Oil Cooler recommendation

team-gpracing

team-gpracing

Well-known member
Hey guys, I've been having some oil cooler issues and I'm hoping to get some recommendations from my Prod brethren.

We're running fairly high pressure and can't seem to keep a cooler in the car. Stock aluminum Mazda 2nd gen coolers have failed at lower pressures, so I tried the Chinese eBay ones. You can guess how that went. I finally decided that I would contact Setrab. Before the most recent race, I purchased a cooler from them that had an operating pressure of 145, and max of 165. It didn't last the weekend. The cooler failed and caused me to spin and catch on fire. Not fun.

We're going to reduce the pressure in the engine before the next race but is there anyone else out there that runs high pressures that can offer some recommendations on brands?
 
Where are they breaking? With high pressure like that we found that we had to secure the hoses to the body much better and close to the cooler fittings.
 
I think the first question to answer is........Why are you running so much oil pressure? I've never heard of a production engine requiring so much pressure to maintain the hydrodynamic fluid journal to bearing insert clearance.

That kind of pressure consumes a LOT of horsepower and really heats the oil excessively at the same time. I'm wondering if you reduced the oil pressure to say 70 psi hot if your oil temp wouldn't also drop quite a bit (since you are not compressing it and therefore heating it) at the same time solving your problem.

FYI......I believe that the air cooled flat 12 Porsche 917 engine was designed to run on super low oil pressure at WOT (35psi) for these reasons.

Just de-shim (is that a word?) the pressure relief valve.
 
Running any oil pressure higher than what is required to eliminate bearing scuffing is a performance disadvantage.
 
Joe, they are breaking in the lines/fins. The connection points are fine.

Jay, thanks for the info, I never thought that it would be a performance hindrance. We are indeed going to take a shim out to bring some pressure down.
 
Mounting is critical too.

You don't want it under any tension. For example, mounted on both top and bottom where the thing it's mounted to might flex. Same idea with the lines.

-Kyle
 
I mounted the Setrab per their instructions, with bushings. And the lines have plenty of room to move if necessary.

The Mazda and ebay coolers mounted in the stock location, so no issue there.
 
I'm with Jay. Way too much pressure.

FWIW, Ford flathead rod bearings were full floating (babbitt on both sides) and oil pressure over 60 PSI would wash the babbitt off the bearing.

RJS
 
Racing Beat sells a 105-115 psi racing only oil pressure relief valve for your rotary. I think they know a little about what works best. I run a TRU-Cool oil cooler because it seems to have a little tougher construction than some others.
 
Very good point Tom.......the Racing Beat guys are pros.

Call them to find out if and why you need such high oil pressure. And then what cooler works. Maybe dropping to 110 psi will allow the Mazda unit to live.
 
Yes - those pressures are crazy. Most pumps need a pressure relief, especially when the oil is cold and the start pressures will be higher. I have heard of Spridgets blowing up a Fram oil filter when the relief plunger was jammed shut...I don't think there is anything going on in rotary to require that psi - but Racing Beat will know. Fix the cause rather than spending big dollars to fix the results.
 
120 pounds is normal for a prepped rotary. Anything higher is overkill. Jesse Prather builds my motors and they are set at 120+/- with no problems.
 
I have been building performance rotary engines for over 30 years. The optimal range for oil pressure is 80 to 110 lbs. The higher range for high horse power bridge port and peripheral motors. Any more than that and you will have bearing issues and oil cooler failures. Not to mention horsepower loss which every little bit counts. Pineapple Racing makes a tool to test oil pressure without filling the engine and running it.
 
You didn't say when the cooler failed. What was the oil temp and RPM when it failed.? Warm the oil temp up to 130 MINIMUM before adding anything more than 2,500 RPM. Cold oil is very destructive under high pressure, hydraulic hammers.

Is it possible the cooler is too rigidly mounted in an area where you may have chassis flex. I broke a large radiator at Rockingham, NC. Exiting the infield with too much impact on entering the banking caused the front frame to flex and broke the cooler. It was a very abrupt transition angle on the road to banking, no blending to soften the impact.

Don't understand the reason for such high pressure. Reference the Mazda Comp instructions for their recommendations, you are well over their suggestion. Max should be about 10 pounds per 1,000 RPM. As others have said it adds to increased energy consumption (loss of HP), increases oil temp, and can be destructive to the bearings and oil coolers.
 
John, we were half way through the session when the cooler failed, so the temps were at operating. The cooler is mounted from the top, to the front engine brace with bushings as Setrab dictates. When it failed, I was at a smooth portion of the track, heading into a turn.

Don Walsh, we're using a 110 psi regulator and it is shimmed to allow more flow, so the motor is at about 115 at idle and at full load is around 135, so like I said, we're going to remove the shims to get it back to around 110.



I appreciate the info guys, and I am planning to bring the pressure down, but my question was more along the lines of cooler recommendation. I have had terrible luck with coolers. I went through three of the Mazda and eBay ones with my last motor, which wasn't running this high of pressure (80-100). I chalked that up to old/cheap coolers. Now I've gone through two with my newer motor. That's why I went with the Setrab.
 
I mount my cooler from the bottom but all the way through the cooler with all thread . Lines are supported about a foot from the cooler. Had two failures with mocal coolers, switched to setrab and haven't had a problem since.
 
team-gpracing":15dlq7py said:
Don Walsh, we're using a 110 psi regulator and it is shimmed to allow more flow, so the motor is at about 115 at idle
Click to expand...

Have you replaced the eccentric shaft oil squirter spring & check ball with a 200 weber air jet? This seems to be universally recommended to increase rotor cooling. I suspect it hasn't been done if you're seeing 115 PSI at idle.

For what it's worth, I have never had an issue with either oil coolers or lines and use the unmodified Racing Beat pressure regulator. I use the stock second gen RX7 oil coolers.
 
mstutt":2oelhejy said:
Have you replaced the eccentric shaft oil squirter spring & check ball with a 200 weber air jet?
Click to expand...

Yes.

Aaron, is there any concern with pinching the cooler when through mounted on the studs? Do you have a picture? Mine is only mounted from the top.
 
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