I remember reading a post from MIA i think that said the wastgate opens at 9.5 lbs (compressor outlet) so the actual boost the engine sees is about 8.5lbs. I just got my car back today and havent driven it too much, but when i punch it, it looks like my gage reads about 10. i am using a defi mechanical boost gage. Everything feels good, i was just wondering what other peoples boost gages were reading.
thanks
andy

 

Ideally you want your vacuum reference to be off of a charge pipe, or off of your turbo's compressor outlet so it see's an exact pressure before any pressure drop. However, your boost gauge should be plumbed off of your intake manifold, which would be the absolute pressure, so if you have any pressure drop occuring the gauge would be indicating it.

once you verify where your boost gauge is reading from you should be able to see if you are overboosting, or not boosting enough

 

The wastegate spring is actually a 9 PSI spring so the wastegate should be open once the compressor outlet reads 9 PSI. With the pressure drop across the intercooler and charge piping you should see 8-8.5 PSI of boost. If you are getting more then that I would start by verifying all your vaccum lines are routed correctly.

 

Andy what was the verdict? When my Z was running I only had 8-8.5 no creep here in Hawaii. I have a DEFI gauge also and my vacuum was 20-22

 

vacuum is 22-25 idle. Yeah no creep at all. It reads about 8-9 at steady boost. I guess i wasnt looking at it closely enought at first. The gage i have reads in 2.5 lb increments, so that with gage error, i dont think i have any problems....except today the pipe between my intercooler and turbo popped off....Back to sonics tomorrow. This thing is FAST

 

That's odd..

 

Make sure they are placing the tbolt clamp on the far side of the beed roll in that pipes or its going to keep falling off. Do a search for Turbonetics and beed roll. I created a ghetto gif that shows what I mean...

 

Mine shows about 8-8.5psi on a Defi D mechanical boost gauge. Despite having the new kit with the overboost fix, it still overboosted well past 10psi last friday, freaked me the hell out. Got under the car, all connections and lines were ok, sprayed WD40 on the wastegate valve guide and bushing, hasn't done it since Seriously considering replacing the WG/BOV with Tial units...