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Thread: will forcing more boost on a choked motor work?

  1. #1
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    will forcing more boost on a choked motor work?

    hey another one of my dumb questions here.

    i have an m30. revs really bad. after 5.7k it really falls on it's face.

    can a motor like this be forced to eat
    when it falls on it's face
    so torque remains flat instead of a sharp drop?

    i'm talking like a +10psi increase, whatever it takes.
    or is that just a physical mechanical thing where it doesn't matter how much.

    right now i'm at 16psi and ramps up19, past 5,7k where it falls ramps again to 25psi and 28psi to 6.8k but it doesn't feel like it's pulling up there even at 28psi.

    my question
    have you guys seen something like this where an engine dies hard because it's naturally a low hp motor
    and ramping up the boost turns it into a 2jz? or am i just chasing a dream?

    fuel issues and tuning issues have been resolved thanks to you guys.
    hopefully you guys can help me out get into the 500s.

    i've messed with it and i'm just going to do streight 19psi to 5,7k and ramp it up to 30psi @ 6,8k.
    will see what that does. remember big red? he had like 600hp idk how he did it.

    hx40 58mm, e85, 1500cc injectors, 3'' exhaust with crush bends.

    doing ok.i think. by jet jones, on Flickr

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    It might be more beneficial/efficient to just build the head


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    The rate of acceleration looks like it’s still increasing to me. You’re probably choked on the turbine though. Put an S369 on it. Turbo is way to small.


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  4. #4
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    A little more boost after the torque peak is fine, to compensate for the engine VE dropping. The decreased cylinder filling means you can take a bit more cylinder pressure in this range. 10 psi more is a bit much, though.

    I agree with Someguy that if the turbine housing is what's choking the motor, more boost won't be much help, and it's time to upgrade the turbo.
    Matt Cramer
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  5. #5
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    Quote Originally Posted by Robocop View Post
    right now i'm at 16psi and ramps up19, past 5,7k where it falls ramps again to 25psi and 28psi to 6.8k but it doesn't feel like it's pulling up there even at 28psi.
    It falls on it's face and ramps again because your actual boost is always higher than your target. Why?

    If you're running closed loop boost control that would never work.

    Fix your boost control, that should avoid the dip/hesitation that you see of the boost output DC pulling back all of a sudden.

    Of course I cannot see your scaling and like I've said before posting images of datalogs is useless and if the scaling isn't correct we're wasting our time giving you info.
    Last edited by NOTORIOUS VR; 11-20-2019 at 09:42 AM.

  6. #6
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    Notorious!
    ya sorry I was thinking about it then got lazy.
    thanks for the time if you want to check it out.
    https://drive.google.com/file/d/12w4...ew?usp=sharing

    Someguy, u serious?
    isn't that a 69mm turbo? lol feels like ur trolling me i'm pm you.
    Last edited by Robocop; 11-20-2019 at 06:05 PM.

  7. #7
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    You have a dip in RPM at 5900, along with that you have a steep increase in IAT right after (near vertical). It's unclear if the dip is because of the PID boost correction happening or if something else happened (valve float, wheel spin, etc).

    As Matt said, you can have a rising boost profile to help the VE of the motor, but not when you have massive restrictions in your head + turbo combination.

    I think there's a few things you can try here to make things better.

    1. take some timing out (3-4 deg) before doing the following steps as a precaution.
    2. bring your act. AFR in line to your req. AFR - your VE is increasing but rarely is that the case and it's clear that it isn't here as well.
    3. Tame your boost request - 290 kpa by redline is a lot especially if you don't know what is going on (EBP) - it seems like you're 220 kpa request is easily met (215 act) until about 5300 RPM which is when you start to ramp up boost just as the boost starts to taper. So it does indeed look like you might be out of turbo (compressor and/or turbine), and probably head flow if everything is stock there.
    4. start to add some timing back in closely monitoring acceleration vs time using the same stretch of road - if you're gaining try a little more, if you're not then back it off until you lose a little and then add it back. It's crude and you really should be using a dyno to dial in timing on Ethanol to be honest.

    You're talking about a big red - I just did a quick search about what you're comparing against... looks like he has a wildly different setup (in 2010):

    620 RWHP 28psi T88H turbo - 8.5:1 comp
    3mm over sized valves ported head with 18% flow increase...

    unfortunately, all that should show you how inefficient the M30 is

    graph.png
    Last edited by NOTORIOUS VR; 11-21-2019 at 10:10 AM.

  8. #8
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    M30 is a total turd for high RPM flow. Do you at least have some reasonably hot cams in the thing?

    If you have stock cams and a stock head, I wouldn't even try to spin it up towards 7k. I feel like my 3S-GTE flows like a tractor over 6k RPM, and it probably flows way better than an M30.


    IMO, his MAT/IAT doesn't look too bad, other than it leads evidence to you being really out of turbo as you push past 20 psi at high RPM.

  9. #9
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    Quote Originally Posted by Def View Post
    M30 is a total turd for high RPM flow. Do you at least have some reasonably hot cams in the thing?

    If you have stock cams and a stock head, I wouldn't even try to spin it up towards 7k. I feel like my 3S-GTE flows like a tractor over 6k RPM, and it probably flows way better than an M30.
    as is the M20... they're just dinosaurs technology wise.

    IMO, his MAT/IAT doesn't look too bad
    Agreed over all it's alright - but the near vertical rise over a short period indicates something is up.

  10. #10
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    Thanks bimmerforums jedi masters! hahaha

    looking back if i could put in a m52 or whatever i would have
    but this thing's had an m30 back when m30s where every bmw at the yards
    and there was maybe 1 e46, if ur lucky.
    now it's reversed. zero m20s. once in a while an m30. it's a dead motor.

    i have a catcams "turbo cam"
    idk if it was a bonehead move knowing nothing at all about cams.
    here it is. let me know.
    www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=110&CAMSETUP_id=1428&Lang uage=english

    It feels torqueier,
    but didn't give me the top end i was after.
    could be a turd idk...

