Greetings,

I have been reading many posts about "Supercharging" or
"Turbocharging" and I would like to puke out some information
regarding this topic.

First of all, crank driven or turbine driven, it doesn't matter they
both are "Superchargers".  But the industry defines crank drive as
"Supercharger", and turbine drive as "Turbo".

Q: "Which is more efficient?"
A: Hands down the turbo wins.  Turbo's only work when your foot asks
for power, offering a small amount of parasitic drag when boosting.
Superchargers on the other hand are typically boosting constantly, and
offer considerably more drag than the turbo. Now there have been some
great ideas tried in unloading a supercharger, but power is still
needed to turn the heavy "screws" regardless.

Q: "Turbo's use free power".
A:  False. A turbine gets inserted into a relatively free breathing
pipe and voile! you have a restriction. Efficiency is therefore
reduced. A Turbo creates parasitic loss by adding resistance to the
exhaust stroke (pumping) where Supercharging offers no backpressure.

Q: "Which is more reliable?"
A: The Supercharger. Even if both are systems are expertly installed
the user/operator variable makes the turbo far less reliable. Why?

Turbo's must be slowly warmed up so that the shaft bearings don't wear
out prematurely, and more importantly so engine parts don't crack or
seize from rapid heat expansion. Turbo's also need to cool down before
shutting off the engine, otherwise the great heat retained in the
turbine housing will cook the oil in the bearings. A typical
Supercharger can rotate upto14,000 rpm's while a turbo can reach up to
150,000 rpm's, so on paper the turbo bearings look like the first to
fail.

Turbo's can cause serious damage to your engine if the waste gate
malfunctions and causes boost to spike upwards to 24psi. This can blow
headgaskets, melt pistons, or send a connecting rod flailing. On a
Supercharger boost varies just a few psi between idle and max rpm, so
overboost simply cannot happen if the supercharger was setup properly.

Heat, lot's of heat! This is why a supercharger was not a cheap option
in the original XJR (More below) since there was very little space
between the engine and the chassis.

Q: "What is turbo lag?"
A:  Ah, here is where the supercharger is superior! Imagine driving in
a turbo car traveling down the freeway – mash down the throttle and
there will be a brief moment where the turbo is spinning up before it
can offer any boost to the engine. This flat spot is called "Lagging".
Superchargers are constantly working/always boosting, so when you mash
down on the throttle… you're out! >>>>>>>

"Why not a turbo in the XJR?" Because of space in the original XJR
modifying the chassis was a disturbingly expensive way to go, so why
not mount it elsewhere? Well moving the turbo into a remote spot only
created unacceptable lag- A turbo needs to be mounted as close to the
exhaust ports as possible to give the exhaust gasses a smaller area to
compress in before pushing past the turbine. Increasing the length in
turn increases lag time because of the volume the gasses must
fill,*then* build pressure before being able to propel the turbine up
to speed. However using ceramic roller bearings instead of bronze
sleeves, and choosing a turbo of variable vane intake geometry design
can minimize turbo lag in such applications.

Q: "Is it true that Superchargers make more power?"
A:  False. Turbochargers are capable of very high levels of boost and
can push an engine to higher peak power levels. Many years ago many
engine builders played with turbocharging dragster engines, their
mouths salivating from the huge horsepower levels obtained in dyno
testing. Once on the track, reality set in… that brief instant of lag
before the boost came in simply made the horsepower advantage
pointless. But that was small compared to the almost uncontrollable,
violent power output when boost came on. You don't win races by frying
the tires…and this is why dragsters use the Supercharger.

Q: "I want more power, which system should I buy?"
A: Well that is personal preference but if you want ease of
installation, ease of tuning, and instant throttle response without
all of the complexity then a Supercharger is the one. But if you want
maximum power, flexibility, Hoover turbine whine, pop off hisses, gee
whiz goodies, and controller knobs and switches begging to be cranked
up, then a turbo is for you.

Q: "Is there an advantage in having a turbocharger?"
A: There is believe it or not, a huge advantage to a turbo. Altitude.
A supercharger cannot compensate for altitude changes; you go higher
the richer your engine will run (Unless computer controlled). A
turbocharger on the other hand can also be called an "Altitude
Compensator", because it simply will keep spinning until max boost is
reached and the waste gate opens.  So your power will be the same at
sea level as it is at 8,000 ft. with the turbo.

The XJR and others have gone to the Supercharger for simplicity,
reliability, simply being able to handle the abuse of being driven
hard down to the market and being shut off without a cool down.
Besides, they are easy to work on and install.

Thanks for reading,

Best Wishes,
Blake Dodson