If you are an LS fan, your favorite letter in the alphabet should be B, since it is the first letter in the most awesome word in the English language: boost. Perhaps the best thing about any boosted application, including our Kenne Bell-supercharged LS3, is its ability to easily extract extra power. Increasing the power output of a blower engine is a simple matter of cranking up the boost. When it comes to superchargers, everyone knows that more boost equals more power, right? What if we told you that one of the best ways to improve the power output of your supercharged engine was by running less boost? Have we lost our dang minds? Well, that remains to be seen, but rest assured that it is not only possible to produce more power with less boost, but it is actually preferable to do so. In addition to the extra power, dropping boost means lower charge temperatures, which in turn lowers the chance of harmful detonation. So let’s see if we have everything covered. Less boost, more power, and a reduction in harmful detonation. Where do we sign up?
As you might have gathered from the deck, the answer to all our supercharged performance lies in proper cam timing. It’s not exactly breaking news that the LS engine family responds to cam swaps like a Kardashian to a camera. What blown LS fans might not realize is that the factory LS3, or even the blower-specific LS9, cam might not be the hot ticket. Despite (in the case of the LS9) being designed specifically for not only a supercharged, but a positive displacement supercharged, (LS) application neither of these factory cams were designed with maximum power in mind. Their design constraints included longevity, emissions, and idle quality—all of which were counterproductive to power output. That said, it can be argued that the factory LS9 cam is likely the most powerful of the factory offerings (a title shared with the nearly identical LS7), but even the most powerful factory cam is no match for those available from the aftermarket. Enter those LS cam gurus over at Brian Tooley Racing.
Knowing the LS family already responds well to cam timing, the question on the table was: Does this general receptiveness carry over after the introduction of boost? Discovering the answer obviously meant spending some time on the dyno (always awesome), but it also meant locating both a test mule and supercharger system, to say nothing of the test cams. Solving the test engine dilemma was as easy as wheeling over our GM LS3 crate engine from Gandrud Chevrolet. Though not designed specifically for boost like the LSA or LS9, the LS3 offered plenty of power potential and worked well in our testing because we purposely kept boost and our tune at safe and reasonable levels. The LS3 was combined with a Kenne Bell 2.8L twin-screw supercharger. Capable of supporting over 1,000 hp, the combination was more than powerful enough for our simple cam test. Additional safety and power came from the fact that the 2.8L LS3 kit from Kenne Bell featured an integrated air-to-water intercooler. Already efficient thanks to a 4x6, twin-screw rotor pack, the intercooler was just icing on the (already cool) ice cream cake.
Equipped with boost and ready to run, it was time to select cams for our Kenne Bell-supercharged 6.2L. Since this was a supercharged test, naturally we selected one of the factory blower cams. We passed on the less-powerful LSA in favor of the more popular (and powerful) LS9. Compared to the 0.480-inch lift, 198/216-degree duration split, and 122.5-degree LSA offered by the mild LSA cam, the LS9 was better in every respect. The LS9 (from the ZR1 Corvette) offered a 0.588/0.562-inch lift spilt, a 211/230-degree duration split, and 122.5 LSA. To keep things interesting, we also tried the factory (naturally aspirated) LS3 cam. Though not designed for boost, we wanted to see how a naturally aspirated cam would fair against the dedicated blower grinds. The LS3 cam checked in with a 0.551/0.525-inch lift split, a 204/211-degree duration split, and (tighter) 117-degree LSA. The final cam selected for the test was a Stage 3 (positive displacement) blower grind from Brian Tooley Racing (BTR). We specify positive displacement because BTR offers blower cams for centrifugal superchargers that differ from their positive displacement offerings. Yes, they are that specific over at BTR. The Stage 3 cam offered more lift (0.617/0.595-inch lift split), more duration (231/248-degree duration split) and a slightly tighter LSA (120-degree +5) than the factory cams. Despite the wilder specs, the BTR blower cam featured no overlap, coming in just under the wire at -0.5 degrees.
To get things started, we installed the LS3 on the dyno, plopped on the Kenne Bell supercharger, and started our testing with the factory LS3 cam. Running a 3.65-inch blower pulley, 75-pound FAST injectors, and a Holley HP management system, the supercharged LS3 produced peak numbers of 712 hp and 617 lb-ft of torque. The peak boost registered was 10.6 psi at our maximum engine speed of 6,600 rpm. The power and boost were still climbing rapidly, but the goal of the test was not maximum power, but simply to demonstrate the merits of a cam swap. For each test, the air/fuel and timing were kept constant at 11.8:1 and 23 degrees (using 112-octane fuel). After swapping in the LS9 cam, the peak power numbers jumped to 744 hp and 628 lb-ft. The LS9 cam equaled the power output of the LS3 down low, but pulled away from 5,000 rpm up to 6,600 rpm. Equipped with the LS9 cam, the peak boost was up from 10.6 psi with the LS3 cam to 11.1 psi. I guess those engineers over at GM know a thing or two about designing a supercharged LS cam.
