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Thread: Boost Creep

  1. #1
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    Boost Creep

    Ive been playing more and more with my 332 this past week and have made it the DD for the week as well.

    I downloaded the manual for the Eboost2 and upped the boost setting from zero (wastegate spring..essentialy EBC was off) up to 14psi on the Eboost2. With this as the boost setting, accoridng to my boost gauge the car would build ~17 psi (didnt ever hit 18psi as I have the Eboost2 alarm set to 18psi and it never went off).

    Today I turned the EBC setting down to 12psi and and was hitting ~15psi according to my boost gauge.

    Im not sure which wastegate spring is in there, but I was previously seeing 12psi with the EBC essentially off, so Im guessing the spring weight is somewhere around there? Or would it be something like a 9psi spring that allows me to hit 12psi?

    Here is the way the wastegate dump is plumbed back into the exhaust:




    Is 3psi an unacceptable amount of creep?

    Is there anything I could do to make the car achieve whatever boost is set into the EBC (no creep...)?
    915whp '98 M3 Sedan /// 37k Mile '95 M3

  2. #2
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    The thing is, where ever you have the EBC referencing boost is offset from where the wastegate is referencing boost. If the wastegate and the EBC are referencing the same point for boost, you cannot have "creep" really. Think about it - if your wastegate is set for 1 bar, and you have a (lets say) 8 psi spring, even if you get CREEP past 1 bar, the wastegate should just open sooner/more to compensate unless you are out flowing the wastegate. With your setup you have the wastegate recird'd at a pretty mcnasty angle as well as the dump tube being like 2.5' long it seems. This would contribute to creep greatly.

    Things to check:

    - Does wastegate open at proper PSI on spring pressure?
    - If yes, put a 1 bar spring in it and see if it creeps past that.
    - Does wastegate and EBC reference same source?


    If the above proves to work and problem still remains - through EBC on the ground and man up to spring action!

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    jon is afraid of technology

  4. #4
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    Quote Originally Posted by multiplex View Post
    jon is afraid of technology
    Just remember how nice your car idled with the ICV unplugged


    Yeah yeah it works now... but itoldjaso!

  5. #5
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    Go search for a MBC called "The Boost Machine" on yahoo or google, It's fromfrom ModShackTTuned... That should help with your boost creep issue. I can't post a link yet, I'm too new.

  6. #6
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    Thanks guys.

    I dont believe the problem is associated with the Eboost2 being sub-par as MANY people have had great success with it.

    Ill look into the other things you suggested Jon.
    915whp '98 M3 Sedan /// 37k Mile '95 M3

  7. #7
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    Quote Originally Posted by 95RogueM3 View Post
    Thanks guys.

    I dont believe the problem is associated with the Eboost2 being sub-par as MANY people have had great success with it.

    Ill look into the other things you suggested Jon.
    Yeah the EBC is more than likely fine - it takes time figuring things out especially when it can be the very nature of your wastegate method. You just need to see what sort of creep you're getting on spring pressure and where you are getting your pressure reading for the wastegate vs the EBC. What WG is it by the way and what turbo?

  8. #8
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    Quote Originally Posted by UrineMachine View Post
    Yeah the EBC is more than likely fine - it takes time figuring things out especially when it can be the very nature of your wastegate method. You just need to see what sort of creep you're getting on spring pressure and where you are getting your pressure reading for the wastegate vs the EBC. What WG is it by the way and what turbo?
    Tial 44mm and GT35R. I believe they are sourcing the signal from the same place, but I couldnt say for sure (I havent really dug into it yet).

    I would like to know which # spring is in the WG...Ill have to look into that too, I guess.
    915whp '98 M3 Sedan /// 37k Mile '95 M3

  9. #9
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    Are you running the Spa manifold? I too have boost spike problems when on and off the gas under boost. I run 11 psi with a GT35R, Tial 44, and Profec B boost controller and willl see 16 psi spikes. I think the problem is the sharp angle and small hole for the wastegate piping on the Spa manifold!
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  10. #10
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    Quote Originally Posted by tonym View Post
    Are you running the Spa manifold? I too have boost spike problems when on and off the gas under boost. I run 11 psi with a GT35R, Tial 44, and Profec B boost controller and willl see 16 psi spikes. I think the problem is the sharp angle and small hole for the wastegate piping on the Spa manifold!
    No, I am running the AA Manifold. (Log-Style). I think my largest "over-boost" seems to be about 3psi above the setting I have chosen.

