Problem fixed.

 

I hope this is not the way things are, I was planning on the vast fueling kit with a MBC very soon. Interested to see if anyone else is having the problem.

 

I was told by a certain local tuner shop that what I am feeling is the car getting "throttley". They said this is because my wastegeate is staying closed at idle. Does this make any sense because after that they told me this was the nature of MBCs on S4s (some work, some don't) and that they had software that could make my car as quick as a STG 3 with a MBC.. hmmm...

 

Could be a vacuum leak. Check all your connections. Also could be a boost leak...good luck finding it.

 

Whiplash- I had my regular mechanic use his "smoke machine" to smoke out the vaccum lines when I first noticed the problem.. he didn't find anything. Correct me if I'm wrong, but my best guess is it has something to do with the way I installed the N75 and N249 with my MBC. I searched the forums first but I couldn't find a good picture or diagram that tells how to use the N75 and N249 with a MBC. My primary concern is the one-way check valve(?) I removed by the fuel pressure regulator.. it went to a long, stiff black sort of line that led to the driver's side turbo area..

 

I dont have an S4 so I cant really tell you how to hook it up...try finding someone in your area that has experience modding S4's and ask him/her to take a look.

 

Any ideas people?

 

E-mail vast, they answered my question in an hour a few weeks ago. And it was a general question (i wasn't looking to buy anything)

 

I e-mailed Kurt at Vast, but does anyone else have some ideas?

 

These are four photos of the n75, n249, and the one-way check valve by the n249 and fuel pressure regulator and a photo of the diagram I followed. Basically, the ambient and compressor side are attached to the n75, while the wastegate side vents. N75 is plugged in. There is a "T" AFTER the compressor side leaves the n75 and it goes to the compressor side of the MBC as well as the compressor housing. Now my N249 is a little trickier.. I have a "T" connecting the intake manifold pressure hose to the bypass valve hose as well as to the one-way check valve. Before the check valve (first nipple on valve unit) is connected to the top of my N249. The bottom two nipples from my N249 are capped off. The N249 is plugged in. After the actual check valve, the first nipple is plugged up and the straight nipple is connected to my the semi-hard, unflexible plastic hose that runs to the driver's side turbo area.

The diagram I followed:


My N75


My N249


The vac lines by the fuel pressure regulator



Please, any help would be greatly appreciated.