Build Turbo Kits

Learn How To Build Turbo Kits

Intercooling

Compressing a gas such as air creates heat. The work done by a turbocharger in compressing air creates an increase in the temperature in the air entering the intake. The hot air is less dense than cooler air, and can cause detonation that can lead to broken pistons etc. In some turbo systems, charge air temperatures can reach up to 350 degrees F. We want to cool the charge air in order to pack more air molecules into the cylinders, reducing the likelihood of detonation and engine damage.

Air to Air Intercoolers

An intercooler is a heat exchanger. Tubes run through the intercooler containing the hot charge air from the turbo. In an air to air intercooler, heat is transferred from the tubes to fins on the outside of the intercooler. Cool air flows over the fins, transferring heat to the air. The result is a cooler, denser air charge entering the cylinders, resulting in better performance with a lower chance of detonation.

Air to air intercoolers range in size and configuration. Be sure to look at the maximum flow and horsepower supported when purchasing an intercooler. Higher horsepower systems will of course require larger intercoolers than lower horsepower outputs.

Air to air intercoolers come different configurations. For example, two inlets with one outlet for twin turbocharging, one inlet and one outlet for singles, side exit, top exit etc.

Some people running twin turbo systems utilize two smaller air to air intercoolers rather than one large one. What type(s) you choose depends on your horsepower level, available installation space etc.

Air to Air Intercooler on a 98 Trans Am. . Photo courtesy of Nick Nagrodsky aka ddnspider.

See more of Nick’s Trans Am build at http://my.fit.edu/~nnagrods/mp/

Air to Water Intercoolers

Another type of intercooler that is becoming more popular these days is the air to water intercooler. The air to water intercooler is a heat exchanger that transfers hot air in the charge pipe to cool water.

In the air to water intercooler, a reservoir holds water that is pumped through the intercooler. A fan is sometimes used to cool the water in the reservoir. The charge pipe runs through the intercooler, where it contacts cool water. Heat from the charge pipe is exchanged into the water.

The air to water intercooler is used mostly in drag racing applications. A few people are running them on the street, but most daily driven forced induction applications use the air to air intercooler. One advantage of the air to water type is that ice water can be used in the reservoir at the race track, giving incredible cooling effects and increasing horsepower.

Air to water intercooler.

Water/Methanol Injection

An alternative to heat exchanger types of intercoolers, is alcohol and water injection. In this type of system, a fine mist of methanol and water is injected directly into the intake charge providing chemical cooling. The effect of this is a cooler intake charge, and also cooler cylinder temperatures.

Water has a high latent heat of vaporization. That is the amount of heat that is absorbed when it turns from liquid to vapor. In simple terms, water absorbs a lot of heat. Another advantage to using a water and methanol mix, is that the methanol acts as an octane booster helping to stave off detonation, and allowing a more aggressive timing curve.

Injection systems use a high pressure pump and misting nozzles to provide a fine mist into the charge. The mist should be introduced into the system after the MAF, as water flowing through the MAF will cause inaccurate readings and cause problems. Many systems inject the mist into the throttle body just before the throttle blade.

A boost referenced switch is sometimes used to fire the pump that supplies the mixture. The switch, such as a Hobbs switch can be selected or set to turn the pump on at a desired boost pressure.

An injection system also utilizes a solenoid that opens when the pump is on, and closes when the pump is off. This prevents water from dumping into the engine should the pump malfunction and stay running.

A check valve is sometimes used near the misting nozzle to prevent the mix from dripping into the throttle body when the system is off.

Misting nozzles for methanol/water injection come in many different sizes. Below is a listing of common nozzles used and flow rates.

Nozzle Flow Rates:
M1(.011") 1.0 GPH @ 100 PSI, 1.2 GPH @ 150 PSI
M2(.015") 2.0 GPH @ 100 PSI, 2.4 GPH @ 150 PSI

M3(.020") 3.0 GPH @ 100 PSI, 3.6 GPH @ 150 PSI

M4(.024") 4.0 GPH @ 100 PSI, 4.8 GPH @ 150 PSI

M5(.035") 5.0 GPH @ 100 PSI, 6.0 GPH @ 150 PSI

M7(.045") 7.0 GPH @ 100 PSI, 8.4 GPH @ 150 PSI

M11(.073") 11 GPH @ 100 PSI, 13.2 GPH @ 150 PSI

There are programs online available to calculate the required gph flow rate for any application. A Yahoo! or Google search will turn up online calculators for gph requirements. For example, a 350 cubic inch displacement engine running at a maximum of 6000 RPM and having a boost pressure of 5 psi requires about 8.5 gph. Looking at the chart above, we could use an M7 nozzle at a pump pressure of 150 psi.

Injection can also be set up as a staged system. Multiple pressure switches can be used to turn on multiple nozzles. For example, if you are producing 15 psi at 6000 RPM (12 gph required), and 8 psi at 4000 RPM (8.6 gph required), you could stage an M7 nozzle to fire at say 5 psi, and an additional M3 to fire at 15 psi with a 150 psi pump.

You will be happy to know that off the shelf windshield washer fluid contains a methanol/water mix. Washer fluids will contain different amounts of methanol depending on the temperatures for which they are designed to be used in. The higher the resistance to freezing, the higher the methanol content contained in the fluid. Do not use washer fluids that contain cleaning agents. Look at the ingredients before buying. A good test is to shake the bottle and watch for foam. If no foam is present, the fluid does not contain cleaning agents.

Many race fuel and speed shops sell methanol at reasonable prices.