    In that picture you have an open dump as well. George @ ICS reported awhile ago that when he had an open dump on his blue car, it would creep/spike, but then when plumbed-back to the exhaust he was able to cure the spike.

    Mine doesnt really come off the manifold at a sharp angle, instead its just a port on the log section of the manifold directly before the collector...

    Hopefully you get your creep worked out too.
    915whp '98 M3 Sedan /// 37k Mile '95 M3

  11. #11
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    I'd heard that also even though I don't understand why plumbed back in would help. Dang it, I sure liked the sound of that open wastegate but I'd rather not hurt the motor! Thanks
    1998 M Roadster,arctic silver,black leather,31,000 miles,6 spd conversion,VDO
    boost and oil pressure gauges in windshield pillar,Porsche Turbo "big" brakes with stainless
    lines,3.23 Quaife,aluminum flywheel with McLeod dual disc competition clutch,GT35R
    ball bearing turbo @ 12 lbs boost on 9.8 compression,TT 36 lb injectors and remapped
    ecu,Greddy Profec B boost controller and bov,368 hp and 355 lbs torque,custom 3"
    stainless downpipe and exhaust piping with no cats,Magnaflow exhaust,coil overs and
    camber plates,TC Kline springs,Koni adjustables,reinforced shock and tranny mounts,Kmac
    polyurethane control arm bushings,Ireland subframe mounts,Dinan strut brace,competition
    HMS roll bar,custom 2 " widened M wheels with Kumho V700 tires,315/35/17's rear and 255/40/17's front, Hamann rear spoilers,BMW deck spoiler.

  12. #12
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    So change the wastegate spring!

  13. #13
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    In my experience ebc= boost creep.

  14. #14
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    You may need to replace a weakened WG spring or switch to a better EBC.


  15. #15
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    I've got the SPA manifold and wastegate, paired with a Profec B spec II, and I'm dead nuts on in all gears.

    Try lowering the gain value on the ebc and tell us what happens.

  16. #16
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    I doubt its the ebc,sounds like chaning the spring might work....

  17. #17
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    Running a 44 on a 35R with lowish boost may creep also.

  18. #18
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    Quote Originally Posted by bbaz View Post
    I've got the SPA manifold and wastegate, paired with a Profec B spec II, and I'm dead nuts on in all gears.

    Try lowering the gain value on the ebc and tell us what happens.
    I have tried going both ways on the gain but still have the spikes. Its really not boost creep because when my foot is planted on the floor the boost stays at the 11 psi setting. Its when I get out of the throttle and right back in it that I get the spike. If I don't flip out when the boost gauge spikes and keep my foot on the floor, the boost controller will quickly catch it and bring it back to 11psi. I get the spikes even when the controller is off so I'm starting to think it has to be the atmosphere wastegate dump! By the way, I'm running a 7 lb spring.
    1998 M Roadster,arctic silver,black leather,31,000 miles,6 spd conversion,VDO
    boost and oil pressure gauges in windshield pillar,Porsche Turbo "big" brakes with stainless
    lines,3.23 Quaife,aluminum flywheel with McLeod dual disc competition clutch,GT35R
    ball bearing turbo @ 12 lbs boost on 9.8 compression,TT 36 lb injectors and remapped
    ecu,Greddy Profec B boost controller and bov,368 hp and 355 lbs torque,custom 3"
    stainless downpipe and exhaust piping with no cats,Magnaflow exhaust,coil overs and
    camber plates,TC Kline springs,Koni adjustables,reinforced shock and tranny mounts,Kmac
    polyurethane control arm bushings,Ireland subframe mounts,Dinan strut brace,competition
    HMS roll bar,custom 2 " widened M wheels with Kumho V700 tires,315/35/17's rear and 255/40/17's front, Hamann rear spoilers,BMW deck spoiler.

  19. #19
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    Only other suggestion I've got is to lower the Boost Start setting. If it's too close to the Set Boost value, it will cause spikes.

  20. #20
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    Quote Originally Posted by 95RogueM3 View Post
    Tial 44mm and GT35R. I believe they are sourcing the signal from the same place, but I couldnt say for sure (I havent really dug into it yet).

    I would like to know which # spring is in the WG...Ill have to look into that too, I guess.
    I think that the spring in the wastegate was changed. I used that wastegate when the car was on a stock motor. I originally had a .4 bar spring in there! I could run 6 or 7 psi with no problem at all and no creep.

