Switchable stock to MBC layout diagram

[zeusenergy]

Well, I am going to be trying this setup out soon. I have a Manual Boost Controller installed now, and it's inline with the N75. It's peaky but I can increase the boost as a test. Some of you may remember the boost guage install I did a while back. It was installed to keep track of an MBC. I was going to wait and just chip the car later, but I can't help myself.
I've got the "bug" now and can't leave it alone for a minute. Reading up on other's setups and what they have accomplished with the 1.8T has gotten me thinking. Now of course a manual boost controller (MBC) can only be turned up so much before you hit limp mode, unless you have a chip, or install a diode between ground and the violet/gray wire on the charge pressure sensor that lives on the stock intercooler. It cost me $2 for two 4.3V, 5 watt zener diodes. I got them from an electronics store in my area. I also picked up a 330 ohm, 10 watt resistor to get rid of the N249 DV control solenoid. The MBC is made from a threaded coupling, two barbed hose fittings with 1/4 inch hose barbs, a 1/4 inch ball bearing, and a utility spring that can be changed out or added to. In all, this stuff cost under $12. The MBC is not extremely adjustable but that's not my goal. I want a fixed 15-16 PSI boost pressure when all is said and done. I expect to peak on surge around 18-19 PSI. Right now without a diode the car makes 14.5 PSI on peak, and it falls down to 10-11 PSI instead of the stock 8-9 PSI. Power has increased a little and on initial peak pushing almost 15 PSI, low gears like to spin the tires if ASR is disabled! I surprised myself coming out of the parking lot after I installed the MBC. It pulled like a raped ape. I'm sure that some of you are thinking "so what, I'm running a garrett or K04 or whatever" and this thread really isn't for you per say. It's for the people who want to get some more power out of their stock setup and spend an insignificant amount of money to do it fairly SAFELY! keep in mind this is a work in progress, and I will be posting more pix and results as time goes on. I'd like to document the whole process so others can just connect the dots to DIY.
With a diode installed, the car no longer gets it's signal for dropping boost down if things get out of hand. Also, bypassing the N75 wastegate control can make your car feel like an on-off switch with partial throttle. I wanted to be able to take advantage of the extra power I know the 1.8T and it's K03 can provide, but at the same time have stock driveability and failsafes when I don't need the extra power.

There is a way to make the setup perform like this using a simple 3-way solenoid valve from a variety of different junkyard donors. I've made up a diagram of what the setup will look like when done, and it shows the stock N75 and the MBC side-by-side, with the solenoid switching between the two. The key here is to wire both the solenoid and the diode ground connections to a single switch, for easy single-wire switching. i would like to try out two methods, one where the bump stop of the gas pedal acts as a switch to enable MBC mode, and another that's just turn it on or off with a regular switch. That switch might just be an output from the ASR button, sort-of a sport mode that disables traction control and at the same time adds around 40 horse or so

If you don't know how these solenoids work....
There is a common port that at rest, connects to a normally open port on the solenoid body. When you power up the solenoid the NO port closes, and the NC port opens up. This will force all wastegate control into MBC mode. The picture below should be more descriptive. If you need more detail, I have a PDF file version here:

http://shaw-clan.com/beetlepix/turbosolenoid.pdf

[zeusenergy]

As an FYI, an even simpler way to accomplish the same thing is to put a normally open solenoid before or after the N75. It will open first even in parallel setup with the MBC. And when you throw the switch, the N75 will be bypassed, allowing the MBC to take over at the higher set boost level.
I'll be taking some pix in a while showing the location of the wiring for the charge pressure sensor, N249 bypass, and overall engine pics. I will be testing the N249 to see if it can be used as the solenoid in this setup as well.

[zeusenergy]

Let's dive in....

[zeusenergy]

here's the MBC. Wicked simple, just not easily adjustable.

[zeusenergy]

[zeusenergy]

[zeusenergy]

Here's the funniest part of all. I'll be using the most controversial part of the NB to mount the boost switch in....
THE BUD VASE!!!!!

[zeusenergy]

N249 location and hose identification underhood:

[IMG][IMG][/IMG][/IMG]

[zeusenergy]

The N249 DV control solenoid won't have enough flow for use as the main solenoid in this project. I need to visit the boneyard tomorrow and grab me a 1/4" barbed three-way....
EDIT: I couldn't find anything bigger than an N249 or similar ones out of SAABs, the older 900 turbos had a great round version- but it's functionality is similar to an N75 with bleed. And sourcing NEW ones costs over $175!!!!!

So instead I'll use TWO N249 style valves. Run them in parallel, wire together, twice the flow.
BUT I will NOT be using the N75 any longer.
Testing out the MBC alone today, I've got 14 steady PSI with no diode connected yet! And the driveability really isn't bad at all. I can live with it. So instead, I'll put in a second MBC and set that one to 18 PSI on the switch with diode. Wheeee!!!
14 steady is REALLY fun as is! 18 will be ridiculous for what I need. Maybe I should set the high boost to 16-17?

EDIT: I did use an N249 style valve by itself and it proved to work WONDERFULLY! So you could re-use the N249 to do this dual-mode system.