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A4 1.8T BOOST MOD

Discussion in 'Tuning' started by Mikey-S, Feb 20, 2007.

  1. Mikey-S
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    Mikey-S New Member

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    Hi, me and a couple of friends are going to the nurburgring towards the end of the summer and we're taking an A4 1.8t each to have a play around. These are going to be cheapies, say around £1200 for the car, then stripped out with coilovers etc. We're obviously after more power so I'm trying to up the boost (don't forget cheap), and with most cars this would be easy but the A4 calculates boost using air mass and rpm (no map sensor) so if I were to up the boost with something like a bleed valve the ecu would simply cut the fuelling and/or ignition and maybe even go into limp as soon as it detects an overboost. How can I kid the ecu into letting me use more boost? Thanks.
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  2. Beerzo
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    Beerzo Masa'warty 3200... Talk To Me!

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    [​IMG]Could try a manual boost controller and let the lamda sensors do the work but i would fit a boost gauge and AFR gauge as well to make sure you aint over boosting and running lean.

    Or you could just get them chipped. Are you driving them there and back?
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  3. Mikey-S
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    Mikey-S New Member

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    Hi. Yes we are planning to drive them there... not sure if they'll make it back though. We're not spending lots of money so chipping them is out of the question, we're planning diy mods more than anything. I'm a car technician working for Jag but have worked for VW / Audi in the past so I know my way around cars pretty well. I had a friend who fitted a manual boost controller but when the ecu sensed a boost of around 12 psi the car went into limp basically because it was unable to control the boost. When these cars are chipped it is then possible to use a manual boost controller because the ecu accepts the higher boost pressures. What I need to do is to kid the ecu into thinking it's only got around 7psi when in fact it's got 14psi.
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  4. macca
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    macca Member

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    i'm trying to think, but if the ecu knows it is overboosting with a bleed vavle it must be detecting it with a sensor, so you need to fool that sensor as well, maybe disconnect or more probably a resistor?

    without looking at my car i can't think what there is to detect boost. unless it can detect purely from the maf.

    hmmm, looking at the way you described it in your original post though, i think remap is only way?
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  5. Mikey-S
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    Mikey-S New Member

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    The B5 A4 1.8Ts don't have a map sensor, as I said it's just calculated by air mass and rpm so if I were to fit a manual boost controller and the boost is raised then the air mass is also raised causing the ecu to cut fuel or adjust the timing to avoid overboosting and possibly blowing the engine.
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  6. jcb
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    jcb Active Member

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    buy the car, strip them out as planned, sell the bits on Ebay and use the money on a £500 remap to get a nice 200+bhp upgrade.
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  7. billybravo
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    billybravo MODERATOR Moderator

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    i run a MBC on my 1.8T but my car is chipped as well i dont get limp mode but see around 1.5bar of boost
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  8. netwave
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    netwave New Member

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    Did anyone ever find out a cheap mod to fool the ECU on the A4 1.8T Sport?
    my car dies on slight over boost too!
    Added an adjustable fuel pressure regulator , so wont burn lean on higher boosts...
    cant do the zener mod either, no map sensor...cars too old on a 1999 plate, chippings expensive for such an old car.
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  9. jcb
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    jcb Active Member

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    the resistor mod the US guys on vortex use, fools the ECU into thinking it is at a lower boost, I belive as it is MAF based the MAf compensates for fuel which is why it doesn't just melt everything on lean charge
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  10. the rock
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    the rock New Member

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    how would you connect the MBC tho? before the N75 valve or after it on the way to the wastegate?
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