First I need to credit this concept from the forum post:

http://www.audizine.com/forum/showth...hlight=mbc+n75

I saw the MBC offered from JHM to adjust boost from inside the car and placed my order. I have a completely stock 2001.5 S4 with a GIAC X ECM. You may say its crazy to install an MBC with K03s because of the following reasons:

- Need a TCD (Throttle cut defender) so the rapid boost build will cause the ECM to cut the throttle
- You will quickly kill K03s
- You need a certain tune to work well with MBC
- etc..

Well I agree. I don't want to kill my sweet little snails. I found the post above and thought this was a great way to actually protect my turbos (plumbing N75 and MBC in parallel), Switching to stock for emissions testing, and going all out with MBC stand alone when I go Stage 3 or go to the track with my Giac X tune (hopefully it wont cut my throttle). The one difference (and purpose of this post) is to replace the manual valves with solenoids to switch back and forth inside the cab.

The pictures below show my pair of solenoids mounted to my sweet custom bracket (thanks lowes). The solenoids are Normally open so there is no way to screw up my turbos if a solenoid fails. I then will wire these to a on/off/on rocker switch in the cab (to accessory power). I plan to do the install this weekend so will let you know how it goes. The hardest part was sourcing the solenoids for cheap. Here is a total of the project:

- (2) STC Air Solenoids (PN 2V035-1/8) - $25
- (1) single pole double throw on/off/on rocker switch - $3
- Brass air fittings (2 plugs, 2 1/8" NPT barbs, and 2 10-32 UNF barbs - $10
- metal angle steel - $4
- Hardware to mount bracket - $3
- JHM in cab MBC - $165
-------------------------------
Total = $210

All in all not too bad. The worst part is that you have to order packages of 10 for some of the brass fittings from McMasterCarr. I just couldn't quickly find any cheaper. My only concern is drilling in to the battery when I mount it and adding too much volume to the boost lines causing a delay in Waste gate response. Let me know if you have any questions or ideas.

Solenoids and bracket:


Bottom:


Stolen concept:

soo both the valves can never be closed? Wouldnt you only need one between the t fitting and the n75, so when its open they are in paralell, and when its closed pressure is only going to the MBC? Or in that case would the second solenoid go between the top t-fitting and N75 to prevent pressure from going back to the n75 the wrong way?

I understand the concept, but dont understand your placement of them in the picture. Unless the switch makes one open and the other close than they can never both be closed. And if theyre both open its paralell. If one is open and the other closed than the MBC will no longer be in paralell, just as an optional stand alone. Also in that case im pretty sure you need a valve to prevent pressure going back into the n75. Because in standalone the boost and wgp should be connected with a loop of hose

It dosnt sound like this is well thought out, or it was explained poorly, or im retarded

Ok. I like options so I put a valve before both Boost controllers. Here are ALL the options:

1) Parallel using N75 and MBC - leave both valves open
2) Use only N75 - close MBC valve
3) Use only MBC - close N75 valve
4) Use none - (Does not make sense)

If I only had one valve I could not switch back to stock (#2). One could argue to just wind the MBC up to something like 25 psi which it would never reach but then I would loose the MBC setting...

Your suggestion about putting another valve behind the N75 to prevent boost from back flowing is a good one (#3). I have considered that and hope I do not. I figured when running #3 the boost would flow through the N75 back to the the closed solenoid valve and I would be ok. The thing I may not have considered is the other end of the N75 (the one that goes to the PVC plumbing). When does that open?

I am thinking I could install this thing and try running #3 and if the boost continues to build the boost is leaking through the N75. What do you think?

I appreciate anyones input! Especially before I install it on Saturday.

So you have 2 switches, one to controll each solenoid? Thats a pretty cool idea it seems like it should work good. The more i think about it im not so sure #3 would be needed. If something does happen you have the option to correct it at the flip of a switch too

#3 would not be needed now with my K03s. After I go stage 3 it will be handy . Thanks for the input.