Larz

Summer is just around the corner and so are steaming hot days. Our cars have a hard time staying cool as it is. So let's dicuss anything and everything that can be done to keep that 2 rotor we all know and love cool. I have some thing I'd like to inquire about.
Does anyone make a thermostat that opens at a lower temperature?
Is it safe to drill a couple holes in the OEM thermostat? If yes, then how many and how big?
Can I run without a thermostat at all during the summer safely?
How much heat have members here dropped using additives like Purple Ice or Water Wetter?
How much of an effect on cooling does an aftermarket bumper have?
What is the best coolant/water mixure for summer?
I have been considering going with a dual oil cooler set up in my 93 Touring. I noticed fluidyne has made a kit, but haven't heard anyone's feedback on it yet. I've heard mixed reviews about the crooked willow kit.

DaleClark

iTrader: (55)

IMHO, lower temp thermostats are a bad idea. Many times they make the car run *too* cold, or slow the warmup time. While the car is warming up, fuel economy is reduced, and with $2.50/gal gas, I'd like a quick warmup .

No thermostat is also a bad idea - that can also cause a lot of problems, even overheating.

IMHO the key to keeping the FD happy is first off, having a good, solid cooling system. Good antifreeze/water mix, no leaks, no crap clogging the radiator, etc. Use a real Mazda thermostat, and run a temp gauge to keep an eye on things. I think a lot of the cooling problems people experience are from neglect.

Second thing is the fans. A good first step is the '89-91 FC thermoswitch to lower the temp the fans kick on. I'm working on a better solution for running the fans - stay tuned for that one, I gotta guinea pig that idea first .

Dale

rotorsownyou7

This is my stage, finding out how to keep temps low. Still in the thinking process.

HobbeZ

there are a bunch of ways to keep it cool ones not listed so far is water injection and the typical upgrades radiator and intercooler, better ducting etc.

Kento

Circumventing the thermostat is a bad idea, simply because the coolant flow rate is set up for the car's cooling system. If you run the coolant through the radiator too quickly, you lose heat transfer (the radiator can only get rid of so much heat in a certain amount of time), and eventually you'll overload the cooling system.
Less than a proper mix of coolant/water, despite what some might claim...
Only as good as the ducting and its seal is...
60/40 to 70/30 water/coolant ratio. Actually, the less coolant you use, the quicker the heat transfer ability; unfortunately, the corrosion that results will be extremely harmful to your cooling system and engine.

A search would have easily yielded all this info.

Kento

Water injection will have little effect on your engine's running temperature if it has cooling issues already.

tt2323

go all out and throw a vented hood on also

PhoenixDownVII

LOL You make this post as if the question has never been asked before:

There are many ways that *make sense* in keeping the car cool, but considering the options and their effectiveness, I will contest that having a fan-switch mod is probably the best thing you could do (Besides being sure everything in place, stock or not, is working right).

Stock radiator has plastic end-tanks and is small, so replacing that will enable you to hold more coolant and have a bigger space to radiate the heat or cool it all down,..

A vented hood lets heat escape...

A mazda thermoswitch lets the fans come on sooner,...

Duct-work allows more air to the radiator..

But above all, I really feel being able to have your fan come on and force air to move will have the greatest effect.

With my stock FD I have the Ac-3 option (turning AC on and to the power of 3 will cause BOTH fans to automatically engage)...the temps always go down, despite the obvious strain the engine now has with the AC engaged.

Replace that "dead" switch (the fake one by your fog lights) with a fan switch,

PhoenixDownVII

Oh and BTW- It took a 90 degree day, humid, sitting in traffic, for my car to see above 200f, and it didn't reach 215 at all either.

Heat in the engine bay is another thing, but coolant temps can be remedied.

spurvo

Like has been said, an adequate mixture for summer and a cooling system that holds pressure work fine for all driving over 35 mph (unless you run FMIC...). Under that, and you have to rely on the ECU's temeprature settings for fan operation, which do work but leave precious little headroom. Best defense is a temp gauge that tells you something meaningful. Personally, I linearized my stocker. Thermostat open temp (180F nominal) is at the bottom mark, and 210F (fans come on with electrical load) is midway between the C and H. Easy enough to monitor.

