A Kenne Bell twin-screw supercharger is all you need to add big power to your LS3!

Words and Photos By: Richard Holdener

Okay, we might have a screw loose, but sometimes you just want to go big. What better way to go big with your LS3 than with a little boost? Not to put down the other forms of power persuasion like cams, nitrous, or even increased displacement, it’s just that boost is so awesome. Heck, it can even be combined quite successfully with all those others, making a good thing even better.

To illustrate the benefits of boost to your LS, we set up a test using an LS3 crate motor. Supplied by Gandrud Chevrolet, the LS3 crate motor was a factory fresh 6.2L plucked from the assembly line back before the LT series took over. Rated by GM at 430 hp (436 with optional exhaust), the LS3 featured plenty of positive attributes, including displacement, compression, and massive, rec-port head flow. As good as it was in stock trim, we scheduled a couple of tests to greatly enhance the power output of great little crate. The plan for our LS3 started with boost from a Kenne Bell supercharger, followed by a cam and throttle body upgrade.

Our GM LS3 crate motor came from the good folks at Gandrud Chevrolet. Run with headers, a Meziere electric water pump, and Lucas 5W-30 oil, the stock 6.2L produced 492 hp and 489 lb-ft of torque.

For our crate motor, we selected a Kenne Bell supercharger kit designed for a 2010 Camaro. Available with different displacement superchargers, we selected a 2.8L for our otherwise stock LS3. Capable of supporting more than 1,000 horsepower, the 2.8L was not only more than sufficient for our power needs, but featured both Liquid Cooling and air-to-water intercooling. The Liquid Cooling channeled water internally to the hot (discharge) side of the supercharger to equalize the case temperature to minimize distortion. The system also featured conventional air-to-water intercooling to help lower the inlet air temps under boost. Combined with an already efficient twin-screw supercharger design, the result was a system that maximized the power gains for each pound of boost.

That cooling and efficiency was then combined with a high-flow, Mammoth intake manifold to eliminate restrictions in the inlet system. Airflow restrictions in front of the blower result in less boost and power out of the blower. The Mammoth was designed to accept throttle body sizing from stock (90-mm) up to the massive 168-mm, oval throttle body from Kenne Bell.

The first order of business was to prep our 6.2L crate test motor for the Kenne Bell supercharger kit. Lucky for us, the LS3 was basically a stock 6.2L Corvette crate motor that featured the impressive LS3, rec-port aluminum heads. We simply replaced the damper (crank pulley) with a Camaro/Truck offset and added a Meziere electric water pump with idler (so it free spun). Kory at Turnkey Engine Supply and Mike over at Kenne Bell hooked us up on the remainder of the drive system required to run the supercharger without all of the factory accessories.

Before installation of the supercharger, we ran the stock LS3 on the dyno with Hooker headers, no accessories, and Lucas synthetic oil. Equipped as such, the normally aspirated LS3 produced 492 hp at 6,000 rpm and 489 lb-ft of torque at 4,700 rpm. The difference between this power output and the 430-hp rated output was a function of the lack of factory accessories, exhaust and air intake, along with us running an optimized tune (and a slightly lower water temp).

After the normally aspirated baseline, we installed the Kenne Bell supercharger.  Off came the stock intake and (manual) throttle body and on went the lower intake, injectors, and finally the polished 2.8L supercharger. Also present was the Mammoth intake, bypass valve, and FAST 90-mm throttle body. We selected a set of 60-pound injectors to ensure adequate fuel delivery, and the supercharger was set up with a 3.75-inch blower pulley that resulted in a peak boost pressure of 9.9 psi at 6,500 rpm. Thanks to plenty of belt wrap, the new 6-rib drive assembly ran flawlessly during testing. Nothing is more frustrating than belt slippage, but this system produced a dead repeatable boost curve run after run.

After installation of the Kenne Bell kit, the supercharged LS3 pumped out 672 hp at 6,500 rpm and 618 lb-ft of torque at 4,100 rpm. The supercharger offered not just massive peak power, but huge torque gains through the entire rev range. The peak power was up by 180 hp, while the boost added 129 lb-ft of torque. Adding 180 hp is only something that can be accomplished with a power adder, and we were just getting started with this Kenne Bell kit.

After adding the supercharger, we started to get greedy and focused our attention on the camshaft. Everyone knows that normally aspirated LS motors respond well to cam swaps, so why not supercharged combos? To find out, we decided to run a cam test, but rather than select what should be in there (meaning a dedicated blower cam), we selected a normally aspirated cam (designed for a cathedral-port application to boot). This test told us what happened if you installed the “wrong” performance cam in your blown LS.

