1987 Mazda Rx-7 FC(Big turbo, front mounted, stock port, S4)

I got the car tuned and running great at 18psi from street tuning. Still have to do dyno tuning to get everything perfect. Something I noticed though is that the car runs great from regular street driving and some spirited driving. But then after consistent abuse on the highway I believe that the car starts to over heat. I've taken it up to temps 96c from the Apexi on the highway, gotten scared, and began to let it cool off by continuing to drive normally. Temperatures come down within the minute. I want to road race the car so obviously if this keeps heating up like this then I won't be able to. I guess I'd like to know what your take on this is.

Cooling:
New waterpump
50/50 distilled and coolant
40 Below coolant additive
Godspeed Radiator
Blackmagic 3,000CFM fan
Samco Hoses
Undertrays and radiator cooling panels
Air conditioning is STILL installed
OEM FC Oil cooler set-up.
Greddy 2 row front mount

Maybe I just need better ducting and to install a pusher fan on the condenser side to increase the velocity of the air after it becomes slowed down from hitting the front mount? Maybe I'll just have to delete the entire AC set-up to combat this, even though I'd really like to maintain it. Thoughts if any? Banzai Racing has suggested the Godspeed isn't adequate and suggests the Koyo-n-flow.

 

i had the same problem doing track days, after about 10-15 min at wot it would start running hot, and this was with the tmic. your fmic is definately not helping, but i would bet your problem is likely just poor ducting to the radiator. make sure there is no room for air to escape around the sides. also the stock undertray can bow down and let air bypass the radiator from underneath. I ended up trimming the undertray shorter so that it ends at the bottom of the radiator, and ziptie it right there to the radiator, and it helped a lot

you could try lowering your antifreeze mix to 75/25 water/af, since water cools better than antifreeze

 

front mount, air conditioning, road racing.

a couple of these things do not belong in the same sentence or require major modifications to work.

in fact i'd also recommend to try putting the stock mechanical fan back on too, even the best E-fans can't compete with it.

and last but not least is a high flow 165F thermostat which will fully open around 180F.

as for the radiator i have had the opposite results, the koyo has less capacity and honestly isn't worth $450 bucks.

 

I have several thoughts:

-During warm weather run distilled water + Water Wetter...you don't need antifreeze at all

-Ditch that Black Magic pos and put a big Lincoln fan on, it will fit your Godspeed perfectly and pull way more air

-Say goodbye to the AC condensor, it kills airflow to the rad

-Pusher fans are in general a bad idea, avoid if at all possible

-96° C ain't all that hot, if that's as high as it goes under sustained load, I'd say you're actually fine as is. Remove the AC and switch to WaterWetter, probably all you need to do.

 

Wasnt there talk of this? I remember a discussion with racers where they cut holes in the thermostat because of the sustained high rpm, high heat coconditions.
Might work without having to change too much.
And yeah ditch that fan

 

road race cars don't have fans at all.

 

Do not add any more fans. If it is getting too hot while beating on the car more fans are not going to help you.

What does your radiator shroud look like or do you have one?

Duct everything all the way to the bumper to force as much air as possible through the mess of cooling devices

Also consider a vented hood to help all the hot air escape.

Drilling a couple 1/8" holes in the thermostat may help keep the car slightly cooler. If you do that you may have to switch to a undrilled thermostat in winter.

 

good point but if you must have a fan then it should be one that can handle the job, i can't picture this is a hardcore road course car that has a fan waiting in the pits and never sees the street besides on a trailer.

 

yeah it does sound like a dual duty car, so it will need a fan. point is, that the fan does nothing once you're moving

 

Aaron suggested the Blackmagic fan in one of his large posts as being a good choice. The fan moves 3000 CFM which if my information is correct is slightly more than the OEM clutch fan. The car is mainly a night/weekend and a fun day car. I'd just like to be able to take it on the track and not worry about overheating the damn thing in half a lap :/

 

Your car looks good. You are losing a ton of air out the sides around your FMIC. You will want to have ducting to seal off the bumper opening and rear of the intercooler to the core support area.

Also consider a different fan shroud, or modify yours with rubber flappers in it so you get better airflow through the core when moving.

The fan setup I run is a dual 11 inch SPAL. The flaps above and below the fans promote more airflow through the radiator at speed.



Mounted in the car:

 

i think once you throw a FMIC and some boost into the mix you still need a fan unless its very cool out, I think a thicker radiator actually hinders it a bit

the flaps are definitely a good idea, I almost wonder if its better to just pop some holes in the thing

my LT1 FC car ran ice cool with the most basic of fan, no shroud and a cheap $185 summit racing radiator

 

You do not want an E fan running above 35-40 MPH.. it will actually slow airflow.

OP- if you have your fan running all the time at speed.. stop doing that, it is not helping your cause.

 

If "the thing" you refer to is the fan shroud, then yeah, the more holes, the merrier.
But you must cover them with sealing flaps.

When the fan starts it creates a low pressure area in the shroud as it evacuates all the "easy" available air, the flaps seal the vent holes and force the fan to pull through the rad core. Without flaps, the fan is more than happy to pull air through the less restrictive shroud holes and ignore the rad as much as possible. You basically end up recirculating engine bay heat through the fan.

The adage "You can lead a horse to water but you can't make it drink" is applicable here. You can position a fan right on the radiator core but if it can find a less restrictive source to pull air through, it'll do it every time.

It's science, bitches!

 

Eww, lt1; besides, moot point since the rotary runs hotter

 

that was the point I was getting across - turbo rotary with FMIC and oil cooler is a different cooling animal

 

I did a little research before doing my radiator mod and I read that some of the cheaper radiators don't completely separate at the end tank to make it a true double pass radiator. Not that Koyo is the holy grail, but it is bolt on for us fc with rotary engine. Of course everything put together will add up