slc oil coolers

I used the same coolers as use on my 427 cobras. Thanks to a cue from Cam for 27 dollars I got shields from ebay for the grazziano, blasted them and they are like new. I am waiting on a 120 degree fitting for the transaxle cooler.slc 003.JPGslc 004.JPGslc 002.JPGslc 001.JPG
 
clean and simple. I see so many put massive coolers on these cars yet OE transaxle coolers are so small (or non existant).
has anyone done temp measurements on these transaxles to see how hot they are getting??
 

Howard Jones

Supporter
I have a G50 (Quaife TBD) in my SLC (450HP) with a temp sender in it and the gauge has never read more than 225F or so. I also have a cooler on my R21 Renault (Single shaft upgrade and Quaife TBD) that is in my GT40 and I have never seen the oil in it above 180F and without running the circulation pump. If I turn on the pump then the oil temp in the GRBX drops way down to the 160F range.

I have been told that friction type LSDs run 20-30F hotter than Torque Bias Differentials style limited slip systems.

These data points are both on several 100F days. I have concluded that in the case of my GT40 (350 odd HP) that either the power being transmitted through it isn't enough to heat it or in both cases the run time isn't long enough. The above data was all on track and with 20-30 min sessions with at least an hour setting in the paddock with the rear body opened. Doing this drops all the fluid temps well below 120 -150F. I did run one 45 min session a month or so ago a COTA with my SLC and the temps were still well below the range that I believe the GEBX oil is damaged at. However on that day the air temp was in the high 70sF.

I believe that on a street car they are not necessary IMHO. On a track car with high HP (>550ish) and run for fairly long sessions, something like 1 hour or longer, then maybe. Long runs such as 4 hour or longer endurance races then they more than likely are necessary.

My advice would be to install a GRBX temp sensor and gauge and monitor what you have. I would recommend GRBX oil should be held at 225F - 275F with a max of about 300F. I am not a oil expert so I will add this link below.


 
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Thanks Howard and thanks for the video of your car tracked at COTA. It is my understanding that the grazzianos have some sort of internal pump in them hence the fittings or plugs that came in it for circulating the oil. It was either loop it on the transaxle or send the lines to the cooler and I figured easier now then later to install the cooler. I agree a street car probable does not need a cooler, only the true oil temp would tell. In my vintage cars during fender to fender competition I have seen as high as 275 degrees on engine oil temp and based on change in transmission performance probable the same. I don't expect that in this car, but after watching you at COTA I have to take it to the track! it will be high plains raceway.......................m
 
probably the best solution is to feed the oil to a water to oil cooler. I don't run a heater in my car, and using the heater loop is a convenient way to make that happen if I chose.
 

Howard Jones

Supporter
A very knowledgeable engine builder when asked told me that the oil pulls out about a 1/3 of the total engine fluid cooled heat load with the other 2/3s going into the coolant. I tried the heat exchanger method and ended up changing over to a normal air to oil cooler for the engine oil. I didn't like the idea of dumping all that heat back into the coolant at the same time I was trying to optimize coolant temps with a new and expensive radiator.

Without a total aero drag performance concern why not put that oil heat into the air instead of back into the water. However I do believe that all these mid engine SLC 's will need a oil cooler. There is just to much heat retained in the engine room with all that exhaust heat and lack of air flow.
 
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Without a total aero drag performance concern why not put that oil heat into the air instead of back into the water.
If you use the heater circuit for the oil coolers, it will get your oil up to temp quicker. I suspect most every engine builder will agree that is desirable. You may also get by with much shorter oil plumbing runs with oil-water.

If you run an oil-air cooler, you probably want to run a thermostat on it. Of coarse that is one more possible failure point. No free lunch!

However, with oil-water you DO need to have enough radiator capacity. I ended up putting a second radiator on one of my side vents. That along with a few other changes took care of my cooling issues. But with water cooled Turbo, 2 x waste gates, oil-water heat exchangers, 2 radiators, 2 water pumps, it is a plumbing nightmare.

Can't blame folks for taking the KISS approach.

As for needing an oil cooler, put in an oil temp gauge and see!

If you have marginal cooling, a simple oil cooler in a side vent may be all the extra help you need.
 
I realize after running my gt-40's that heat in the ass end is a problem. I saw that RCR offered some louvers that take up part of the rear glass or lexan on the clam shell on the left and right sides, narrowing the rear glass. they are louvers and looked pretty good. I imagine they let out a lot of heat and I will be coming up with a similar solution. If anyone is running those please let me know your thoughts...........m
 
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