    So, getting a new turbo then.
    and ya it's going to be a borg


  11. #11
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    Quote Originally Posted by NOTORIOUS VR View Post

    Agreed over all it's alright - but the near vertical rise over a short period indicates something is up.
    You guys would cry at my IAT graphs then... My personal "best" was 80 F to 148 F at the end of a pull.

    SMIC mid-engine life...

  12. #12
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    ^ do you have a build thread?
    wondering what a boost lord drives.

    no bmw?

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    Quote Originally Posted by Def View Post
    You guys would cry at my IAT graphs then... My personal "best" was 80 F to 148 F at the end of a pull.
    Hey we all need goals!

  14. #14
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    Quote Originally Posted by Robocop View Post
    ^ do you have a build thread?
    wondering what a boost lord drives.

    no bmw?
    It's an SW20 MR2. It's not that crazy, trying to keep this like a "nice fun street car" build. My last turbo car (S13 240SX) went a bit overboard... hah

    https://www.mr2oc.com/threads/defs-9...meness.676696/

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    this thread has gone super off-topic but i made it so whatever.

    fx400 6 puck ceramic is slipping.
    the way it slips is interesting.
    it starts to chatter hard, then if i keep on it it slips like cream cheese.
    now i don't know what to do for a clutch. no other options for the m30 i guess.

    after a night of fking around 26psi the turbo made a loud rub sound i thought maybe a belt was slipping
    or bov was opening on boost, or amount of blow by out the cover was making the sound. torn coupler. very confused.

    nope, the turbo broke and there is allot of shaft play.
    it still boosts up there, but it makes a hardcore boosting old school supra sound.
    very loud. too much back pressure? a ton of side to side some rub marks on the mouth. Not allot of in/out. s366sxe ordering tonight.
    Last edited by Robocop; 11-25-2019 at 03:14 PM.

  16. #16
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    compressore is trashed, exhaust wheel idk if supposed to look like that.
    found out it actually has a big ol 18cm turbine housing people are saying it's about 1.00 a/r.



    Play by jet jones, on Flickr







    Trashed wheel by jet jones, on Flickr
    We have contact by jet jones, on Flickr
    Normal? by jet jones, on Flickr
    Last edited by Robocop; 11-25-2019 at 08:31 PM.

  17. #17
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    it's starting
    think this thing will help the old m30 breath up top?
    New turb by jet jones, on Flickr

  18. #18
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    What turbo did ya get?

  19. #19
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    Sure looks like a S300 BW. Expect it to put down insane torques. Last M30T i built was a beast on boost.
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  20. #20
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    it's a s366sx-e
    .81ar 3'' vband.

    The holset actually had a 60/82 compressor and 64/76 turbine on a 18cm housing.

    right now i'm waiting on a 2.5'' to 3'' 90 coupler.
    changed from 3an to 4an on the feed.
    going tomorrow to get a 3.6'' diameter flat v-band for the exhaust i'm sure a diesel place will have one, hope.

    what u think notorious?
    what's your honest opinion?

  21. #21
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    I ran some quick numbers through the BW Matchbot... seems like you should be good with that turbo

    1.jpg

  22. #22
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    ok.
    hell yeah. loving it so far.
    i like to bring threads to a conclusion, sorta.

    comparing borg to holset.

    Sound wise.
    hx40 sounded like a jet. pretty loud, pretty sweet.
    sxe sounds much more higher pitch and much quieter i can barley hear it.
    more like a noising diff, but my ears can barley pick it up.

    Spool. sxe blows away the hx40 completely.
    no hard data just what i feel. power comes in faster and smoother.
    cells 2k-3.5k range where in the high 13 - low 14afr on boost, so.. hx40 was a slow spooler.

    interesting thing feathering it in 5th getting on boost turbo will go cha cha cha cha chatter unless i completely let the bov kick in.
    strange wondering what that means technically.

    right now it's at wastegate 18-19psi obviously lights the tires off way harder that's all i got
    in terms of estimating the power.


    spools faster
    more power
    more stealth.

    garbage weak ass fx400 clutch slips in 4th at speeds.
    but i'll try to ramp up the boost to see if this is the cure for the original rev out problem.

    K by jet jones, on Flickr
    Last edited by Robocop; 02-01-2020 at 06:34 PM.

  23. #23
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    Ahhhh good ol compressor surge. I've got a 15psi spring in my BOV just so I can hear the stututu. That's your *cha cha cha chaaaa* noise, it's fine and I've been doing it for 10k+ miles and turbo is in great health.

  24. #24
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    Yep, that cha-cha-cha sound is compressor surge. Essentially you've built up enough shaft speed at a higher flow rate to build a good pressure ratio, then you ease off the throttle and there's enough energy to keep the PR up (vertical on compressor map), then you cut back on the mass flow (move left on map), past the surge line.

    It's kinda rough on a turbo, but not as bad at part throttle. It's no bueno when it happens repeatedly under full throttle, as there's a lot more shaft power to wreck stuff when the aerodynamic stall of compressor surge kicks in.

    The cha-cha-cha sound you're hearing is the flow separating from the blades as the flow stalls out on the compressor geometry, then as the pressure ratio drops due to this stall, it reattaches and builds pressure again... then stalls again etc. etc.

  25. #25
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    Love this thread Robocop...just stumbled across it while searching for M30 turbo projects.

    Did you convert to a coil-over-plug system? I've never seen that on an M30, would love details or info on how such a conversion is done.
    Last edited by Smoky540i; 02-04-2020 at 10:04 AM. Reason: typo

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