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  1. #26
    SupraForums Member okinawa-supra's Avatar
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    Looks like he is in sequential mode. At 28 seconds in the video, he is at 3500 RPM and floors it. right at about it 3800-4000 RPM the Turbo system seems to “transition” with the slight dip in boost. I believe while your in full boost with both twins online your only boosting to what ever that gauge goes too. But its not much More psi than while it was on the first turbo.

    It almost like your in “stock” boost.

    Here is a link while I was testing my 94 sequential system. Almost the same transition and it boosts to about 12 psi (the supra is stock)
    Maybe you have a weak wastegate.
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  3. #27
    SupraForums Member okinawa-supra's Avatar
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    I would also “pressure” test your system. When i hooked up coupplers to my system and applied the air compressor, i was surprised to find many little leaks. Its also not uncommon for intercoolers to crack and leak under pressure.
    Good luck.

  4. #28
    NiSmO [email protected] supergoji's Avatar
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    copy, will report back.
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  6. #29
    SupraForums Member supralover93's Avatar
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    ok, small update,

    i followed steps to pressurize Port "A". system holds pressure. after i release pressure from the pump and remove it, i removed caps from Ports B and lots of pressure came out leading me to believe the new pressure tank is holding just fine.
    one possible issue though. the EBV doesnt open until about 13psi and isnt fully open until about 21-22psi. also discovered my brand new POS mityvac pressure tester is leaking. while the system was pressurized i could hear a creaking while the pressure very slowly leaked down. noticed that the EBV was slowly closing while the pressure was leaking but wasnt closing smoothly. it was a little like it was sticking and closing in small steps until fully closed at about 12psi.
    after i figure out my pressure test leak i'll test all of the VSVs but i'm thinking my EBV is bad. any ideas?

    thank you
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  7. #30
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    mityvac disassembles pretty easily. you can probably find which part of it is leaking. If I remember corectly, I just made a silicone gasket around it and works just fine again! good luck figuring out your seq operations!

  8. #31
    SupraForums Member supralover93's Avatar
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    ya, if they dont replace it thats probably what i'll do.

  9. #32
    Stock Twins King Stu Hagen's Avatar
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    Quote Originally Posted by supralover93 View Post
    ok, small update,

    i followed steps to pressurize Port "A". system holds pressure. after i release pressure from the pump and remove it, i removed caps from Ports B and lots of pressure came out leading me to believe the new pressure tank is holding just fine.
    one possible issue though. the EBV doesnt open until about 13psi and isnt fully open until about 21-22psi. also discovered my brand new POS mityvac pressure tester is leaking. while the system was pressurized i could hear a creaking while the pressure very slowly leaked down. noticed that the EBV was slowly closing while the pressure was leaking but wasnt closing smoothly. it was a little like it was sticking and closing in small steps until fully closed at about 12psi.
    after i figure out my pressure test leak i'll test all of the VSVs but i'm thinking my EBV is bad. any ideas?

    thank you
    EBV VSV is a common failure. It either leaks or it fails the resistance check. I would read what it shows for resistance. A poor EBV VSV can lead to a lazy transition but really has nothing to do with overall boost. Its sole purpose is to gradually open the actuator to prespool. I did tests years ago and found that the ECU hardly ever even opened the valve. If the valve (VSV) never opened the the rear actuator would slowly open linear to boost pressure. An brand new VSV may pulsate at 10-11psi opening and closing to maintain exactly the 10psi prior to full transition. If it was stuck open then that is where you could possibly see 11psi pt higher. Same effect as pulling the hose.

    I think what you are seeing is near factory spec on the opening PSI characteristics if I am not mistaken

  10. #33
    SupraForums Member supralover93's Avatar
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    Thank you Stu. I checked to see if it holds pressure, which it does but did not do a resistance test. I will check that today.

  11. #34
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    So your boost level goes to 10-12 psi pre transition, then still end up at 10-12 psi after transition with your electronic boost controller.
    You pulled off the hose to your ebc and you got 20+ psi post transition. Stu mentioned electronic boost controller being the possible problem, I dont understand why you are still looking at the ebv. May be there was a misunderstanding of stu saying ebc, and you took it as ebv. Am i missing something?

    on another note, when I pressure tested my system years ago, the ebv would crack open at around your range from what I can remember and so shouldnt be too much of an issue. Total system not boosting over a certain level should be limited to the wastegate being leaky and not allowing you to build up boost or electronic boost controller not able to stop the air pressure to the wastegate actuator and hence opening it up and again not letting you build your boost.
    Last edited by shenofjo; 05-16-2019 at 04:14 PM.

