2JZMKIV Posted May 1, 2015 Share Posted May 1, 2015 1996 rz bpu j-spec with aem infinity-8 turbos parallel mode Whilst tuning on dyno today after hitting certain level of boost around 4000 rpm-4200 (0.9-1.0 bar) boost drops rapidly after 4300 and there was no boost at all like 0.2 max we checked for leaks there was none, tuner said catalytic converter could be blocked i have a sort of bpu exhaust system it was on the car when i bought it has 2 cats and after that its hks type s muffler no matter what we did we could not get any boost nor power after 4000 rpm car was pushing 185whp which is a joke there is OBVIOUSLY something wrong here i need to know before i start tearing everything apart could it be the turbos ? or catalytic converters ? waste gates ? and also if i remove 2 cats and replace it with normal pipes would my car go into over-boost ? please help because i'm really stuck and totally feel like sh*t. Quote Link to comment Share on other sites More sharing options...
marc_p Posted May 1, 2015 Share Posted May 1, 2015 1996 rz bpu j-spec with aem infinity-8 turbos parallel mode Whilst tuning on dyno today after hitting certain level of boost around 4000 rpm-4200 (0.9-1.0 bar) boost drops rapidly after 4300 and there was no boost at all like 0.2 max we checked for leaks there was none, tuner said catalytic converter could be blocked i have a sort of bpu exhaust system it was on the car when i bought it has 2 cats and after that its hks type s muffler no matter what we did we could not get any boost nor power after 4000 rpm car was pushing 185whp which is a joke there is OBVIOUSLY something wrong here i need to know before i start tearing everything apart could it be the turbos ? or catalytic converters ? waste gates ? and also if i remove 2 cats and replace it with normal pipes would my car go into over-boost ? please help because i'm really stuck and totally feel like sh*t. What happens if you put it back to sequential? Also, can it actually rev past 4000rpm? is it just the boost that drops off? Quote Link to comment Share on other sites More sharing options...
Scooter Posted May 1, 2015 Share Posted May 1, 2015 "Problem 2: I don't get a 2nd turbo rush, and as soon as I should it dumps all boost instead. The IACV is opening but the second turbo isn't spinning. All the air boosted by #1 turbo now has an easy path back to the non-pressurised side of the turbos via a non-spinning #2 turbo. In effect, it all goes 'backwards' through #2 instead of going into the engine. You'll maybe see .2 or .3 of a bar of boost but that's about it. This usually means the EGCV isn't opening. The turbo can't spin as it has no exhaust gas flow path. Although annoying, this won't do long-term damage as #1 turbo won't generate much boost because the engine loses a lot of power, so no overspeeding or overheating." - - - Updated - - - http://www.mkivsupra.net/vbb/showthread.php?35926-The-sequential-system&highlight=sequential Quote Link to comment Share on other sites More sharing options...
marc_p Posted May 1, 2015 Share Posted May 1, 2015 "Problem 2: I don't get a 2nd turbo rush, and as soon as I should it dumps all boost instead. The IACV is opening but the second turbo isn't spinning. All the air boosted by #1 turbo now has an easy path back to the non-pressurised side of the turbos via a non-spinning #2 turbo. In effect, it all goes 'backwards' through #2 instead of going into the engine. You'll maybe see .2 or .3 of a bar of boost but that's about it. This usually means the EGCV isn't opening. The turbo can't spin as it has no exhaust gas flow path. Although annoying, this won't do long-term damage as #1 turbo won't generate much boost because the engine loses a lot of power, so no overspeeding or overheating." - - - Updated - - - http://www.mkivsupra.net/vbb/showthread.php?35926-The-sequential-system&highlight=sequential It says he's running in parallel mode though. Quote Link to comment Share on other sites More sharing options...
Scott Posted May 1, 2015 Share Posted May 1, 2015 Take the car to someone who knows the 2JZ. Who did the parallel mod? How did they do it? Something isn't right. From the symptoms it almost sounds like it's running in sequential and the second turbo is blown. After the transition from one turbo to 2, the gas exits through the second turbo and down through the exhaust leading to next to no boost. Quote Link to comment Share on other sites More sharing options...
