original_amo Posted May 28, 2018 Share Posted May 28, 2018 (edited) Hi guy's, Just wondering if someone has come across this issue i am facing with my supra. The cars a 6 speed single running a garret gtx42. Issue i am facing is the cars not boosting over 12 psi? The car has been with the mapper who started to map it on the dyno. The car was making 525 bhp @ 16psi. He stated he couldn't get it to boost any higher than 16 psi. The mapper tried to re plumb the waste gate to run infinity boost but the mapper says its not boosting any further. He told me i had a faulty waste gate and stated it needs to be changed. So i had a new precision turbo waste gate fitted running a 16 psi spring combo. The mapper states the cars now pulling 400 bhp @ 12psi and still won't over boost if re plumbed. There is a Titan Motorsports MAC boost solenoid plumbed. But I've been told this has been by passed and makes no difference to trying to get the car to boost any further. I have checked all boost leaks and there is none on the pipe work from the turbo to inlet. The turbo i know is in perfectly working order. The ecu used is a AEM Infinity. I have not seen any ECU settings. Any ideas as i am running out of options? I can't also under stand how its now running less psi with a new waste gate and spring. Any help or advice is appreciated. Edited May 28, 2018 by original_amo (see edit history) Quote Link to comment Share on other sites More sharing options...
Mk4Gaz Posted May 28, 2018 Share Posted May 28, 2018 Mine is the same as this, was mapped and got to 1.4 bar on the dyno, but started misfiring. Since that day, I can't boost over circa 0.9bar, and it starts misfiring on boost when things start to get hot in the engine bay. I've tried new plugs, new oem coil packs, a different ignitor, checked all the plumbing, coil pack clips are 3 years old and all look good. I have noticed it seems to run a bit rich, but not sure how related that is. If you manage to fix yours, I'd be keen to know what it was. Quote Link to comment Share on other sites More sharing options...
jagman Posted May 28, 2018 Share Posted May 28, 2018 How did you check for boost leaks and did you go over 16 psi? Quote Link to comment Share on other sites More sharing options...
original_amo Posted May 28, 2018 Author Share Posted May 28, 2018 mines is not miss firing just don't boost any more, However I did have a miss firing issue on my first start up and replaced all the things you stated. My issues was a sensor ground the mapper found and issue was resolved. He said it was a pin the loom car side pushed back. Quote Link to comment Share on other sites More sharing options...
original_amo Posted May 28, 2018 Author Share Posted May 28, 2018 How did you check for boost leaks and did you go over 16 psi? I didn't check the boost leaks the mapper said he tested for them. He found a leak on the turbo elbow on the aluminum welds and BOV. This was all corrected ground back and re welded, BOV was removed and replaced with a straight pipe but still don't boost any higher. However it made the same sort of boost if not more when it was leaking at these areas and with the old waste gate. I double checked all the clamps/jubilees on the hoses from the turbo to intake. Quote Link to comment Share on other sites More sharing options...
Mike2JZ Posted May 28, 2018 Share Posted May 28, 2018 Check something in your exhaust system like a backbox or resonator has not collapsed and is not blocking the flow of gases. Excessive back pressure will cause a turbo not to boost as it should. Quote Link to comment Share on other sites More sharing options...
original_amo Posted May 28, 2018 Author Share Posted May 28, 2018 Check something in your exhaust system like a backbox or resonator has not collapsed and is not blocking the flow of gases. Excessive back pressure will cause a turbo not to boost as it should. This is true but the cars made more power with this exhaust system on the old set up. The system has been on the car for 1200 miles. I have spoken to many people they have stated that this should be okay even to see 600 bhp. I will take the system off and leave just the down pipe on to see if it makes a difference. But I don't think it will. Quote Link to comment Share on other sites More sharing options...
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