I'm considering the PES SC and the APR stage 3 for my 1.8T, I know that the APR stage 3 includes a larger turbo. What does the PES kit include? Well, obviously a supercharger, but what is a supercharge and how does it work?

A supercharger does pretty much the same thing as a turbo: it forces pressurized air into the cylinders. However, a turbo is turned by exhaust gases, whereas a supercharger is turned by a belt off an engine pulley.

Which one is more efficient as far as raising horsepower? I don't know; there are a lot of variables involved. I'm sure someone else out there knows more about it than I do and can fill you in.

StevenN '96 2.8qm Emerald Green

...They're kinda like the Indians and Pakistanis, it's hard for the world to tell them apart but they know each other and hate each other." - Jim Hemphill

Interesting quote (thanks Eton Chen). In a nutshell, the PES kit for the 1.8T is a replacement for the turbo (i.e you can either sell or throw away the turbocharger). The basic principle behind turbocharging and supercharging is the same: to increase the pressure at which air is forced into the combustion chamber. Turbos do this by using exhaust gases to spin a turbine which feeds an intake manifold with extra air. Superchargers do this by using engine torque at the crankshaft (via a belt and pulley) to spin a device that feeds extra air into the intake manifold. Supercharged engines are generally more responsive since boost is available at any rpm. Turbocharged engines generally suffer from some degree of 'lag' which is related to the amount of time necessary for the exhaust gases to spin the turbine, but they are capable of producing more absolute power per cc of displacement.

Perhaps some of the real gearheads on this forum can embellish my response...

Bob W.

nt

Not trying to start a debate between the supercharger guys and the
turbocharger guys, but heres some more info.

A turbocharged engine will produce more power per unit of fuel used
than any other type of engine induction (supercharged or normally
aspirated). This is simply because the supercharger requires engine
power to turn while the turbocharger gets its energy from the exhaust
gases. The engineers often call it the "free lunch". It's not quite free,
but it's close.

Supercharger fans often say that the benefits gained from a turbo
are cancelled out by the added restriction of the exhaust. Garbage.
It's been proven time and time again by many engineers on dynos
that two similar engines, both with the same amount of boost, but
one turbo'd and the other super'd, that the turbo engine will have
a higher output. The difference usually comes out to the amount of
power it takes to turn the supercharger.

This is not an insignificant amount. On a lot of average street super
converions kits, 20 HP would be pretty common for how much HP you
will lose to the supercharger under boost. Race cars can easily take
50, 100 or more HP to turn their superchargers. Just take a look at
the drive belt on top fuel cars and you realize how much energy is
being dumped into the supercharger.

There are other problems with superchargers, depending on the type.
The common ones you're probably familiar with is the roots type
which you see on hot rods and dragsters. These are known as
positive displacement compressors. That is, they put out a fixed
amount of air for each revolution. This means the supercharger is
always putting out boost (excess air) even when you don't need it.
The amount of boost is determined by the size of the drive pulley
you select. If you set it at 10 PSI, then you always get 10 PSI at
any engine RPM (not exactly, but close enough for this explanation).

If your engine doesn't need this extra air, then it must be bled off
usually with some sort of bypass valve which also helps to "unload"
the compressor, saving energy from the engine when you don't
want/need boost.

Another problem with a lot of superchargers is that this air comes
out in pulses instead of a continuous supply (like a turbo). This is
because of the nature of the roots blower construction. This can make
it difficult to match to the engines intake manifold which. Newer types
get around this by changing the shape of the impellors so they look
like a helix (as in the PES kit) or a screw. This increases the efficiency
of the compressor and delivers a smoother airflow.

Another type (like the Vortech kits on 5.0 mustangs) use a centrifugal
compresor (like a turbo) connected to a high speed drive mechanism.
This "gearbox" is used to turn the belt driven pulley from a lower RPM
(like 6,000 RPM) to a higher RPM that the centrifugal compressor needs
before it starts producing boost (>100000 RPM). These have only become
practical recently, as it is diffucult to make a gearbox capable of turning
that fast and also accelerating quickly (like when you let off the gas or
shift). These are also a good design as they combine the higher efficiency
of a centrifugal compressor with instant response because of the direct
drive.

Now, you may be thinking, with all the problems with superchargers, why
would anybody want one? They have a lot of advantages. They provide
instant throttle response (no turbo lag). They also provide more consistent
power (boost) across the entire RPM range and are capable of delivering
full boost even at low engine RPM's (just off idle). And finally, they are
more reliable.

HUH? The turbo guys are looking at that. I'm not saying turbocharged
cars are unreliable. The success of many factory turbocharged cars by
Audi, Saab, Volvo and others proves this. But superchargers don't have
to put up with a lot of the crap that turbos do. You don't need to let your
supercharger cool down after a hard drive, and if you forget you're not
going to risk your bearings. They don't require cooling or oil lines which
could become plugged or cause problems over time. And, they don't
run so bloody hot, meaning they aren't subjected to the thermal stress
of heating and cooling that a turbo is.

As to which is really better, this is a debate which will go on for some
time (like politics, everyone beleives they are right). Both systems have
reached the point where they are capable of excellent performance and
reliability, and both have advantages over the other.

Positive displacement superchargers are behind the throttle plate. This means that they run in a vacuum at low throttle, therefore no boost and no bypass valve.

This brings up another issue. A supercharger should not be much drag if the boost from a turbo is flowing through it. Therefore, combine the APR 300hp kit and the PES supercharger for the 1.8T and what do you have? I'm not sure, but it should be interesting :-) Wanna try it Cameron?

Todd W