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Thread: Stock boost per revs - MPS Gen 2

  1. Default Stock boost per revs - MPS Gen 2

    Some interesting reads on stock boost. i have read through them but i have a specific question.

    we had a gen 2 on the dyno and when you load in 4th - boost shoots to 19psi and by the time you get to 6000rpm, it has dropped all the way down to about 11psi.

    I gather something is wrong with this car cause by reading your previous threads, the car should hold 15psi without any hassles, especially in 4th gear.

    my question is - when you load the car from say 1500rpm all the way through to red line.......what should the psi spike to? what should the mid-range boost be? and what psi should it hold/drop off to on top.

    I am referring to a stock MPS 3.

  2. #2
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    I was going to ask if MPS is stock until I read last line.

    I don't remember having any spikes on a stock tune (then again I only got a boost gauge after a few other mods) I spike now, the highest I've seen is 22psi which I believe is related to the tune I run/ran at the time.

    In 4th gear the MPS3 should be getting full boost (as they are limited in lower gears), should hold 15psi to about 5,500RPM. After 5,500RPM the MPS loses power considerably. Unless you modify, 5,500RPM will be peak power output

    I wouldn't load the car as early as 1,500RPM personally. I'd take it to AT LEAST 2-2.5K before giving it full beans. I think Maximum torque is 3,000RPM if I remember

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  3. #3
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    Is it a series 2 gen 2? maybe they are running a different tune?
    did you buy it new? maybe it already has a flash?

  4. Default

    note : this happened on the very first run - so the car was stock std when this took place - so there was no flash or previous tune.

    it made 189kw stock (opposed to 191kw) - but what bugs me is how erratic the boost gauge was during the run spiking to 19psi and dropping off all the way to 11psi after 5500rpm.

    but i have my answer i guess - and that is that it should hold boost and not drop below 15psi all the way through.

    the fact that it was spiking that much, tells me something is wrong with this vehicle. could be the actuator or possibly a boost leak on the cold side.

  5. #5
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    Can't comment too much cause I never checked boost gauge prior to doing mods. If it's at least holding 14/15psi up to 5,500RPM then it's probably fine.

    Over 5,500RPM is over revving for a stock MPS so I wouldn't worry about it.

    The spike doesn't necessarily mean something is "wrong", could be a tune fault. Has your friend got access to a hypertech or Cobb AP to flash it with and see if there is a difference.

    Logging some data on a cobb might be a good idea to see what's happening.

    I used to spike at 22psi and hold at 16psi with the hypertech tune.

    The below is a spike of 21. don't have a picture of 22psi


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  6. Default

    i might be misunderstanding you when you say "The spike doesn't necessarily mean something is "wrong", could be a tune fault".

    The car was not tuned when this happened - it was 'stock std'. so this happened, and has been happening before the car was tuned in any way.

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    The stock tune isn't great. I get hesitation all the time, which I think might be a tune fault. In saying that the spike is strange for a stock tune.

    Dropping off the power after 5,500RPM sounds normal to me and typical of stock MPS's

    Usually a spike would be result of a flash tune or something, I don't see why it should happen on a stock car with stock tune.

    Some log data and seeing what's happening at RPM increments might be worthwhile.

  8. Default

    ok now i get you.

    Yes my thinking for the boost leak is that the stock ECU sees this and compromises the boost to reach target, probably overboosts and rectifies it as the revs climb, and before you know it, its at 5500 where the boost drops below 15psi, and due to the boost leak - keeps dropping, to 11psi.

    the same could be said about a faulty actuator or wastegate.

    have you guys played around with a bigger turbo exhaust housing yet?

    Rog - i cannot find your thread for your turbo upgrade - which turbo will you be fitting? are you running software, stand alone management or piggyback ?

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    With the cobb AP you can run logs and see what's going on. There are limitations but on a stock MPS I think they're going to be an ECU controlled situation where it's not asking for more power.

    There are other limitations, for example if you're running a bigger turbo you can experience fuel cut at high RPM. A high pressure fuel pump is required. Engine knock can also be a common occurrence on the MPS

    Actuator and wastegate sound fine to me as it all seems to work ok under 5,500RPM. If your mate wants to rev over 5,500 and make power he's going to need to modify a few things, TUNE being one of them.

    You won't find a thread for the turbo upgrade cause I haven't done it yet. Should be going ahead in a few weeks. The yellow RR on my sig takes you to my ride thread where MOST of my mods are detailed (which I need to update)

    Other guys have done turbo upgrades and there should be a few threads knocking around. I'll be running the ATP GTX28R turbo and 3" HTP turbo inlet pipe.

    Yep, I'll be tuning with the Cobb Access port which is probably one of the best bang for buck tuning options for the MPS I think

    With great power comes great fuel consumption...
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  10. Default

    Quote Originally Posted by Macaveli View Post
    note : this happened on the very first run - so the car was stock std when this took place - so there was no flash or previous tune.

    it made 189kw stock (opposed to 191kw) - but what bugs me is how erratic the boost gauge was during the run spiking to 19psi and dropping off all the way to 11psi after 5500rpm.

    but i have my answer i guess - and that is that it should hold boost and not drop below 15psi all the way through.


    the fact that it was spiking that much, tells me something is wrong with this vehicle. could be the actuator or possibly a boost leak on the cold side.
    Is it 189kw at the wheels, because that would not be stock. They are suppose to be 190 at the flywheel from factory.

  11. #11
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    The stock tune is load based so boost will fluctuate as its only using what it needs to meet its load targets.

    Sent from my GT-I9300 using Tapatalk 2

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    As above. No way it was that stock.
    Somewhere between 150 and 170.

    Sent from my Nexus 4 using Tapatalk 2

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    Btw.. How do you know the psi? Did you install a boost gauge?
    Maybe that is where the leak is..

    Sent from my Nexus 4 using Tapatalk 2

  14. Default

    @Jmac, yes a boost gauge was installed. will have to see where the leak is, if there is one. it made 189kw (on the flywheel) - not on the wheels, so it was stock, but again, the boost is load-based like @leadfootrob mentioned so you cannot say that nothing is wrong. the only thing that points to something being wrong is that the car was erratic in its boost. what stock MPS boosts 19psi ? its a bit mind-boggling but we fill find out whats going on....thanks for the info and help.

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    stock boost is around 15/16psi

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  17. #17
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    at 3000rpm, on stock map, the car is requesting load of 1.69, whilst it does target ~15.5psi, the car will add boost (ie WGDC) in order to meet it's load targets... im assuming that's slightly what happened...
    with the car being loaded up from 1.5k rpm, it probably hit it's boost target of 14.5 @ 2750 (1.68 load again) and then had too much air flowing through it to effectively reduce the boost enough... thus causing the boost spike
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  18. Default

    thanks for the info and help guys. appreciated!

  19. #19
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    No problemo

    Sent from my Nexus 4 using Tapatalk 2

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