Project S2000 – Part 9 – Oil Cooling

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Let’s look at the scenario of the oil cooler in front.  I recorded oil temperatures of over 130C at the track.  Air flows through the oil cooler getting heated up and now flows through the A/C condenser.  On the street, this reduces the performance of the A/C system as we now have warmed up air hitting the condenser. On the track, the A/C is off, so we can ignore the condenser, but now we have hot air hitting the radiator.  Let’s pretend the air coming off the oil cooler is 100C.  100C air hitting the radiator does absolutely nothing to reduce the temperature of the coolant if the coolant is also at 100C.  If the coolant is at 90C, then the air coming of the oil cooler would actually heat up the coolant!  I actually have no clue what the air temp coming off the oil cooler would be (depends on ambient air temp, oil temp, oil cooler effectiveness, air flow rate through the cooler, oil flow rate), but I made up that number to illustrate the concept.

Okay okay…. I’ll guesstimate the numbers a little more closely.  If the oil going into the cooler is 130C and the air temp is 30C, then the air coming off the oil cooler has to be somewhere in the middle.  I could calculate it based on a guess for oil flow rate, knowing the specific heat capacity of oil, knowing the size of the cooler, guessing an effectiveness of the oil cooler, and flow rate/speed of the air (and specific heat capacity of air) going through the cooler.  The faster/more volume of air going through the oil cooler, the cooler the air will be coming off of it.  Without making any real calculations, a slightly more accurate guess would be the oil temp dropping from 130C to 100C and the air temp rising from 30C to 50C (which is highly dependent on airflow rate).

The front end of the car.  I’m saving the blocked off openings for possible future use.

In the middle of the main opening is the horn and the A/C dryer (at least I think it’s the dryer).  As they are right smack in the middle, they prevent putting a big oil cooler there.

So, I opted to put the oil cooler behind the radiator.  Using some make pretend numbers again, let’s say the air coming off the radiator is 50C.  If the oil is at 130C, then the oil will still be cooled by the 50C air.  Not as good as fresh air at 30C, but still a big temperature difference of 80C.  This is a preferable situation compared to having the oil cooler in front where the temperature difference between the air coming off the oil cooler is 50C and the coolant around 100C.  That’s only a 50C temperature difference.  Heat transfer is all about temperature difference; the larger the difference, the greater the heat transfer.

To enable the oil cooler to fit, I had to get a SPAL 11″ slim fan to replace the stock one.  I cut off the stock connecter from the stock fan and wired it up on the SPAL.