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help with over boost

2603 Views 16 Replies 7 Participants Last post by  speeduphoria
hi i have a problem wit over boost my 85 turbo z over boost ever time i get on it it flashes to14 pounds and then shuts down untill it comes back down is there anyway to trick the map sensor so it doesnt do this it is really annoying any help would be great thanks :)
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are you running a g-valve?

im guessing you are so you can make a cut out raiser or zener diode:DDG- Map sensor trickery

I would not go over 15lbs though, what grade gas are you running?
everything is stock so where do i get the diode and is it hard to install it is just getting so u cant have fun with it because it shuts down:)
Are you trying to get boost over 14 psi?

If you are. I would look at getting a computer chip and bigger injectors just for a start.

Or are you trying to control the boost and keep it at 14 psi or close to it?

This I have done to my 1989 2.5L turbo caravan. I just got rid of the waste gate solenoid and put a G valve between the wast gate and my vac block. This worked assume for me. I turn it down when I run on the highway (7 to 8 psi) and turn it up in town (10 to 12 psi).
Is this car been converted to t2??? If it is, I would say you should go for a cal with a 3 bar map and bigger injectors. The cut out will be raised much higher. Thats only if you have gone t2 and have a better flowing exhaust. If you dont have an intercooler I would suggest not going over 12 psi at the MOST.
Also another way would to put a map bleed on it, and put an afpr on it and you then control the fuel for boost. But thats only if you have the supporting guages such as a/f, boost, egt etc. There are many ways. Donovan's Dodge Garage can direct you in all the ways you can do this in greater detail.
it is all stock all i want to do is keep it from going past 14 and cutting out you cant smoke mustangs like it is 12 pounds would be fine is the solinoid bad why do they do this :)
first do you have an aftermarket boost guage and are you sure it's working correctly??? Second you just need to set your g-valve lower (if you are running a g-valve????). Also shown in the link above is how to do that. The diode is not necessarily bad, just puts more responsibility on the user to keep from leaning out his motor and blowing the crap out of it . 12 psi shouldn't be an issue with fuel and or boost cut out. But we need to know how you are controlling boost so we can solve the problem. Your motor stock shouldn't be running that high of boost.
so is it easier to put diode in or lower valve it never did this before but now it does what gives :bash:
it might just be that a vac line some were is off or you have a vac leak. just asking./ did you check all your vac lines?
yes definitely totally forgot. Check the vac line to the wastegate as it could have fallen off never letting your waste gate close and causing you to overboost. When the line is unattached it take the control of boost away from your computer.
how about buying a computer like the FWD stage 2 that has the over boost issue removed. The stock computers can overboost at 13 PSI, the map goes to 15, another reason for a real computer in the thing.

New vac lines are always nice and an easy thing to do. Not only can you overboost the turbo but the map could see less boost and lean the engine melting your pistons. Other than a FWD computer at least get an old MP computer for it off ebay. Something.

If the vac lines leak the wastegate doesn't get the air it needs and neither does the map. So you have a combo bleed setup, ugly. Go through the whole vac harness and fix it all and get a FWD stage 2 for 14PSI. About a $100 computer and $20 in vac lines, keep the boost and not blow up the engine.
so th diode thing is not good does any one have a computer but i will check vac lines to see thanks guys for your help
please spend 5 hours reading every single sub-page on this site

Donovan's Dodge Garage can direct you in all the ways you can do this in greater detail.
I have experience with G-valves & zeners; if you need help ... AFTER reading everything you can find on the web
grate. there is a guy on here that helped me a ton. his name on here is NAJ. when i had the same problem as you i just redid my entire vac line setup. here is a diagram of what i did.

just replace the wastgate valve with a G valve and your set.

when i redid my lines i went to a hydrolic store and made a vac block from brass fittings. i also got 1/8 inch hard plastic line not soft rubber tube. this keeps every thing consistent.

as for a G valve i made my oun.

i used a spring out of an old pen

now that i have no air box. i just let my BOV sit there in the open.

i really hope this helps you out. if it dose let me know. i always like to hear if things go good.

talk to you latter:

Anthony Marcotte
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so th diode thing is not good does any one have a computer but i will check vac lines to see thanks guys for your help
Aftermarket computers like FWDs can give you more fuel all the way to 14.7 PSI of boost. Then they can just turn off the overboost cutout. So a new computer really helps. The diode gets you to the max of the factory computer, which is normally less than what a custom computer can give you. Many at this point up the boost untill the maxxed out computer just isn't giving anymore. I have been guilty of this too lol
hey guys check vac lines one was split so i fixed it with a new line it is a bit better but still goes past point of shutdown i think i will try diode but where do i get one thanks for all the help
if you cant control boost then dont put a diode on it, your wastegate is obviously not working properly
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