Does the supercharger decrease my fuel mileage? Not under normal driving conditions. However, if you use the boost it will, of course, use more fuel. You can't make power without fuel.
What kind of performance increase can I expect from my Kenne Bell Supercharger Kit? Approximately 30-50%. Check out the individual catalog listings.
Why is a supercharger better than other performance modifications? A Kenne Bell Supercharger is by far the best performance value of all. You can spend more money on exhaust, headers, cool air, chip, cam etc. and not get anywhere near the performance you would from the supercharger kit. Besides, the OEM's aren't leaving much HP - if any - in the above mentioned products. That is precisely why they are now resorting to supercharging for big performance gains. See our "Bolt on parts vs. supercharger" comparison that Super Ford Magazine did on a Mustang. Pay particular attention to the low and mid range gains with the supercharger.
What parameters determine how much boost my
engine can run on 91, 92, 93 or 94 octane? Good question. One of the top 3 most
commonly asked.
COMPRESSION RATIO - Lowering the compression ratio allows the engine to
run more boost with the same octane. For example, 8.0:1 vs 9.5:1 can tolerate
another 3 psi. 3 psi gives 38HP. The 1.5 lower CR loses 3% (2% per point)
or around 9HP in a 300HP engine. That nets 29HP (38-9=29). Now you know
why OEM's use low compression ratios on supercharged engines.
AIR CHARGE TEMP - The supercharger itself determines how much boost the
engine will accept. Some superchargers require an intercooler. Others,
such as the Kenne Bell, don't need intercoolers because the discharge
air temp is cooler. 1 psi boost increases supercharger air discharge temperature
10°-20°, depending on supercharger type. A 6 psi "rated"
kit usually requires 8 psi "total" boost (+2 psi to overcome
inlet and outlet losses). Consider two 8 psi superchargers: 8x10=80°,
8x20°=160°. The 160° supercharger should use an intercooler.
An air to water intercooler will lower that 160° to around 80°
(160°-80°=80°) or the 80° temperature of a more efficient
supercharger without an intercooler.
BOOST - Both higher compression ratios and boost increase cylinder pressure
and demand higher octane fuels to eliminate detonation. Fuel octane determines
the amount of boost an engine will accept. Kenne Bell runs 6-7 psi on
all our Ford, GM, Chrysler and most other kits with our Twin Screw superchargers.
1.5 octane will support one psi of boost. Example: If fuel octane is 91
or you add a can of NOS Octane Booster you can typically run 8 psi. Intercooled kits can typically run 3-4 more psi.
IGNITION TIMING - Retarding ignition timing will allow the engine to run
more boost but not without a penalty. 4° retard=16HP.
AIR FUEL RATIO - You can't make horsepower without fuel. Richer air fuel
ratios reduce power but permit higher boost levels on a given fuel octane.
Leaner ratios make more power but need lower boost so a lean mixture with
high octane makes the most HP. We thoroughly understand all the parameters
of supercharging. Supercharger kit tuning demands ignition timing, air
fuel ratio, fuel octane, boost, compression ratio, discharge temperature
and supercharger parasitic losses all be carefully considered in the design.
What causes detonation? 1. Lean fuel mixture, 2. low octane fuel, 3. excess
boost, 4. lack of fuel, 5. advanced ignition timing, 6. vacuum leak, 7. "hot" spark plugs, 8. overheated engine, 9. excessive inlet
temperature (underhood filter) and incorrect readings from cheapie non calibratable wide band $35 VW Jetta oxygen sensors.
Why does Kenne Bell use a 6 rib belt to drive the supercharger and others use an 8 rib belt? Because our Twin Screw supercharger has less parasitic loss than others and therefore requires less HP to drive - which means the engine develops more HP with a Kenne Bell. Also, since Kenne Bell superchargers are a larger displacement than the competition, we use larger pulleys for better belt grip. Some of our "competition" high boost kits use 8 rib belts.
Do I need an adjustable fuel pressure regulator? Unless you're playing with an '86-'93 Mustang, don't bother.
What is the most ridiculous aftermarket product? Hands down, it's the "little intake fans" and the "throttle body spacers" with the bore grooves. Right there on the list has to be those "underhood exposed filters" that suck in 200° underhood air instead of ambient (70°-100° air from the fenderwell). 10° air temp rise is -1% HP. That's how dynos are calibrated for temperature changes. Does anyone really believe that all those OEM manufacturers designed expensive plastic inlet systems - for the last 20 years - that pull cool air from the fenderwell, hood or grill because they didn't have anything else to spend their money on? Then there's those "factory calibrated" mass air meters that do not use a chip or re-calibrated processor with oversize injectors. They unwittingly reduce the voltage signal to the mass air meter to compensate for the larger injectors at WOT but they neglect all the driveability issues. The result is over advancing timing, lean mixtures, detonation, surging, bucking etc.
Why is knock protection so important? Knock (detonation) can destroy your engine if it is not negated. Suppose your wife or a friend unknowingly fills your tank with 87, or you get a "bad batch" of gas, the engine overheats, someone installs a pulley that raises supercharger boost, the wrong spark plug heat range is installed (too hot) or a vacuum leak develops and the engine leans out. That's when an engine needs knock protection. No one in this industry has more experience than Kenne Bell with knock protection. It's also why we prefer "tuners" leave our kit calibration as is. The knock sensors are "sensitized" to distinguish knock from supercharger noise.
