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Thread: Boost Cut

  1. #1

    Default Boost Cut

    N00B ALERT.. ha

    is boost cut the stock limit of 5500rpm where it just dies ?? or something else ??

    also is the ATP boost cut defender for eliminating this ?

    annnd.. i notice they all say install at your own risk with purchase ?? is there high risk involved with KABOOMING your engine with to much boost once u install this ??

  2. #2
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    Default

    we were all noobs once.

    5500 is boost cut - we all have it (or did have it)

    Boost cut defender will fix it, but there are other systems which are better in the long run, tunes such as standback, piasini etc etc will allow you to dial in the boost you want. Things like intakes and even exhausts can extend boost - more through the fact that the turbo is alreadu spinning and "carries on a bit more"

    Fit at your own risk is a standard disclaimer. Make friends with your local dealer and guage their opinion on things - lol - my service manager has changed my pod filter for me on my CAI...

    Boost levels upto 19PSI (some would say 21PSI) are safe - I have been running 17 for the past 12 months, now going to 19.

    MPSGarage run theirs at 21PSI, but they have upgraaded a heap of stuff on their cars.

    Jim
    Faster than swallowtails Passat...and it has a letterbox

  3. #3

    Default

    yea i knew a full tune would get rid of it all together as well as open doors to a lot more options.. just was reading into BCD on US forums and there wasnt alot of info on it... i think mainly because everyone gets a tune done eventually...

    BUT.. us with little coin to splash around haha... thought this may be an option to keep the mod bug happy and also give me a little more go ??

    has anyone found a how to install guide or done this on here??

    oh and if one was to install the Boost Cut Defender... would this then raise issues with fuel cut ?
    Last edited by PaulG; 17-02-2009 at 08:38 AM.

    BLACK 06 MPS3 - HKS SRi/K&N - SU REM - TWM STS & Bushings - Custom MP

  4. #4

    Default

    I could be totally wrong, but here's how I understand things:
    Boost cut is when the MAP reading exceeds 4.9~5v whereas fuel cut is when certain currently unknown engine criterias are met. Fuel cut seems to happen more often at lower temperatures. If you're getting boost cut, you can try a MAP clamp.

    The engine falling flat on it's face after 5500rpm is nothing to do with boost cut, but turbine efficiency, throttle plate closing and boost mapping. Things to improve post 5500rpm performance include tuning, improved IC, aftermarket dump pipe and test pipe etc.
    Nuliaj: Hatches are only really half a car anyway.
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  5. #5
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    Default

    The stock MAP on the MPS is a 2.5 bar unit, so it will take 36 psi to reach its 5v threshold.
    Boost cut is when the ECU sees 18 psi, for more than 2 seconds (why 2 seconds ?,to avoid cutting on boost spikes), I would strongly advise against a boost cut killer this completely removes the boost cut, so if your waste gate were to fail and you suddenly boosted to 30 psi nothing would intervene to stop this (except maybe a rod escaping the block, and fragments of piston and valves ratting around in your sump).
    A MAP clamp can, and has been used successfully, however you should have some tuning to support any boost increases.
    I also wouldnt run more than 18psi on the stock TMIC, see my post in the intake section about intercooler pressure drop etc.
    5500rpm is NOT boost cut, it feels flat because the little spinning wheel is at the top of its efficiency ceiling, unable to push much more air, the throttle plate closure is there to help protect the turbo, yes breathing mods help reduce the load on the compressor wheel at these revs.

    Fuel cut on the other hand seems to occur at random times, for random reasons, with no definite parameters to pin point the cause, from what I have read, fuel cut wont necessarily save your engine from exploding either, CPE have recently added a fuel cut eliminator flash to their ensemble.

  6. #6

    Default

    I'm sure I read in the US forums of guys who are maxing out at 5v and are runnning nowhere near 36psi, are you sure that's correct?

  7. #7
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    Default

    Yeah, the US guys are maxing out their MAF sensors, and have experimented with larger housings to compensate, however I believe this makes the car a pig to drive down low.

  8. #8

    Default

    You're right I'm confusing MAF reading with MAP reading. Some of the guys maxing the MAF at 5v are looking at 4" intake/inlets including bigger MAF housing.

    I still don't think the fuel cut issue is random, though I do think we have no idea what the different parameters causing it are. IMO I think CP-e should've first worked out what causes the fuel cut and then tweaked the settings rather than disable fuel cuts altogether.

  9. #9

    Default

    cool that what i wanted to hear ... haha... thanks

    oh well... dream on i will... thought i could wiggle 100 bucks away without the girlfriend knowing.. haha full tune is just out of the question for a LOOOOONG TIME ...

  10. #10

    Default

    Quote Originally Posted by jimred07 View Post
    we were all noobs once.

    5500 is boost cut - we all have it (or did have it)

    Boost cut defender will fix it, but there are other systems which are better in the long run, tunes such as standback, piasini etc etc will allow you to dial in the boost you want. Things like intakes and even exhausts can extend boost - more through the fact that the turbo is alreadu spinning and "carries on a bit more"

    Fit at your own risk is a standard disclaimer. Make friends with your local dealer and guage their opinion on things - lol - my service manager has changed my pod filter for me on my CAI...

