Words And Photos: Richard Holdener

A couple of months back, we ran an intercooler test on a turbocharged LS, but that test involved simply shutting off the water flow to the core. For this test, we illustrated the difference between having and not having an intercooler on a Vortech supercharged application. What we will see is that no matter what form of forced induction you run, it is always beneficial to combine it with intercooling.

In addition to the changes in power, we also logged the change in inlet air temperatures and the change in boost pressure that resulted from replacing the discharge tube with the intercooler and associated plumbing. Running the Vortech V3 supercharger on a small and mild 4.8L resulted in elevated boost pressure (with our available pulley combos), so it turned out to be the perfect candidate for an intercooler test. The non-intercooled combo produced over 15 psi, so this is not a situation you would attempt to run on pump gas. All of our testing was run using the safety of race fuel, so we felt confident tuning the combination at the elevated boost levels, even without the intercooler.

The test was rather straightforward, involving a 4.8L test motor equipped with a Vortech V3 supercharger. The 4.8L featured forged JE pistons, TFS Gen X 205 heads and a Stage 1 truck cam from Brian Tooley Racing. Also present on the test motor were 83-pound injectors and a HP management system from Holley along with a stock truck intake and Accufab throttle body. All testing was run with a Meziere electric water pump, Lucas synthetic oil and long-tube headers.

The Vortech kit featured a self-contained V3 supercharger that required no oil drain in the pan. Vortech also supplied the necessary mounting brackets, tensioner and dedicated aluminum discharge tube, complete with blow-off valve. The combination of an ATI Super Damper and 3.80-inch blower pulley (the biggest we had), resulted in a boost pressure curve that started at 3.3 psi and climbed to a peak of 15.2 psi. Run with 22 degrees of total timing and an air/fuel mixture of 11.8:1, the (non-intercooled) supercharged 4.8L produced 699 hp and 565 lb-ft of torque.

Using the dyno to log all the valuable data came in handy during testing. Run without an intercooler at 15.2 psi, the charge temperature exiting the supercharger rose from 104 degrees to a high of 184 degrees. Naturally we wanted to drop the elevated air temperature so we installed an intercooler. Vortech offers a number of intercoolers, but we chose one we had on hand from previous testing. Having tested the CXRacing core at over 1,000 hp, we knew it was more than adequate for this supercharged 4.8L. Using aluminum tubing from DNA Motoring, the CXRacing core was positioned between the outlet of the supercharger and the inlet of the throttle body. Although optimum power would come with ice water, this test was performed with 90-degree dyno water running through the core. The intercooler tubing was also configured with a Race Port blow-off valve from Turbo Smart. Naturally we were excited to see the power and temperature differences offered by the intercooler.

It goes without saying that the air/fuel and timing curves were duplicated for both combinations, but the power and temperature differences were significant. Run with the intercooler, the power jumped by as much as 40 hp at 5,900 rpm thanks to a drop in inlet air temperature of 84 degrees. Rather than rising from 104 degrees to 184 degrees, the inlet air temp with the intercooler leveled off at a peak of just 100 degrees. These results are all the more impressive when you consider this was with 90-degree water used for cooling. The other interesting bit of information we gather during testing was that the boost curve dropped slightly after installation of the intercooler. The change in boost increased with engine speed (see graph), but this was not due to a restrictive intercooler core, rather a combination of the additional length of inlet tubing, the number of bends and the significant drop in air temperature. As with the previous test on the turbo motor, this test once again shows that importance of chillin’ out your supercharged LS application with intercooling.

Adding the intercooler to the Vortech supercharger made a significant difference in power. The intercooler was worth as much as 40 extra hp at 5,900 rpm, and who couldn’t use an extra 40 hp, especially when it helps reduce the chance of harmful detonation?

This graph illustrates the significant drop in inlet air temperature offered by intercooling. Run without the intercooler, the charge temperature rose by 80 degrees, from 104 degrees to 184 degrees. After installation of the intercooler, the temperature stabilized significantly, rising from 90 degrees to only 100 degrees. Remember, this was using 90-degree water running through the core, so additional cooling is possible with cooler ambient or (ideally) ice water in the intercooler.

This final graph shows the difference in boost pressure with and without the intercooler. Adding the intercooler dropped the boost pressure by a maximum of 1.4 psi at 6,500 rpm. The difference was less at lower engine speeds, but before we starting thinking a restriction in the intercooler core is responsible for the pressure drop, know that the increased length of tubing (and bends) and change in temperature contributed to the majority of the change in boost pressure. The core had been run successfully at over 1,000 hp with minimal pressure drop so we know it is efficient at this power and boost level.  Vortech also offers a number of intercooler options to help your supercharged LS chill out.

Sources

Brian Tooley Racing
briantooleyracing.com

CXRacing
cxracing.com

DNA Motoring
dnamotoring.com

Holley/Hooker
holley.com

JE Pistons
jepistons.com

Lucas Oil
lucasoil.com

Trick Flow Specialties
trickflow.com

Turbo Smart
turbosmartusa.com

Vortech Superchargers
vortechsuperchargers.com