The cam in question was one of our favorites (for an NA combo) from COMP cams. The 281LR HR13 cam (pt#54-459-11) featured a .617/.624 lift split, a 231/239-degree duration split, and 113-degree lsa. The COMP cam also required installation of a three-bolt cam sprocket (see photos), as the factory LS3 featured a single-bolt cam and sprocket. Run with the COMP NA cam, the power numbers jumped from 672 hp and 618 lb-ft to 724 hp and 645 lb-ft of torque. As with the blower upgrade, the cam swap improved power through the entire rev range. I guess blower motors like NA cams too!

The final test involved replacing the 90-mm FAST throttle body with the massive 168-mm, oval throttle body from Kenne Bell. Positive displacement superchargers do not like airflow restrictions, and even a 90-mm throttle body becomes restrictive at this elevated power level. Any restriction to the blower reduces airflow out of the blower. The result is a drop in boost pressure combined with a loss of power. The amount of restriction increases with the power and boost level, meaning the gains offered by a throttle body upgrade (like this 168 mm) will increase with boost and power.

LS3 Crate Motor-NA vs Kenne Bell (9.9 Psi) 
There really is no better way to add massive power to an LS3 crate motor than with boost. The Kenne Bell, 2.8L twin-screw supercharger offered both efficiency and capacity. Equipped with an air-to-water intercooler to keep charge temps down and a pulley combo to produce a peak boost pressure of 9.9 psi, the supercharger kit increased the power output of the stock LS3 crate motor from 492 hp and 489 lb-ft of torque to 672 hp and 618 lb-ft of torque. The upgrade increased the power output of the LS3 by 180 hp and 129 lb-ft of torque.

KB SC LS3-Stock vs Comp Cam 
Knowing that LS motors respond VERY well to cam upgrades, we decided to perform the time-honored tradition to our supercharged LS3 crate motor. Normally, we would install a dedicated blower cam, but rather than go that route, we decided to run a normally aspirated we had sitting around just to see what happened.  Would the NA cam (designed for a cathedral-port application no less) even work on the supercharged LS3? You bet! After installation of the COMP 459 cam, the power output jumped to 724 hp and 645 lb-ft of torque. Due to the increased efficiency of the new combination, the boost pressure dropped from a peak of 9.9 psi to 8.4 psi. More power with less boost — the best of both worlds (and yes, you can now turn up the boost with a pulley change to get even more power at an equal boost level).

KB SC LS3 Throtle Body Test-90-mm vs 168 mm 
One area often overlooked on supercharged applications is the induction system that feeds the supercharger. We know boost comes out of the blower, but the boost out is a function of the airflow in. If you restrict the air into the supercharger, you restrict the boost and power out of the blower. To illustrate this, we replaced the 90-mm throttle body on the Kenne Bell Mammoth intake (used with an adapter plate) with a larger, 168-mm (oval) version. The Kenne Bell throttle body offered an increase of 1,000 cfm over the 90-mm throttle body. Run on our supercharged, cammed-up LS3, the throttle body increased the power output by 23 hp and increased boost pressure by .2 psi.  As with any airflow increase in front of the supercharger, the gains offered by the throttle body will increase with boost pressure and power level. We have seen gains exceed 60 hp with this throttle body at 18 psi.

Tested at 500 hp, the throttle body might be worth nothing, but tested at 900 hp, we have seen gains of 60 hp. Run on this supercharged LS3, the throttle body upgrade resulted in an extra .2 psi of boost and 23 hp, from 724 hp to 747 hp.  The cam swap resulted in a drop in boost (due to increased efficiency), while the larger throttle body increased the boost pressure thanks to increased airflow. If you are looking for big power from your LS3, you’d have to have a screw loose if you don’t at least consider boost from a Kenne Bell supercharger.

The final test involved installation of this 168-mm, oval throttle body from Kenne Bell. By increasing airflow to the blower, the throttle body upgrade increased the boost pressure by .2 psi and increased the power output up to 747 hp.

Sources: COMP Cams, compcams.com; FAST, fuelairspark.com; Gandrud Chevrolet, parts@gandrud.com; Holley/Hooker/Weiand, holley.com; Kenne Bell, kennebell.net; Turnkey Engine Supply, www.Turnkeyenginesupply.com