Adding a second oil cooler
 

I currently have a setrab oil cooler and I want to add a second one. Can someone advise on how to go about running the lines? Is a thermostat required?
Thanks

A thermostat isn't necessarily required but it is advised. The cooling power of twin 19s without one will give EXTENDED warm up times. Really extended.

To add a second cooler you can reference the scientific diagram below. For ease of install you can use a 10AN union and build off of what you already have instead making a whole new line. If you choose not to use a thermostat then the lines will simply go straight. Keep in mind that there is a TO and FROM with a thermostat. Majority of the time they will be labelled. the FROM and TO are in reference to FROM the cooler and TO the cooler. Front housing is your TO and oil filter is your FROM.

https://cimg3.ibsrv.net/gimg/www.rx7...de814dedcc.jpg

Remember to block off air flow to the second one for winter.
If not, your oil most likely will run too cold.

lol I appreciate the scientific drawing... Would just any thermostat work or does it need to be a specific one.

@cewrx7r1 I'm in TX so most likely that won't be necessary but weather is changing so could possibly apply.

We like the mishimoto. The mocal has given us some stupid issues in the past so moved away from it. The improved racing one is nice but really expensive. Any 10AN 180F thermostat will work but we would advise sticking to name brand "performance" parts. The mishimoto has swappable temperature options if you ever decide to have it open at a cooler temperature for some reason. It's default 180F.

Stock duals from an R1 or R2 work great and fit perfectly. I've had no overheating issues ever with mine, even during track days in the middle of the California desert. Just make sure they're ducted properly.

Cheap, simple, OEM, and unless you're making big power, works just as well as the expensive kits. :nod:

Thanks for the recommendations. Would there be a benifit to add small 300cfm fans behind the coolers to turn on when stopped or in traffic? I was thinking that the Haltech 1500 could switch it on and off based on a certain signal.

not really. i had an oil temp gauge in my R1 for a while, and oil temp basically tracked with speed, if you're over ~20mph temps were fine. so you could put a fan on, but it wouldn't run very much

Noted.. Makes sense

Reference pictures from my one off Scrubby McBubbles dual setrab kit with Improved 185* thermostat

https://cimg5.ibsrv.net/gimg/www.rx7...8bf845a8d3.jpg

https://cimg4.ibsrv.net/gimg/www.rx7...56cc34f604.jpg

https://cimg0.ibsrv.net/gimg/www.rx7...640b382938.jpg

https://cimg5.ibsrv.net/gimg/www.rx7...edb0f7fdc4.jpg


https://cimg1.ibsrv.net/gimg/www.rx7...d0857682a3.jpg

https://cimg8.ibsrv.net/gimg/www.rx7...549aa33c61.jpg

I went with the Improved 165* thermostat. It starts to open at 160f, and gives full flow at 181f. OEM opens at 150f, and the Mazda performance recommendations are full flow at 180f. Please correct me if I'm wrong. I also deal with ~90f+ ambient temps so I need some extra cooling capacity

Bear in mind those temps are relative to the cooling capability of the coolers themselves. Twin 19 row coolers vs the oem, the 19s will outperform. So having the aftermarket coolers open so cold isn't really necessary considering they will cool better than stock.

The stock twin coolers having full flow so soon may be whats needed for them to work as far as heat dissipation. Not saying they're bad, because they're not, but a taller cooler will work better than a shorter one and shouldn't be treated the same as a shorter one.

Having the twin 19s run full flow at 16xF is way too cool. If you're not monitoring oil temp, you should. Also look into what temperature your weight oil is optimized for. You may be running "cold" oil with the thermostat running so cool.

Even here in Florida in the balls death heat of summer, twin 19 row 180F thermostated coolers will maintain sub 190F temps. Sitting still or on the highway they work very well.

FDAUTO's diagram is on the money, and how my setup has been for 20+ years,

For the record, Mazda Competitions recommends Oil Temps:

• NORMAL: 195-230
• MAX LIMIT: 250

Personally been running a Mocal A0T2-10 (-10AN inlets/outlets) w. the 180F opening last 20-ish years. Stock front bumper, twin Mocal coolers, Mocal AOT2 Oilstat, and custom cooler ducts, and my oil temp tracks 10-20F above Coolant Temp (170-190F), including up to 100F in Dallas. That said, I don't have much data with ambient temps <50F. Maybe this year.

A guy who runs 6s in the 1/4 in a rotary said you can't damage a rotary with low oil temperatures (140*F). With his decades of experience and that everyone tends to run thick 20W50 weight oils, and since only the e-shaft with wide bearings is lubricated, it kind of makes sense... I have not read or seen any bearing damage from oil being too cool.

Issues I see with very low oil temps -

- Oil is thicker and the engine uses more power to overcome the thick oil so there is a bit of a loss in horsepower
- Cool oil temps will also mean lower water temps quite possibly since rotaries do so much cooling with oil. If the car runs cooler than standard operating temp you will still be in startup enrichment so the car will be burning a LOT more fuel.

Dale

issue #3 is that the thermal pellet in the E shaft opens at 65c...

Not an issue as long as your oil thermostat opens after 149, right? Or, replace the pellet with a plug

-uses more power, probably insignificant compared to the issues with oil temps being too high.

-maybe slightly longer warmup periods but I doubt running big coolers and a 140*F thermostat would really cause any issues with the water temps, especially if you have a thermostat in your coolant system. I don't think anyone ever complains about issues with rotaries running too cold.

I have an oil temp gauge and with the mocal it would be tough to get the car up to oil temp unless I start beating on it. I live in a populated area so this isn’t ideal. Cruising around and seeing oil temps at 100f was concerning. Covering the passenger oil cooler raised temps some.

I swapped to an Improved racing Tstat and get 160 cruising and 185-190 when having fun. 210 when flogging it.

I have 25 row coolers unducted. I do have FEED ducts ready to go in if my car starts to get warm as I track my car and push it harder.

For the street you definitely want at least a 140* thermostat, which is what I'm using.

Where are you measuring your oil temps?

I measure mine at the oil filter pedestal.

So depending on how effective your oil coolers are, your actual oil temps could be 20-40* higher.

You should measure your oil temps in the pan, not post-coolers.

With the dual stock oil coolers, my oil temp measured at the filter pedestal is consistently 140-150*F (this winter, 40-50*F ambient) while cruising on the highway. Is that bad?

That's the temp of oil going into the engine. What we really need to know is the oil temp the engine is operating at (oil pan). Most numbers on this forum are at the oil pedestal mount which will vary greatly on the size, ducting, and effectiveness of the coolers. None of which actually tells us how hot a given engine is running.

Appears to be no rubber mounting used there on that kit, or you haven't used them? I'd make a point in ensuring that any heat exchanger is not subject to vibes......always costly ramifications if they crack.