FAQ's

How much boost do I lose per 1000' elevation? None. Our supercharger always produces it's rated boost over atmospheric pressure. Approx. .5 psi per 1000' of atmospheric pressure is lost due to elevation. Boost plus atmospheric pressure is called absolute pressure. 14.7 psi at sea level +5 psi boost = 19.7 absolute psi. How much power do I lose from altitude? If God's atmosphere weighs 14.7 psi and you lose 2 psi it's power loss on a 100% VE engine. By the same token a +2 psi boost is a 13.6% power increase.

What is VE? Volumetric efficiency. It's a measure of an engine's ability to use or "pull in" all 14.7 psi of the atmosphere's weight. Street engines are typically 75% VE or .75 X 14.7 = 11 psi. They are utilizing 11 psi of the atmosphere's 14.7 psi. Some racing engines are 100%. Others are 110° because they use the intake runners to "ram" in more air and the exhaust to "scavenge" or suck out more air. Superchargers "pump: or "force" more air in than the 14.7 psi. 7.35 psi boost (22.05 psi absolute) adds approx. 50% more HP or 50% to the VE of an engine. It's all just boost.

How does Kenne Bell determine supercharger size? We use superchargers that are typically over designed for the application. By turning slower (less rpm) for a given boost, the supercharger will be quieter, run cooler, last longer and discharge cooler air. That is the principle behind the "BIG BORE" series.

What is a supercharger? A supercharger is an air pump that forces more air into the cylinders than can be "sucked" into the engine naturally by the pistons. The supercharger develops boost or back pressure because of it's ability to pump more air into the engine than the engine can consume. In other words, the supercharger overpowers the engine. If the supercharger fails to maintain peak boost, and the boost "drops off" then it is too small for that particular engine. That's why there are superchargers of varying size - and efficiency.

What causes the air to enter the engine? The pistons and rings create a vacuum in the cylinders on the intake stroke. At sea level, atmosphere weighs 14.7 psi (per square inch) and exerts 14.7 psi of pressure on everything that covers the earth's surface. This pressure is what forces the air into your engine on the intake (vacuum) stroke. When you suck on a straw in a glass of water it is the weight of the atmosphere on the water that forces the water up the straw. Your mouth creates the vacuum in the straw the same way the piston creates the vacuum as it moves down the cylinder. If the engine is able to ingest or use all 14.7 psi it can attain a 100% VE (volumetric efficiency). Conversely, an engine would never be able to function if it was in a vacuum chamber.

How is supercharging better than raising the compression ratio? Both increase torque and horsepower by squeezing more air fuel charge into the same area. In the case of higher compression ratio (milled heads or domed pistons) the increased power from this higher compression helps ONLY on the power stroke. The higher compressed air fuel mix will fire with a bigger bang. Again, that is the only point during the 4 engine cycles where higher compression helps. However, with a supercharger, the cylinder is fully pressurized during all 4 cycles. The higher boosted air is forced into the cylinders during the entire intake stroke and is blown out the exhaust on the exhaust stroke. It just doesn't get any better than this.

Will a higher compression ratio improve my fuel economy? Yes, but it also requires an accompanying increase in fuel octane whereas a supercharger only demands higher octane when in boost.

I'm upgrading my injectors. What is the best way to increase my fuel system volume? No question about this one - the Kenne Bell BOOST-A-PUMP™. It has the ability to increase the capacity of any electric pump from 1%-80% (adjustable for flow and/or pressure) without heating the fuel. It even regulates the input voltage and compensates for alternator charging fluctuations.

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