where should my boost start?

[gkjnr 0]

i,ve got a boost gauge on my charged vr and its been chipped by vince and seems to pull very well,my question is where should i see the boost gauge at different rpms its an 8 psi pulley and in second gear when i floor it no boost is shown on the gauge til 4000rpm then it climbs steadily til the redline where it peaks at 8psi in the higher gears when i floor it it seems to not make boost as quick and not as much it still goes like feck is this a normal boost curve for a supercharger?theres no leaks and i,ve sprayed the belt with belt dressing so i,m hoping theres no slipping i really just want to know at what rpm the boost should max out and if it will climb steadilly as the revs rise

[xyber 1]

what psi does the gauge go up to?

[gkjnr 0]

8 psi but it dosnt get there til 7000rpm

[xyber 1]

sounds about right, the charger pressure increases directly in line with the engine revs, so if you have an 8psi (max) pulley it wont reach full boost until the top end of the revs

If it was making 8psi at 5000 rpm you still have 2000rpm to go so the boost would keep climbing inline with the revs

I think boost on chargers if it was shown on a graph, instead of a steady straight line increase it would be more of a banana shape with not much going on, then a sudden increase further up the revs until maxed, that how I imagine it anyway

[rigs 0]

Depends on the type of charger

The vortech etc... ones boost more later in the rev range a bit like a turbo.

Others give you whatever your boost threshhold is no matter what speed the engine is at.

There are benefits to both

[6potmkII 0]

chargers run off the cranck pulley, the vortech and Z chargers only produce there max boost just before the limiter and as seaid rise with the revs, faster the revs go faster the charger spins thus creating more boost. in higher gears ur revs build up slower therefore so will your boost

[gkjnr 0]

got it thanks all

[rigs 0]

They are presumably centrifugal changers. They make more boost at higher speeds. At 4000rpm your charger will be blowing more than twice the air in to the inlet than at 2000rpm.

Your "normal" displacement chargers create the same boost at any engine speed.

[FishWick 21]

Yes they are centrifugals

They are not Positive Displacement "Roots" type blowers.

Not true about same boost at any rpm. At low rpms PD chargers leak air. True, you'll get say, 8psi at 3000rpm and 8psi at 6000rpm, but at 1500rpm, you'll get about 1-2psi.

It's about packaging. Not many, if any, roots PD chargers are anything like as compact as the Rotrex, so won't fit a VR6 as nicely within it's cramped operating area.

Aside from the Lysholm screw, PD chargers are massively inefficient. They're not called "Heatons" for nothing :-)

[rigs 0]

Your statement is as broad and sweeping and incorrect as mine

[xyber 1]

got it thanks all

This book is well worth a look through to get your head around chargers in general, I read through it whilst I was deciding on weather to stay N/A, charge or turbo

http://www.amazon.co.uk/Street-Supercharging-Install-Blowers-S/dp/1884089291/ref=sr_1_1?ie=UTF8&s=books&qid=1208533701&sr=8-1