The grind featured a .615/.595 lift split, a 229/244-degree duration split, and 113-degree (+4) LSA. The cam was combined with a dual-spring upgrade to replace the factory LS3 springs. Other components used on the test engine included a FAST management system and injectors, Hooker long-tube headers, and a Meziere electric water pump.
Running 5 quarts of Lucas oil and the longest of the three runner configurations, the LS3 produced 562 hp at 6,400 rpm and 512 ft-lbs of torque at 5,200 rpm. Installation of the medium-length runners increased peak power to 568 hp at 6,800 rpm, but torque dropped to 490 ft-lbs at 5,300 rpm. The final test involved installation of the shortest runners that resulted in 577 hp at 7,100 rpm, but torque dropped further still to 478 ft-lbs at 5,300 rpm. Each successive decrease in runner length resulted in increase peak power but a drop in torque (in this case, below 6,500 rpm).
The adjustable intake offered three bolt-in runner lengths to dial in the power curve to a specific combination.
The LSXR adjustable intake looked just like the original, but under the lid was a surprise.
FAST Adjustable LSXR Intake on a Mild LS3 (Horsepower)
FAST LSXR Long Runner: 562 hp @ 6,400 rpm
FAST LSXR Medium Runner: 568 hp @ 7,000 rpm
FAST LSXR Short Runner: 577 hp @ 7,100 rpm
Largest Gain: 20 hp @ 6,700 rpm
Looking at the numbers, you might be tempted to pick the intake combination that offered the highest peak power. Unfortunately, we do not live by peak power alone. While the middle and shorter runner offered higher peak power numbers, there was a trade-off in power elsewhere in the curve. Only above 6,500 rpm and below 3,400 rpm did the middle or shorter runners offer more power.
FAST Adjustable LSXR Intake on a Mild LS3 (Torque)
FAST LSXR Long Runner: 512 ft-lbs @ 5,200 rpm
FAST LSXR Medium Runner: 490 ft-lbs @ 5,300 rpm
FAST LSXR Short Runner: 478 ft-lbs @ 5,300 rpm
Largest Gain: 45 ft-lbs 4,400 rpm
The results of this test on the mild (cam-only) LS3 clearly show the effects of changes in runner length. The trick LSXR adjustable intake allowed me to show the drop (or increase) in torque at lower engine speeds offered by shortening or lengthening the runners. The shortest runner offered the lowest peak torque, followed by the middle runners. The longest runners offered the highest peak (and average) torque production.
Test 7: Stock vs Kenne Bell 102-mm Throttle Body on a KB SC LS3
About the only thing better than a modified LS engine is a supercharged one. Nothing adds zing to an LS like some boost from a Kenne Bell twin-screw supercharger. While twin-screw kits are efficient and powerful, boost is only the beginning. The reality is that superchargers are only as good as their induction system.
Nothing chokes off the power potential of a supercharger faster than a restrictive throttle body or associated inlet components. Knowing this, the question is, How much power is a throttle body upgrade really worth? As an airflow device, the modified power output determines the amount of power hindered by the flow restriction inherent in the stock inlet system. This means that the more powerful the engine, the more restrictive the stock components become. This should not come as a big surprise, since the factory inlet system and throttle body were never designed for the elevated power levels offered by a Kenne Bell supercharger. The inlet system that General Motors designed to support 425 hp has no business on a supercharged engine making 600 or more horsepower.
It is important to stress here that power gains offered by the throttle body are entirely dependent on the engine combination. As a simple airflow device, the higher the power output of the test engine, the larger the throttle body required.
As an example, installation of a larger throttle body capable of supporting 1,000 hp is of little use on a 425-hp engine equipped with an (already oversized) throttle body capable of supporting 750 hp. The 750-hp throttle body is already oversized for the application, so there is no need to upgrade on the NA engine. Things change on (draw-through) supercharged applications, where elevated power levels are more commonplace. Although 600-hp NA Camaro engines are less common, supercharged LS3s exceeding 600, 700, or even 800 hp are everywhere.
This round of testing on a Kenne Bell supercharged (2010 LS3) Camaro illustrated that a throttle body upgrade on a 600-hp application (9.3 psi on stock engine) was worth 8 hp. Performing the same test at 13 psi (678 hp) was worth 26 hp (up to 702 hp) and an amazing 34 hp at 17 psi (from 755 hp to 789 hp). The higher the boost (and power) run on the test engine, the greater the losses associated with a restrictive throttle body. It is important to note that testing the same throttle body upgrade on the NA LS3 was worth 0 extra hp.
Airflow increases dramatically when you install a Kenne Bell twin-screw supercharger.
This round of testing was performed on a 2010 LS3 Camaro equipped with a 2.8L, twin-screw supercharger kit from Kenne Bell.
Stock vs Kenne Bell 102-mm Throttle Body (13psi) (Horsepower)
Stock 90-mm LS3 TB: 678 hp @ 4,300 rpm
KB 102-mm TB: 702 hp @ 4,400 rpm
Largest Gain: 26 hp @ 4,700 rpm
A throttle-body upgrade offers power gains that are in relation to the power output of the test engine. Tested on the stock NA, the larger throttle body was worth nothing. Tested at 13 psi, the upgrade was worth 26 hp.
