Project S2000 – Part 9 – Oil Cooling

Project S2000 – Part 9 – Oil Cooling

Project S2000 – Oil Cooling

by Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

Tracking the S2000 and monitoring the oil temperatures has taught us one thing: it runs hot!  Even with the reduced coolant temperatures afforded by the Koyo radiator, the oil temperatures were still too high for a car to be tracked for long-term reliability.  This is occurring at completely stock power levels even (the more power an engine makes, the more heat it makes and consequently needs to reject).  High oil temperatures lead to reduced oil viscosity and faster oil breakdown.  Low oil viscosity can mean inadequate oil film strength and thickness with the end result being metal-on-metal contact between engine components.  While low oil viscosity may not grenade your engine immediately, it will lead to accelerated wear of components.

I tried a band-aid approach of using high viscosity oil (15w-50) relative to the recommended fill (10w-30) for my track day in the summer heat of the desert.  This approach may solve the oil viscosity and pressure issue, but does not address the issue of oil breakdown with excessive temperatures.  Also, rod and engine bearings are made of relatively soft metals that don’t take well to being heated to high temperatures.  Lastly, high oil temperatures mean a hotter running engine leading to a higher propensity for detonation.

I decided on an Earl’s Temp-A-Cure oil cooler.  This line of coolers was designed for the typical air speeds and oil flows seen in automotive use.  They’re made of high grade aluminum and are furnace brazed to create the most thermally efficient joint possible between the tubes and fins.  Earl’s choice of fin density was selected to maximize heat transfer to the outside air.  I’m using a 34 row cooler with a 10.5″ height and 13″ width.  I also opted for the optional mounting bracket kit.  My old roomie left behind a roll of rubber that had adhesive on one side.  I applied the rubber strips to the surfaces that would come in contact with other objects when mounted.

The S2000 engine, along with other high performance engines, uses piston oil squirters.  The purpose of the piston oil squirter is to spray oil at the back side of the piston and reduce the temperature of the piston.  A cooler piston reduces the likely-hood of detonation.  Spraying cooler oil at the piston is obviously better than spraying hotter oil at the piston.

So we can see that the benefits of running oil at its proper operating temperature are multifaceted.  Doing so will extended the service life of the oil, reduce engine wear, and reduce the likelihood of detonation.  Now the challenge was to figure out an oil cooler setup for the S2000 that fulfilled the role of both a daily driver and track day vehicle.

Earl’s -12AN Auto-Fit Ano-Tuff fittings use a military spec hard anodized coating for corrosion resistance and toughness.  The fittings were paired with Pro-Lite 350 hose.  When assembling the fittings to the hoses, remember to use either some motor oil or Earl’s assembly lube.  Installing the fittings onto the hose was a snap. 
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17 comments

  1. Why did you choose such a big oil cooler? the aftermarket does not offer such large applications.

    Does it have to do with the flow rate of the s2000’s oil pump at high rpm?

    I have oil cooler setrab of 18 lines and I see that after 5 minutes on the track the pressure drops to 64psi in vtect and the temperature to 233f

    my car is supercharger kraftwerks and the oil cooler is located behind the supercharger intercooler

    thanks

    Reply

    1. Part of the reason was because I put the oil cooler behind all the other heat exchangers, so it was getting the hottest air. Check out the article that is Part 23: Testing air temps through coolers and vents. I also only had one chance to do this setup without testing various combinations, so I went large to be safe. The benefits being more cooling, greater oil capacity, and less pressure drop. I don’t think I’ve ever seen below 75-80psi in the VTEC transition with oil temps at 240F.

      Reply

    1. Use an oil cooler with more rows. The greater number of rows, the lower the pressure drop and the more cooling. Also, what size lines are you using? I’m using -12. Lots of kits use -8 which is too small in my opinion. I would say at least -10.

      Reply

      1. Why does a greater number of rows equate to a lower drop in oil pressure? Is it because the greater number of rows allows for more paths for the oil to flow and thus less restriction to flow? Also, If I were to take a 30 row oil cooler core and make it into a triple pass where each pass has 10 rows, would that create a pressure drop equivalent to using a 10 row single pass cooler?

        Reply

        1. Pressure drop is a function of velocity and distance. Pressure drop increases to the square of velocity. And the longer the distance, the greater the pressure drop. So with more rows, you have more flow area, which reduces the velocity for the same mass flow rate.

          A 10-row single pass would have less pressure drop than a 30-row triple pass, assuming the cores are the same width. This is because in the 30-row triple pass, the flow distance is triple the 10-row assuming the cores are the same width. And there’s going to be additional pressure drop each time the oil has to make a turn in the triple pass.

          Reply

  4. I use a line of 16 lines behind the intercooler of my kraftwerks kit and the car easily goes up to 240f.

    ask, if I add one of 42 lines behind the radiator with a fan, the temperature will I be able to control it better? What do you recommend doing to keep control of the oil temperature of my car?

    The water temperature is stable at 220f

    Reply

    1. Bigger oil cooler will certainly help. But you also need to address your coolant temps which are too high. Consider that that fans turn on at 212F. Sure, you CAN run at 220F, but it reduces the reliability of your engine and hurts power. My car is naturally aspirated, but coolant never goes over 190F even when I did track days in 103F temps. Make sure you have your heat exchangers well sealed (I used foam stuffed around them) and you certainly need a vented hood if you don’t have one already.

      Reply

      1. hello I have a question I am using the original car water radiator thermostat, would you recommend changing the sensor to a mishimoto of less temperature? I use the street car too

        Reply

        1. No, changing to a lower temp thermostat does nothing for reducing temps at steady state conditions. It just delays how quickly the temp will max out.

          Reply

  5. A friend suggested to me a rather convelling idea about oil cooling: If for example we keep the original donut (oil cooler) to circulate water (circuit with a radiator on the bumper, and an electric pump that activates with a mano connected to the oil temperature) .. What do you think?

    Reply

    1. Yup, should work just fine. Keep in mind the OEM setup is circulating 190degF coolant. If you have a separate circuit with front mounted radiator, it should cool the coolant down close to ambient. So figure it’ll be at least 80degF cooler coolant compared to the OEM setup. You might need a variable speed pump to regulate the oil temp and not cool it too much under everyday driving conditions.

      Reply

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