RX7 Oil Cooler
RX7 Oil Cooler Howdy. I've got my LS1-powered 944 up and running. One issue I'm having is over-cooling of the engine oil. Like some others on here, I'm using a Mazda RX-7 FC unit with an integral thermostat which seems to open around 140 F. On track my oil isn't even getting over 150 F which is too cold. Does anyone know of a replacement thermostat for the OEM RX7 oil cooler that opens more like 190 F?
Thanks,
Rich
Thanks,
Rich
That must be a heck of a cooler!
Maybe call a thermostat manufacturer like Stant - they might be able to find you something warmer. The thermostat is probably a common design, which they have it warmer temperatures.
If you're unable to find a warmer thermostat, you can always run an external one.
Maybe call a thermostat manufacturer like Stant - they might be able to find you something warmer. The thermostat is probably a common design, which they have it warmer temperatures.
If you're unable to find a warmer thermostat, you can always run an external one.
Howdy. I've got my LS1-powered 944 up and running. One issue I'm having is over-cooling of the engine oil. Like some others on here, I'm using a Mazda RX-7 FC unit with an integral thermostat which seems to open around 140 F. On track my oil isn't even getting over 150 F which is too cold. Does anyone know of a replacement thermostat for the OEM RX7 oil cooler that opens more like 190 F?
Thanks,
Rich
Thanks,
Rich
Andrew
Thanks for the thoughts, Guys. It is quite a cooler.
But I'm not finding a higher temp thermostat to put in it. Those rotary engines really cook their oil so the factory thermostat opens at 140 F. I will probably have to resort to an external thermostat. This is a pain as I'm running an external filter and accusump in the same loop of oil lines with the cooler. This is because this application of the LS1 requires a custom pan that doesn't have a filter boss, just in/out AN fittings due to clearance with the headers.
Here she is almost ready to roll. The nose panel is a custom fiberglass deal with vents, not painted yet. Clearly I've over done it on my oil cooling.
Thanks,
Rich
But I'm not finding a higher temp thermostat to put in it. Those rotary engines really cook their oil so the factory thermostat opens at 140 F. I will probably have to resort to an external thermostat. This is a pain as I'm running an external filter and accusump in the same loop of oil lines with the cooler. This is because this application of the LS1 requires a custom pan that doesn't have a filter boss, just in/out AN fittings due to clearance with the headers.
Here she is almost ready to roll. The nose panel is a custom fiberglass deal with vents, not painted yet. Clearly I've over done it on my oil cooling.
Thanks,
Rich
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TECH Resident
Joined: May 2004
Posts: 792
Likes: 2
From: SoCal
Rich,
What was the amient temperature on that track day? Taping up coolers and radiators is not uncommon on track cars when the ambient temps are low.....Though that's not usually a problem here in SoCal. Perhaps a sliding panel of some kind for easy adjustment? Yeah, that RX7 is a heck of a cooler; some of the Porsche 914-6 guys use them because they're so big, which is good for an air cooled motor like that.
Andy1
What was the amient temperature on that track day? Taping up coolers and radiators is not uncommon on track cars when the ambient temps are low.....Though that's not usually a problem here in SoCal. Perhaps a sliding panel of some kind for easy adjustment? Yeah, that RX7 is a heck of a cooler; some of the Porsche 914-6 guys use them because they're so big, which is good for an air cooled motor like that.
Andy1
It was a sunny 60 degree day. So yeah, temps were low and reducing airflow to the core would let it heat up. For the short term I'm going to just put the original non-vented nose panel on which will have that effect.
In the long term, I'll probably have to add an external thermostat. I'd like to have lots of cooling headroom but have the system automatically compensate for cold days. Given the single loop I have currently, adding the thermostat is a bit tricky. Do y'all think it's work properly if I hooked it up without the return oil passing through it? Basically as a Y instead of an X?
Here's Mocal's installation instructions:
http://www.racerpartswholesale.com/d...hermostats.pdf
Thanks,
Rich
In the long term, I'll probably have to add an external thermostat. I'd like to have lots of cooling headroom but have the system automatically compensate for cold days. Given the single loop I have currently, adding the thermostat is a bit tricky. Do y'all think it's work properly if I hooked it up without the return oil passing through it? Basically as a Y instead of an X?
Here's Mocal's installation instructions:
http://www.racerpartswholesale.com/d...hermostats.pdf
Thanks,
Rich
Okay, it's done. I installed a Mocal 501 thermostat capping the "in from cooler" port. In a test drive last night the oil came right up to 160 F, and then fluctuated around 165-175 F in traffic. The thermostat is supposed to start opening at 160 and be fully open at 180. It's also got 3 handy 1/8" NPT ports for sending units that I made use of and simplifed the ugly tree of brass fittings I had before.
So far so good. Saturday I'll see what it does on the track.
Rich
So far so good. Saturday I'll see what it does on the track.
Rich
Update: I've given up on the RX7 oil cooler. It was an interesting experiment but the temp still wouldn't pass 175 F and oil pressure was marginal. So I have now installed is an Earl's bar&plate style cooler plumbed with the thermostat in the standard fashion. Oil pressure is much better, sitting at 40 PSI at idle and passing 60 PSI at 4k PRM. We'll see how the temp goes when I next hit the track.
Cheers,
Rich
Cheers,
Rich
Another update: The little Earls cooler didn't work, oil temps were too high. So I tried a Z06 oil cooler located in front of the radiator. This brought oil temps down but water temps went through the roof and I blew a water pump. So now I've gone back to the RX7 cooler.
I removed the Mazda thermostat entirely, using the Mocal thermostat which bypasses the cooler below 160 F. And I switched to a lighter oil (Mobil 1 5W40) and vented the hood into a low pressure zone to exhaust hot air out of the engine bay. Things are now great with oil reaching 210 F when pushing hard and water staying right at the thermostat opening temp of 170 F.
Rich
I removed the Mazda thermostat entirely, using the Mocal thermostat which bypasses the cooler below 160 F. And I switched to a lighter oil (Mobil 1 5W40) and vented the hood into a low pressure zone to exhaust hot air out of the engine bay. Things are now great with oil reaching 210 F when pushing hard and water staying right at the thermostat opening temp of 170 F.
Rich
Is the RX7 T-stat something that you can dis-assemble and shim the bypass valve or spring ? to change the bypass to not open until a higher temp ?
Shim to Increase or cut to Decrease the t-Stat springs or valve?
Shim to Increase or cut to Decrease the t-Stat springs or valve?
Teching In
Joined: Aug 2011
Posts: 1
Likes: 0
Check out improved racing.com and look at there thermostatic oil cooler adapter for the LS1 it bypasses at the adapter so no extra lines needed. You run the adapter then 2 lines to the FC oilcooler with no thermostat and you are done. Thermostat starts to open at 180* and fully open by 200* im pretty sure with the size of the FC oilcooler an opening temp of 180* i dont think the thermostat will ever fully open unless you are at the track.
