hannibal

Cooling Tech (excerpts from several chapters in the RX-7 book)


Heat Shielding (Intake Chapter)

For street use, a heat shield or box that surrounds and isolates your air intake is always a good idea. It may not be necessarily, however, if you spend your time at high speed track events where lots of cooler air is rushing into the engine compartment. Stop-and-go driving is the real culprit since it allows time for the engine compartment to heat up. A standard air velocity system will have no choice but to suck in that hot air. To keep some of the hot air away from the air intake, a heat shield box is recommended. The best boxes are made out non-heat absorbing material, such as plastic, rubber, or carbon fiber. You can also make your own if you have the time and patience.

One of the best things you can do for a 2nd or 3rd gen RX-7 (or GSL-SE) is to fabricate a heat shield to fit between the turbo manifold and the intake manifold. There is currently no one making such a product at this time, but there are a few custom units floating around. The idea we are trying to drive home is to try to disburse as much heat as possible. This rule of thumb is important with any hopped-up car, but it is critical for a rotary engine. One knock can cause detonation, and then it will be time to check the limit on your Mastercard!

Cooling Tech (Intake Chapter)

It is common knowledge that colder air entering your intake system will yield more horsepower than warmer air. Some RX-7 drag racers have been known to install an NOS system not to feed NOS gas into their intake. They have the system in place just so that they can give their intercooler an occasional squirt of freezing NOS gas to help keep the incoming air cooler.

As we discuss in Chapter 10, the drawback of any turbo or supercharging system is that as they compress the air, heat is generated. Turbos use exhaust gasses to compress the air, so the result is even hotter air. ThatĄŻs why you need an intercooler. Now stay with us on this one. Colder air, by nature (of should we say, science), is denser. Denser air combusts with more gusto than air at normal atmospheric pressure. So if you can get both cold and dense air, you will have more power than youĄŻll know what to do with.

2G and 3G turbos, and even non-turbo fuel injected rotaries can benefit from a cooler intake. The same theories hold water for carburetored 1G RX-7ĄŻs. ItĄŻs just harder to get to the intake manifold to cool it with these cars. There are, however, aftermarket heat shields available to keep the intake temperature from climbing too high when exerting the engine.

The fuel injected systems have intakes that are right on top of the motor. RX-7 autocrossers routinely put ice on the manifold to cool it between runs, or they squirt it with cold water. Autocrossing doesnĄŻt really get your engine too hot since you are only out on course for one minute at a time. But thatĄŻs long enough to get the turbo and intake hot. But be careful where you spray the water - keep it on the intake and away from any other electrical components.

In the next chapter, weĄŻll discuss exhaust systems, but some of that info is pertinent here Your intake manifold and engine block will remain cooler if you are efficient at getting the exhaust gasses away from the engine and out the tailpipe. A better exhaust system will also help keep the intake slightly cooler.

Colder is Faster (and vice versa - from Turbo chapter)

Another thing to consider, whether or not you trade up for a more potent turbo system, is to install an aftermarket intercooler. Your stock Mazda unit is designed to cool down the compressed air before it enters the intake manifold, and for the most part it does a good job. But good automotive engineers never sleep. They always seems to find ways to improve on a good thing. And thanks to the growing popularity of the import drag movement, the motivation to find ways to go even faster has given birth to a new breed of intercooler technology.

Again, the more you can cool down the compressed air before it is mixed with fuel, the more horsepower your engine can generate. Denser air makes for better and more complete combustion. So if you can replace your stock unit with a more efficient, racing-type intercooler, your engine will respond with more lively performance. One of the best examples of aftermarket intercooling can be found in Manassas, Virginia, home of Peter Farrell Supercars. Farrell has designed a unit for 2G and 3G cars that works better than the stock system, is less restrictive, provides denser air to the intake, and looks cool all at the same time.

Cooling Tech (from turbo chapter)

As mention in several of the chapters, a cool engine is a happy engine. But there are some things that are working against keeping your rotary happy. For a third gen car, one of these things is the stock air separation tank (AST). The ASTĄŻs task is to break up air bubbles in the cooling system. The problem is that the stock unit has been known to burst, and is not very efficient at dispersing heat. Both Excellent Performance (Pettit) and Tri-Point offer a solution to this problem. A more efficient, aluminum AST that wonĄŻt burst, and also helps to disperse heat since itĄŻs aluminum.

There are also a variety of aftermarket radiators and oil coolers available. Both will provide added cooling, possibly just enough to keep your car out of the red when its hot outside. If you are inclined to do so, we recommend replacing your stock radiator hoses with stronger silicone ones. Some racers can even use steel braided hoses, which also help to radiate some heat (it all adds up). Water Wetter (radiator additive) has also been proven to reduce coolant temperatures.
Finally, 3G cars may need to replace the sending units for oil pressure and water temperature as they are prone to failure. If your car doesnĄŻt have a temperature indicator, it is a must to have this gauge a rotary engine.

THERE IS MUCH MORE COOLING ADVICE THROUGHOUT THE RX-7 BOOK
These are just some selected excerpts from various chapters