I have a boost gauge installed to the vacuum line and I'm wondering what boost should I be seeing at idle? At total WOT I've seen in the area of 16-17psi (pulley and intake upgrade) but at idle it's in the negative 10-20 range. What does that mean and how can I best improve it? Thanks.

 

At idle, the boost relief valve is open, and there is no pressure from the S/C.
The Super V8 we did some while ago read some -22 at idle, and up till ~12 at full pull.
No mods on that one, and measured after fresh "everything" with gauge spliced at the S/C housing hose.

 

Planet Soarer: Estimating Boost and Eaton Pulley Change

 

Which pulley and intake mods have you done?
Would be interested to know if boost holds steady all the way to redline, or if it starts to drop off as you overdrive the Eaton.

 

That seems about right for vacuum, you must be running either an upper and lower pulley combo or have charger mods if your m122 is putting out 16-17psi, thats pretty healthy

 

Thanks for your help.

I have a Eurotoys lower pulley and recently got a 3.5" silicon intake.