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Discussion Starter · #1 ·
So I installed a MBC on my passat 2003 b5.5 5spd..

I got a CEL light today and I'm alittle worried..what happend?

I'm spiking about 20 holding 15-16 psi vacuume is at 22 inHg....I still have the n75 electrically connected and one nipple going to the intake.

Another wierd thing is sometimes when I'm in 5th after awhile it hits soft limp and only boosts as 3psi but 2min later it just goes away and drives normal...sometimes


Is my turbo going to take a sh!t?? I mean it would be a better excuse to go bigger but still....;)

Thanks alot
 

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My post disappeared. 20psi is alittle too much for the stock ko3. The fact that you hit limp mode is not good either, you running a stock n75 and are you chipped.
 

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Discussion Starter · #8 ·
Well the CEL went away and its not hitting limp mode...

I don't have access to vag come.

Its running alittle odd it feels like it looses power as its spiking. For some reason I still think the wastegate is staying open.

My friend has been running 20psi on his chipped gti for over 25000mi with no problems, is 20 too much?
 

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fibbing is lying. how old are you? :D:D:D

you're running like crap because you're WAAAAAAY lean. you can't just crank up the boost and not add more fuel unless you like holes in your pistons.
 

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you're running like crap because you're WAAAAAAY lean. you can't just crank up the boost and not add more fuel unless you like holes in your pistons.
x2 you have to be careful with a mbc. more boost needs more fuel. a chip does this, increases boost and remaps the ecu. the stock ecu can only handle about 11-12 psi of boost. vag-com logs will tell you what your fuel trims look like. until you get access to vag-com to properly tune the mbc, TURN DOWN YOUR BOOST.
 

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Well the CEL went away and its not hitting limp mode...

I don't have access to vag come.

Its running alittle odd it feels like it looses power as its spiking. For some reason I still think the wastegate is staying open.

My friend has been running 20psi on his chipped gti for over 25000mi with no problems, is 20 too much?
If the diverter valve is being overloaded with pressure, it will open and vent that pressure before it ever gets to the engine. I'm guessing that's what's happening here.

You REALLY should be using a VAG-COM if you're going to manually tune your car. You have no idea what's going inside your engine if you're relying on the idiot lamps on the dashboard. Saying you don't have access to one is like saying you don't have access to a Bentley service manual -- there are 11ty billion places online that sell them, if you can afford tuner parts then you can afford one, and if you have any idea the kind (and cost) of damage you can do without proper information then you sure as hell can afford one.
 

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ill turn the boost down.
You need to do more than turn the boost down. To tune properly with an MBC, you pretty much need a VAG-COM, period. Without one, you will have an awful hard time getting the performance your car is capable of, while not damaging the engine.

SirWired
 

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You using the correct spring? With my MBC, I was given two different springs to use. SOunds like you need to switch to the stronger spring
 

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So I installed a MBC on my passat 2003 b5.5 5spd..

I got a CEL light today and I'm alittle worried..what happend?

I'm spiking about 20 holding 15-16 psi vacuume is at 22 inHg....I still have the n75 electrically connected and one nipple going to the intake.

Another wierd thing is sometimes when I'm in 5th after awhile it hits soft limp and only boosts as 3psi but 2min later it just goes away and drives normal...sometimes


Is my turbo going to take a sh!t?? I mean it would be a better excuse to go bigger but still....;)

Thanks alot
I think you should do a little more research before you start adding boost to a DBW Passat. MBCs can only be added to AEB motors (98-99) because our motors dont have boost limitations set into the ECU, yours does.

The CEL is from running lean...you're running super lean, the stock ECU has enough fueling for around 11-12 PSI, you've obviously over shot that limitation. Also, The ECU hits soft limp when actual boost is like 500mbar over spec boost.

Just get chipped and be done with it, don't mess with an MBC.
 

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[Marvin Martian]

Where's the KA-BOOM?!?

There's supposed to be a giant, earth-shattering KA-BOOM!
[/Marvin Martian]
 

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I think you should do a little more research before you start adding boost to a DBW Passat. MBCs can only be added to AEB motors (98-99) because our motors dont have boost limitations set into the ECU, yours does.

The CEL is from running lean...you're running super lean, the stock ECU has enough fueling for around 11-12 PSI, you've obviously over shot that limitation. Also, The ECU hits soft limp when actual boost is like 500mbar over spec boost.

Just get chipped and be done with it, don't mess with an MBC.
I have my MBC set to hold about 13-15 PSI with no problems to report after about 10K miles.
There is one side affect though: unless you are WOT or atleast 3/4 open, the ECU will cut the throttle plate once the difference between the requested and actual boost becomes too great.

I have done several runs with the VAG-COM connected and fuel starvation is not an issue. The requested vs actual boost is. Under WOT, the ECU will disregard it though it seems.
 

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Discussion Starter · #19 ·
i am chipped.

i was holding 15psi before, and turned it down to hold 15-16...

am i still looking at problems?
 
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