SpenceSTL

Ok, herein lies some of the experiences I've had lately setting up a manual boost controller in my 98.5 NDBW 1.8T

I've been reading the forums a lot on VWVortex, and right now a very popular mod has been to add the manual boost controller from BoostValve.com to the supply side of the N75 (on DBW cars). I've been very disappointed in the boost inconsistancy of my car(GIAC 1 Bar chip) and so I decided to give it a try. My tech sheet said that for non-DBW cars to try hooking up the controller as a straight Manual boost controller, eliminating the N75 valve altogether. This is how I currently have the valve configured. I installed it as the following gimp picture depicts, and connected my Vag-Com to moniter and make sure that I'm not leaning anything out......
<img src="http://pictureposter.audiworld.com/31095/current_boost_controller_setup.jpg">
With the Controller configured this way, I have a few impressions. I was able to set my pressure to 16PSI with no problems. I now jump to 16 PSI in all gears, and hold it, until the inherent flow restrictions of the K03 taper it off near redline. Before this setup, I would only hold between to 12psi in first and second, and up to about 15psi in the higher gears. The car feels tremendously faster and more torquey, especially in the lower gears. Boost comes on very very fast now, and holds rock solid in all gears.

Sounds great doesn't it? In actuality, there is one issue with my setup. With the manual boost controller set up, the car tries to build boost ALL of the time. Any time you get over about 1/4 throttle of pedal travel, the boost jumps immediately to max setting (16psi) and holds there. This makes freeway cruising difficult, as you have to feather the pedal to maintain a constant speed without getting seriously into boost.

I struggled with coming up with a way to get all of the benefits of my full manual setup, with the smoothness of the factory setup, below you will see my "idea".

You will notice in the gimp drawing below, that I have re-connected the N75 in to the mix, while still leaving my manual setup in place. The N75 and Manual Outlets connect to solenoid valves, and then to a Y connector, which connects to the Wastegate Actuator valve. The N75 uses a normally open solenoid, which allows air to pass any time the valve is not energized, and the MBC uses a normally closed valve, which opens when energized. The two valves are both wired to come on with the same switch, opening the MBC airpath, and closing the N75 airpath.
<img src="http://pictureposter.audiworld.com/31095/proposed_boost_controller_setup.jpg">

I think that this will allow me to have my full MBC setup with the push of a button, while allowing the factory setup to perform as designed any time that I am not looking to push the car hard.

I welcome any ideas, critiques, questions, as I'm about the order the solenoids to try this.

AntiSocial

Let us know if you find a way to control boost while involving the knock sensors.

Audi2ptzero

intake tube and to the turbo housing?

I am also wondering why you hooked up the MBC to the BPV and intake manifold instead of to the turbo like the car comes stock with the N75 valve?

johnAWD

If you knock, tweak until no knock.

AntiSocial

Bye bye rods.

SpenceSTL

The N75 is still hooked up as it was originally, with the exception of the outlet, which is plugged. The reason I routed the MBC as it is currently is that I didn't want to unhook the N75 (this is still kind of experimental) and needed a source of manifold pressure/vacuum. It just seemed like a logical place to draw it.

SpenceSTL

completely functional. My understanding is that when the knock sensor detects pinging, it pulls timing back, not boost. Please feel free to correct me if I'm wrong there.

Audi2ptzero

since the valve just adjust how much pressure is sent to the wastegate. Unplugging it will do the same thing as long as you loop the inlet and outlet of the valve.

I actually use a HKS EVC 4 boost controller on my K04. It replaces the N75 valve and I dont have any part throttle issues at all.

xr4tic

All you need is a larger turbo that won't spool up so fast

Seriously though, what you have proposed will not work. Not even close.

The way you have it setup, the N75 will bleed boost off of whatever the manual valve is set for, causing the boost to go even higher.

So you need to have the supply line go to BOTH the manual valve and N75, with the solenoids in front of them. Problem is, the N75 could still bleed off air, so a one-way valve would be needed.

I drew up a diagram, but I'll have to email it to you, I'm out of room in my picture poster....

I'm also concerned that you said that the boost tapers off. The manual boost controller should hold it at whatever boost it's set for. A K03 should not run 16psi at redline, and since that is what your boost controller is set for, your K03 is trying, but it just can't. the reason why it can't is because it is crossing the Surge line (the compressor is trying to push more air than the compressor can physically provide) and overspinning. This is VERY VERY BAD, mmmkay. It can cause the compressor blades to move back and forth, hitting the housing.
If you're lucky, you'll just have to replace the turbo when it goes, if you're not lucky, you'll be taking the motor apart to pull little metal bits out that should not be there.

This is why a manual boost controller is a VERY VERY BAD idea for a K03 (unless you set it for 10psi or something like that, and what's the point in that?)

Electron Man

...the ECU will cut boost and/or add fuel attempting to bring CC temps down (to eliminate knock).

By taking boost control "away" from the ECU (it no longer controls N75) you only have two defense mechanisms (timing retard and fuel enrichment) to protect your connecting rods. Rods will be the first to go if knock can't be eliminated...that could get expensive.

Might consider buying a 55gal drum of racing fuel so you can mix 3-4 gallons in with each tank of premium. It will be cheap insurance (for the engine) while you are searching for the boost limits of your set up.