oil efficiency

[dave wj]

Not sure which area to post this in, engines or cooling, so apologies if in wrong one

I guess most folks think the cooling of the engine is primarily down to the coolant running around the engine / rad. I've read on several occasions that the oil also fulfils this function, but not come across any figures.

Does anybody have any figures with regard to the efficiency in which oils of different viscosity/type are able to do this,ie, what percentage of heat dissipation could be down to the oil especially re the RV8?

Apologies if I'm asking the impossible or going over old ground, but this really has got my curiosity bubbling.

Many thanks.

Dave

[kev_the_mole]

Dave,

figures quoted are that the oil helps to dissipate up to 30% of engine heat and an oil cooler would increase this figure. Synthetics can be better than natural oils and then it gets into stuff that only polymer chemists and thermodynamicists could possibly comment on and that's where i bail out

[kiwicar]

Hi Dave
I heard roughly the same as Kev, engine with a cooler about 1/3 of the cooling system's capacity, add an ally sump with fins adds about 5%, drilling holes in the main oil gallery to direct jets of oil to cool the underside of the pistons, on a super/turbo charged engine adds another 5%-7%, provided you fit a bigger cooler. generally higher hot viscosity number better heat capacity and synthetic is better than mineral, but beyond that it is for the specialists.
Mike

[dave wj]

Thanks Kev, thats very interesting. 30% is quite significant. I'm still running in having only covered about 1000mls so I'll avoid synthetics for the time being.
Ever tried valvoline oils??

Cheers

Dave

[dave wj]

Thanks mike, just beat me to it there.
If I understood correctly, to achieve the 30% cooling, it would be advisable to fit an oil cooler?
Are ally finned sumps available for RV8s?

All the best

dave.

[kiwicar]

Hi
ally sump would be a custom job. For 30% you would probably need an oil cooler.
The figures I quoted are general for a water cooled engine. Maybe a bit more for an ally engine block bit less on an iron big block engine.
If you look at a suzuki gsx bike engine of the '90s the oil did 85% of the cooling with only the base of the cylinder block finned for air cooling the rest from the oil cooler and finned sump.
Most "aircooled" engines probably actually rely for 50% of their cooling from the oil, depends on engine.
It all depends on where the Oil passages go and what flow rate is available from the pump.
Mike