Oil Temperature

teamidris · Post by **teamidris** » Sat Apr 14, 2012 8:01 am

I'm trying to get this right in my head. I've been designing heat exchangers for a few years now, so I had a different view point during my last engine change

Some of the oil will be come out of the crank and will be above block temperature, but I wouldn't think by much. Some of it is coming off the piston underside, and it will be very hot. So I assume the oil temperature in the sump is a combination of both. (100 deg.c plus some higher).

Then the sump does some cooling (or not, depending install) so that the oil pump gets some quite hot thin oil. If the oil leaving the pump or the filter is measured to be too hot we fit an oil cooler. But how much effect does that have? I'm thinking that the engine block galleries heat the oil back up and that the flywheel main bearing probably gets oil at water jacket temperature?

I'm not doubting an oil cooler increases the oil pressure, as I used to run one myself

But I wonder how much is oil-cooler and how much is extra coolant for the bottom of the block?

So I'm coming round to the thought that the oil needs cooling before it enters the oil pump for best effect on oil pressure?
That maybe its better to fin the outside of the sump? Or, that an electric pump sucking oil from the sump, cooling it, and pumping back into the sump would be way better for back pressure than an 'in circuit' cooler. (probably easier to control as well)

[Which I suppose is part of what dry sump does, but I didn't want to make it a dry sump thread

]

stevieturbo · Post by **stevieturbo** » Sat Apr 14, 2012 8:22 am

You cool it where most practical.

After the pump, before the engine. Simplez.

And the block heats and cools the oil. The engine block in general should never go above 100degC, whereas the oil will. So here the block will offer some cooling.

But really, wouldnt worry too much at only 100degC

kiwicar · Post by **kiwicar** » Sat Apr 14, 2012 8:58 am

Hi
some numbers I saw a few years ago said that on an engine with an average cooler about 25% of the heat loss is due to the cooler, that is infact the sort of size you match it for. The rest is from the sump and radiation from the block itself. Obviously without the cooler all the heat loss is from the block and sump. On drag racing powerglide and TH350 & 400 gearboxes it is common to replace the stamped steel pan for a deaper finned cast ally pan, this greatly increases the cooling capacity, you still fit a cooler, but the cast sump is a big help to cool the trans fluid.
Personally if I were building a rover V8 I would investigate a cast ally finned sump and directing cooling air from below the car at the sump before fitting an oil cooler, you get cooler oil without the extra flow restriction.
Best regards
Mike

stevieturbo · Post by **stevieturbo** » Sat Apr 14, 2012 10:17 am

Would most RV8's even need a cooler though ? IMO use decent oil, and unless temperatures are going over 120degC then you've little to worry about.

teamidris · Post by **teamidris** » Sat Apr 14, 2012 11:01 am

I agree, I bet 90% wouldn't need one. And Some of those have it fitted in the bottom rad tank, so its more of a conditioner.

I thought about a finned gearbox cooler for the landys on the second gearbox. It's good free cooling

I might re-visit that. It'd be nice to do it with rad fin rather than just ribs.

landrovernuts · Post by **landrovernuts** » Sun Apr 15, 2012 6:55 am

If by second gearbox you mean transfer box then the finned bottom covers all ready exist made by Rocky Mountain (Ashcrofts sell them also) For series transfer boxes they are just a finned cover and for LT230s they have additional oil capacity as well as finns. Should also be easy to make up an alloy finned sump for a V8.

Toby