Can someone plz explain in detail how boost works? And explain how it works when ur actually switchin gears....like when ur in first and it builds up to 6psi then when u throw it in second and slam on the gas it drops down to 0psi and so on and so forth for every gear? Any info appreciated

 

depends on the kind of s/c u get. roots type will hold boost when switching gears at wot better than a centri. which will drop to 0 when shifting, but will build back up quickly.

 

As far as the centri's go, when you shift (assuming you are letting off the gas), the TB closes and the pressurized air in the intake is recirculated by the by-pass valve so as not to try to re-enter the head unit from the wrong side. When you get back on the gas, the head unit will be spinning at the RPM it always does relative to the engine's RPM. If you're brave (or have something better than the stock tranny) and don't let off the gas, you will still be in boost.

I'll pay attention tonight when I leave work and see exactly where the boost needle goes as I'm driving and get back to you tomorrow...

 

A supercharger is an air compressor used to force more air (and hence oxygen) into the combustion chamber of an internal combustion engine than can be achieved with just normal atmospheric pressure. The air that goes into an unblown (unsupercharged) engine is drawn in by the vacuum created when the piston goes down in the cylinder bore. This air goes into the unsupercharged engine at amospheric pressure which at sea level is 14.7 psi (pounds per square inch).

On a blown engine the boost is the amount of additional pressure the inlet charge has over atmospheric that goes into the engine. So if your blower makes ten pounds of boost that means your inlet charge is atmospheric pressure (14.7 psi) plus the ten psi of boost for a total of 24.7 psi.

The additional mass of oxygen-containing air that is forced into the engine improves its volumetric efficiency which allows it to burn more fuel - which in turn makes it produce more power.

 

www.howstuffworks.com

 

I ran to 5k rpm last night in 2nd gear and hit 8psi, then shifted. The boost gauge dropped into the vaccuum side during the shift and then jumped back up to around 4 psi when I got back on the gas (didn't catch RPM's cuz I was looking at the boost gauge and scooting along pretty good) in 3rd.

So there's your answer on what boost does during shifting. There are good replies to this post but I highly recommend the stickies in this section as they have excellent information.

 

Thx for info and replys