Boost and all that sort of stuff

[Rossco 0]

Right ive been running my car as a G60 for about 4 months now and im fully lovin it, carefully run in big daz stage 4 unit with a 68mm pulley and all the stuff, boost return kit and all. Im a bit puzzled about how the boost guage goes, if im driving along at about 3000rpm and i floor it it will wind all the way up to about 9psi and it will sit there till about 4500rpm then it will climb up a bit finally hitting about 14psi by the time its time to swap cogs.

 

Is this correct for what im running, the actual belt is the shorter one for the smaller pulley but i can twist it about half a turn and when i was putting the tensioner on i managed it by hand.

 

My theory is i think the belt is slippin with all the uber notes its creatin, is it possible??

 

Cheers guys

[Jim 1]

Mine used to do the same thing mate.. used to fly round to about 10PSI quite early in the rev range and then gradually crawl up to about 13PSI as you got into the higher revs.

 

Never really thought about it before but would love to know the reason for it..

[h100vw 0]

Boost is a product of engine speed. The faster you spin the charger the more you get. It whizzes to 9-10PSI cos it is making that already, just most of it is being bypassed back to the charger inlet. When you dump the pedal it shuts off teh return and everything goes into the manifold. Then the pressure rises as you accelerate.

 

Easy?

[Jim 1]

Figures.. cheers ;)

 

To be honest I thought it was something like that (i'm learning.. slowly) but didn't wanna say it and turn out to be wrong ;)

[Rossco 0]

Boost is a product of engine speed. The faster you spin the charger the more you get. It whizzes to 9-10PSI cos it is making that already, just most of it is being bypassed back to the charger inlet. When you dump the pedal it shuts off teh return and everything goes into the manifold. Then the pressure rises as you accelerate.

 

Easy?

 

Aye the theory is golden, ive got all that figured i was just wondering whi it took almost 2000rpm for it to move off 9psi, as the boost is created from engine speed surely the boost should rise with the revs but it doesnt, its completely still???

[olly elworthy 0]

the reason the boost climbs more after 4500 rpm is the standard head does not flow well enougth to allow all the air you are producing with the charger into the engine hence creating a restriction and an increace in manifold pressure,, thats the reason,,

[h100vw 0]

Confusion between pressure and flow. Pressure is a measure of restriction as Olly says.

 

Gavin

[Rossco 0]

So end of the day all is well then??