ktwister

Hi Guys,

I run a Gen 1 RX7 here in OZ in what is called Improved Production. I am keen to get some pictures/thoughts on mounting of a "front mount" oil cooler. I currently have one upright (parallel) with the radiator, and from the oil temps it does not appear to be working very well.

The radiator is mounted on a slant (with the top going back towards the engine etc), I have been told to lay the oil cooler almost flat and box in the entire front section to create a high pressure area, any thoughts?

bcty

haha run a vmount setup with the oil cooler

ktwister

VMOUNT ?

Carl Byck

I run two TII oil coolers flat against my radiator, one at the top, and one at the bottom. You need to ensure proper airflow no matter where you place them.

Dick Elliott

Most of the dual oil coolers on Mazda's are only bandades to make up for a hot running engine. If you get the engine to run 160/180 degs when you race, one second gen RX-7 oil cooler will work fine. Make sure you mount it with the rubber insulators and a couple inches in front of the rad. Gut the inside of it by removing the thermostat and pluging the hole. In the Mazda racing how-to book, they show the cooler laying flat with a air deflector guideing the air in to and down through the cooler. The hot air then goes under the car and not through the rad. This aid cooling too. Mazda says this is the best way. I have never seen anyone except the factorys do this even though they say too. Try it/ you'll like it. DICK

Carl Byck

An oil cooler is for cooling, to say that that is a bandaid is plain ignorant. That is what it is for. Roughly 1/2 of the heat rejection in a rotary takes place through oil cooling, it therefore makes sense to dedicate roughly half your cooling efforts to cooling the oil. A single cooler may be sufficient(barely) for a stock motor, but to suggest that a single stock cooler on a modded or race motor is sufficient is an invitation to a short lived motor. How exactly do you propose to get a road race car to operate at 160 with any type of cooling? What kind of road race car are you running, and how do you keep your temps at 160-180? I have a custom radiator with easily twice the capacity of the stocker, two oil coolers, a vented hood, and a cut out bumper. My car runs 180* at the track, try running your suggested set-up, and you will be replacing plenty of motors. Regards, Carl

Sleeperx7

"I have a custom radiator with easily twice the capacity of the stocker, two oil coolers, a vented hood, and a cut out bumper."

I'm about to mount a second oil cooler on my FC n/a. I know how to mount it physically and all, but when I'm done, how much oil should I be putting in my engine? Also, did you have to do anything to the second cooler you put in?

Logan

Dick Elliott

I realy must have step'd on your pet project. Sorry, but as a retired factory backed Mazda racer of the1980's in IT-S, IT-A, GT-3, & GT-2 all I can say is the factory cars never ran two coolers on any GEN 1 REX race car. And GEN 1 REX race cars is what this posting is about. All factory cars I ever saw had the cooler laying flat like my posting said . No hot air through the rad at all. I realy don't know how any air ever gets to your rad with two factory coolers in front. Look at NASCAR. Coolers are to the side of the rad. You are running factory racing coolers aren't you? After racing for over 50 years, I've learned to look at new ideas. You realy should try to yourself. And I for one would never call your ideas ignorant. Just out dated. If you want to know how the factory did it just ask.

Carl Byck

Sorry if I came on strong, but i have seen two GTU cars with dual coolers. I do not know if they were campaigned that way, or retrofitted after the fact. I think my point is that the two coolers work, assuming sufficient air flow. I think it would be difficult to set up the flow top to bottom. I have seen many modern designs where the radiator is the front of the box, The IC the top, and the sides sealed, but I have not seen a bottom mount cooler of any kind used with success. HKS is using a bottom mount IC in their most recent "V-Mount" FD IC design, but I do not know how well it works. I have a sealed flat bottom on my Fc, where would you suggest mounting my two oil coolers given a choice? I am sorry that I mis-took your few posts for inexperience, but for your idea to work, I believe alot more explanation is required. Thanks for sharing your experiences with the forum. Carl

Dick Elliott

Carl!
The way the factory had us do the cooler makes a lot of sense. By placing the cooler flat before the rad, all the heat from the cooler goes under the car and none of the heat hits the rad. To do this we completely sealed the area in front of the rad, with the grill the only opening. We then placed the cooler flat on this sealed floor with a cut out the size of the cooler under the cooler. Then we made a sheet metal deflector to guide the air back to the cooler and down through the cooler and out under the car. If your air dam is any good you should have negative air pressure under the car to also help draw the air through the cooler. The deflector on my car looked like a front opening hood scoop, with the cooler at the back. Once the air entered the deflector, it could only get out through the cooler. Don't make the deflector so big as to take away need'd air for the rad..In the late 70's early 80's Mazda went to NASCAR for cooling help. What they had us do was lean the rad back at the top 15 deg. and reseal it to the air intake. We also used a shroud after the rad to increase the air speed through the rad. Rex's don't seem to have an air flow problem after the air goes through the rad. Jacking the rear of the hood up did nothing good for the cooling. We used the factory rad and the factory racing cooler. Water temp was 160/180 deg with 160 the best HP/speed. Oil temp was 200/230 degs with Kendall dino oil. Mazda told us they wanted the oil and water to be the same temp, but we never could get them the same. Hope this helps you run cooler. DICK

ktwister

Guys,

Thank you very much for your thoughts they are much apprecaited.

