Hello all new Z owner from Canada
 

I’m new to forums in general and would love if someone can help me figure a few questions out. If not please send me in the right direction. I bought a 2011 370z 6mt has a GMT supercharger kits along with all supporting mods.

The SC kit is their stage 2 with rotex c38-91. My question is about boost pressure. My gauge shows good vac at idle and wide open near redline shows around 4psi. Is that normal or is that low ?

I’m the case that is low suggestions why that would be so I can work on it. I have don’t countless hours of searching and reading but the only thing I can figure is changing pully size.

Hope someone can help and thanks

Hello all new Z owner from Canada
 

That’s low. Either the belt is slipping so the supercharger isn’t generating boost or the boost is escaping via a boost leak. No supercharger kit for this car would come with a pulley that only makes 4psi.

Or your gauge is broken. Is this an aftermarket in-car boost gauge or are you reading from the ECU?


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I agree it does seem low. I am reading off an aftermarket defi vac/boost gauge. So far I have only tried the spray and pray method to try and find a possible vac leak. My next suspect is the belt as well. The car only has 9000km on it since the kit was installed so my initial thoughts were probably not the belt.

Another thing to check is your bypass valve. If the bypass valve is not fully closing, you’re just venting off boost.

rebuilding the bypass valve is cheap/easy if that is the case.


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That is todays project and hopefully that answers some questions. I did find a YouTube video of a yellow z doing a dyno pull with the same setup. That car was running 4.5psi of boost and made 400hp at the wheels. The is nothing for information there and the video is 12 years old. So I’m curious to know why it was setup like that when I have seen countless other pieces of information which say it should make 500-500 at the wheels. My car is running rich so I am also going to swap the spark plugs with GTR plugs and see if that helps. The nearest tuner is 3hrs away so I am going to do what I can before taking it there.

The GTM stage 1 kit made ~8psi boost. The stage 1.5 and stage 2 should make more than that. If you’re truly making only 4psi you have a problem.


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I discovered my BOV was not closing. I have since cleaned and oiled it and am now marking 7psi of boost. I still have to adjust it a bit but it’s working much better then before. I just bought the car so it’s taken a bit of time to go through things and try to see what and how things have been modified. The car is still running very rich though. I appreciate the help and any advice.

I’d also recommend a BOV rebuild kit with new orings. Wouldn’t hurt. Pretty sure the stage 2 kit should easily make over 10psi of boost


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Do you know what pullets you have? I can't imagine a pulley setup that would make 4.5 would be used. 400 wheel on that boost seems really healthy i wonder what fuel. I'm using an ATI Super damper and a Kraftwerks pulley to get 10-11 psi at 7300 RPM, that's making 470-480 wheel on 100 octane. I need to do E85.