The supercharger

[scottyp]

Alright, the great debate of forced induction. blower or snail, SC or TC? Well not to debunk either method but the supercharger has pros over the turbo charger...on the same token though, it does have it's cons. First let's look at the difference.

powering mechanism:
As we all know, turbo chargers are powered by exhaust gasses as they pass over the turbine spinning the compressor and thus forming boost. The supercharger produces boost by means of a belt driven shaft that turns the impeller or impellers. This belt is routed around a pulley on the blower as well as one on the crankshaft thus, the rotation of the crankshaft provides the rotation for the supercharger but at a price. Since the supercharger is belt driven that means you have another device that is robbing the crank of power during operation, thereby lowering your potential for power. Look at it this way. Say you took an engine and strapped a turbo on and flowed 8 PSI and gained 35% more power. Later you take that same engine and put a blower at 8 psi on...you would realistically gain 25-30% more power over stock. The difference is due to the power drain on the crank.
Advantage turbocharger.

tuning:
I'm not gonna lie. tuning a fuel injected, forced induction engine is a pain in the ass when you're dealing with fuel injection, specifically multi-point. However it's not too bad if you know what you're doing. A supercharger comes from the factory with the pulleys you need to run a specified boost setting. all you do is put it on and make any fuel mods to keep up with the demand. Once it's on, you do a couple tweaks here and there and you're set. No multiple point adjustments (boost controller, etc, etc.)
Advantage: supercharger

simplicity:
Supercharger kits are the most simplistic forced induction item ever. You strap it on, do a quick fuel tune and you're ready to go lookin for trouble. As I said before you don't have to worry about a lot of other devices like a wastegate, BOV, boost controller, etc... everything you need comes in the kit. If you want to up the boost, you change the pulley ratio, plain and simple. Some kits come with a relief valve, but really is not needed. As your engine runs and engine speed changes, the supercharger's speed and therefore amount of air flowing is dictated by the turn of the crank. Due to this your ECU has preset maps for preset RPMs to determine the proper amount of fuel to run. the car does all the work for you here.
Advantage: supercharger.

[scottyp]

Types of Superchargers: Below are the 3 main types of superchargers and some of their characteristics.

Roots Type: the roots type blower is the grandfather of all superchargers. These first started showing up as early as the late 30's on large machines and eventually to drag cars and some street rods in the 40's and 50's. It totally eliminates the intake manifold and takes the place of it as it nestles on top of (or in our case to the rear of) the head(s) of the engine. The impellers are a typical fan-type impeller that create compressed air as it is fed in. The fuel delivery is generally through the top (as in V-8 engines) and is sometimes compressed with the air as it's delivered depending upon application. Some exceptions to this are the jackson racing supercharger kits which utilizes the MPFI system. Roots type blowers are the least efficient as well. They typically pull in about 50-65% volumetric efficiency depending on the impellers.

Centrifugal Type: The next generation of superchargers. These started showing up originally in the late 70's when some Drag racers were switching to fuel injection and wanted to use a supercharger. It generally sits off to a side of the engine with piping running to the intake manifold. This compressed the air before it reached the fuel delivery point making it easier to determine the fuel flow ratio without running too rich or lean. Design wise these are just turbo chargers without a turbine housing. The air comes in, through the compressor and out to the IM. They flow air more efficiently than a roots-type blower. Due to modernization, computers have really helped these along. More efficent fan-style compressors were made allowing for greater volumetric efficiency taking it up to 60-75%.

Twin Screw: How I forgot this one in the past still escapes me but a big shout to boosted J30 for reminding me. The whipple type blower is the biggest overhaul to superchargers in 30 years (at it's first inception somewhere between the late 80's and early 90's) It is also very unique and utilizes a design which would have been thought to never work before the time of computer designed parts. This bad boy uses a roots style case and gear driven, corkscrew style impellers. These impellers were designed with smooth flow, and efficiency in mind. Whipple type superchargers are the most efficient of the three with VE ranging from 70-85% at low RPM but as the RPM goes up it loses its efficiency. Cool for low end torque but the ride is over at around 4500

[scottyp]

Now in the last post, I talked alot about Volumetric Efficiency (VE). This determines how well a compressor device (turbo or super) flows air without turbulence. This is extremely important when dealing with superchargers. Because they're powered by your engine as opposed to the waste of your engine, you want it to work as efficiently as possible to produce power. As a supercharger creates boost, it also creates turbulence inside the compressor housing. The more turbulence inside the housing, the more your engine has to work to create the power to turn it. So, higher VE = more power due to less power loss at the crank.

[AmberFireDaK]

Correct me if I'm wrong but Whipple is a brand name not really a type of SC.... I always thought the 3 main types were roots, twin screw, and centrifugal

[scottyp]

yeah you're right. I forgot to change that before I posted it, I haven't looked over those articles in a long time. the twin screw supercharger is however also known as the Lysholm supercharger

[AmberFireDaK]

Originally Posted by scottyp

yeah you're right. I forgot to change that before I posted it, I haven't looked over those articles in a long time. the twin screw supercharger is however also known as the Lysholm supercharger

Lysholm eh? good to know