onlytrueromeo

Considering a major overhaul on my oiling system and going for the improved racing external thermostat and oil filter mount like teams had posted some years back.

Also have a new csf radiator and FAL 490 fans on order. Car is not turbocharged yet (I am doing all the other upgrades first) but I want it to last. Has 15k stock miles on it - not bad for an 04.

Do I go for the 165F or the 185F oil thermostat?
https://www.improvedracing.com/remote-engine-transmission-oil-filter-mount-with-thermostat-env-171.html

kevink0000

I'm NA, but in Arizona. My 2 8s have shown that if you keep the keg cooled properly, the stock coolers work fine. I also use FD thermostats in them.(165 open IIRC)

If this was mine, I would build in more cooling margin first for the coolant, not the oil. It is unlikely to see high oil temps, even on the track, if the coolant temp stays at design temperature. (180).

If your oil temp shows high after you can maintain coolant temp properly, then that should be step 2 in my opinion.
FWIW

The problem is that few people get the cooling system to that point.

samakijoe

.

Keven: What would be your suggestions for coolant up grades for his situation??

onlytrueromeo

Thanks for the input- I wholeheartedly agree. I have a new csf radiator and the FAL 490 fans going in with lower fan setpoints through versatuner. I've removed the battery and airbox and am building an FR4 plate above, set on 2.5-3" studs, significantly increasing the airflow through the radiator. Will do a full foam treatment as well.

This is way overkill for NY weather but I'm an engineer and want it done right. I do plan to turbo in the future.

I'm thinking the 185 cooler will be best here. I have the stock coolant thermostat right now, and this is similar to that.

kevink0000

It depends. His climate and usage pattern will dictate that. Both of my 8s have a large second radiator, needed in AZ. But I also have stock airflow blockers, so there's that.

There are some turbo guys who I am sure will chime in with what they did with their builds. I would take what they say, if they are getting good results, especially since OP is going to go FI at some point.

The stock size, regardless of radiator config (even 2x pass) , is too small for normalizing engine temp above about 90 degress F, in my usage, just normal street driving.

A 12A FB had a bigger radiator, and delivered less that half the HP, was hundreds of lbs lighter, 2 passenger only, and had normal underhood airflow. Those cars had no problem maintaining temp as delivered in any US climate. The RX8 as delivered did not.

Add high throttle or FI and that already marginal RX8 threshold temp goes down.

I will add this here, since it is likely to come up as a strategy:

I don't believe re-routing coolant flow at the junction is a wise move. That is there to prevent sudden temp changes due to thermostat activity in my opinion. This engine does not tolerate large temperature deltas, and the engineers designed accordingly. Every Mazda Rotary coolant diagram that I could find, and even a picture of a Cosmo engine bay, shows at least one hot loop feedback right into the cold side radiator pipe, prior to the pump, just like the RX8 has.

If you do some quick math, you find the radiator size as the primary problem. Combine that with a laydown design, and underhood restriction, and here we are.

onlytrueromeo

Not following this - I wasn't planning to reroute the coolant lines. What are you recommending here?

kevink0000

Just in case this comes up in the discussion. Getting in front of it.

My POV is the if you fix the primary radiator issue, many other things fall into line, not the least of which is engine longevity.
If temps remain stable at all times when running, your engine will last longer. If you're seeing 210 under load and then cooling back down to design temp every time you drive the car, it will not last as long if that temp was even all the time.