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Thread: boost response after gear change

  1. #1

    Default boost response after gear change

    just wondering, why is it the that my ms3 2nd gen doesnt stay on boost between shifts on anything above 2nd gear? it has to rebuild boost after each change. is this somthing that can be tuned out or fixed with mods because its pretty damn annoying coming from other turbo cars that had no issue holding 90% of boost between shifts making the car feel much more aggressive of gear changes.

    thanks in advance

  2. #2

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    Have you put in a VTA bov?

  3. #3

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    Quote Originally Posted by rayd View Post
    Have you put in a VTA bov?
    nah car is completly stock motor wise.

  4. Default

    From what I know it's completely normal, the only reason why I would think you lose complete air pressure is the stock bpv does a great job releasing all that air. Some aftermarket bpv/bov will release pressure slower which in turn means you hold more boost between shifts. I have a forge bpv but no boost gauge to tell you if its the same for this bpv, but it does feel the same between shifts

  5. #5
    Join Date
    Feb 2012
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    Wollongong
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    Default

    Eerrrmmm
    Last edited by ledfootrob; 12-05-2013 at 06:57 AM.

  6. Default

    Quote Originally Posted by ledfootrob View Post
    Must be something up, you will always lose some pressure but only minimal and if your stock the K04 spools super fast anyway. More info on your car might help.

    Sent from your mums phone
    Yup, if its wot runs you mean then just get a Cobb accessport and set flat foot shifting and be done! 100% boost between shifts.

  7. #7

    Default

    the cars has only 3k on the clock, i mean it just feels lazy between shifts even if i really put em through quick. i wasnt sure if it was somthing mazda had the computer do to help with drivline strain. even my old rb20 cefiro picked up boost in half the time my mps does

  8. #8

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    Quote Originally Posted by DarkSoul View Post
    Yup, if its wot runs you mean then just get a Cobb accessport and set flat foot shifting and be done! 100% boost between shifts.
    yeh cobb ap is definately on the books just trying to get my head around warranty and what mazda can/cant prove if anything ever goes wrong

  9. Default

    Quote Originally Posted by rgpmps3 View Post
    yeh cobb ap is definately on the books just trying to get my head around warranty and what mazda can/cant prove if anything ever goes wrong
    Just keep in mind if you have only done 3000ks on the car to give it some more time to settle, I would say to see how things go for the next 7000ks and if your still not happy then cobb it up!

    Spend the time on this forum to read what cobb ap has to offer and it is completely reversible - if mazda ever asks anything on services you can say you disconnected the battery due to going on holidays / battery died and you replaced it ect.

  10. #10

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    Quote Originally Posted by DarkSoul View Post
    Just keep in mind if you have only done 3000ks on the car to give it some more time to settle, I would say to see how things go for the next 7000ks and if your still not happy then cobb it up!

    Spend the time on this forum to read what cobb ap has to offer and it is completely reversible - if mazda ever asks anything on services you can say you disconnected the battery due to going on holidays / battery died and you replaced it ect.
    yeah i was told the ecu records how many times it has been accessed, so mazda can say that they have only plugged into the ecu x amount of times but it shoows up it has been accessed x amount times more, this is where im stuck. i was told this by a mzda service guy so it could be true but it could also be him trying to scare me from doing it.

  11. Default

    Best thing to do is ask the guys on this forum or mazdaspeed forum the guys from US. Not sure about that one

  12. #12
    Join Date
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  13. #13

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    Quote Originally Posted by SarcasticOne View Post
    yeah i have read all that just wasnt sure if this was somthing people didnt know about

  14. #14
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    Default

    Huh?!

    Its completely normal on a turbo MANUAL car.
    You lift off throttle to change gears and the BOV (Blow Off Valve) opens, releasing boost.
    You press throttle and turbo spools with exhaust gas and creates boost.

    If you have a Cobb Accessport you can enable FFS (Flat Foot Shifting) which goes towards eliminating this.

    On an AUTOMATIC because the throttle does not close you do not loose boost between gears.

