Adding the Boost Machine brings the Modshack TTuned Intake System to full stage 3 specs. This is a very sophisticated pneumatic controller that has the ability to increase boost, set boost onset, eliminate spiking common to N75 controlled systems, and improve boost delivery and general operational smoothness.

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Installation instructions here

A4 install and thread here..

Alternate VW Parallel install info here..

Consider the BM a signal "Conditioner" or variable N75 if you will...

It will:

1) Allow enhanced Boost within reason, but this is not it's sole function. Smooth delivery of boost and absolute control over how that boost is delivered is the most notable feature of the BM. Throw away your N75 H/J/K or whatever you are using. The BM takes the place of all of them and is infinitely variable. It works best with the stock N75

2) Control Wastegate "Creep" by restricting a signal to the wastegate in low boost situations. What this means simply, is that under normal operation, some pressure is sent to the wastegate at low RPM's, therefore cracking the seal and spilling a little boost. Adjusting the onset or relief valve will keep this bleed to "0". This will allow faster boost recovery during shifting, and allow you to move the Boost curve down in the RPM range so the car feels punchier at low and mid throttle positions.

3) Control "Spiking". Spikes are transient high boost conditions that occur as you appply throttle in high torque condidtions. Spikes happen quickly, before the N75 gets an ECU signal and trys to control them. Since the BM is a pneumatic valve, the actual control defaults to the regulator setting. Without spikes, the boost delivery will be smoother and the chance of hitting an overboost "Limp" condition are reduced. Boost differential between Peak and Hold is generally reduced.

Note: The BM is not meant to replace a chip. Stock tuning parameters have fairly low threshholds and will often put a car into limp mode with small amounts of increased boost. VW's are particularly susceptible to this and operation on a stock ECU will generally be disappointing. Not recommended for the 150hp motor as a result. An alternate Parallel install has been tried to deal with chronic VW surging problems with some success and is detailed in this Vortex thread.

Bob Kunz (DasTT on AW) did this write-up and it summarizes the Boost Machine in a more technical fashion:

I take the analytical approach here because of my engineering background. Mostly though I just can't see me turning dials without knowing the underlying principle at play. A quick review of my understanding....

It's all about controlling the pressure signal to the waste gate since this controls how much of the exhaust is used to generate pressure on the charge air side. Higher signal (pressure) to the waste gate allows more exhaust to bypass the turbine. In the absence of any control, the charge air pressure is fed back to the waste gate diaphram.

When this is the design a spring is used to counter the feedback pressure. This sets the maximum charge air pressure (boost) by opening the waste gate when the boost gets to the spring value. The boost then settles in around the spring value.

Even with electronic controls a waste gate spring is still used to set the limp mode maximum boost. For the 225 with a K04 I believe this is about .4 Bar or 6 psi. Below this boost level the engine doesn't need any control.

The control on our engines is the N75 valve. It's purpose is to bleed off the pressure signal to the waste gate. If we completely bleed off the signal (100% duty cycle from the ECU) then the turbine gets all the exhaust to generate boost on the compressor side. At the other end (0% duty cycle) the system operates like a direct feedback system and boost is limited to the waste gate spring value.

The bleed off rate of the N75 is what makes boost smooth or not (i.e. other versions of the N75 change the oriface size or effect of duty cycle on how much of the signal is bled off) and is designed to work with a particular engine/turbo combination. This is genberally controlled by the ECU program. In general reducing the oriface size will delay boost but hold it longer.

The ECU attempts to compensate but the feedback loop has a pretty long time delay as well as having the ECU predict N75 duty cycle based on other inputs. In the end, the system has to learn driving habits and make best guesses at how to control the duty cycle for the N75. This is the primary reason for spikes and surges.

Enter the boost machine. I'll assume the parts of the machine are well known by this group. The two valves set the onset of control (the relief valve) and the maximum pressure signal (the regulator valve) available. The third control (one way valve) releases pressure in the line to the waste gate when boost is reduced (i.e. the DV operates) by dumping it back into the charge air side.

The BM is placed in-between the charge air port and the N75 valve. It's operation can now be understood quite simply. As pressure builds on the charge air side, no signal is allowed to the N75 until the relief valve setting is reached.

Then the pressure signal matches the charge air pressure until the regulator setting is reached. At that time, the pressure signal to the N75 is fixed to the regulator setting. This does two things. Firstly it allows the turbo to spin up uncontrolled until a certain charge air pressure is reached.

Then we are in the area of "normal" control via N75 only. Then we move into restricted control through the N75. In this restricted mode we have limited the ability of the ECU/N75 to reduce boost. As far as the N75 is concerned, the boost is at the regulator set point. It basically operates as a pressure "Clamp"

The ECU however is going to eventually decide that it can no longer control boost because it is measuring a boost higher than its command boost. The algorithm is likely very flexible given the issues in controlling this kind of system but pushed to the limit the ECU will post a DTC.

In setting the regulator (clockwise increases its set point) above the expected maximum boost and the relief valve at zero (completely CCW) we are operating without interference.

As we reduce the regulator pressure (moving it CCW) we will find the point where the regulator takes over control from the N75 through restricting the pressure signal.

A little bit lower (CCW) and we are "adding" boost. We're allowing the turbo into un-controlled space again.

The turbo of course will attempt to boost well beyond its efficiency and as has been pointed out somewhere around 22-24 lbs is where the point of deminishing returns occurs.

The relief valve can then be brought up to a point beyond the waste gate spring value but below the regualtor value to effectively become the new spring value.

But the advantage is that no pressure will flow keeping the waste gate from "creeping" open just a little.

The combination of the relief value and the one way valve on shifting means we'll snap the waste gate closed preserving revolutions in the turbine (all the exhaust through the turbine).

This combined with release of charge air through the DV will keep the turbo spinning faster in-between shifts. This in turn, results in a faster on-boost recovery when the shift is complete.

These are assembled with parts that have been proven on my car for almost 4 years now. Hundreds are currently in operation around the world. Norgren and Metalworks valves, Hose techniques silicone and solid brass fittings, all combine for a maintenance free assembly.

A custom bracket that mounts on the strut tower, instructions, hardware, and Go here and click on colors are all included for an easy 15 minute install. Chipping is highy recommended as fuel and timing maps are more aggressive for supporting enhanced boost.

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Cut and paste into your Paypal statement and forward payment to seschwing@earthlink.net I will acknowledge on receipt.

Boost Machine complete: $150

Shipping: $

Total: $

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