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Old 02-17-2009, 02:40 AM   #1
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Default FC RX7 Oil Cooler Mounting

I picked up an RX7 oil cooler from a pick'n'pull yard for $8. Monsterous thing. The cashier thought I was trying to cheat him by calling it an oil cooler. But for $8, I probably did cheat him pretty good!

But anyone running one of these in their car? I trying to figure out a good way of mounting it. Any picture?

Anyone try and mount any oil coolers in general on the steering rack? I think that's where I want to try mounting it. I really don't want to hang anymore weight that far out front. Already have a godspeed rad and a 18x12x3 core intercooler hanging out there.
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Old 02-17-2009, 04:00 AM   #2
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Mounted anywhere will help a lot with temps. Steering column would work i guess, probably not the ideal setup but would probably be fine. Obviously in front of the radiator is going to be way better but sounds like you are dead set against that. You could make a bracket with some flat aluminum stock from your local hardware store and bolt it down there.
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Old 02-17-2009, 09:46 AM   #3
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I also have one and am wondering where I am going to mount the monstrosity.
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Old 02-17-2009, 09:59 AM   #4
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Mount it at the base of the undertray, just behind the bottom tank on the rad. There's a gap there were some air does flow under the radiator tank.
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Old 02-17-2009, 10:58 AM   #5
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if you have the intercooler I think you do, you should have a gap on either side of it because it doesn't fill the entire mouth. Maybe try mounting it off to one side of your intercooler. But then poor radiator. Maybe V-mount is the future? Lots of room for coolers and flow
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Old 03-07-2009, 03:26 AM   #6
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I would not install the RX-7 oil cooler on a piston engine. Because of the design of a rotary engine the oil is used to do a large percentage of the cooling and a large amount of heat is absorbed by the oil. Hence the need for a large cooler.

Using one in a piston engine, especially a 4 cylinder will reduce you're oil temps too much which will create a loss in power and increased engine wear. The RX-7 also runs with like 90+psi of oil pressure part of the reason for this is because of the huge pressure drop the cooler causes.

If you need an oil cooler, many newer cars have a simple oil cooler that is just a straight tube with some cooling fins on it that gets mounted near the front of the vehicle. This type has minimal pressure loss and will keep a good balance in oil temps. Honestly I don't see the point in needing one unless you're running a turbo or supercharger.
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Old 03-07-2009, 12:00 PM   #7
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Originally Posted by Kyrasis6 View Post
I would not install the RX-7 oil cooler on a piston engine. Because of the design of a rotary engine the oil is used to do a large percentage of the cooling and a large amount of heat is absorbed by the oil. Hence the need for a large cooler.

Using one in a piston engine, especially a 4 cylinder will reduce you're oil temps too much which will create a loss in power and increased engine wear. The RX-7 also runs with like 90+psi of oil pressure part of the reason for this is because of the huge pressure drop the cooler causes.

If you need an oil cooler, many newer cars have a simple oil cooler that is just a straight tube with some cooling fins on it that gets mounted near the front of the vehicle. This type has minimal pressure loss and will keep a good balance in oil temps. Honestly I don't see the point in needing one unless you're running a turbo or supercharger.
The Rx-7 oil cooler has an integral thermostat, to keep it from overcooling.
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Old 03-07-2009, 12:53 PM   #8
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Quote:
Originally Posted by rippledabs View Post
I picked up an RX7 oil cooler from a pick'n'pull yard for $8. Monsterous thing. The cashier thought I was trying to cheat him by calling it an oil cooler. But for $8, I probably did cheat him pretty good!
You found an FC RX7 in a Detroit yard? Where boss, tell me too.....


EDIT: I mistook FC for FD, but was this at parts galore?
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Old 03-07-2009, 01:48 PM   #9
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The RX-7 also runs with like 90+psi of oil pressure part of the reason for this is because of the huge pressure drop the cooler causes.
Miatas hit 90psi well shy of redline.

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Honestly I don't see the point in needing one unless you're running a turbo or supercharger.
Hmm...this is miataturbo.net right?

Considering detonation can occur due to hot spots on the pistons(and poor timing advance), and the Miata motors have nice oil sprayers that cool the backside of the pistons, I can't think of a better, cheap insurance policy besides a coolant reroute than a good oil cooler.

Admitted, this thing is big, but the OP said that. If you can find a way to mount it, more power to you. And if you find it for $8, you're just awesome.
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Old 03-07-2009, 07:18 PM   #10
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Originally Posted by The_Pipefather View Post
You found an FC RX7 in a Detroit yard? Where boss, tell me too.....


EDIT: I mistook FC for FD, but was this at parts galore?
Yep, parts galore. I actually pulled 2 of them. I gave one to my buddy with a 914.

There was another one that I left, but there was some silicon on it. I think it was cracked and the owner repaired it.

This is the one at 8-mile. There is a 91 miata there too, if you need misc parts. It's been picked pretty clean. The one on warren has a couple FC RX7s too. I guess detroit people love their rx7s.

Planning to come out for some autocrosses pipefather?

Last edited by rippledabs; 03-07-2009 at 08:03 PM.
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Old 03-07-2009, 07:43 PM   #11
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Got it mounted to the steering rack! All plumbing is in too.

I'm a little worried about ground clearance, it's not the lowest point. It is about 5" to the ground. The lowest point is that front subframe brace that's 4.5" to the ground.

I'm also lost some oil pressure. At full warm up and idle, the oil pressure gauge on the dash is saying 20 psi of pressure, and at 3-5K rpm, there is only like 40 psi. What is normal?

