wojtrek Posted July 30, 2008 Share Posted July 30, 2008 (edited) Hi, this is my first post... I have checked where I could, searched, browsed etc. and could not find the solution to my problem... so here it is I have a european (I'm from Poland) Supra TT, 6spd from 94, LHD, not a J-spec. The car is bone stock and is in sequential mode. The problem I have is that the car does not build boost at low rpm and by low I mean below 3500rpm. It would probably be easy to say what might be the problem but it is more sophisticated than that. You see, when I start the car, after night for instance, drive until I reach normal water temp etc and then hit gas harder I will have boost below 3500rpm, but only until I go pass 3500rpm, once I go to 4000rpm or more, the low boost is gone. After I start the car and don't go beyond ~3800rpm I can drive for hundreds of miles (once did 150miles) driving under 3500rpm and I have boost so the 1st turbo is working fine - car pulls strong etc. but once I go past 4000rpm (maybe it's 3800, never checked exactly what RPM) there will be no more boost under 3500rpm unless I stop the car for a few hours and then drive again - the boost is back. This does not affect the boost above 4000rpm - the second turbo is OK since I always have stock boost there. It seems that some sort of switch, after switching to position that it's suppose to be at above 4000rpm will not switch back whatever it is switching to what is should be at low rpm. And that is switching back to what it should be after the car is off for a few hours. It can't be a bad turbo itself - since I can drive for 100miles and have boost whenever I want to, that can't be it. I tested ALL VSV's, the resitance is OK, they flow air (or not) like they are supposed to. So cant be it. The pressure tank I did not check, but there is pressure in the system after I stop - I checked that, so the pressure tank holds pressure like it should. I tried TTC - working OK, starts building boost from 3500rpm and hits full boost at around 4000rpm. So, what could be the problem here? I want to upgrade my car with the GT28R hybrids, since I like the idea of sequential operation in my Supra, but since there is something wrong with the system I will not do it before I fix this... Any help much appreciated! Thanks, Wojtek Edited July 30, 2008 by wojtrek changed the title, so it's more clear to viewers (see edit history) Quote Link to comment Share on other sites More sharing options...
markybhoy86 Posted July 31, 2008 Share Posted July 31, 2008 im no expert on these so this is my first guess, to me it sounds like the IACV is sticking somtimes. i don't know if thats right or not but i did try lol i that post has things to do with the turbos in it including a drawing of the pressure map system. hope that helps M http://www.mkivsupra.net/vbb/showthread.php?t=35926 Problem 4: I can't get any boost on the first turbo, it oscillates around a low boost pressure. A rare one this, your IACV is stuck open, and every time turbo #1 makes boost it takes pretty much the easiest way out - via the non-spinning 2nd turbo and back out to the air filter. It's like Problem 2 but happens all the time, not just at the transition point. Quote Link to comment Share on other sites More sharing options...
wojtrek Posted July 31, 2008 Author Share Posted July 31, 2008 thanks for the reply. The VSV for IACV is working fine as is the IACV valve itself, i checked with a vacuum pump. so I don't think that is it. just maybe it is an ECU problem, soon I will connect LEDs to all 4 VSVs to see when they are operational etc and maybe then I will see which valve is open/closed when I have boost in the lower rpm from first turbo, and just maybe I can see which VSV (if that is the problem) is not coming back to it's previous state or something... Quote Link to comment Share on other sites More sharing options...
Jim_1979 Posted July 31, 2008 Share Posted July 31, 2008 My car was the exact same when I had it mate! The piping on the EGCV was the wrong way around. Have a look here and make sure it's all plumbed up correctly. Jim Quote Link to comment Share on other sites More sharing options...
wojtrek Posted July 31, 2008 Author Share Posted July 31, 2008 Jim, I owe you one! you were right, the EGCV valve piping was the other way around! I bought the car stock, I never suspected that someone, probably by mistake, put them on the other way around... thanks. Next time you're in Poland let me know, I'll buy a pint or two of whatever you want cheers. Quote Link to comment Share on other sites More sharing options...
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