RX7 oil cooler installation

I received a RX7 oil cooler from E bay yesterday and it did not come with any instructions. There are three fittings on the side tank. One is for what I would assume is the thermostat. This leaves a connection on the bottom and a connection on the side. Could someone please tell me which is the "in" and which is the "out"? Thank you, Gil.

Without pics it's hard to know what you have, but most oil coolers don't care which way you hook them up. It should flow the same in either direction

I am going to have to figure out how to post a picture. I made a few attempts and failed. There are several advertised on EBay. Here is the link to the listing: https://www.ebay.com/itm/aluminum-oil-cooler-Mazda-RX-7-RX7-FC3S-S4-S5-13B-1986-1992-91-90-89/282564062930.

Putting pics on here is sometimes a big pain.

The 2 nipples closest together is what I will call the top of the oil cooler. Either one of those can be used to put your fitting in. Mounting location and space will determine which one is best to use. The on the bottom is the other place to put your fitting. Just leave the plug in whichever nipple you don't use. In most cases you would put the inlet fitting into the top area of the oil cooler tank, and the outlet fitting into the bottom of the tank. The tank with the nipples has an internal divider plate to direct oil to the opposite end of the cooler and then flow back to the fitting end.

After looking closely at the oil cooler with all of the caps removed, I can see that the cap on the "top" (opposite end from the piece of 8 mm round stock that is welded to the tank) is for the thermostat. There is a spring and spool valve that the top cap holds in place. The cap on the side lines up with holes in the spool valve that would allow oil to flow out (or in) from the cooler core to the side port if the spool valve were open. The cap on the bottom (where the piece of round stock about 8 mm in diameter is welded) points up towards the thermostat. If you blow air into either the bottom or side ports, air comes out freely in either direction but it is just going through the side tank because the thermostat is closed. You said that it doesn't matter which port you use for the in or the out, does the thermostat change your opinion?
Thanks, Gil

Not knowing how that oil cooler is made internally, it's very hard for me to say. Most coolers i've dealt with, used external thermostats. So with yours having it built in, then I would guess that it would bypass the cooler portion until the thermostat opens.

I'm running an oil cooler from an FC RX-7 Turbo. It's a 2-pass with two ports on the same end. There's a wall between two chambers on that end and a by-pass thermostat in between. It only works one direction as the deal that heats up to open/close it is in only one chamber.

I finally figured out how the thermostat works in this oil cooler.  I didn't push the valve hard enough against the springs to make it uncover the rest of the holes in the spool valve housing.  Hopefully I can post some pictures of the cooler and the valve.  Unfortunately, when I pushed the valve enough to make it flow through the cooler instead of bypass, the circlip fell off that holds the valve together.  That didn't give me much confidence. Looking at the thermostat valve and its springs, I would think that the oil must flow in from the side  port and out from the bottom port.  If it went the other way, the oil flow would push the valve off the bypass seat because it the only thing holding it down is gravity once the springs relax.   I have read how the thermostat can be removed and the bypass hole is blocked with a nut and bolt.  Is it necessary to have an oil cooler thermostat on a car that is mostly street driven?  

Yes, the thermostat will allow the oil to come up to temp. If you constantly over-cool the oil it'll never flash off the water content that it picks up naturally in the sump. Lots of street cars don't even have an oil cooler, relying instead on heat exchange with the coolant.

So if you can use it, the built-in thermostat is great. Here's a diagram I found on the RX-7 oil system. I used this routing initially but have changed things further since in adding an Accusump.

Rich,
Thank you for the information. My car will be used 98% of the time on the street and maybe one track day per year. Do you think an oil cooler is even necessary? I am using the large dual pass radiator that TPC sells. I read all of your posts regarding coolant and oil temperature at the track and my conversion is very similar to yours so that's why I bought the oil cooler.
The problem I have with the cooler I purchased from E Bay is that the circlip that holds the small inner spring fell off when I pushed the spool valve down far enough to seat it in the bore. If that happened when the engine was running, it would have gone in the engine. The snap ring seems pretty cheap to me. I probably could solder the retaining cap on but once I start messing with the cooler, I can't send it back.
I appreciate your input, Gil

Nice, that's a great radiator. And yeah, sounds like you'll need the oil cooler and a thermostat. Street cars that don't get driven hard can get away without a cooler. And race cars that are always driven hard can get away without a thermostat. But dual use and you'll need both.

Odd that thermostat came apart on you like that. I took mine out so long ago I don't really remember the mechanism. But yeah, I blocked that hole you can see in there between the two chambers with a bolt and washer. And used an external thermostat from Earl's.

Is there a rule for where the remote oil filter should be installed? I currently have the oil filter before the cooler. If I put the filter after the cooler, I could use the existing thermostat in the oil cooler because the filter would catch anything that came out of the cooler if it were to come apart. If I use the internal cooler it would save a lot of money on fittings and an external thermostat.

Not sure of any "rule" but my filter is after the cooler. Agreed it's a nice and tidy thermostat setup if you can re-use it.

remote filter placement is one of those things people can argue for hours about. the way i look at it is if the filter is after the cooler the filter will catch any debris that could come from your oil lines or from the cooler, however if you have an engine failure any debris ends up lodged in the cooler, and ultimately the cooler needs to be replaced as it may become clogged. if the filter is before the cooler any debris from the engine is filtered out before oil goes through the cooler. if there was debris in the cooler or oil lines it could end up in your engine.

on my car the filter is before the cooler, and i made sure to thoroughly clean the oil lines after i built them, and rinse the cooler out well before it was put in the car.

Thanks for the help. I'm going to put the oil filter after the oil cooler and use the internal thermostat that came with the oil cooler. For the cost of the oil cooler, I would replace it if a catastrophic failure happened.
I'm inching closer to my first road test.
Gil