what is the difference btw the two, and which would you recommend? which is less "stress" on the motor

02 z a4 3500 vig., flopac, cutout, magnaflow, sfc, lca

 

this should be moved to the forced induction section...think a similar post is up there now....or do a search in that section im sure this has been asked there a million times

 

Turbocharger: compressor run by a turbine (hence "turbo") which is in turn "powered" (for lack of a better word) by the rapidly expanding exhaust gases spewing forth from your engine.

Supercharger: Compresssor run directly off of the power the engine produces, usually by a belt drive (just like an alternator) or sometimes they are gear or shaft driven.

Both do essentially the same thing, some people like turbos because they dont have any parasitic effects on boost, others like superchargers because there is no "lag" which is experienced with turbochargers. Go to howstuffworks.com and look this up and you'll get a much better explaination.

as far as "less stress" that depends on what you mean by stress. If both given the same compressor for both a turbocharger and (centrifugal) supercharger they would produce equal "stress" as far as detonation and breaking rods and such. However if you mean which takes the most power to run, the supercharger is your answer.

 

aren't superchargers better for the engine though? thats what i heard from some guy, not sure bout the truth in it though

 

AFAIK, and I'm no expert on either form of forced induction, but superchargers are more "controlled".....they are limited by the speed that the engine turns, since they are directly driven (whether it be by belt or gears). Turbos on the other hand can get out of control, since they are driven by the exhaust, the amount of which can vary depending on how the motor is running (high RPM or low, and also how much air the motor can flow). I think that turbos always use a waste-gate, which is basically an over-pressure relief so that you don't try to boost the engine too much. I don't know if there is any type of pressure relief used for superchargers?

 

Superchargers build boost in a linear fashion. As engine speed increases so does boost. Turbos can build full boost as soon as they are spooled up. Depending on the ratios for the turbo and the system setup, it may make full boost at 2500 RPM or it may not make full boost until 4000 RPM or more.

Turbochargers use wastegates to control how much boost they create. The wastegate bypasses exhaust gases around the turbine in an attempt to slow it down. If the wastegate is not sized properly it will be unable to slow the turbine down which will lead to an overboost situation commonly referred to as boost creep. This is bad for the engine, but it is also detrimental to the turbo as well because the turbo will continue to spin faster and faster until the bearings fail which can lead to other nasty surprises.

As for the difference between the two, one is belt driven, the other is exhaust driven. Both produce stress on the motor in the form of boost and heat. In addition, turbos add additional stress in the form of increased back pressure on the motor. Superchargers add additional stress to the crank snout which can break off in some cases.