.

Hence the expresion used to describe the types:-

Air Head or Oil Head.

Ted
Ted Newman

<The oil rads on the older type Boxers was to cool the lubricating oil>
this is just hilarious.
Do you think the oil heat did come just from friction?
The oil does run along the hottest part of the engine to get to the rocker/valve assembly (inside the main stud channels through cylinders and heads, if you want to know)
cheers
(and I DO have a R100RS at home)
Picquart martin

Dear Picquart martin

I am glad you think it is hilarious but I assume from your name you are not English so I will forgive you your extreme bad manners and lack of understanding of the English Language.

Over the last 50 odd years I have owned more motorcyles than I can count and BMWs I have owned singles, twins (both air heads and oil heads) triples and fours although I do confess that I am without a bike at present.

However I am still fully conversant with auto engineering - bikes, cars and trucks - and yes I do know why the oil gets hot and I do know where the oil flows (BTW oil FLOWS it does not 'RUN ALONG' thats what naughty children do) and on the older type boxers as with the BMW K engine the oil is there to lubricate and the coolers are there to cool the lubricating oil and that is all, any engine cooling is secondary and not a prime function. However on the new type boxer the oil also has a prime function of cooling as well as lubricating and that is the point I was making that oil can be used as a coolant.

I hope you do now understand what I was saying and I also hope you can learn from your errors and in future try and reply without having to fling insults around.

Ted
Ted Newman

This thread was discussed on 03/03/2005

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