Dick, you would not have pictures/diags of the set-up you used to run avail would you? I would happily give you a fax number or direct e-mail :-)
And would you have the "full details, name/author" of the book you mention pls?

Another racer has done similar idea to you, lay the cooler flat, box in the entire front section (behind the bumper, yes we have to run a standard bumper). But keen for your input.

At the moment, I am getting approx 150-160 degress oil, 100-110 water temp. I would like to get them closer :-) The oil you mention, was that mineral?

You can see some of the cars at www.ipravic.com.au, my one is the red/silver one.
Regards, Kelvin

Dick Elliott

Kelvin!
The book I keep talking about is the Mazda factory racing guide book that was printed in about 1980. It was not for sale, but given to Mazda racers of that time frame. My engine builder got a copy in about 1984 and I made 10 or so copys fpr all the local racers. I have missplaced my very last copy somewhere in my shop. I'm looking but there's 50 years of parts out there. The book has a picture of a very early Rex on the cover with the add on flairs they used before the box flairs. The posting I made before this one tell all I know. I don't think a deflector is necessary if you seal the front completely. The air would have to go through the cooler, and the negative pressure under the car would help. Useing a NASCAR type rad would help. I'm talking about the rad's with one or more baffels in the end tanks to force the water to go back and forth inside the rad. This prevents the water from takeing the path of least resistance and runs much cooler. The problem with most double cooler set up is they run one cooler into the other. Not good! Any fluid enginner will tell you this just doesn't work as you slow the oil down too much in the first cooler. It will work by using a y shape block to direct the oil to both coolers at the same time. The block would be like a large version of a fuel block for two carbs. You would need one on each side of the coolers. Hope this helps.

ktwister

Dick and Guys,

Thank you for your input, it is much apprecaited.

I will let youknow how I go.

Cheers, Kelvin

NanaimoRx-7

Lots of good info here. I've been trying to think of a good way to snug an FC oil cooler into my SA. I really like the idea of laying the oil cooler flat, it would seem to solve a few of my problems. The difficult part I think will be running the oil lines out of the box and keeping it air tight (or close to).


Hmmm.

Dick Elliott

With the battery moved to the inside of the car, you can run the lines through where the battery sat. I drill'd a couple of holes in the rad side panel and ran the AN lines through to the 86/91 cooler. You must make the holes larger than the hose as the fittings are bigger. I then use the good red heater hose, split down its length, to cover the part of the AN hose that goes through the two holes. I put about 6" on each side of the holes. Tie raps keep the heater hose shut. Doesn't seem to hurt oil pressure to go up and down to do all of this. Theres ways to go through lower, I just never have. Take the t-stat out of the cooler and plug the hole with a bolt after you tap it. Theres no reason not to, if you need to, you could use the hole that you remove the t-stat through, to run your AN line to. Then plug the other hole. Cooler would never know the difference. Try it-you'll like it. DICK

DriveFast7

iTrader: (1)

Anyone have the MazdaComp big oil cooler for sale?

I use a Rx4 oil cooler, 8 rows vs 7 from the 12a cooler. 200-210*F oil temps in 90* ambient. When it heats up to 110* ambient this summer I think my oil will get too hot. Rx4 oil cooler mounted in front of radiator with an adjustable height aluminum splitter directing dedicated air to the oil cooler. And my nose panel has a big duct cut into it for another air source for the radiator. Big Howe 2" thick radiator. Water is at 145-165*F!! Had to put 3 rows duct tape on the rad to bring it up to 190*F

U can see the Rx4 oil cooler in the pic below. Splitter was installed after the picture taken.

Dick Elliott

Mazda factory told us to try (BIG WORD) to run the oil and water at the same temp. Never works out that way, but its a good idea. They (factory) recomend'd a water temp of 160 degs as where the rotary made the most HP. Looks like your near there with your set up as it is. Try placing the cooler flat and well sealed. Then its hot air will go under the car and not through the rad. Then and only then play with the tape or the oil cooler deflector so more air goes to the cooler. DICK

DriveFast7

iTrader: (1)

160F water, that's pretty low. Stock thermostat pops open at 180F. Have you seen a power increase with lower water temps?

Dick Elliott

160 deg is what the factory asked for. We didn't get that very often though. I lived in the SW at that time and 105 deg days were common. Factory said that on a dyno, the engines made the most HP at that temp. We ran about 180 degs most of the time with oil temp about 200 deg. The posting above your states he can run that cool. The criss cross, back and forth rads are the key to running cool. Look at Ron Davis Rad to see examples. He's got them for a price. We alter'd our own tanks and then had a rad shop finish them . The baffels don't have to be perfect to work. Just make the water change directions. DICK