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Thread: 22 vac 0 boost... No leaks???

  1. #31
    Junior Member Backyard Mechanic
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    Default Re: 22 vac 0 boost... No leaks???

    Motor sounds healthy enough, stop being a pussy and give it 4 grand. It looked like you barely have any boost being created yet. The boost would really come on after the type of driving that would see the vacuum approach zero. Keep the throttle open feeding it air. I observed typical vacuum signals of normal driving in the video. Seems like the inlet manifold is solid, Id be suspicious of the exhaust manifold, especially if its a custom tubular manifold. Has it been pressure tested properly? Put up some pics of how its all put together under the bay. Are you running a bigger than stock turbo that will spool later? Why did you get away from the stock exhaust manifold? Stop playing with light throttle. It needs air to spool, its under vacuum conditions, try to get the motor at atmospheric pressure and see if the boost takes over. At the very least you might reveal the fault. Flick your lights on next time so the gauge is readable too!

  2. #32
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 22 vac 0 boost... No leaks???

    Quote Originally Posted by Blackcountryboy View Post
    I "think" I hit 2 psi lol in 3rd at 3k
    Nil desperandum amigo... I have it on good authority that there has never been a reported case of a Toyota being possessed by the Devil I tried to find a graph showing boost vs throttle opening, but it seems that no-one bothers to publish how much power they make at part throttle. It is always at WOT. So I imagine that reports of boost achieved at low rpm are also measured at WOT.

    To be driveable, the power output of a turbocharged vehicle must be able to be modulated by the throttle. Thus output at low and part throttle will be comparable to that of a N.A. vehicle. As I understand it, to build boost the throttle opens, more air and fuel enter the engine, there is a bigger bang and exhaust gas flow increases. This spools up the turbo so that (at a certain point) it starts creating positive pressure. This forces more air into the engine increasing the charge density which allows more fuel to be burned making an even bigger bang etc etc until the throttle is backed off.

    An engine only generates sufficient output to over come the load applied, which is surprisingly little if you accelerate gently up to 30mph. So you won't get any boost if the engine can supply the required output while running in vacuum. To see boost you need to increase the load on the engine... towing a trailer full of readymix is one way, but I believe there are other ways

    Cheers... jondee86

  3. #33
    Junior Member Backyard Mechanic
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    Default Re: 22 vac 0 boost... No leaks???

    To summarise, drive it harder and see!

  4. #34
    Learner Driver Backyard Mechanic
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    Default Re: 22 vac 0 boost... No leaks???

    Sorry to be blunt but I think you are driving it too much like a nana in the video to achieve anything.

    To get any boost, you will need full throttle. At 50% throttle or less I doubt you will see any boost.

    I dont think there is a problem with the car, I think there is a problem with the way you drive it and what you are expecting.

    the sound was very low, but it did not sound in the video like it had anywhere enough load to create any boost at all.

    Get in it warm it up to normal temp, the drive in 3rd gear and hold it at 100% full throttle until you either get decent boost,
    or it reaches at least 7000rpm.

    It will be the only way to see if the problem is the car or your expectations.

    If I drove anything with an average or bigger sized turbo
    I would not have expected to see boost in the drive from what I heard in the video.

    At 1psi of boost in the intake manifold the car will make more power than an Non-turbo car at full throttle,
    so unless you are driving it faster that an NA car at full throttle, it wont see any decent boost.
    - KE70 Corolla Dx -
    - 500hp+ 7AGTE 20V turbo -
    - MRS/Hayabusa turbo **sold**
    - TA63 3TGTE project in the build -

  5. #35
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 22 vac 0 boost... No leaks???

    yer, have to agree.
    whatever speed the car will go in 2nd (80km/hr?) find a road with that speed limit (if you care), shift to 2nd, then floor it until redline and see what happens
    half throttle may not make any boost at all anywhere in the rev range...

    and.. many people saying they make full boost at 3krpm.. or at part throttle.. aren't...

    dyno graphs are usually WOT from well below when boost kicks in.. and the graphs don't show the time component... which could be long before it gets up and boogies

    here's a 3rd gear run with audi.. can see boost and revs etc
    https://www.youtube.com/watch?v=Bg_oC0s3Nrk

    especially from 20 seconds in video...
    it takes about 4 seconds of FULL throttle at 2krpm to even start making noticeable boost (on an engine that revs to 6krpm... so say 2500-3000 start for yours)..

    Miata/MX5 (assume 1.8 or 2L) doesn't get going until 4k in 2nd
    https://www.youtube.com/watch?v=Mh2Z46WXgrA

    4.5krpm+ in this one (where the vid starts)
    https://www.youtube.com/watch?v=bGi0vriTQpc
    Last edited by oldcorollas; 12-02-2019 at 08:03 PM.
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  6. #36
    Forum Member Grease Monkey
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    Default Re: 22 vac 0 boost... No leaks???

    Hey guys,

    Sorry for the late reply. The joy of night shifts!

    Jon/Oldcorollas/Dx20vt/Jondee... I think your all spot on. Think I've finally worked it out thanks to you guys...

    Oh and your also right about me driving like a A big girls blouse hahahaha! Even my GF tells me to hurry the [email protected] or she's driving lol.

    Right... New things you've helped me work out...

    Most of the people talking bout 2k spool are PROBABLY running cast manifolds and internal gates. With a shitty tubular china bay job and a whacking great adaptor in between the manifold and the turbo that would account for 1k of extra spool up time but I'm guessing should make more power at the top end soon as I'm brave enough to give it the full beans unbroken in on the base map. Gonna grow a pair balls on me day off and do another boost test n take her to 4k to see what happens...

    Also defiantly feels more responsive with shorter intake and just one wta cooler. Loads improved.

    Thinking I might advance the both cams a few degrees (better low end power) to see if that helps spool???

    Don't wanna wrap the manifold etc for heat retention cos the wrap went up in flames last time on the motorway! Was the good stuff too so I'm sh1t scared of that stuff. Lucky I had an extinguisher, gave me proper brown pants.

    Any more advice for improving spool? Retarding timing? Advancing cams?

    Seen a sexy cast Top fuel manifold on fleabay but it's like 400 with import tax n shipping. Need to put a cast manifold back on but I gave it away like a plum!

    Anyways thanks again all for ALL the help and replies finding this ghost boost leak.... Think I'm finally getting somewhere now...

    Cheers

    Chris
    Last edited by Blackcountryboy; 16-02-2019 at 05:02 PM.

  7. #37
    Learner Driver Backyard Mechanic
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    Default Re: 22 vac 0 boost... No leaks???

    I would not worry about spool yet, if it is not tuned you will have no idea of what it will actually be in the end.

    Get it running properly, then get it tuned properly, then see if there are issues.

    Bad spool or the feeling of lag can be caused by a crap tune.
    - KE70 Corolla Dx -
    - 500hp+ 7AGTE 20V turbo -
    - MRS/Hayabusa turbo **sold**
    - TA63 3TGTE project in the build -

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