After the less than succesful instalation of the boost control circuit in Megasquirt I decided to fit a 'proper' controller. Having fitted a few electronic boost controllers to turbocharged cars in the past I narrowed the choice down to either a Greddy or Apex-i. The Greddy profec spec-b is the cheaper unit but lacks some useful extra functions. The Apexi AVCR does more than you could realistically ever need & one happened to come along at the right price....
The kit comes with a manifold pressure sensor (MAP), fast acting valve, wiring loom and the control/display module, plus various fittings & vacuum hose. Anyone who's ever fitted one of these will be familiar with the poor instructions - why does anything translated from Japanese to English read so badly?? The booklet has plenty of information, it's just meant for Japanese cars. So make sure you read it thoroughly, paying particular attention to the wastegate plumbing. Dual port wastegate's are plumbed differently to single port.
There are a few wires than have to be connected to the ECU. These are +12v (red), earth (black & green), throttle position (grey) and RPM (purple). There is another wire for speed (white) but this can't be used with a cable driven speedo. Also the orange wire can be used for a 'scramble switch' which allows the boost to be raised or lowered for a short time.
Two pictures showing the display mounted in the centre console. The ashtray was carefully cut out, the aperture smoothed and strips of adhesive foam were stuck on either end. It was then simply pushed into the hole, the foam holding it in place. A twin power socket has been mounted on the side of the centre console, connected to the original wires. Note the 4 electric window switches - a very rare option on the Mk2 Golf.
Setting up.
The Apex-i AVC-R has many functions including in gear boost limiting, adjustable boost response, speed based maximum boost. I'd just like to cover the basic boost control function. Go to the SETTING [A] or [B] menu, [BOOST/DUTY]. Set the boost to your desired maximum (eg 1.20kg/cm).
NOTE - kg/cm is almost the same as bar. 1kg/cm = 0.9804bar.
The maximum boost is controlled by adjusting the duty cycle %. A low setting will rely on the wastegate spring (around 5 psi or 0.4kg/cm on stock VW wategate actuators), a higher setting will hold the wastegate closed for longer. It is important to start with a low setting to avoid overboost & potential engine damage. If your target boost is 1.0 and actual is 0.7 RAISE the duty %. If target is 1.0 and actual is 1.2 LOWER the duty %. Once the actual turbo boost is close to your target the controller will start self learning. It will adjust the duty% to maintain the boost level at your desired target. Raising the boost on an otherwise standard car will not make it go faster, it will probably blow up. The fuelling & spark timing will need to be adjusted also.