so with my 85 i have 2 radiators for it. i switched over to the front mount oil cooler so i have the shorter thicker radiator in there now but i also have the stock 85 rad. the thicker one probably holds a touch more water but the taller one has more surface area to cool the water down with. anyone have any ideas on which one will keep my temps in check better? i have a track even next friday and with 100* weather and wot on a 4.5 mile course, things are going to get warm.

 

It's funny you mention this, b/c I have been thinking the same exact thing. My guess in the larger, 85 rad. There must have been a reason why Mazda opted for a longer 2 row rad when they came out with the 85. Just my 2 cents.

Ryan

 

^^ true. i just thought it was cause they didnt have a huge oil cooler in the way so they could fill the whole space with a rad and thin it up a bit. ill put the 85 rad back in and see if my temps stay down longer. thank god i like heat and dont mind running with the heater on full blast.

 

The only problem with putting the 85 rad back in is that the lines for the oil cooler will not be long enough so the oil cooler will be in the way. I think either one should be fine as long as there both in good shape.

 

Both radiators have about the same cooling capacity. The difference between them is the shorter one is a 3 row while the taller is a 2 row. The reason for the switch was the change to the beehive oil cooler on the S3 12As. You have a good point on the frontal surface area of the taller radiator as it won't carry as much rejected heat to the rear rows that the shorter 3 row radiator will.

Keep in mind that the fmoc reject about 1/3 of the engine heat, which not only helps cool the engine, it also brings the oil temps down which is critical for lubrication and oil life. Either radiator will work well, the fmoc is a must imho. Not only does it cool well, it helps preserve the dowel pin o-rings which always seem to fail prematurely on the beehive equipped engines.

If you're pushing the cooling system when roadracing or autocrossing, you might consider buying a tall 3 row radiator. I hope you're running 20W50 oil in these temps.

 

i just got a koyo for the fc tonight so the stock fc rad will be going in the fb. i was running 10-40 i think but i am changing the oils this weekend so ill go with the 20 fitty. thanks for the tip

 

Which one is better on short radiators?

other than capacity, dont forget to take into consideration that the newer radiators come with more fins meaning it will direct more air to the core for better cooling. Radiators are not rated like the domestic refrigerators but when you hear the term SEER, think about the fins.

 

Coolant capacity is the same, whether it's the tall 83-85 rad, or the shorter 79-82 rad.
That said, the taller rad has the potential to cool better, due to less heat soak from the thickness. Of course, the FMOC will block part of the airflow thru the taller rad, and heat the air that goes thru it.
I stuck with the taller rad when I went FMOC, and haven't had any cooling issues. But, I'm not racing, in 100+ temps.......

 

Keep in mind that the FC rad is taller than the 1st gen tall rad, that's the reason the FC rads are mounted on a slant. You will need to do the same thing to mount it in your chassis. You will also need to mod the shrouds, sides and top, so the air flow goes through the rad and not around it.

To aid cooling, add a bottle of water wetter to the coolant to. It supposedly reduces coolant temps around 10*. Also make sure you can fit the fan shroud and the under tray is a must.

 

ok. i was planning on mounting it at an angle and i got a pair of electric fans for the front of it. i still have all my under tray since i do know the importance of it from fc issues. i think it will work out pretty well. i also have some other cooling ideas in store. stay tuned for them

 

It is true the tall radiators have more surface area, and cool better. They also have more fins.

Wacky, the new short style 3 row radiators still have less fins like the originals. I've never seens a densely-finned short rad for a 1st gen.

To the original poster, examine your oil cooler lines. Do they allow the oil cooler to mount out in front of the rad like the GSL-SE? Or are they the shorter length lines from the 12A '79-'82 cars? If so, just get a short style 3 row rad and mount the cooler below it.

 

lemme rephrase that. the fins has less gaps to re-route the air so it is much more finer than the older one. It cost more that the regular radiator

 

I stongly recommend against mounting the fans in front of the radiator if that's your plan. In the long run, the fans will impede air flow. Mount them on the backside with some sort of shroud around the fans.

 

Not to steal your thread, but I've been searching for radiator options for my 85 and noticed everyone says the stock 85 should be two row. But I took a look in my radiator today and its only a single row. Is that right?

 

If your FMOC is mounted in the space in front of the rad, I'd use the tall rad. Mainly because you don't want a gap where air can flow through without going through one, the other or both.

Air for the most part seems to take the path of least resistance. I say "seems, for the most part" because I'm not an expert in airflow dynamics and even if I was, I couldn't make an assertion about where air will move without a flowbench or a wind tunnel. In any case, If there's a big open gap that air can flow through without going through a rad, it will. You're better to force the air through the taller rad.

That being said, if you're going to continue racing competitively, you might as well save up and grab one of these:

http://www.awrracing.com/pages/cooling.html

Jon

 

It's funny you should mention that because I look inside my '84s tall rad and it quite clearly shows 3 rows, and I was always confused by that reference as well. I thought that maybe I was looking at it wrong or it had been rebuilt at some point with a core that had more rows, just thinner ones.

Can you snap a pic?

Jon

 

Some of the 83-85 12a cars had single row radiators. The only ones that I have seen are cars that didn't come with AC.

 

See and that doesn't make sense either because my car has AC. I go and take some pictures.

 

Here are some pics of the radiator (sorry 56k). I no its a messy engine bay right now And I'm in the process of figuring out what the last couple of owners did to it.


This one I should of turned off the flash but I circled in red the one row.

 

No it doesn't make sense but the radiator easily could've been replaced or who knows, it may have come from the factory with it.

 

Jon, you do like the expensive parts, lol. Both of the AWR radiators are over 525. Way to pricey for my feeble budget. It might be cheaper to have a 3 row tall radiator custom made at a decent radiator shop. Funny thing is, everyone touts how good aluminum rads are, but brass/copper ones reject heat better and don't suffer from electrolysis deterioration.

 

I know that brass/copper conducts heat better than aluminum, but if you've got a car that doesn't have much of a problem with electrolysis, you're better off with Aluminum because it doesn't corrode and go green like the copper ones do.

At least I think so. Plus, this rad is a heckuva lot thicker than stock, and I don't feel like getting a shop to try and make me one. The closest radiator-specific shop with the best reputation is the one that re-cored my stock rad, and here I am less than a year later and it sprung a leak. No warranty either.

Yeah I like expensive parts, nothing's too good for my 7.

You done my wheels yet

Jon

 

i am going to put the koyo in tomorrow and ill take pics. i have never had a problem with the fans up front. they will be on probably 80% of the time anyway so no big deal about impeding air flow and i like the look of open engine bay. plus its easy for me to find push type fans for cheap vs the auto zone pull type at 60-150$ each.

oh yeah and i have the 12a oil cooler lines so they are short. i will probably mount the cooler either flat across the bottom and build a scoop under the car for it or take the easy way out and mount it behind the rad.

 

actually, althoug its not noticeable on cars but for HVACR condensers, the fan will accummulate dust which will cause the motors to fail in the long run. So pusher will make it last longer than as a puller.

 

Funny you should mention that. The only pusher fan I've seen on a rotary is an axillary fan on the TII's that were for the the ac condenser.

Since every e-fan I've seen has some sort of shroud, which has a smaller area away from the rad and a a larger one next to the rad, installing one as a pusher reduces the total draw area, which can reduce the available cfm of air flow. By installing it as a puller, it will draw from the larger area next to the rad and the pinch on the outboard side can act as a venturi, increasing air flow when compared to mounting it as a pusher.