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MBC WITH N75 vs MBC vs N75

Discussion in 'A3/S3 Forum (8L Chassis)' started by AGU-TURBO, May 27, 2011.

  1. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    As above im putting a apexi avc-r on my 1.8t agu
    (basicaly like a manual boost controller but electronic)

    my question is shall i run this in line with my n75 valve or just ebc.
    My other worry is fueling so will it be ok and the ecu will adjust it accordingly or shall i get a adjustable fuel regulator or will a 4br fpr be perfect for the job.
    if im right in thinking as i have no map sensor it won't go into limp mode and run either set up fine but just want to no how it will handle boost either way?
    When ive got it sorted ill get it chucked on jbs roller's and make sure my AFR is ok as i
    m **** with that vag-com lol
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  2. s3dave
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    s3dave TFSI Hybrid

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    I think people have had better results running them together..
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  3. Welly
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    Welly VX220 SC Driver :)

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    OK, not being funny, but my first question is why are you fitting manual boost control?
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  4. Speedy Steve
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    Speedy Steve Active Member

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    Im just running MBC only but Welly got good results using both i wouldnt waste money on a manual boost controller
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  5. JamJay
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    JamJay Member

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    MBC is good for controlling boost spikes. Members on SCN report better performance (much more progressive, boost held for longer) running MBC with N75 rather than N75 alone however I feel that using an MBC for this purpose is only to control an underlying problem where you should find the cause of the spike first *cough* map most likely. I am spiking, I have considered MBC but I will rule out the map first and get it tweaked to accomodate new mods.
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  6. s3dave
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    s3dave TFSI Hybrid

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    Agreed ^^^
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  7. Prawn
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    Prawn My other car is a MINI!!!!

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    why are you fitting the AVCR mate? If you're still on a KKK turbo then there is absolutely no need, or advantage to fitting one.

    I tried an electronic boost controller on my AGU a few years ago, and it was useless.

    Whilst the boost control was consistent and perfect, the car didn't like having no control over boost at all, and as a result, I suffered from terrible timing pull.

    Also, it was almost impossible to setup properly, as it only controls max boost, so no matter how you set the gain, you either get horrific spikes and surging, or a really laggy turbo if the gain is too low.

    generally it turned out to be a totally pointless exercise, and i certainly won't be bothering again.

    part throttle is also horrid without the N75, as it just tries to spool its tits off all the time at part throttle.

    not nice at all.

    Avoid. Your far better off spending money on a decent map than trying to fix things with parts you don't need
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  8. Welly
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    Welly VX220 SC Driver :)

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    My concern here, from reading previous threads, is that the OP is trying to use MBC control to simply up the boost.

    Well, that's not really the way forward. Just wants to see the lay of the land before suggesting things. If it's down on boost, there will be a reason, especially on the AGU (Most likely the MAF).

    Slapping more boost in will only make issues worse.
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  9. Welly
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    Welly VX220 SC Driver :)

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    Well said that man.
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  10. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    Thanks lads, what i was hoping to do was - with a avcr you can set hi & low boost. my plan was to have it set to just over 1 bar max and 0.6 -0.7 low boost. i have a brand new apexi avcr that i bought for my RS so i thought there would be no problem in using it. No i wouldn't ever fit a mbc to cure another problem.
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  11. Prawn
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    Prawn My other car is a MINI!!!!

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    I see your plan, although, unfortunately I just don't think it'll work well at all!

    I was running 22psi on my N75 before fitting the EBC, I had similar ideas to you, as mine had 6 variable boost settings as well as an overboost.

    even at 20psi the car ran really flat with the EBC, you could just feel that it'd pulled the timming out, as despite teh boost it just didn't go anywhere near as well.

    if you want switchable high/low boost, tap a switch into your N75 line and wire it into the glove box. With the N75 switched on you'll have full boost, then with it switched off you'll have about 0.5 bar.
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  12. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    Yeh good idea, i still carn't get my head around this lol, a N75 is just a valve that limits or gives it preasure when the ecu feels fit to do so, but leaving it plugged in the ecu will still think its controlling it there for not throwing any error codes, by fitting MBC-EBC it is doing the exactly same job as the n75 apart from you are getting every thing all at once unlike a n75 were it limits you untill it feels fit, but if you run them in conjuction with one another then you should have best of both worlds.

    Please tell me if this sounds right or tell me what im missing
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  13. Prawn
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    Prawn My other car is a MINI!!!!

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    but is isn't doing the same thing is it?

    the N75 brings boost in HOW the ecu wants it. an EBC doesn't control part throttle at all, as it doesn't know if you're part throttle or full. it simply controls the max boost the turbo can produce.

    the ECU might only ask for 3-4 psi on cruise, and will pulse the (disconnected) N75 accordingly, but the turbo will spool its nuts off and the MAF will see huge airflow that's not in accordance with that the n75 is pulsing at. so it gets confused

    If you run them in series then whether the EBC is plumbed in before or after the N75 makes no difference.

    if it's before, the N75 won't see any of the boost until it's already at peak level, so that'll make no difference.

    if it's after, the N75 will be letting small amounts past on part throttle, but the ebc won't let this air through to the actuator until it's reached peak.

    You can run an MBC in parallel with the N75 like Welly has done to cap spikes caused by the N75
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  14. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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  15. JamJay
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    JamJay Member

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    If you fit and MBC in conjunction with the N75 and set it to say 1.5bar, the MBC will bleed off boost pressure over that value even when the N75/ECU is telling the turbo to produce more. I would imagine that an EBC would work the same in this scenario. How come you want two settings for boost? As far as I am aware it's not just as simple as turning the boost up and down, well not in today's age with all the electronics & sensors, not since old RST's & R5's. You might be better thinking about REVO with SPS which gives you three settings, so you could have low boost, mid & high. With this SPS switch it would also adjust fuelling, timing etc along with boost so that the car runs happily.
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  16. Prawn
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    Prawn My other car is a MINI!!!!

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    yea I solved it mate, it was the MAF!

    JamJay: Revo's SPS adjustment doesn't work on an AGU, so that's out.

    Get a new MAF, wire a switch into the N75 line and have switchable boost that way.
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  17. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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    Thanks for all you'r comments, Ive just been to tps and orderd a new maf and as a mate of min works down there got some extra nocked off so i ordered a n75 j valve to experiment with and if i don't like it ill take it back and try the h valve. will let you my findings lol.

    N75 J AUDI S2: 934 906 283 J

    N75 H AUDI ? : 034 906 283 H
    Last edited: May 27, 2011
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  18. AGU-TURBO
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    AGU-TURBO Audi a3 1.8t AGU

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