Hey guys
Need some help I have a 03 350z with an ipp stage 2 motor w/l19 head stud upgrade and an SFR twin turbo kit (twin 60-1’s) build has 4,000 miles on it! I have a greddy profec boost controller the problem is I used to boost to 15lb on high boost but since spring when I took the car out it won’t boost above 11.5lbs it just cuts out? Runs just as good as ever no issues on low boost goes to 11 psi no problem check for boost leaks like 5x’s nothing blowoff valve is good any suggestions would be great!!

 

Have you checked your waste gates?

I would go ahead and replace all your vacuum lines - I think this could be your issue.

and are you 100% sure you didnt lose any settings in your boost controller?

 

What do you mean it cuts out, but runs good? I'm right near Salem, NH where are you located?

 

It runs great no issues in low boost….it’s great pulls strong you wouldn’t know anything was wrong until you put it on high boost once it hits 11.5 it just cuts out like falls on it’s face I let off the throttle coast a little and continue driving. It will boost in hi boost no problem til 11.5 it’s almost like the waste gate opens early maybe? I vacuum tested the blowoff valve and that was fine! I’m not sure if the boost controller got messed up some how. not really sure what the settings mean 🤷🏻‍♂️

 

I haven’t checked waste gates yet I tested the blow off valve and checked for loose hose clamps! It very well could be the boost controller but I don’t know what the settings were or if I should be messing with them!

 

so it just falls on it face once it hits 11.5psi car still runs it doesn’t stall or run any different it feels like the waste gates just open early not sure if that’s actually what’s happening just feels that way! I’m in Londonderry!

 

If everything else is fine up to low boost (11psi) than I would think something is wrong with your tune (and not likely) and then I would chase your boost control solenoid …

I presume that 11psi is solely spring pressure and youre getting no assitance from the boost control solenoid (boost controller). So you are asking for high-boost and the ECU is giving you a high boost duty cycle on the boost controller solenoid but something is unhooked, unplugged or the solenoid is malfunctioning.

Check your vac lines off the boost controller (which you may have already done) and I’d check the boost control solenoid as it may not be functioning. Make sure it’s plugged in, the wires didnt burn up, get cut, etc. Look up how to do this but you can touch the wires to 12volts and you should hear a click. Google it or look on youtube.

 

so with the boost controller off I’m at 8psi no issues
low boost is 11psi no issues
hi boost used to go to 15psi no issues but now won’t go past 11.5 psi?

 

Very possible you might have a leak somewhere that can only hold 11.5 psi. Anything over it and it leaks too much. First step is to just check all your clamp connections and gaskets. It's unlikely you'd have a boost leak acting like this, but it's possible.

The other tips are on point and likely something to do with the controller. If the controller is off and you're making 8psi, that's your spring pressure.

I would function test it on your low boost map. If it's been tuned for 15psi you should be able to slowly make adjustments to your low boost map and turn it up to see if it will increase beyond 11.5psi.

Also, are you tracking peak vs sustained boost pressure across the curve? Depending on the efficiency of the kit and if it has recirc'd or open dump wastegates, it might bleed some pressure. Mine will peak up around 18psi on high boost and taper down to around 15-16psi.

If it's not taper, it's in the functionality of your wastegates or the controller. Pressure is not being applied to the back of the wastegate spring properly and the gate is opening at 11.5psi.

 

Thanks for taking the time to reply it’s much appreciated! I think it’s most likely the controller too it has no other issues! So to try and get the low boost setting above 11.5 psi would I increase gain or percentage? I literally know nothing about setting up or adjusting the controller.

 

Do you have an external boost gauge that you are getting your reading from. Does the car actually feel slower?

http://www.greddy.com/upload/file/Profec_manual.pdf

 

I just have the greddy profec! no it doesn’t feel any slower still pulls like a mother!!

 

Have you driven the car between seasons with it boosted? I typically have to adjust my Profec a bit with changes in the weather. It could just be that you need to adjust it for summer heat.

 

I'm unsure about this, as I use the HKS EVC-7 for my controller and it uses a single "points" system and boost sample rate. Check your manual for the controller or find one online and see what it says.

 

I would recommend a way to read it another way. Losing ~40-50hp would be noticeable.

 

Any luck on solving this, OP?

 

not yet went on vacation to Aruba for 10 days will be home this weekend and will try to figure it out I’ll keep you guys posted