A lot of people gravitate towards "inverted" superchargers, with GM's LSA being the best-known example. As the name implies, inverted superchargers position the rotors below the intercooler.  This positions the supercharger lower in the intake valley. It's all about packaging.  Air flows into the front of the supercharger, through the rotors, then up through the intercooler. Compressed air then changes direction and heads back down into the cylinder heads. With an inverted supercharger, the "Lid" plays a critical role by housing the intercooler and directing air from the intercooler into the cylinder heads.

While LSA and LT4 superchargers might fit well under the hood, displacement and intercooler efficiency limit output. The LSA supercharger has a 1.9L displacement while the LT4 supercharger has a 1.7L displacement. Both capacities are small by today's standards.  By comparison, the LT5 supercharger measures 2.65L (2650cc). Nice, but the LT5 requires a complicated high-pressure "direct injection" fuel system.

We sell more drive kits for GM LSAs than any other supercharger, but demand for large displacement systems has taken off. If you want big power from a supercharger, we say: "Work smarter, not harder". Choose a supercharger with more displacement and a larger intercooler. Bigger really is better.

Bigger "LSA" Superchargers

You have many options. Magnuson and Harrop both make big inverted designs with up to 2650cc displacement -- Magnuson offers the Magnum 2650, while Harrop offers an LSA2650.  Both designs also accept factory LSA lids.

The big doggie -- the current King of inverted superchargers for LS engines -- is Whipple's Gen 6 3.0L Inverted supercharger. Part # WHR1200-30 (LS3) /WHR1210-30 (LS7). For this article, we'll just call it the "3.0L". Calling this design an LSA-type supercharger is a stretch, but the fore/aft drive offset matches an LSA.  There's also more to the Whipple 3-liter's design differences than just displacement and intercooler volume. The key differences are in rotor design (roots vs twin screw) and intercooler design (single pass vs dual pass). Let's dig in.

Roots vs Twin Screw

Magnuson (shown above) and Harrop both utilize Eaton's excellent TVS (Twin Vortices Series) Roots-type rotor design. In the Eaton design, two rotors with four lobes each are twisted with a 160-degree helix to create the squeeze. The above Magnuson cutaway shows two symmetrical Roots-type rotors. With a Roots supercharger, the rotating lobes trap air in the gaps between the lobes and the outer supercharger casing and force the air volume down into the engine. It's a tried-and-true design that has evolved greatly with computer-aided design and intercooler technology. Hot rodders have been using Roots-type superchargers since shortly after World War II. 

Check out the two asymmetrical rotors in the cutout shown above. This is Whipple's twin-screw design. The name "twin-screw" is weird since the two rotors are completely dissimilar. The 4-lobe "male" rotor on the left interfaces with a "female" 3-lobe rotor on the right. 

Air enters at the front of the rotor pair and is compressed as it moves axially between the rotors. In other words, as air moves from the front of the rotors to the back of the rotors, the volume of air decreases.

Dual Pass Intercooler

Compressed air exits the rear of the rotor pack and moves upwards through the intercooler. The compressed air then makes a U-turn and flows down through the intercooler for a second time before being directed into the cylinder heads.  If you think about it, hot rodders spent decades running mostly 6-71 and 8-71 Roots superchargers without any intercooling whatsoever. Now, we can negate some of the heat created by the supercharging process (Ideal Gas Law). Whipple's inverted design cools the charge twice.  

Which Is Better: Roots or Twin Screw?

The two designs have been tested back-to-back on many occasions. Historically, Roots-type superchargers win out in the low- to mid-rpm range, while twin screw superchargers maintain higher efficiency and stable boost at high rpm. Our friends at Eaton tell us that their high-helix four-lobe TVS Roots design is comparable to twin-screw efficiencies across the rpm range, whereas their 3-lobe design provides peak efficiency at low/mid engine speeds. 

We don't have a dog in that fight. Concept One provides drive systems for both designs. We like that a Roots blower provides instant response at part throttle, and we like simple math: 3 liters is more than 2.65 liters, and a dual-pass intercooler should reduce charge temps more than a single-pass intercooler. Cooler air is more dense. Eaton has a TVS 3100 rotor pack, but it's not available in an inverted configuration - yet.

A Bigger Supercharger Requires Smart Packaging

It's not really a downside, but keep in mind that a bigger supercharger will require some planning. That includes making room for and routing a bigger intake tube to match a bigger throttle body. It all needs to clear engine accessories such as your alternator and water pump. Moving accessories down could lead to chassis clearance issues.  Hanging accessories far outside of the engine envelope seems like the easy solution. However, doing so requires significantly longer drive belts -- which usually leads to belt slippage -- not to mention much heavier brackets.

In a never-ending quest for more power, things have gotten a little silly. We see impossibly small supercharger pulleys, and pizza-sized crank pulleys!  We see people complaining that their mile-long belts keep slipping. As the above dimensions show, Concept One MAX10R drive systems are engineered to be ultra-compact so that you get the shortest possible belts and excellent chassis clearance. Available pulley diameters are reasonable.  Zero-flex brackets maintain consistent pulley alignment and belt tension.

Ultimately, the real benefit of these big superchargers is that they make big power without the need for extreme boost or excessive RPM. Some will always push their superchargers to the limit and beyond. But most will appreciate that larger displacement, high-efficiency superchargers are working smarter, not harder.