The final test of the day involved replacing the LS9 cam with the Stage 3 cam from BTR. Despite increased lift and duration, the BTR Stage 3 cam offered more power through the entire rev range than both of the factory offerings. Run with the BTR cam, the Kenne Bell-supercharged LS3 produced 775 hp and 643 lb-ft of torque, again with power climbing rapidly. The gains offered by the BTR cam would continue to increase with engine speed if we revved this supercharged engine out beyond 7,000 rpm. Power gains are always welcome when making upgrades to your LS, but when you manage to increase the power output through the entire rev range, you know you’ve done something right. Every bit as important as the increase in power was the drop in boost pressure. Equipped with the Stage 3 cam, the peak boost registered just 9.5 psi. This drop in boost now provides you the option of running the combination as is, with more power and a lower boost reading than the factory cams, or cranking up the boost to the level of the factory cams and adding even more power.
01. Our test piece was this LS3 crate engine supplied by Gandrud Chevrolet. Not designed specifically for boost, the LS3 nonetheless worked flawlessly for this test.
02. The key to the efficiency of the Kenne Bell supercharger was the use of their exclusive 4x6, twin-screw rotor pack.
03. To keep inlet air temps down, the Kenne Bell LS3 kit also featured an air-to-water intercooler.
04. Of course, the major player in the Kenne Bell kit was the 2.8L, twin-screw supercharger. Capable of supporting over 1,000 hp on the right application, the supercharger was more than powerful enough for our cammed-up LS3.
05. Mention the phrase “inlet restriction” to the guys at Kenne Bell and watch them get all excited. Knowing that inlet restrictions into the blower reduces boost and flow out of the blower, the 2.8L was equipped with a high-flow, Mammoth intake manifold.
06. Feeding the Mammoth intake was this massive, 168mm oval throttle body. Compared to the factory 80mm throttle body, this 168 offered an additional 1,000 cfm.
07. Boost supplied by the blower is a function of the blower speed relative to the engine speed. Increase the speed of the blower by reducing the size of the blower pulley (or increasing the size of the crank pulley) and the boost will increase. We relied on a 3.65-inch blower pulley from Kenne Bell for this test. No changes were made to the size of the pulley during testing.
08. Since we didn’t have a complete LS3 accessory drive at our disposal, the custom drive system for the Kenne Bell test came courtesy of Mike at Kenne Bell and Kory at Turn Key Engine Supply.
09. Naturally, our supercharged engine required plenty of exhaust. We relied on a set of 1 7/8-inch Hooker headers for our LS3.
10. A consistent and safe tune was a critical element in this cam test. Tuning the supercharged LS3 was this Holley HP EFI management system.
11. The factory LS3 required a single-bolt, 4X timing gear. Equipped with the LS3 cam, the supercharged LS3 produced 712 hp and 617 lb-ft of torque.
12. Out came the LS3 cam and in went the three-bolt LS9 cam. Equipped with the more powerful LS9 cam, the supercharged LS3 produced 744 hp and 628 lb-ft of torque. The LS9 cam improved power over the LS3 cam from 5,000 rpm on up.
13. Having tested both factory offerings, it was time for the Stage 3 grind from Brian Tooley Racing. The three-bolt, BTR cam was designed specifically for positive displacement superchargers and featured a 0.617/0.595-inch lift split, a 231/248-degree duration split, and a wide 120-degree (+5) LSA.
14. Run with the BTR Stage 3 blower cam, the supercharged LS3 produced 775 hp at 6,600 rpm and 643 lb-ft at 5,300 rpm. The boost curve dropped by over 1.5 psi compared to the LS9 cam yet made considerably more power. Sometimes less really is more.
Kenne Bell SC LS3 Cam Test LS3 vs. LS9 vs. BTR Stage 3
In this three-way cam shootout, the obvious winner was the Stage 3 blower cam from Brian Tooley Racing. This should not come as a surprise for two reasons: The first of which is that it’s pretty easy to beat the factory cams in power production because they were never designed to maximize power. They are very popular for blower (and turbo) LS applications, because they are both affordable and readily available. The second reason the BTR cam came out on top was that the head honcho over at BTR knows a thing or two about LS cams, including blower grinds. Note that the naturally aspirated LS3 produced the least power of the bunch, clearly showing the importance of a dedicated blower cam. The LS9 easily out-powered the LS3, but the clear winner was the BTR cam. We loved the fact that this supercharged LS3 produced 775 hp with the Stage 3, but we also loved the drop in boost that allowed us the option of cranking up the boost even further.
Kenne Bell SC LS3-BTR Cam-Hero Run
After running the cam test, we decided we had time for one final hero run. We added 1 degree of timing and ran the engine up to 6,900 rpm. Having produced 775 hp with the BTR Stage 3 cam, we decided the combination was easily capable of eclipsing the 800hp mark. The combination of intercooling, race fuel, and a drop in boost produced by the BTR cam allowed us to safely run the engine up a few hundred rpm. Run out to 6,900 rpm, the Kenne Bell-supercharged LS3 produced 814 hp and 645 lb-ft of torque at a peak boost pressure of 9.8 psi. With another pound of boost and an extra 100 rpm, we think 850 hp is possible and then, naturally, 900 hp would be the next goal. Do you see a pattern here?