How to Supercharge & Turbocharge GM LS-Series Engines - Revised Edition. Barry Kluczyk

versions feature variable valve timing (cam phasing). Manufactured with iron and aluminum cylinder blocks.

      6.0L: Used primarily in 3/4-ton and 1-ton trucks, the 6.0L (364 ci) uses an iron block (LY6 or L96) or aluminum block (L76) and aluminum heads with provisions for Active Fuel Management; some are equipped with variable valve timing.

      6.2L: Commonly referred to by its L92, L9H, or L94 engine codes, the 6.2L (376-ci) engine uses an aluminum block and heads and incorporates advanced technology, including variable valve timing. The L92 was used primarily as a high-performance engine for the Cadillac Escalade and GMC Yukon Denali.

       More About the Vortec 5.3L

      With more than 10 years in service in millions of Chevy and GMC trucks, vans, and SUVs, the Vortec 5.3L engine is poised to become the classic 350 small-block of the LS engine family. They are readily available and affordable on the used engine market. Most feature iron cylinder blocks, but some have an aluminum engine block that is about 80 pounds lighter.

      Adapting a 5.3L to a hot rod project is easier with Chevrolet Performance’s 5.3L controller kit (part number 19256514), which is tailored to retrofit installations by “turning off” some of the production features that are unnecessary for a vintage car, including the cylinder-deactivating Active Fuel Management. It covers 2007–2009 applications (non-cam-phased) with the following engine codes:

      • LC9 (2007–2009)

      • LMG (2007–2009)

      • LY5 (2007–2009)

      • LH8 (2008–2009)

      • LMF (2008–2009)

       An L94 Vortec 6.2L Gen IV is shown. (Photo Courtesy General Motors)

       Chevrolet Performance LS and LSX High-Performance Crate Engines

      Chevrolet Performance has offered a number of LS high-performance crate engines based on production LS engines or the racing-oriented LSX series of components, including the cast-iron LSX Bowtie Block. They include:

      LS376/515: Based on the LS3, it features the “ASA Hot Cam” to help push output to 525 hp and 477 ft-lbs of torque. It is designed for a carburetor.

      LS376/525: Similar to the LS376/515, this version also uses the ASA Hot Cam, along with an LS3-based induction system and port fuel injection.

      LSX376-B8: An economical crate engine that uses the LSX block, LS3 rotating parts, and the LS3 cylinder heads. It is offered without an oil pan or induction system, so that it can be tailored for the project vehicle.

      LSX376-B15: Designed to accommodate additional power adders, or boost up to 15 psi, includes forged pistons, forged crank, and six-bolt LSX-LS3 cylinder heads.

      LSX454: The displacement of the classic big-block with an all-forged rotating assembly and LSX-LS7 six-bolt cylinder heads. It is rated at 627 hp with a carburetor and 580 with an LS7 fuel-injection system.

      Excellent airflow characteristics of the basic LS cylinder head design greatly exploit the benefits of forced induction, as air is easily and quickly moved through the engine. Because of this, a higher-capacity supercharger or larger turbo is often used, when compared to older, previous-generation Chevy small-block designs, to fulfill the airflow capability of a free-flowing LS engine.

      LSX454R: A high-compression (13.1:1) version of the LSX454 designed for drag racing, featuring a mechanical roller cam, high-rise intake, and more. It is capable of more than 750 hp.

Supercharging Versus Turbocharging

      At their most basic, turbochargers and superchargers are air pumps but with different pumping characteristics. The turbocharger is an exhaust-driven pump that saps no engine power when not making boost. A supercharger is an engine-driven pump that is essentially another component on the accessory drive system and requires a modicum of power to drive, even when it’s not producing much or any boost.

      The thermal efficiency, also known as adiabatic efficiency (the amount of combustion energy that is converted to power), is generally greater with a turbocharger system than a supercharger because it recycles a significant amount of exhaust energy to spin the compressor. That exhaust energy is lost to the exhaust system in normally aspirated and supercharged engines. That said, centrifugal and Lysholm (screw-type) superchargers can be up to 85-percent efficient, for comparable efficiency with a turbocharger.

      In general terms, superchargers deliver greater power and torque at low- and mid-range RPM levels with nearly full boost available immediately at wide open throttle (WOT). A supercharger’s effectiveness tends to trail off at higher RPM, while turbochargers typically deliver their greatest power contribution at mid- to high-RPM levels, with boost building progressively in line with an increase of engine speed. Turbochargers are also very good at building mid-range torque, and when properly sized, can deliver excellent low-end power too.

      There are a number of factors to consider before purchasing a bolt-on system. The performance requirements and engine demands for custom combinations and racing applications are different, but for the enthusiast seeking to add a forced-induction system to his or her vehicle, the following points are the most relevant.

      Superchargers (particularly Roots and screw-type blowers) are excellent at delivering low-RPM power, as they are always making at least a minimal amount of boost when the engine is running. That’s because the supercharger is directly linked to the crankshaft via the drive belt. That connection also requires a small amount of horsepower to simply turn the supercharger.

       Power Projections

      Generally speaking, a supercharger will produce about 6 percent greater horsepower for every pound (0.07 bar) of boost, while a turbocharger will produce about 7 percent greater power for every pound. The turbo’s advantage there is due to the parasitic loss of the supercharger’s drive system. It simply costs some power for the crankshaft to drive the blower. The exhaust-driven turbocharger doesn’t have such a drag.

      Turbochargers require no engine power to drive and, therefore, are considerably more efficient than an engine-driven supercharger. However, boost only occurs when the engine RPM rises. At low speeds, particularly off idle, the turbocharger provides no horsepower increase.

      The advantage of turbocharging in a racing application is clearly illustrated in this partially constructed fourth-generation Firebird, as two very large turbochargers were adapted to an LS engine. Except for the older, “71”-series superchargers used in Top Fuel, Top Alcohol, and some Pro Mod–type drag racing classes, there aren’t Roots and screw-type superchargers that deliver the airflow of a pair of extra-large turbos. Even large centrifugal blowers are limited to only one per engine. With a pair of turbos, each driven by half of the cylinders, the only real limit is keeping the engine itself together under maximum boost.

      Apart from the capacity to change the drive pulley on some superchargers, the output of a blower is pretty much determined by the size of the compressor. With a turbo system, a number of elements are easily manipulated to increase power. In fact, the almost-infinite adjustability of turbo systems is one of their primary appeals.

       Performance Range

      As noted earlier, superchargers (particularly Roots/screw types) generally deliver gobs of low-end power and become less efficient at higher RPM. The opposite is generally true for turbochargers; they tend to deliver their greatest