    Boost levels upto 19PSI (some would say 21PSI) are safe - I have been running 17 for the past 12 months, now going to 19.

    MPSGarage run theirs at 21PSI, but they have upgraaded a heap of stuff on their cars.

    Jim
    Is there any evidence out there to state our turbos can run up to 21psi? I'm getting my car re-tuned very soon and would like to run 21psi if i know it can be done.

    My car is currently on 19psi, only reason why i'm re-tuning is because i need to finish my other map. Since then i've added my Upgraded fuel pump and colder spark plugs. So it wouldn't hurt to tune my current map also.

  11. #11
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    Default

    No reason you cant, the turbo is just starting to run out of its efficiency window the higher you go, maybe see what your tuner thinks. There is a theory that after 22psi (@ turbo) there is a world of hot air rushing out of there.
    Are you running an aftermarket intercooler, a reduced pressure drop from the turbo to the manifold will allow a bit more boost ?

  12. #12

    Default

    Quote Originally Posted by MattMPS3 View Post
    No reason you cant, the turbo is just starting to run out of its efficiency window the higher you go, maybe see what your tuner thinks. There is a theory that after 22psi (@ turbo) there is a world of hot air rushing out of there.
    Are you running an aftermarket intercooler, a reduced pressure drop from the turbo to the manifold will allow a bit more boost ?
    Yeah mattmps3, my car's front mounted. I also don't plan to always run on 21psi due to petrol. My other map i'd like to just be running 17psi maybe 18psi.

    Basically i will be changing turbo's on the car in the future, probably stick to the KO4 still but a high flowed one. Just don't want the turbo to go pop during this year though, it'll be a pain if that happened.

    Looks like i'll speak to my tuner, and ask them about running 21psi

  13. #13

    Default

    If you're planning long term and a big turbo isn't in the plans, running higher boost will reduce the longevity of our turbo, especially as it really isn't designed to run high boost. A reworked K04 would allow you to flow more without having to boost as high as well as letting you keep the low rpm responsiveness of the K04.

    Edit: Bah our damn proxy went down and your response went up before mine.

  14. #14
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    Default

    In all honesty I really don't think you'll find that much benefit from an extra 2 psi, as I'm sure you are aware the secret with these engines is the timing adjustments for power increases. Hence the reason meth kits are so popular in the US.

  15. #15

    Default

    While debatable, the vendor dynos show a 10-20hp gain just by swapping to a reworked K04. Push another 2psi would net another 20-30hp which doesn't include tuning.

    I don't know too much about the gains with WMI, what are the typical gains these days Matt?

  16. #16
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    Ahhh, yes but the rework flows 35% more CFM, its more about the volume, not the pressure with these units, different kettle of fish all together there.

    WMI, on a car not specifically tuned for it will do very little power wise, but is a great insurance policy as the water meth increases the octane of the fuel by ~8 points, so 98 octane + 50/50 water meth will yield a theoretical 106 octane, the other benefit is the cooling of the intake charge, its essentially chemical intercooling, so the benfits of a denser / cooler intake charge still apply, i.e the car will adjust its timing to benefit, e.g car will run like it does mid winter, in the middle of summer. Typical results are BAT's lower than IAT's....sometimes even lower than ambient.

    If you are tuning for it you can pull a lot more timing due to the benefits of the higher knock resistance (octane) and make some bulk power, although you woud want a pretty hardcore setup for this as a clogged nozzle could lead to BOOM!

  17. #17
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    ....kinda technical....I was with you upto and including MAP clamp....

  18. #18
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    Default

    Good information, Stickied

  19. #19

    Default

    I thought boost cut and fuel cut was when you're on boost, then it cuts out and kicks back in as though you let off the throttle and got back on it when indeed you have not taken your foot off the throttle ?

    Have seen rods through the block due to this... I am going on a hunch but I think one of the causes may be a faulty crank angle sensor? Correct me if I'm wrong

  20. #20

    Default

    Quote Originally Posted by sinsin View Post
    I thought boost cut and fuel cut was when you're on boost, then it cuts out and kicks back in as though you let off the throttle and got back on it when indeed you have not taken your foot off the throttle ?

    Have seen rods through the block due to this... I am going on a hunch but I think one of the causes may be a faulty crank angle sensor? Correct me if I'm wrong
    You just described EXACTLY what happens randomly to me.
    I don't think it's "boost" cut because it's always coming onto boost that it happens (ie started to spool). Also not sure about fuel cut either, as I just upgraded my hpfp so there's plenty of pressure there, i've monitored it and it's good.

    I've heard this kind of thing referred to as "Hesitation" but as to what causes it, I have no idea. Sometimes it's worse than others, but it certainly gives me the feeling of "This really shouldn't be happening".

    I believe however that this is eliminated when a different map than stock is flashed. Further up in this thread it mentioned "CPE have recently added a fuel cut eliminator flash to their ensemble" but I doubt this is what's happening in the Cobb OTS maps if this in deed is the source of the issue?

    Who else gets this kick back that @sinsin described?
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