stwinn Posted April 28, 2003 Share Posted April 28, 2003 I have a '96 TT JDM. The boost increases by itsel when I drive the car hard. It keeps increasing untill the fuel cut kicks in. I use a Blitz boost controller and it is set to 11 pounds. However the boost keeps climing higher when I run the car hard. I have disconnected the boost controller and left the car stock but the problem still happens. Does anybody have any idea why the boost pressure would go up by itself? Thanks for your help in advance. Quote Link to comment Share on other sites More sharing options...
dude Posted April 28, 2003 Share Posted April 28, 2003 Have you got your cats in , if so do you have an exhaust blow ??? John:flame Dev Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 28, 2003 Share Posted April 28, 2003 It helps to introduce yourself and tell us a little about the car and any mods. It goes down well on here. Then we try to help. Quote Link to comment Share on other sites More sharing options...
stwinn Posted April 28, 2003 Author Share Posted April 28, 2003 Sorry about that, I'm new to this. Here is a little background: My name is Todd, I live in the Cayman Islands. I have a 96 Supra TT that I brought in from Japan (used). It seems to be stock except for the triple plate clutch. It had a boost controller in it, but part of it got stolen in shipping. I have put in: Blitz SBC boost controller, Blitz intercoller and a downpipe (no cats). These are the only modifications I have made. Thanks again, Todd Quote Link to comment Share on other sites More sharing options...
stwinn Posted April 28, 2003 Author Share Posted April 28, 2003 It also has a aftermarket blow off valve. Quote Link to comment Share on other sites More sharing options...
dude Posted April 28, 2003 Share Posted April 28, 2003 You did read the rule about new members having to offer existing members free holidays didnt you If youve got no cats then that is why you are overboosting , the controller can only increase boost not reduce it , you may need to fit a restrictor in the exhaust or put the front cat back on , but if its not going over 1.2 bar i wouldnt worry . John:flame Dev Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 28, 2003 Share Posted April 28, 2003 BTW the free holidays members with post counts over 2000, unless you live in the UK. Does sound like classic boost creep, if you only have a single pipe replacing both cats you will need a restrictor, if you have one repalcement pipe for each cat try sticking the smaller cat back in and see if that cures it. You will need a FCD chip to raise the fuel cut limit as well. Quote Link to comment Share on other sites More sharing options...
kubus1 Posted April 28, 2003 Share Posted April 28, 2003 Do you have a Boost Cut Controler? If you just use the Boost controler or you have de cat, then your pressure will go up. If you go over 1 BAR you will hit the fuel cut. Welcome to the bbs. Cuba Quote Link to comment Share on other sites More sharing options...
stwinn Posted April 28, 2003 Author Share Posted April 28, 2003 Thanks, Why didn't my dumb A$$ mech. know that? I guess it's time to change. Why won't the boost controller stop the boost when it reaches my max setting (18 psi)? Thanks again Quote Link to comment Share on other sites More sharing options...
stwinn Posted April 28, 2003 Author Share Posted April 28, 2003 Yea it's a single downpipe that replaced both cats. Quote Link to comment Share on other sites More sharing options...
kubus1 Posted April 28, 2003 Share Posted April 28, 2003 With a car like Supra you need a mech that really know the car. I was really worried last Saturday that I blew my turbo as I had this horrible whininhg noise on acceleration. I took the car over to Toyota for a check. They had it on the ramp for 20 minutes with two engineers checking things over. They could not establish the fault. I posted one question on this forum, about 10 minutes later I had a reply. About 15 minutes later I found a small vaccum pipe on the EGR sensor cracked. Replaced that with the new one. The car is running sweet!! It feels like someone had just given me a new trubo or lots of ££££. Stick with the guys on here. You will always get a lot of help. Cuba Quote Link to comment Share on other sites More sharing options...
Terminator Posted April 28, 2003 Share Posted April 28, 2003 A boost contoller can only raise boost, not actually control it. If your system has the potential to go over the boost controller limit then it will, unless you restrict your exhaust system to give a maximum boost level below the max level on your controller. IMHO you dont need a bost controller on a J spec with no cats and stock turbos.:flame Dev Quote Link to comment Share on other sites More sharing options...
MONKEYmark Posted April 28, 2003 Share Posted April 28, 2003 hi and welcome, there is a lot of helpful people on here.good place to be for info.when i got my supra i did not know of this board. could have done with the info. the search is a good thing but its always nice to get feedback. also i have j spec with no cats and exhaust. dont have a boost controller too.always could not see point getting a boost controller if its hitting up to 1.4bar. its a bit on high side. they say 1.2 is a safe limit. if you get stuck i am sure someone will help.sometimes gets boring to some people when the same questions keep popping up. Quote Link to comment Share on other sites More sharing options...
richardharmon Posted April 29, 2003 Share Posted April 29, 2003 Originally posted by stwinn Why won't the boost controller stop the boost when it reaches my max setting (18 psi)? I think the waste gates on the stock j-spec turbos are too small to flow enough exhaust gas past the turbine to stop the turbos spinning up when the rest of the exhaust system is de-restricted (no cats or restrictor ring), that's why the boost controller can't do anything about the boost creep. Quote Link to comment Share on other sites More sharing options...
stwinn Posted April 29, 2003 Author Share Posted April 29, 2003 Thanks, you guy's are great! I'm going to come here before I do anything else to my car. Will a external wastegate resolve this problem? If so, any recomendations? Thanks Again. Quote Link to comment Share on other sites More sharing options...
tDR Posted April 29, 2003 Share Posted April 29, 2003 The common solution here seems to be fitting a restrictor ring in the exhaust system to stop the boost spiking. This allows the Wastegate to regain control of the situation. The other not so common solution is to port the wastegate. I'm guessing a turbo swap to UK tubbys would also solve the problem but these may need other supporting changes. ^^ Think I've put the above in order of expense. Quote Link to comment Share on other sites More sharing options...
richardharmon Posted April 30, 2003 Share Posted April 30, 2003 Loads of people run with restrictor rings and don’t have any problems. From what I can gather, hybrids generally come with bigger waste gates and will fit the existing manifold. Am I right in saying that UK turbos don’t fit the stock j-spec manifold? Quote Link to comment Share on other sites More sharing options...
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