Project S2000 – Part 9 – Oil Cooling

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There are two common approaches to installing an oil cooler on a typical street car.  Probably the most common method is mounting it right smack in the middle of the main bumper opening at the very front of the car.  I deep-sixed this idea for a number of reasons which I will explain in a bit.  The second approach, and usually done on cars designed from the outset with an oil cooler (Evo, Porsche 911, etc), is to mount the oil cooler off to the side of the main opening and in front of one of the front wheels.  On the S2000, both the AP1 and AP2 generations have blocked off side openings in the bumper that can be opened up and used to feed air to the oil cooler if the cooler is placed in the side location.

As I’m adding a big oil cooler, I’m ditching the stock oil-coolant heat exchanger (donut); it serves to warm up the oil faster on cold startup and cool the oil once everything is up to temperature.  The coolant typically stays at 90C on the AP2 and the oil at 100C when highway cruising in warm weather with the A/C on.  So when the coolant is warmer than the oil, such as when the car is first started up, the oil gets warmed up more quickly which helps reduce fuel consumption.  When the oil is hotter than the coolant, the coolant serves to take heat out of the oil.  In the place of the stock donut, a Mocal sandwich adapter with a 180F thermostat and -12AN fittings is going in. (EDIT: It turns out Mocal sells a sandwich adapter with a 200F thermostat which is a special order item.  I would have prefered the 200F option.)

A 30mm socket is required to take off the bolt that holds the stock oil donut.  In its place is the shorter stub which is a Honda OEM part.

I eliminated this idea for three reasons.  The first reason is that those openings could be used for brake cooling ducts instead.  The second reason, a side mounted oil cooler would require ducting to be fabricated and also the fender liner to be modified to allow an escape path for the air; I’ll admit, I can be lazy and didn’t want to do that much work.  The last reason, I wanted the option of using that space for some piping in the future that would go along with a big power upgrade.

In removing the stock oil donut, I used a pair of vice grips to pinch off the two coolant lines that went to the donut.  This allowed me to remove the donut and then drain the coolant in a controlled manner.  I have already installed the new stub in this picture.

Back to the front mounted option.  The first issue I ran into on the S2000 was packaging; there’s just too much stuff in the way of where I’d ideally like to mount the oil cooler which limited the possible size.  Like I’ve mentioned before, I can be lazy (well, work smarter not harder!).  I didn’t want to relocate anything I didn’t have to which involves more work.  As this car is my DD, minimal downtime is the goal which means minimal work.  I also have limited tools (drill, hammer, dremel, and an angle grinder), so I try to avoid anything requiring more serious fabrication work.  Secondly, I wanted some of that space free for something else to go there in looking forward to a possible big power upgrade.  Lastly, the flow path of the air and temperatures were taken into account.

On street cars, we typically have an A/C condenser and radiator.  Now we’re also throwing in an oil cooler.  You typically want the A/C condenser as cool as possible to maximize A/C system performance.  The coolant system of the AP2 S2000 tries to maintain a coolant temperature of 90C.  A good temperature for oil is around 100C and the stock Honda oil cooler donut keeps it right at that temperature during highway cruising in ~85F temperatures.  So, in importance of getting as cool of air as possible, it goes: A/C condenser, radiator, oil cooler.  To some companies like GM, maximizing A/C performance is so important that they put the intercooler of the turbo Chevy Cruze BEHIND the A/C condenser!  A/C performance takes precedence over engine performance for them.

Let’s look at things another way.  If you had the option of overheating your coolant or your oil, which would you choose?  The oil of course.  Overheating your coolant leads to a blown head gasket pretty quickly whereas most guys that track their cars don’t even know they’re cooking the oil and their cars still make it home.

The Mocal sandwich adapter installed with the Ark Design adapter for the oil pressure and temperature sensors.  The nipples for the coolant hoses are actually about 14mm diameter, but 1/2″ (12.7mm) ID heater hose will slide over without too much trouble.