  12. #35
    SupraForums Member supralover93's Avatar
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    Thank your the reply. I think your right, I might have misread.
    Only thing that had me confused tho was that my EBV was opening at double the pressure that it's supposed to, that threw everything off in my head. Also, yes I removed the hose that goes from the BC solenoid to the top of the WG and my boost would go to 20+. It's weird because I tested the BC and solenoid and it seems to respond like it's supposed to. Sucks because it's new and I just got it but if it's bad I may just go with a MBC.
    I do want to make sure all of my stock twin components work properly because I would hate to chase any problems after the upgrade.

  13. #36
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    Recheck the routing of the hoses for the ebc solenoids as that can be an issue otherwise MBc and go to town brother.
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  14. #37
    SupraForums Member supralover93's Avatar
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    Thank you. I did discover that the hoses were crossed, unfortunately correcting them didn't solve the issue.
    I was also thinking, if it takes 13+psi to open the EBV and I'm only hitting 11-12, doesn't that mean that the EBV would never open?

  15. #38
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    Static pressure from a pump is different than dynamic pressure in the system with air pushing against the valves on top of the actuator so helping to open them. Seriously, you are dealing with a messed up ebc or poorly routed or wired or both. Go mbc and call it a day unless you really gonna be on this set up for awhile. Add a few spring hooks onto the wastegate and ebv and have fun

  16. #39
    SupraForums Member supralover93's Avatar
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    We'll great news guys. It was all operator error. I wasn't using the controller correctly. After carefully reading the manual again I made some adjustments and now it boosts with no issues. Now I just need to make some fine adjustments so it doesn't over boost, and apparently it has a setting which you can adjust to improve boost response.

    Thank you all for the help, I'm still glad I was able to test the system, I learned A LOT during all of this.

    I just have one question I wasn't able to find an answer to. This controls only the first turbo, so if it's set to go to 16 psi, what controls the second turbo to do the same? I'm assuming both turbos above 4k rpm output 16psi correct? Because you can't have a pressure differential.
    I believe many years ago Stu even ran dual boost controllers and is doing something similar now but with a standalone and MAC valves instead of VSVs.

    Thank you all again for the help.

  17. #40
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    yeah brother, i kinda knew this was it. the wastegate controls the boost of the whole system when in true twin above 4k rpm. Under sequential, the ebv bleeds any excess boost pressure to the second turbo for prespool. that's why you cant boost more than your 0.5bar until after the transition. there are several ways to increase the boost pressure before transition, but under the condition that your wastegate holds higher pressure than your ebv.
    1. add a spring to the ebv actuating arm similar to wastegate spring mod.
    2. add washers to the ebv mounting point (harder to get to)
    3. add a boost controller into the ebv actuator.

    An additional point to consider is boost pressure vs ignition timing from stock ecu. I have been running 13 psi on pre transition for years and the timing with methanol injection and stock ecu with piggyback has been a nightmare to tune and figure out. What I am realizing is that perhaps running the higher psi in pretransition may be enough to trigger ecu to pull timing which effects the timing overall in the later RPMs after transitioning.
    I noticed WOT pulls in sequential, the timing would be in the low teens and then gain timing as RPM rises, whereas WOT in TTC would yield higher initial timing with RPM overlay of the runs. This might not bother 6speed manual people but my AT 3 gears tend to get me in transition more often than not on the road.

    Currently I am still testing out this theory and poss. revert back to stock pretransition pressures to see how timing changes and maybe consider meth injection pass stock boost even before transition. will see. PM me if you want me to look at your set up if you are in Sac / Folsom area.

  18. #41
    SupraForums Member supralover93's Avatar
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    Thank you for the info. Where I'm sac are you? I've had my Supra since 2001, surprised we haven't met.

  19. #42
    SupraForums Member supralover93's Avatar
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    Also, if your pulling timing at 13psi pre transition the what's happening at full boost?

  20. #43
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    Problem with obd1 data logging is staring at excel sheet of 3-5 data points at a run. Basically, the Ecu goes into more conservative timing and you end up making less power than you could at a given boost level. If you plan on running race gas then you should have no issue with higher pretransition boost.

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