Second is fan control. The Miata thermoswitch kicks in earlier than the stock switch (208F instead of 221F). There has been talk that the second gen RX thermoswitch bolts right up, also has 208F as it's set point, and no wiring modification needed. Personally, I like paying attention and making sure I'm on it... so I did the David Dysney fan mod that taps a switch into the fan relays. I trigger 2 & 4 for low speed, 2, 4, & 3 for medium speed. Works VERY well, even sitting in traffic in 90F ambient.

The biggest killer for our engines is the heat stored in the exhaust manifold. This cast iron lump simply holds the heat. You can see it glow nicely at night if the heat shield is removed, as mine is. This has the manifold running at ~850F or so (I've measured it with a thermocouple before). If you shut the engine off with that kind of heat, it simply sits and cooks the O-rings right in that area. Running the engine for 3 to 4 minutes with the fans on brings the manifold to ~350F, which is still bad but far less destructive. This would recommend a turbo timer IF the thing could also run the fans while on, then shut them off after shutdown. Even better would be electric pump that circulates coolant after shutoff with the fans on. Someday...

Big *** radiator for the street probably doesn't mean a whole lot, but welded construction versus aluminum fingers bent over plastic endtanks with heat cycling does, so a Fluidyne rad makes sense (so does a Koyo if you want to play with things a bit). Oil coolers are great, though I don't know enough to be able to speak to engine failures due to oil temps being too high..

Drilled/removed thermostat actually hurts the cause. The ECU see engine temps too liow, runs the car rich in warm up mode, actually heats things up worse! Stick with the stock T-stat, replace all original coolant hoses, flush the coolant regularly, and deal with the fans and temp monitoring. You will be fine

DCrosby

Start with a good radiator, and an AST that doesn't explode, and you'll be fine... I Boosted my FD in the desert of Ca. where ambient temp was 104, up a mountain and never saw more than 216 on my defi gauge. That said it was with a Koyo, Aliminium AST, stock fans and the fans on low all the time, untill the ECU kicked them into High... all on a stock ECU.

akiratdk

nice writeup~~~

dsketchy

whats an ast??? sorry im new.

spurvo

AST = air separation tank, a handy little unit that is supposed to remove the air bubbles from your coolant system that are caused by water cooled turbos boiling the coolant in the turbo housings. It is the plastic tank bolted to the intercooler that has a radiator style spring pressure cap. It can be replaced with an aluminum unit from Pettit, or a billet one from Jason at the RX-7 store I believe. The general connections for the AST involve a hose running from the front of the filler neck on the engine (where there should be a flat cap with no spring) to the lower left side of the AST, a hose running down from the bottom of the AST to a small bung on the bottom of the radiator, and a hose running down betweeen the battery and said AST, which then runs across the IC mount brace under the IC (intercooler ) and intake box to the overflow bottle just behind the passenger headlight bulkhead. The plastic unit is infamous for splitting along it's glued seams and dumping a pile of coolant all over the place as well as leading to a massive and immediate overheat as you run with no coolant pressure. The aluminum replacement won't split, though the cap lands on the Pettit can bend or corrode and reduce the sealing efficiency (mine hasn't to date...).

Larz

I still can't believe nobody has designed a thermostat that opens at a slighlty lower temperature. And nobody has made an electric water pump. Perhaps I could fabricate something out of Summit, run it with the car set to the on position on the ignition, and keep it running with a turbotimer to circulate coolant for ten minutes after shut down. Maybe some sort of electric fan mounted by the turbos could be used to cool them and the manifold down during operation.

93redFD

Any problems from running the fans on high all the time? how much of a load are they on the battery?

maxcooper

A thermostat that opens at a lower temperature would not change your car's propensity to overheat. It doesn't matter if the thermostat started to open at 160F or 180F if your car is overheating with the thermostat fully open.

-Max

1sicsol

I aways open the hood and turn the fans on to cool down on hot days.

Mahjik

iTrader: (1)

There is really no need. However, you'll burn out the fans probably before you run down a battery.

If the car is running so hot that you have to run the fans on all the time, something is definitely wrong else where.

Kento

Well, obviously you're going to need the fans running if you're circulating the coolant, otherwise it's wasted energy. You'd better hope that your battery has a lot of reserve capacity and is in excellent condition, otherwise you won't be able to restart your car when you get back. Running the fans and an electric water pump puts a major energy drain on the battery...

BUMBLEBEE7

iTrader: (1)

i use a 160 thermostat 3 Row radiator and a good electric fan and i try to stay away from taffic areas.