Before the cooler. I had about 25 at idle, and 50 psi around 3-5k.

However, the oil cooler holds an extra quart of oil, and I poured in a fresh quart of 10-30w that i had laying around with the 10-40w that's in the engine. Will this also affect the oil pressure?

I'm planning to change the oil out next weekend. Gotta study for midterms for the rest of the weekend.

Last edited by rippledabs; 03-17-2009 at 12:05 AM.
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Old 03-08-2009, 02:49 PM   #12
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There is a 91 miata there too, if you need misc parts. It's been picked pretty clean.
Did you happen to see if the diff was still on it? I just lost my 1.6 diff a couple days ago and don't feel the need to spend on a torsen just yet.

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Planning to come out for some autocrosses pipefather?
Yes. I've been wanting to do NASA and Waterford Hills OTD's this year but treading a little cautiously with money these days. Car still needs a lot of prep to be track worthy, wheels, cage, torsen; it all adds up to a lot.
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Old 03-08-2009, 08:13 PM   #13
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There was a diff on it, but the car has like 150k miles on it, and it didn't look like it was taken care of.

I just got a torsion swap, about to go in soon, I can sell you my old viscous diff.

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Did you happen to see if the diff was still on it? I just lost my 1.6 diff a couple days ago and don't feel the need to spend on a torsen just yet.

Yes. I've been wanting to do NASA and Waterford Hills OTD's this year but treading a little cautiously with money these days. Car still needs a lot of prep to be track worthy, wheels, cage, torsen; it all adds up to a lot.
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Old 04-09-2009, 03:30 PM   #14
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any new updates to the upgrade how are your temps? how is your oil pressure?? i was thinking of doing one also. do you run an oil thermostat?
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Old 04-09-2009, 07:44 PM   #15
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any new updates to the upgrade how are your temps? how is your oil pressure?? i was thinking of doing one also. do you run an oil thermostat?
Yeah, so far so good. I don't have an oil temp gauge yet (planning to get one soon)

When i first installed the cooler, i got some big oil pressure drops. I was at 15 psi idle, 35 psi 3-5k. but i replaced the filter with an oversize filter (about 2x the size in volume), and the oil pressure returned to 25 idle and 50 psi 3-5k. at full warmup.

I am running the stock built-in oil thermostat in the cooler. It's working so far. I get about the same warmup time, and the cooler is gets hot after warmup, so i'm sure the oil is flowing.

I deleted all the pictures because i'm outta space, and I can't delete old attachments. I think the MODs are working on fixing that.
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Old 04-13-2009, 10:50 PM   #16
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how well do you think it is working?? and did you say the oil cooler itself has a built in thermostat?? what new oil filter are you useing to make up for the oil pressure drop? i hope you oil pressure is good and that your motor is getting all the cool oil it needs.
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Old 04-15-2009, 01:53 PM   #17
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Originally Posted by locomonkeyboricua View Post
how well do you think it is working?? and did you say the oil cooler itself has a built in thermostat?? what new oil filter are you useing to make up for the oil pressure drop? i hope you oil pressure is good and that your motor is getting all the cool oil it needs.
Oil coolers from RX7 have built in oil thermostat. The oil filter, i'm not sure where it came from. I just went into advance auto and found one that fits.

Without a oil temp sensor, I can't really determine if it's working or not, but my coolant temperature doesn't have as much heat rise after boost runs. But from other members in the forum, the RX7 oil cooler is enough to keep oil temperatures under control even at the track.
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Old 10-16-2011, 09:51 PM   #18
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Originally Posted by rippledabs View Post
...
When i first installed the cooler, i got some big oil pressure drops. I was at 15 psi idle, 35 psi 3-5k. but i replaced the filter with an oversize filter (about 2x the size in volume), and the oil pressure returned to 25 idle and 50 psi 3-5k. at full warmup.

I am running the stock built-in oil thermostat in the cooler. It's working so far. I get about the same warmup time, and the cooler is gets hot after warmup, so i'm sure the oil is flowing...
Hi all, this is my first post over here at MiataTurbo, although I'm a regular over at trubobricks. The searching I've done lead me to this thread.

I've been helping a friend tune a 94? Miata with a PnP MS2-extra EMS and a T25 turbo.

He installed an RX7 cooler per my suggestion (turbobrickers love those things) with a remote oil filter. Now he's saying that his oil pressure is ok at warm up but gets similar rippledabs's pressure - around 20psi idle and never over 40psi.

He's running 1/2" ID lines to the filter then to the cooler then back to the block. He's thinking he should up size the lines to 3/4" but isn't that overkill?

He's running 10w-30 I suggested going to a thicker oil. I know my Volvo is really just a tractor motor, but I'm always running Delo 15w-40, is it ok to run delo 15-40 in a 1.8+T application.
We agreed that a larger filter since there's space should be installed soon. Isn't 50psi still too low?

I hope he can put up some pics of his build, it's pretty sweet.

TLDR:
My friend's running an rx-7 cooler, and experiencing low oil pressure. Isn't there a problem to only having 40psi oil pressure at 4k rpm? What is the psi spec for these engines?
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Old 10-17-2011, 07:16 PM   #19
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I believe the factory manual says something along the lines of 33 psi @ redline = bad.

I've heard time and time again that 10 psi per 1k rpm is safe. That's about what I see, close to 20 psi idle, 30-35 above idle, close to 45-50 at redline. This is all warm. I've stopped being paranoid about it being low at idle because my hydraulic lifters don't make any noise.

Subscribed for more info, I'm worried that my oil pressure will get dangerously low with this rx7 oil cooler once I finally get around to installing it.
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