I´m planning on installing a VEMS unit on a stock 89 Porsche 911 Carrera 3,2.
Plans
- Motor 3,2litre normally aspirated
- number of cylinders=6 ?
- trigger system is 2 VR sensors on flywheel / starter ring gear
- rev sensor is sensing 129teeth per crank rev
- TDC sensor is sensing 1 pin on flywheel (don´t know yet how many degrees before TDC)
- no cam or distributor sensor
- stock NTCII at cylinder head #3
- AFM (flap type) will be removed, will use TPS instead (exchanging stock idle and WOT switch)
- idle control valve is the "silver cigar" BOSCH thing, not sure if stepper motor or PWM ?
- IGN distribution will remain untouched in first step, stock coil, stock distributor
- stock fuel injector BOSCH 0-280-150-158 low-Z (2-3 Ohms)
- wideband O2-sensor will be used intead of stock narrowband
- no MAP, no airtemp sensor planned
- Firing order for the Carrera is 1-6-2-4-3-5
- wiring should remain mainly stock with stock-DME-connector and only additional wires for wideband, TPS and so on
- planning to use alpha-N only
Now to the open issues:
- primary trigger: 129 is quite hard to divide.
129 means 258 for a full eingine cycle, the max value for "Coil-type" + "normal" is 255 !
So i need to use "Auditrigger DivbyN" option and a "Audi trigger divider" of 43.
So number of teeth on wheel becomes 3 (carrying over what I see on the AUDI configs)
First trigger tooth will be 0
Next trigger tooth 1
Angular width of teeth is 120°
trigger pattern is 0-5-4-3-2-1 ?
- write firing order also
"Auditrigger" option for the ECU.
- any drawbacks due to the 129 teeth variant, like rev limit or so ?
- if really 129, than 43 tooth per event per (if 6cyl). But with divby3, 14*3=42 tooth or with divby4, 11*4=44 tooth can be configured, so per-cylinder spark delay (~2.75 degree) can be used to compensate this tooth.
- secondary trigger is the TDC-mark on flywheel
- what to do for the low-Z-injectors ? is the 30V flyback ok and do i need the inline resistors (6,8 Ohm) ?
- order with "low-Z extension" option if you keep the high-Z injectors (and configure PWM-ing: ~35% PWM duty after 1msec full-voltage)