fastphil666 Posted April 16, 2021 Share Posted April 16, 2021 Had an intermittent thing with my tt auto. Sometimes you'd put your foot down and get 5psi of boost which didnt go up even when the 2nd turbo should join the party. If you came off the throttle and back on, id get 9psi then 17psi at 4.5krpm, all good. Suspected a leak at the dumpvalve. Took it apart and put it back together. The circlip that joins the dv to the adapter, should it allow the dv to spin in the body or should it be rock solid? Before removal it couldnt be turned but its free-er now. The issue occurs more frequently now, so i think i was right. Think boost is escaping through the circlip join?? Quote Link to comment Share on other sites More sharing options...
m12aak Posted April 16, 2021 Share Posted April 16, 2021 Get some soapy water in a spray bottle and spray it on the circlip join, if you see bubbles (might need to blip the engine it whilst it's idling to build a bit of boost) it's leaking. Quote Link to comment Share on other sites More sharing options...
Noz Posted April 16, 2021 Share Posted April 16, 2021 Spraying in the valve itself too is an idea. May be leaking. Always worth removing it and seeing if you hit boost. On my single the turbo just kept loping Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 16, 2021 Author Share Posted April 16, 2021 Well, ive just had half an hour spare. Linked a bike pump to the dumpvalve pipe, it held 40psi fine, so that will do for me. Ive always suspected a dodgy vsv but have bench tested all 4 an they were fine. I need to vacuum test the pressure tank, but im thinking of trying ttc just to rule stuff out. Ttc bypasses all vsv's, and the pressure tank? Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted April 16, 2021 Share Posted April 16, 2021 Probably going to be the AICV VSV, common problem. But get rid of the dump valve anyway, they sound shit Quote Link to comment Share on other sites More sharing options...
Mike2JZ Posted April 17, 2021 Share Posted April 17, 2021 IACV VSV is typical failure for intermittent second turbo. Also. Remove your air filter and stick a mirror down air intake and check the air intake hoses as seen above (black rubber bits). They tend to collapse and can strangle turbo's from doing their job. Also a common failure. Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 17, 2021 Author Share Posted April 17, 2021 19 hours ago, Mike2JZ said: IACV VSV is typical failure for intermittent second turbo. Also. Remove your air filter and stick a mirror down air intake and check the air intake hoses as seen above (black rubber bits). They tend to collapse and can strangle turbo's from doing their job. Also a common failure. Ive got aftermarket ones of those and have checked them after reading about them falling apart. All good. 21 hours ago, Swampy442 said: Probably going to be the AICV VSV, common problem. But get rid of the dump valve anyway, they sound shit I have checked all vsv's previously using a guide. Were all ok but i know they can be intermittent and fail at any time. Ttc should let me know if any of them are at fault though. In the case of the dumpvalve i have thought about fitting a recirc adapter to it, the autobox should benefit from a recirc valve? Quote Link to comment Share on other sites More sharing options...
Mike2JZ Posted April 17, 2021 Share Posted April 17, 2021 3 minutes ago, fastphil666 said: Ive got aftermarket ones of those and have checked them after reading about them falling apart. All good. I have checked all vsv's previously using a guide. Were all ok but i know they can be intermittent and fail at any time. Ttc should let me know if any of them are at fault though. In the case of the dumpvalve i have thought about fitting a recirc adapter to it, the autobox should benefit from a recirc valve? Agreed put it in TTC, thats also a good test. If you still make no boost on TTC then could be a leak or something more menacing. The BOV on a Jspec car does not need to be recirculated for the ECU & engine to function properly. So in that respect, won't make a difference to your problem. Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 17, 2021 Author Share Posted April 17, 2021 1 hour ago, Mike2JZ said: Agreed put it in TTC, thats also a good test. If you still make no boost on TTC then could be a leak or something more menacing. The BOV on a Jspec car does not need to be recirculated for the ECU & engine to function properly. So in that respect, won't make a difference to your problem. If it was a permanent no boost in 2nd turbo, i would be really worried. It will work 99% of the time, sometimes it will make a loud boost noise but only show 3-5 psi on the gauge. Come off the throttle and go again an it would boost and transition fine. I'll try ttc for a good 100 mile drive and see if it works 100% of the time, if so i'll look at a new iacv vsv. Thanks folks Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 23, 2021 Author Share Posted April 23, 2021 Just had a thought, i notice my issue mostly when ive dropped down in manual mode (auto tt car) to 2nd. The car is at say 45mph and just under 4krpm. If i boot it then, it sometimes doesnt make full boost for sequential, about 17psi in my case. Am i asking too much, in going into load at the transition point to 2nd turbo so the system hasnt pre spooled 2nd turbo (using egcv) Is it fine and im finding a hole in the system? The way sequential works means it has to make boost on 1st turbo, pre spool 2nd and change to parralell, im asking it to do that in around 1k rpm range. Quote Link to comment Share on other sites More sharing options...
mattdavies Posted April 23, 2021 Share Posted April 23, 2021 6 minutes ago, fastphil666 said: Just had a thought, i notice my issue mostly when ive dropped down in manual mode (auto tt car) to 2nd. The car is at say 45mph and just under 4krpm. If i boot it then, it sometimes doesnt make full boost for sequential, about 17psi in my case. Am i asking too much, in going into load at the transition point to 2nd turbo so the system hasnt pre spooled 2nd turbo (using egcv) Is it fine and im finding a hole in the system? The way sequential works means it has to make boost on 1st turbo, pre spool 2nd and change to parralell, im asking it to do that in around 1k rpm range. I would double check the obvious hoses, i had a issue were one of mine on the AICV VSV wasnt seated fully and had this issue. there is also the two pipes from towards the front, one of mine used to unseat itself and cause the same issue as you describe Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 23, 2021 Author Share Posted April 23, 2021 I have just run the car in ttc mode, just to diagnose. Man its loud!! it seems quicker though? So my question now, what does ttc bypass? Pressure tank, all vsv's or all the above? Am i closer to diagnosing the issue? Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted April 23, 2021 Share Posted April 23, 2021 TTC bypasses the whole system, opens all the valves. All it proves is both turbos are working fine, as a few of us said, just get an IACV VSV and replace it, theyre very cheap, about 80 quid last time I bought one. Its not any faster just seems so because of the lag Quote Link to comment Share on other sites More sharing options...
fastphil666 Posted April 26, 2021 Author Share Posted April 26, 2021 I think your bangnon the money with it being iacv valve. Thats the one highest in the engine bay, the one you bypass for ttc. After its run on friday i checked resistance as i have previously. This time however it was all over the shop, 65ohms at one point but wouldnt settle down. Ranged from 50-65ohms in about 5 seconds of checking. I only have a cheapo multimeter so i'll have to check again with a better one. Didnt want to buy a vsv if it was a split pipe, having checked and renewed all vacuum lines im happy its the iacv if my resistance results were correct. Quote Link to comment Share on other sites More sharing options...
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