    So..the wastegate and plumbing will flow well enough not to have any creeping or overboost issues. You probably have a .8 bar spring in there or something, so just buy a different spring from TIAL and swap it out. That's one of the reasons I built it right on top with easy access.

    The creep issues are from the boost controller or the way the signal to the controller or wastegate is routed. Good Luck Rich!

  21. #21
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    Could a possibility also be that the wastegate is too small for the application? I'm experiencing boost creep where I'll hit peak boost (say 13 psi on my GT35r) and it will stay put for a second, and then when the RPMs start to increase past 5k, boost will continue to build. I never had this problem before, just started. And, this happens with my EBC off....I was curious if maybe I need to go to a 44mm wastegate (I have a 38mm tial right now).
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  22. #22
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    Quote Originally Posted by BMWManiac View Post
    Could a possibility also be that the wastegate is too small for the application? I'm experiencing boost creep where I'll hit peak boost (say 13 psi on my GT35r) and it will stay put for a second, and then when the RPMs start to increase past 5k, boost will continue to build. I never had this problem before, just started. And, this happens with my EBC off....I was curious if maybe I need to go to a 44mm wastegate (I have a 38mm tial right now).
    Actually...the car has a 46mm wastegate on it!

  23. #23
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    Quote Originally Posted by tonym View Post
    I have tried going both ways on the gain but still have the spikes. Its really not boost creep because when my foot is planted on the floor the boost stays at the 11 psi setting. Its when I get out of the throttle and right back in it that I get the spike. If I don't flip out when the boost gauge spikes and keep my foot on the floor, the boost controller will quickly catch it and bring it back to 11psi. I get the spikes even when the controller is off so I'm starting to think it has to be the atmosphere wastegate dump! By the way, I'm running a 7 lb spring.
    I get the same thing with my modified TT Stage 2 kit and a GT35R. It's annoying, but I know what to look for and avoid the situation.

    I think that it's more the fact that the EBC expects a certain speed of spooling and overboosts if that part is taken out of the equation.
    A word of Internet Forum wisdom: Disregard any advice that begins with "I've heard..."

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  24. #24
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    Its good to know I'm not the only one who experiences this problem! Do you dump your wastegate to atmosphere or plumb it back into the exhaust? My system is very much like yours in that it is very close to a TT Stage2 except I'm running a .098 headgasket or about a 9.75 compression ratio. It scares the poop out of me everytime it spikes even though I know if I keep my foot in it that the boost will normalize. I've never heard any detonation when it spikes even though NickG says I probably wouldn't anyway.

    Have you talked with Nick and has he given any suggestions?
    1998 M Roadster,arctic silver,black leather,31,000 miles,6 spd conversion,VDO
    boost and oil pressure gauges in windshield pillar,Porsche Turbo "big" brakes with stainless
    lines,3.23 Quaife,aluminum flywheel with McLeod dual disc competition clutch,GT35R
    ball bearing turbo @ 12 lbs boost on 9.8 compression,TT 36 lb injectors and remapped
    ecu,Greddy Profec B boost controller and bov,368 hp and 355 lbs torque,custom 3"
    stainless downpipe and exhaust piping with no cats,Magnaflow exhaust,coil overs and
    camber plates,TC Kline springs,Koni adjustables,reinforced shock and tranny mounts,Kmac
    polyurethane control arm bushings,Ireland subframe mounts,Dinan strut brace,competition
    HMS roll bar,custom 2 " widened M wheels with Kumho V700 tires,315/35/17's rear and 255/40/17's front, Hamann rear spoilers,BMW deck spoiler.

  25. #25
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    Quote Originally Posted by tonym View Post
    Its good to know I'm not the only one who experiences this problem! Do you dump your wastegate to atmosphere or plumb it back into the exhaust? My system is very much like yours in that it is very close to a TT Stage2 except I'm running a .098 headgasket or about a 9.75 compression ratio. It scares the poop out of me everytime it spikes even though I know if I keep my foot in it that the boost will normalize. I've never heard any detonation when it spikes even though NickG says I probably wouldn't anyway.

    Have you talked with Nick and has he given any suggestions?
    Well, I'm also running a 38mm wastegate, that probably has something to do with it as well.
    A word of Internet Forum wisdom: Disregard any advice that begins with "I've heard..."

    97 M3/4 - S54, TRM Coilovers, UUC SSK/Sways/LTW Flywheel




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