  15. #15

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    Quote Originally Posted by Jmac View Post
    Huh?!

    Its completely normal on a turbo MANUAL car.
    You lift off throttle to change gears and the BOV (Blow Off Valve) opens, releasing boost.
    You press throttle and turbo spools with exhaust gas and creates boost.

    If you have a Cobb Accessport you can enable FFS (Flat Foot Shifting) which goes towards eliminating this.

    On an AUTOMATIC because the throttle does not close you do not loose boost between gears.

    Lets not forget about a few things people with turbo cars like to do to make there car sound "better" which cause a huge increase time between boot building up on throttle release and/or gear changes.
    which are:
    1. Completely closing the BPV flange off to make the car "dose"/"flutter"/"surge" which only slows down the spool momentum of the turbo and increases the time it takes to spool back up
    2. use a VTA BOV which causes a rich condition on lift off/gear change since the counted air is lost and the ECU compensates by injecting fuel which causes the engine to bog between shifts. (this also happens in case 1 which makes it twice as dumb...

  16. #16
    Join Date
    Jan 2013
    Location
    Sunshine Coast, Queensland
    Posts
    158

    Default

    Quote Originally Posted by Jmac View Post
    Huh?!

    Its completely normal on a turbo MANUAL car.
    You lift off throttle to change gears and the BOV (Blow Off Valve) opens, releasing boost.
    You press throttle and turbo spools with exhaust gas and creates boost.

    If you have a Cobb Accessport you can enable FFS (Flat Foot Shifting) which goes towards eliminating this.

    On an AUTOMATIC because the throttle does not close you do not loose boost between gears.
    +1
    I was thinking the same thing, Didn't want to say anything just in case I looked like an idiot :P
    My Baby 2005 Mazda6 MPS Dark Purple

    Mods|Corksport SRI+Airbox|Corksport TIP|CP-e REM|JBR EngineMounts 80A|20% Tint|Autometer Cobalt Series Gauges (Boost & Water Temp & Oil Pressure)


    Ordered|Corksport TMIC|Cobb AP|


  17. #17

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    Quote Originally Posted by Zebbstar View Post
    +1
    I was thinking the same thing, Didn't want to say anything just in case I looked like an idiot :P
    i relise it is normal to have some spool time between gear shifts and you dont need to let me know how a turbo car with a blow off valve works. i have driven many different breeds of turbocharged cars including my own and i find the lag between shifts excessive in comparison.

  18. #18

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    Quote Originally Posted by rgpmps3 View Post
    i relise it is normal to have some spool time between gear shifts and you dont need to let me know how a turbo car with a blow off valve works. i have driven many different breeds of turbocharged cars including my own and i find the lag between shifts excessive in comparison.
    My Mate has a Stock MPs takes longer to build boost than mine, when I got DP and TIP this realy helped spool times.get yourself a Dashhawk so u can look at boost in real time, and don't forget the mps is boost restricted in the first couple of gears.

  19. #19

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    Quote Originally Posted by chef View Post
    My Mate has a Stock MPs takes longer to build boost than mine, when I got DP and TIP this realy helped spool times.get yourself a Dashhawk so u can look at boost in real time, and don't forget the mps is boost restricted in the first couple of gears.
    thanks for the info, this is the information i was looking for, yeh i know they have the stupid restrictions in the first few gears, first gear i reckon my mum diesel merc pulls harder lol! might look into dump pipe to try and help this issue

  20. #20

    Default

    Since owning the car I have never experienced what you would call LAG between gears... It is alot less then my WRX (TD06 20G + FMIC).

    The COBB AP runs more aggressive tune (timing, boost, wastegate duty, etc) thus making the car spool faster (minor difference).
    The only way to eliminate the issue is to enable Flat Foot Shifting. Honestly though the time saved on a track is minimal, only bigger turbo's need FFS.

    On the few track days I have done I can manage to swap cogs before I lose all positive manifold pressure pretty much kick the clutch, next gear...
    SG9 XT: VF34 P20, Tomei headers, STI intercooler HSD coilovers, Brembos and much more...

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