LCubed
LCubed GRM+ Memberand New Reader
3/29/24 11:46 p.m.

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?

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
3/30/24 12:23 a.m.

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.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
3/30/24 12:28 a.m.

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
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.

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
3/30/24 10:38 a.m.

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.

LCubed
LCubed GRM+ Memberand New Reader
3/31/24 12:12 a.m.

@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.

Stampie
Stampie GRM+ Memberand MegaDork
3/31/24 8:18 a.m.

Came for square body content. I'm disappointed. 

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
3/31/24 8:22 a.m.
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.

 

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
3/31/24 1:39 p.m.

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.

RSXSTurbo
RSXSTurbo New Reader
1/10/25 3:40 a.m.

I really hate to bump an old thread. I've picked up this exact project unfortunately but in a high boost water cooled turbo rsx. I don't want to add an external cooler, I don't have the room for it nor do I want to experience any sort of oil pressure loss since I'm no professional. Was there any luck in the search for a better oem style cooler? I don't need one to lower temps, I need one to work with my an hose conversion. I have converted EVERY single hose to ptfe an hoses with the proper sizes and fittings. Took me days to do it all, but I'm down to the last piece. That oem oil cooler. As you know it has 1/2" barbs, I need it to match my 10an hoses back there. I first looked at Aeroflow's 1/2" barb to 10an adapter, seemed like a great idea until I heard they don't fit Japanese hose barbs. Moved on to the next idea, T7 engineering 10an adapter plug kit for the joint fittings on the block. Great idea but still leaves me with two 1/2" barbs on the oil cooler. If anyone knows of an aftermarket sandwich plate that is designed similarly to this oil cooler please let me know as they come with 10an fittings already machined. Would save me money, head ache on tons of fittings configuration, and obviously better cooling with an aftermarket oem style cooler if it exists.

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
1/10/25 2:40 p.m.

In reply to RSXSTurbo :

Any type of remotely conventional oil cooler is going to cause some pressure loss, an oil-to-air cooler will cause a little and an oil-to-water cooler will cause more. The only way to cool the oil without any pressure loss would be to cool the oil in a part of the system that isn't pressurized, like the return side of a dry sump system or with some kind of dedicated oil cooling loop attached to the pan. A good oil-to-air system will cause a negligible amount of pressure loss.

If you just want to hook up another oil-to-water cooler with AN fittings it shouldn't be too hard to find an aftermarket one with the fittings you need, or at least good adapters available. What fittings does the stock cooler use for coolant? And I'm assuming you've switched to AN fittings for coolant as well, and the oil is now 10AN?

LCubed
LCubed GRM+ Memberand New Reader
1/10/25 10:25 p.m.

Not sure this will help you RSXSTurbo, but I did manage to swap an EJ25 oil cooler onto the K20 after designing and machining a custom threaded adapter. The oil filter between the two motors is the same shape but the EJ25 cooler is about 3x the volume. I haven't been back to Road Atlanta when it's hot enough with the new oil cooler to see how effective it is. Anecdotally, it seems to cool off faster during a cool down lap, I'm just not sure if it can keep up where the OEM K20 cooler couldn't.

To add AN fittings to the cooler have you considered weld bungs? Could probably weld to the end of the barb without damaging the brazed connections.

wvumtnbkr
wvumtnbkr GRM+ Memberand UltimaDork
1/10/25 11:14 p.m.
GameboyRMH said:

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.

Water cools much better than air.  

From my experiences with endurance road racing, the stock gm water to oil cooler (right at the filter) work wonderfully and oil temp is always within 15 to 20 degrees of the water temp.

z31maniac
z31maniac MegaDork
1/11/25 1:51 a.m.
LCubed said:

@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.

250 wouldn't bother me with regular changes using quality oil. Are you monitoring pressure at that temp as well? 

My N55 135i the stock oil cooler thermostat didn't OPEN until the oil hit 240. 

You'll need to log in to post.

Our Preferred Partners
IgYziJ4x8nBVG15Ixi8UODeulcqWuw2xvybOFBQgTMjEdE5d6474WmPrxsxcyGwP