Race Engine Forum UK

Hi Guy.

Took this line from the "Oil pressure control" thread.

...but do use an oil cooler and gauge and keep the oil temp to 85 deg C max or you will certainly run a bearing.

And this from the "Engine Monitoring Gauges" thread.

...So I say put the oil temp sender in the return line so I know what temp it's going in at.

So if I understand it correctly you measure the oil temp after the oil cooler but before the engine? Why I'm asking is because of my engine already got its temp / pressure sensors taped in here, so was wondering if I can still use these holes to fit new "better" gauges and trust the values I get. The engine sits in my Dedra Integrale and has oil thermostat built in to the mount that holds engine in place (can't remember the correct word right now). I have currently seen temps around 80 - 85 degrees on a "normally" hot day whilst driving at the track, so If its a good place to monitor oil I will continue to do so, otherwise I will change it now when the engine is out of the car.

Regards
Mikael Olsson
Sweden

Mikael, hi

yes, I would want to know the temperature of the oil going into the main engine gallery. You don't want to run the oil real hot whatever claims are made for the stability of the oil by the manufacturer in terms of its viscosity at elevated temperatures, because if the oil temperature is very high, the bleed-off rate in the bearings (rod especially) will be so great that the oil pump won't be able to supply sufficient delivery to prevent metal to metal contact. The problem is less acute on the models with the later crank nose driven pump than the early type where the pump is driven off the auxiliary driveshaft because the later internal-external crescent pumps have a much higher delivery (something incidentally that helps fast priming of rings and bores to reduce cold-start emissions, especially when coupled with oil sprays in the crankcase). However, I have not determined any power gain running oil over 85-90 deg C. Lower than 70 deg C measurable power loss..

If an oil cooler is fitted you can have two gauges - one on the outlet line from the pump (or in the sump in the case of a wet sump engine - the Fiat Strada 130TC has an OE sender there) that measures the exit temperature and one on the return line and then of course, by looking at the temperature reduction you can assess the effectiveness of the cooler. That's a good thing.

If the engine had no cooler then of course it wouldn't matter where you put the oil temp gauge, because the delivery line and and sump temperatures would be pretty well the same.

GC