Scooter Posted May 1, 2015 Share Posted May 1, 2015 It says he's running in parallel mode though. ah yes....my bad Quote Link to comment Share on other sites More sharing options...
2JZMKIV Posted May 1, 2015 Author Share Posted May 1, 2015 It is still running in parallel mode i know it sounds like its in sequential but its not engine revs up to 7000rpm fine but boost goes down boost is not stable up to 4000rpm either it hits 0.5 then other pull 0.9 and after 4000rpm no boost at all Quote Link to comment Share on other sites More sharing options...
2JZMKIV Posted May 1, 2015 Author Share Posted May 1, 2015 Take the car to someone who knows the 2JZ. Who did the parallel mod? How did they do it? Something isn't right. From the symptoms it almost sounds like it's running in sequential and the second turbo is blown. After the transition from one turbo to 2, the gas exits through the second turbo and down through the exhaust leading to next to no boost. Car was parallel when i bought it i could tell from the boost coming it used to pull fine 1 bar of boost had sard ecu before and still has hks evc 4 boost controller Quote Link to comment Share on other sites More sharing options...
Westy Posted May 1, 2015 Share Posted May 1, 2015 Sounds like the exact same symptoms I'm currently having with my black car. 6hrs in the garage couldn't provide the solution, but they aren't supra specialists. Symptoms didn't change between sequential and TTC. Interested to hear replies here. Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 2, 2015 Share Posted May 2, 2015 Who did the parallel mod? How did they do it? Something isn't right. This is the question that needs asking at this stage, anything else is making assumptions around the answer to this 4000rpm is the sequential transition point. Your second turbo isn't coming online properly, or, it's being taken offline in (pointless) parallel mode due to part of the sequential system still being in the loop. Quote Link to comment Share on other sites More sharing options...
2JZMKIV Posted May 3, 2015 Author Share Posted May 3, 2015 This is the question that needs asking at this stage, anything else is making assumptions around the answer to this 4000 rpm is the sequential transition point. Your second turbo isn't coming online properly, or, it's being taken offline in (pointless) parallel mode due to part of the sequential system still being in the loop. i am pretty sure its not about that because i got the car 6 months ago and i was driving it until i switched to aem infintiy 8 and it pulled fine on 1 bar with stable boost after ~4000 rpm on stock ecu no one messed with the sequential system after i got the car and again i am pretty sure it was on parallel mode and no one messed with that place ever so if you are saying it can switch itself back to the sequential mode then i would accept it and as far as i know parallel mode is necessary because even the slightest upgrade on car messes with the sequential system and it becomes inoperable. Quote Link to comment Share on other sites More sharing options...
Ian C Posted May 11, 2015 Share Posted May 11, 2015 Parallel mode is most unnecessary and usually causes problems. If not mapped around then you get a really nasty lean spot at 3500-4000rpm due to the stock fuelling map not understanding the boost curve parallel produces. You can do pretty much anything to the car around the stock sequential system and it still works so whoever told you that blew some smoke up your backside There are several different ways of achieving parallel mode, some more permanent than others. There are several things that happen at the sequential transition point. If one of these things has started happening again because of the way the parallel mode was achieved then it could be causing your problem. Losing all boost at 4000rpm can only be explained away by the second turbo not spinning and all the boost from the first turbo going through #2 backwards and back out to atmosphere when #2 is attempted to be brought on-steam by the sequential system. So either the EGCV isn't opening or the second turbo impeller wheel is blown - either way you're in sequential mode of some sort for that behaviour to take place. If #2 turbo was busted or the EGCV wasn't open in parallel mode you'd never make any real boost at any revs. Quote Link to comment Share on other sites More sharing options...
2JZMKIV Posted May 15, 2015 Author Share Posted May 15, 2015 that really makes sense thank you so much its good to have this forum and people like you Quote Link to comment Share on other sites More sharing options...
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