Hey GRM! I have a K20A2 in my MR2 Spyder I use for time trials / time attack and I am looking for thoughts/input on oil coolers that could possibly be used in place of the factory RSX Type-S cooler I have. Some MR2 Spyders have added an air to oil cooler in the RHS rear fender scoop area. While I could do this it would make some engine servicing more of a pain in the butt and possibly add more drag so it’s not really a desired option, which I why I'm on the hunt for a water to oil cooler.
From previous searches on GRM, I came across the recommendation to use the transmission cooler from a 2500 Ram which I mocked up in cardboard to see if I could fit on the rear subframe. This setup would require a filter sandwich plate and some short -10AN lines, it’s a little tight but would leave me with short oil lines and that cooler is about 10x the volume of the factory “donut” cooler. Another option I thought of was using an oil cooler from a VW 1.8T, just because I happened to have one lying around, it’s about 3x the factory volume and looks like it might fit though it would need a custom adapter machined. The Laminova ECD54 series of cooler is interesting though seems like it would be difficult to fit on the rear subframe which is the preferred location to minimize oil flow losses. I also like some of the options from the Ford V8's/V10 though they have a large thru hole and much larger filter size which makes me wonder if I could even fit them on this motor.
Has anybody else tried to swap oil coolers from other OEM vehicles onto performance engines to help add more heat rejection to the oil system while maintaining the benefits of the OEM water to oil cooler? Am I just over complicating this whole thing and should just add an air to oil cooler in the fender like what others have done?
Keep in mind that oil-to-water coolers running on the same radiator as the engine don't give much cooling power, if you want the same league of cooling you'd get from an oil-to-air cooler you'll need to hook it up to a dedicated radiator which will also need its own water pump and overflow tank. You could use a half-width ("Honda style") radiator or a motorcycle radiator to save space. Oil-to-water coolers also tend to have more pressure drop.
If being able to disconnect the oil-to-air cooler would help with maintenance you might want to consider adding male-to-male AN fittings in the lines somewhere easy to get to, they're a lot cheaper and safer than quick disconnects and not a whole lot slower to disconnect and reconnect.
Also in terms of drag, if you can put the oil-to-air cooler at the back of your radiator stack there's surprisingly little cooling downside to that setup, the fluid it's cooling is hotter than anything else in the stack so it's not a big deal that it's starting with relatively warm air.
kb58
UltraDork
3/30/24 1:10 a.m.
My Midlana car uses a mid-mounted turbo K24, so it has the same issue as you. I used an oil-to-coolant heat exchanger from BAT and it worked great. After start-up, coolant warms up faster than the oil, so it helps oil temperature come up faster. Once up to temperature, oil temperature cannot stray far from coolant temp regardless how hard the engine is run - assuming that the (front-mounted) coolant radiator is up to the task. If I built another mid-engine car it would use the same cooler. I would not count on being able to duct any useful amount of cooling air into a rear engine compartment - unless you use a roof-mounted intake duct.
To stay on-topic, I did not use an OEM-style exchanger because I wasn't confident that it could handle the heat load of the turbo engine.
Well, because Honda, and their use of a single oil filter for basically everything, you might be able to find an OEM solution for the sandwich piece from a sport bike like the cbr1000.
@GameboyRMH: The male-male union idea does seem like it could help add serviceability.
@kb58: That's why im interested in the water to oil cooler, I'll see if I have room to run the BAT style cooler. I was hoping maybe somebody else had "frankenstiened" different oil coolers onto an engine because I like the simplicity of not needing to add oil lines.
Looking back at some track data, I may only need a little bit more oil cooling because the oil temp climbs to 250*F (where I then do a cool down lap) after about 3-4 laps in ~90*F ambient around Road Atlanta, though this was before fully ducting the radiator. In cooler weather, ~60*F the oil temperature appears to stabilize at around 240*F during full session at Road Atlanta. Maybe I'll go scrounge around a junkyard with a measuring tape and wrenches to see what might fit the K20 but be a little bigger than the factory cooler.
Came for square body content. I'm disappointed.
Robbie (Forum Supporter) said:
Well, because Honda, and their use of a single oil filter for basically everything, you might be able to find an OEM solution for the sandwich piece from a sport bike like the cbr1000.
Same as Subaru EJ engines too.
Those oil temps aren't so bad, maybe test with your ducting and see what temperatures you're getting now. If you can get them to settle around 250 on long stints that's totally acceptable, that's what my Toyobaru with a big oil-to-air cooler gets.
