Define Boost and Vacuum For Me
 

as im still learning...

boost is anything above atmospheric psi, right? an air compressor for your air tools creats boost, does it not? stagnat air, is atmospheric psi. hit the nozzle on the compressor hose, and psi is released.

now, the engine sucks. meaning has vaccum. in order to create boost, does the boosting device first have to create enough psi to equilize the vaccum before iot can begin injecting a psi greater than atmospheric?

i personally think this is a good question, so please dont flame or no0bitize me. im just trying to learn therories here.

crista

A turbo or supercharger flows a certain CFM.

an engine flows a certain CFM.

when the engine flows less than the supercharger/turbo then you have boost.

Not really a 2nd Gen specific issue. Moved to Rotary Performance.

1st, air pressure = amount of air. Atmospheric pressure = just normal air we breathe, hear sounds in, toss paper airplanes, etc. The pressure is from gravity holding our atmosphere to the earth, it's actually the weight of all that air.

Boost = positive - more than atmospheric - air pressure, so it pushes on things. It's slang for pressurizing the motor's intake air more than atmospheric to force more air into the motor. Force more fuel in also (air-fuel ratio is critical) and out comes more power! It's a wonderful thing.

Vacuum = negative - less than atmospheric - air pressure, so it gets pushed on by air that's at atmospheric pressure. How does it apply to motors? All internal-combustion motors are air pumps. They have a cycle:

1) Intake - mechanically sucking air-fuel mixture into a chamber by increasing the chamber volume, then

2) Compression: squeezing the mixture by decreasing that chamber volume, and

3) Combustion: setting it on fire so that it's rapidly expanding gases expand the chamber volume and do work to move the car, then,

4) Exhaust: the chamber volume decreases but a port is opened for the burned gages to exit, and then the cycle repeats...

Vacuum is created in NA (or naturally aspirated, unboosted) motors by the first step, Intake. At operating speed the motor is sucking so much air out of the intake manifold that there's less pressure in there than the ordinary atmosphere out in the engine compartment. We measure that negative pressure as vacuum, and it's useful as a measure of how much air the motor's sucking in.

Hope this helps!