Vanos - BMW's variable intake / exhaust timing system.
My engine uses Single vanos, which only advances the intake cam.
From here: http://www.bmwworld.com/technology/vanos.htm
Just off idle, the DME energizes a solenoid which allows oil pressure to move that cup gear to advance the cam 12.5 degrees at midrange, and then at about 5000 rpm, it allows it to come back to the original position.
Firmware can only handle an off-on situation (not off-on-off).
There is no need for firmware changes to support single VANOS, use one of the misc output functions to be active within a certain RPM range, you may have to use the inverted function on the output depending on the logic function of the VANOS solenoid.
Dual vanos changes both of the exhaust and intake cam timing, PWM controlled (not on/off like single vanos).
- cam-sync must measure valve-position, with respect to primary trigger (crankshaft) position
- target valve-position in function of (RPM, load)
- the error signal is used in a software PID controller
- the output of the PID controller is called command signal:
- command can drive 1 PWM signal in the suzuki VVTI (we're testing on Suzuki engine first; than on BMW and Mitsubishi).
- BMW needs 2 output PWMs: when command is 50..100%, solenoid A is powered (0..100% duty). When command is 50..0%, solenoid B is powered (0..100%). BMW also needs 2 high current output stages (Beyond stepper current limit. Maybe 2A ? Anyone can measure solenoid resistance ?) HIGHSIDE endstages (perhaps PNP transistor on heatsink, with diode flyback).
- controlling both intake and exhaust valves is theoretically simple, just double everything.
- However, to be able to use a third VR-trigger input (in PS2 keyboard data input, often used for wheelspeed HALL signal), a VR=>HALL is also required in the 4PNP amplifier box.
I think BMW M-Power dual VANOS did not work with PWMing. Each camshaft actuator have oil chamber with two solenoid valves (4 valves total. Low-Z. PNP actuated!!!).One valve can feel up chamber, other bleed it. If both valves is unpowered, chamber have constant volume and camshaft angle is fixed. One valve can advance it, other - retard. It is easier from software point of view, but more complex in hardware. It is my piece of "reverse engineering". Flyback diodes are inside valve units. Also system uses camshaft "trigger wheels" with complicated patterns. What patterns exactly ?
Yes, the current implementation using 1 PWM-output for intake and 1 PWM-output for exhaust cam actuation. For BMW dual-vanos it will need to be changed to "double-output-channel" and perhaps 1-shot (variable-length) instead of pwm strategy.
Some more vanos info:
Most other aftermarket ecu's have lowside drivers too, just remove the connector from solenoid (this houses the flyback diodes in direction opposite to direction desirable for use with VEMS) and crimp on a new one.