FAQ's

What is the basic difference in operating principle between the Twin Screw, Roots type and centrifugals? All superchargers make good "peak" horsepower given the same boost level. Superchargers pump more air into the engine than it can normally use with the atmosphere's 14.7 psi boost. Hence the supercharger builds up back pressure (boost). The twin screw and Roots type are "positive displacement" superchargers and build the same boost at any rpm 2000 up. However, it is a well known fact that size for size the twin screw is much more efficient than the Roots type (lower discharge temp and less parasitic loss) this includes new 2.3 TVS. The centrifugal is not a positive displacement type. It is essentially a belt, ball or gear driven turbocharger which pumps relatively little air flow at the low and mid range rpm bands. It depends solely on engine rpm to build boost. The higher the rpm, the higher the boost - typically 1 psi per 1000 rpm on a 5-6 psi kit. The delivery air volume increases as the square of the rotational speed of the impeller. Nothing (advertising, opinions, or spin Doctors etc.) can change these basic physical operating principles.

I've installed big tires on my truck. It killed my low and mid range. Headers, exhaust and inlet did very little, if any, to help. Will the supercharger work with this combination? Unfortunately, the mods you made help most at high rpm. The supercharger will provide big gains (torque and HP) from idle on up even with big tires. Outside of increasing your engine displacement, the supercharger is the ONLY practical way to get back that lost torque.

Should I go to a bigger stroker engine or supercharger? A supercharger makes an engine think it's 40-50% bigger with 40-50% more boost. Both work equally as well IF the inlet and exhaust tracts are adequate in size. The supercharger does have the advantage of being able to compensate for or overcome these restrictions. Just turn up the boost fuel and octane until the engine feels as big as you want it to be. Our '05 100% stock Mustang 4.6 GT developed 274 RWHP at 26 psi it produced an incredible 775 RWHP with only the supercharger kit and cat back. Supercharging has one other advantage over the stroker. It uses less fuel because it's "smaller" except when in boost. That's why the OEM's are choosing smaller supercharged engines in lieu of their bigger displacement naturally aspirated counterparts. Factory big blocks are gone forever.

What does the lower parasitic losses from a Twin Screw supercharger do for performance? Any horsepower losses from a water pump, alternator, AC system, transmission, rear end etc. is deducted from the engine output. Example: Automatic transmission is 90% efficient (10% parasitic loss). 10%X300HP=30HP lost from transmission friction and/or pumping losses. A superchargers parasitic losses are based on the HP required to operate it under boost. Example: The Kenne Bell Twin Screw uses up to 30% less HP than the Roots type so the Twin Screw engine makes more power. The gains by the new patent pending Liquid Cooled Supercharger is even greater.

What effect does the cooler air charge temperature from a Twin Screw have on performance? A cooler air charge allows the engine to accept additional ignition timing and/or higher boost. Both increase engine output.

How much more boost can I run with an intercooler? Typically 3-5 psi with the same octane.

How much more boost can I run with octane booster? Here's a good rule of thumb. NOS #12007 Off Road Octane Booster: 1 can in 17 gallons = 1.5 octane for 1.5 psi. 1 can in 8-1/2 gallons = 2.5 octane for 2.5 psi. Torco - 7 octane: See Jim Bell's Supercharged Turbocharged Tech Tips.

Can I determine how much boost I'm losing through the inlet system?
Theoretical Boost = (((Supercharger size in liters x Pully Ratio) / (Engine L / 2)) x 14.7) -14.7
Example: (((1.5x2.4) / (5.0 / 2)) x 14.7) - 14.7 = 6.4 psi.
If your boost gauge indicates 5 psi your inlet system restriction is 2.35 psi (7.35-5=2.35) or 32%! . The supercharger has lost 32% of it's efficiency. 2.35 psi inlet loss is akin to being at 4500' elevation where atmospheric pressure is not 14.7 psi (sea level) but instead only 12.35 psi (14.7-2.35=12.35 psi). In summary, whether you lose boost from inlet restriction or altitude, the horsepower drops proportionally.

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