mnmike

Ive done a lot of reading/searching and have tried diagnosing this problem but am still baffled. My 86 944 turbo has a tial 38 mm wastegate, manual boost controller and some sort of custom aftermarket chip (cant figure out for sure what). The car hits about 14 psi on the aftermarket boost gauge and at a bit over 5k rpm cuts out. Today it was slightly cooler outside and it would do it at about 4.5k rpm. The boost controller is turned all the way down. I then removed the boost controller but then it would boost quickly well above 15 psi (id let off as soon as it got up there) but didn't cut out. Then I tried a different boost controller and with that one turned all the way down it would boost even higher-the nipples are very small compared to the other boost gauge if that makes a difference.. Even with the first boost controller it occasionally wont cut out?? Can anyone help me?

mnmike

anyone?

trivgar

Sounds to me like you're hitting the overboost protection. Turn your boost down. It sounds like you probably have stock chips because they can't handle more than like 13psi or something. If you boost too high for too long, it will cut out the fuel supply to the engine, like hitting a rev limiter. Most aftermarket chips have this removed as far as I know. Or at least raised.

And if it's colder outside the car is going to boost higher without changing the boost level, which would explain it cutting out sooner.

And what do you mean, when you say you removed the boost controller?

mnmike

when i removed the boost controller I just put a plastic nipple basically connecting the two hoses together.

I thought the overboost was at 13 psi? I could get it well over that (though just for a split second because Id let off the gas in fear) with the boost controller removed and it didn't cut out? I just got a autothority stage II chip for like 100 bucks that I'm going to put on, so hopefully that will take care of it. I didn't know the overboost was tied in to the chip so that would be great if that solves the problem.

mnmike

whats weird is the tial has a .8 spring in it, so without the boost controller the car should hit exactly 12 psi correct?

edit: found a diagram (though I cant post links yet..) here on rennlist, post by jbrown titled vacuum hose diagram. My boost controller comes from a T line which is odd because according to the diagram, the boost controller should go straight to the turbo on one side, and straight to the wastegate on the other, hmm.

facboy

ah mate, it sounds like you're running your tial in dual-port mode. in that case, removing the boost controller is probably going to achieve the opposite effect of what you desired (ie it will increase the boost). you should disconnect the line that went to the boost controller altogether, and either block off the open connection on the T (or remove the T altogether and run a straight through connector).

that should put you in single port mode, which will just be spring pressure.

ckathens

Mike: Glad to see you've joined up with Rennlist!

Facboy is right - I installed the boost controller/WG combo in a dual-port mode. Are you sure you turned the **** the right way to turn down the boost on the Lindsey Racing MBC i had installed? YOu said it was at 14 psi but it had been at ~11.5 psi before I sold it to you. I do remember turning the **** a very small amount last THursday when we did the transaction, but I thought I turned it down and NOT up. Perhaps we both were turning the **** the wrong direction?

If you installed another boost controller and that did the same thing, you may have installed that controller backwards! I had the same exact issue when I first hooked up the boost controller, since I had switched the lines accidentally.

Mike, call me if you have questions or need help!

-Steve

mnmike

yeah I just kept turning it the same way as you steve, Ill try the other direction and let you know, cause I have it cranked all the way to what we/I thought was down. Ill try the other way and report back

mnmike

Fixed the problem, turned out turning the boost controller counterclockwise towards the - symbol actually turns the boost up. Thanks!

trivgar

If you run a single port wastegate, you turn it towards the minus sign to increase boost. Sorry should have said that in my first post too haha.