Adding Oil to Coolant cooler
 

Sometimes my oil temp climbs much quicker than the water temp. I have twin aftermarket coolers. Idea is to balance the heat load between all the coolers more effectively. I'm thinking after the oil coolers and after the radiator, so the liquids returning to the engine are closer to the same temp. I've seen this done on autocross cars tube chassis where the oil coolers are completely deleted, and a much larger radiator is fitted, and on another FD on Youtube, but I don't know where the oil/water cooler is fitted in the loop.

1) Terrible idea?
2) Better before, or after coolers?
3) Other concerns?

Anyone tried this before?

what are the temps you are seeing?

Oil spiked to 121c, water was ~107c then started to climb higher

what size oil coolers
what radiator configuration
what weight oil and type
what fans and what temp do they come on

also what temperature oil and coolant thermostats?
what was the ambient temperature and how much power are you tuned for?
was this on track, street, or?

Canyon runs, lots of elevation gain and tighter lower speed corners. V mount. Was on non sequential twins ~350whp, just finishing an 8374 street port build. I believe they are GReddy coolers 11x6ish. Lower temp water thermostat, not sure about the oil temp.

Ambients are always high here in Thailand. Low 80s-high 90s F. Always a struggle.

Anyone tied the two systems together? What were the results?

Not on an FD, but my F2000 Zetec-powered racecar uses a combination of air-oil and coolant-oil heat exchangers. The combination is very effective - warms the oil quickly after start-up, and controls the peak oil temperature better than either alone would do.

So as long as you have a radiator that has the capacity to dissipate the extra heat, I would recommend it.

Where did you tie them into the system? Before or after the individual coolers?

I have a dry-sump system. My oil-to-air cooler is on the dry-sump pan exit line (after the scavenge segment of the oil pump) that feeds into the oil tank. You already have air-oil cooling. My oil-coolant heat exchanger is on the hot water exit from the engine and on the pressure side of the external pressure oil pump.

For your setup, I'd place the oil-coolant heat exchanger water side in the hot water exit from the engine, and the oil side before the air-oil cooler(s). That will, IMO, give you the best efficiency, keeping the oil closer to the coolant exit temperature, while allowing the air-oil coolers to still have a good difference between the air and oil temperature. It will also enable warming the oil when it's cold and the coolant is warmer.

Is this your oil cooler kit? If so, they're small. Most other kits have twin 19row or twin 25row (as I have).
Also, proper ducting of the coolers and Vmount is essential to make sure no air escapes around the cores.
https://cimg7.ibsrv.net/gimg/www.rx7...ee71614fd7.jpg

A short term 'spike' in oil to 121c isn't too bad. That is 250f and within the capability of most good synthetics. If it was running that temp for 1/2 hour consistently, then I'd be a little more worried. What is the mean temp? I.e. what is it at most of the time during that run?

Coolant at 107c /225f is a bit more worrisome. What's the ducting situation on that vmount? How long is it at that temp?

This suggests to me a lot of periods in hard boost….similar maybe to a track session? If so, that doesn’t give much time for the engine to shed much heat thru it’s existing systems.
Not sure if there’s a silver bullet answer, but a WI system put an end to the temp spike I saw after periods of hard boost. Might be something to consider.