Koyo single pass or twin pass radiator?
 

The car will be seeing the track alot this coming summer, both solo1 and solo2. Ambient temps rarely get above 30*C (mid 80's i think in *f) and i have the choice of a koyo single or twin pass rad from my local shop.

Im tempted to say the single pass will be sufficient, will it?

As far as mods go the car is maxing out the stock twins, so somewhere over 300 at the wheels.

Tracking even in cooler temps is still hard on the car. I would suggest twin pass.

What kind of intercooler setup are you running? And single or dual oil coolers?

M2 large IC, single oil cooler (stock), vented hood. Its also my normal practice to run 2 bottles of water wetter in the cooling system.

it appears that the single pass koyo is already 2" thick compared to a 1" thick stock rad, which would make the twin pass VERY thick (3"?). or is the 2" thick version that most people end up with the twin pass?

I am not sure if you are grasping the number of passes versus thickness of the core, let me explain it to you. All drop in radiators (excpet for a 2-3) are all single pass. What you are getting confused with is the number of tubes or rows. The Koyo is a twin tube (52mm total, iirc they are 21mm each), the stock, Fluidyne (36mm), PWR (40mm), MazdaComp (33mm), Griffin (36mm), etc are single tube.

There are pros and cons to a thicker and thinner radiator, thicker will have the potential to offer better cooling ONLY if you get adequate air flow through the core. A thinner is better beacuse the air can pass and transfer the heat better.

Now let me explain the number of passes. The above all are single pass (sigle or multi tube), the coolant flows from 1) top to bottom. In twin pass the coolant would flow 1) top to bottom 2)bottom to top, and a three pass would flow 1) top to bottom 2) bottom to top 3)top to bottom. Typically 3 pass is the highest you want to go, and with the FD radiator layout its a perfect fit. If the radiator is seeing clean air (as with you case) you can run any of the combinations listed above, if the radiator is seeing dirty air (running fmic) it would be best to run a twin or triple pass, naturally for drop in a triple past would be best.

I had just assumed that there would be extra thickness involved in running the rad twin pass. I should really hassle the shop for the dimentions, however i think the single pass will work for me. It seems that alot of people have had luck with tracking mazdacomp rads in hotter temps and its got less capacity. And really airflow in solo1 isnt a problem.

Twin pass and dual core are two different things. Running dual core will make a thicker radiator, multiple passes doesn't necessarily make it thicker.

I would use a thinner water radiator and pay attention to the oil coolers. When I track raced large-bridgeported SCCA, GT-2/3 engines (12A), revving them to 9400 RPM, some of the engine builders claimed that a Mazda rotary gets up to 60 percent of its cooling from oil. I was using some pretty sizable Mazdasport oil coolers to keep my oil and the engine happy.

I also raced my FD with the stock radiator and the dual R1 oil coolers for two full seasons at around 11 psi boost and never had ANY problems. There were some hot days, being in CA.

Koyo makes two Radiators for the FD, R1443 single pass and R1443N triple pass.

Thats good to know, I might have to look into a better, or more than likely secondary oil cooler.