Got my 93 FD touring and I just swapped my BNRs for a Single Borg 366 with inconel heat shields and all the goodies, now to move onto the eye soar that is the oil coolers. For some reasons my search option wasn't working today, cause I'm sure somewhere in this gold mine there is a post about single vs dual oil coolers. What do you all prefer? Large single oil cooler or dual oil coolers for your single turbo applications?

 

Two Large 34 Row or FC Oil Coolers run in Series with High-Flow Oil Thermostats (ImprovedRacing) if using a 34 Row, non-OEM style.

You can't have enough cooling for these cars, don't fool yourself. Drive harder...

 

Excellent ! 2 it is!

 

I would suggest running them in parallel if you can. It requires spending a bit more in fittings but will perform better than in series.

 

****, you know what? I have to agree here! The pressure loss of Dual FB/FC Oil coolers is seemingly an issue since they run the entire length. I should probably mock my system up differently after reading this...

That being said, if you run Dual 34 Row Earl's Thick style with an independent oil thermostat, I believe the Series/Parallel pressure loss debate isn't an issue. I believe it's ONLY due to the oil cooler construction and the FB/FC extremely long tube design would benefit from Parallel.

https://www.rx7club.com/race-car-tec...cooling-935723

 

My comment was more aimed at cooling efficiency of an air to liquid cooler. You want the delta T between the oil and the ambient air as large as possible and this is achieved by sending hot oil from the engine to both coolers in parallel instead of the second cooler only getting already cooled down oil from the first cooler in a series setup.

 

Don't you mean in parallel? The higher the delta the more efficient the cooling will be for a given surface area of cooler.


*Edit* Sorry, this had already been mentioned. The banner mid thread made me think your post was the end of the thread. My bad.

 

OP, what is your application for the car? Are you tracking or auto crossing? Street car with occasional spirited drives?

To play devils advocate, I don't feel %90 of us need dual oil coolers. Honestly a nice clean set of R1 coolers is plenty for the majority of FD owners. My dual oil coolers have been a pita as far as leaks at the fittings. Also they are too efficient, I can't get the car up to temp while driving unless in traffic. I haven't had them on the track yet which is a shame but I'm sure they'll help the once or twice a year I go if I'm lucky. I'm ready with my flame suit on. ;-)

 

My car is a heavily modded R1 with stock twin coolers.
Even in warmer Houston winters, I need to block one of the coolers for normal driving.
If I don't, the oil temperature going back into the engine is too cold.

This was unknown to me until a friend added twin coolers to his FD. He though that there was a problem with winter oil temps..
We both placed thermal sensing strips on the engine oil outlet, and oil filter inlet. He was correct. The outlet was barely hot enough and the
filter inlet was too cold.

This was discussed in another oil cooler thread a couple of years ago. Be watchful in winter for oil temps.

 

Which is what I addressed at the first reply on this thread.

 

So you don't have the same experience with your oil being too cold with dual 34 row oil coolers?

 

^ An inline oil thermostat would fix that i would imagine.
For what its worth FC coolers cool like a beast and have a 65c thermost bypass inbuilt.
Im running one of those out front of my 420rwhp fb in stacked configuration witha giant I/C and koyo dual pass. The oil never gets warmer than the coolant.

 

I have an inline thermostat and the problem still exists, the factory R1 coolers also have a built in thermostat. I live in Los Angeles which is never really cold and I have the issue.

 

^Which dual oil coolers setup do you have?

 

Which thermostat? Where is it located? You're running an inline thermostat AND the internal ones on the R1 Oil Coolers? Why is that exactly? They should be just fine without an external thermostat.

 

I'm also a bit confused how you could continue having problems with an inline thermostat. The oil would bypass straight back to the engine like that and there is no way the number of coolers has any effect on the temperature of the oil.

Also, if your setup is like the R1 setup and in series, the oil would have to bypass through 2 coolers which could potentially lead to it taking longer to warm up/staying too cold. If you plumb it in parallel it would only have to go through 1 cooler bypass and better yet if you use an inline thermostat like the improved racing unit it would go through no coolers.

I don't really see why people are so negative towards this type of setup when they don't even have the configuration being suggested to OP

 

I have a mocal 185 degree thermostat with dual earls 25 row coolers and my oil doesn't get to temp. I brought up the R1 because some owners have the same issue with the factory coolers and thermostat. I'm pretty sure Mazda got it right with their lines and thermostat. I bet a lot of people have the problem and don't even know it because they don't have an oil temp gauge.

 

It is do to the heat sink affect of all that metal around the thermostat.

 

I believe that a fan on the oil cooler would benefit more than 2 coolers or even the fc cooler swap... they sale a kit that comes with a fan for different trucks transmissions. Point is add a fan and have it activated by thermoswitch or whatever you choose.. I'm in the process of doing that to my recent build.. it's my 5th rx7 and I have yet to have a cooling problem but better be safe than sorry plus it's a cheaper mod than adding more lines +coller...

 

Well I just bought a second FC cooler and all the fittings and lines to make a parallel setup. This will be going on my full bridge n/a GXL track car that used to get up to 235-240F after only a 20 minute session on track as measured at the oil pedestal. It usually doesn't get above 180F in town. Will be interesting to see if I have issues getting up to proper temps off the track with a parallel setup still using the stock in cooler bypass thermostats.

 

This is exactly what I'm doing. 2x FC Oil Coolers with stock thermostats run parallel on a s5 13bt streetport w/ 9174 attached.

 

Sounds too me like the most preferd setup is dual oil coolers in parallel, which is what my gut was telling me. Sufficient cooling plus minimal chance of the oil pressure dropping due to a series setup. Thanks for the input guys, this forum really is a gold mine of information!!! When it's installed I'll post pics. This thing is gonna rip at the next BeastCoast Shootout event!!

 

Quick survey: those of you noticing low oil temperatures, do you have the oil squirter themostat deleted? It's supposed to be closed until 60C oil. Without measurement it's hard to say whether that would help or hurt.