suprasurrey Posted October 4, 2012 Share Posted October 4, 2012 My 1994 tt auto BPU Supra has lost boost recently and can manage only 0.75 bar. Also, the boost tails off at higher RPM making me think the 2nd turbo isn`t coming online. I`ve just tried TTC mode and it doesn`t make any difference. Am I right in thinking you bypass both vsv`s, or am I doing something wrong? Quote Link to comment Share on other sites More sharing options...
Dim Sum Posted October 4, 2012 Share Posted October 4, 2012 I carried this out too, to test for leaks and etc and also made a thread about TTC mode. here's the link to the thread http://www.mkivsupra.net/vbb/showthread.php?276324-True-Twin-Conversion-Mod In there is two link so you can have a read to see if you carried out the bypass correctly. Quote Link to comment Share on other sites More sharing options...
suprasurrey Posted October 4, 2012 Author Share Posted October 4, 2012 That`s the link that I used after searching on here and on Google. Both vsv`s are now not connected to anything so I guess I have done it correctly. Any other ideas why my boost is low? Quote Link to comment Share on other sites More sharing options...
Dim Sum Posted October 4, 2012 Share Posted October 4, 2012 Any other sign's on the turbos? No blue smoke? do you hear the second turbo spool up? could be a boost leak? Any other symptoms/ Quote Link to comment Share on other sites More sharing options...
suprasurrey Posted October 4, 2012 Author Share Posted October 4, 2012 I tried the tin foil test and the exhaust valve didn`t move. Forced the exhaust valve open by pressurising the pipe and cable tying it. I`ve just been for a run and managed to reach 0.95 bar, much higher up the rev range than usual. I`m guessing that I have a split pipe which is not allowing pressure to build and open the exhaust valve. There was some smoke, but I read that this is usual when trying TTC mode for the first time. Quote Link to comment Share on other sites More sharing options...
Dim Sum Posted October 4, 2012 Share Posted October 4, 2012 (edited) If that is the case then when morning hits maybe worth replacing or check each hoses for leaks. I would probably replace all the hoses while you are at, might as well afterall these are 15 years old cars. It could be a boost leak but its just a matter of process elimination when problem finding. At least your turbos are if you fine if you are hitting. 0.9 bar. Edited October 5, 2012 by Dim Sum (see edit history) Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted October 4, 2012 Share Posted October 4, 2012 I'm almost certain it is a boost leak. You wouldn't get over 0,4-0,5 if it was the Valves themselves Quote Link to comment Share on other sites More sharing options...
suprasurrey Posted October 5, 2012 Author Share Posted October 5, 2012 Thanks for the replies. I`ve already replaced all of the easy to get to pipes. I have also pressure tested the intercooler piping and there are no leaks. I think I need to look into why the exhaust valve doesn`t open when in TTC mode now. Quote Link to comment Share on other sites More sharing options...
suprasurrey Posted October 7, 2012 Author Share Posted October 7, 2012 I have now found out what the problem was. One of the pipes from the pressure tank to the rear left hand side of the engine had split. After much struggling I have replaced the pipe and now have both turbos boosting as normal. Quote Link to comment Share on other sites More sharing options...
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