Members Page/Alex Jenkins - VEMS wiki www.vems.hu

MembersPage/AlexJenkins (2014-06-29 11:06:36)

I am trying to specify a pnp system for my 1989 Porsche 964 Carrera 4. The VEMS PnP unit is built by Peep Paadam of vems.ee

The car as it is 25/06/2014

Mechanical

Management

55pin Motronic
Twin spark
Twin distributor
Twin coil (not coilpack or cop)
Standard 218cc/min at 3.8bar high impedance injectors (Bosch p/n 0-280-150-731 193.9cc/min @ 3bar 16ohm). Note while there is agreement on the flow at 3bar, when run at 3.8 suggested flow values run from 218cc to 250cc)
2 wire style Bosch ISV
Intake "resonance flap", vacuum actuator, electrically activated
Carbon canister vacuum switch

Sensors

VR crank trigger on flywheel 60-2, missing tooth is 84 degrees BTDC
Hall sensor in distributor
4WD wheel sensor on rear diff, Hall
2x ABS wheel sensors
Cylinder head temperature sensor (NTC)
2 knock sensors
Narrowband O2 is fitted to most models, but this car had a factory option selected to remove this
Standard AFM (Flap style)
AIT (NTC type inside AFM)
Altitude potentiometer
Standard idle and wot switch (no analog TPS)

PLAN

Source Porsche 964 PnP unit from Peep Paadam (vems.ee) to agreed specification, with suitable base map.
To begin with I will keep the twin coils and distributors, unit will be supplied with additional earths to allow coilpack/wastedspark at a later date.
Fit an analog/potentiometer TPS (from Opel Omega A - as per Peep's suggestion)
Remove AFM and add a separate MAT.
Add wideband 02
Convert to Speed Density (MAP) operation
Test idle and review if AplhaN+Map compensation would be better

TODO

Measure and make bracket for TPS
Measure and make AFM replacement pipe and hose joiners and either source top-hat adapter to keep std airbox
Wire old AFM plug for AIT/MAT sensor (neatly and reversibly)
Check continued operation of HVAC (this car does not have AC). There is one pin on the ecu which comes from the HVAC instructing not to cut fueling on overrun if heater is on - this is to maintain heat exchanger temps
Check continued operation of ODB for ABS and 4WD diagnosis and testing
Operation of "central informer" check engine light
Find standard DME injector dead time table
Find standard DME injector sequential vs batch fire operation
Find standard AIT vs ignition retard and fuel adjust tables
Check the distributor hall sensor is sufficient for ecu to camsync for full sequential injection and standard injectors will fuel adequately in full sequential mode.
Check Peep will have performed O2 calibration on supplied unit
Check best location for MAP sensor take off (before or after)
Check best location for AIT/MAT sensor
Is EGT sensing desirable and retrofittable to PnP unit
Find guideline EGT for aircooled 911
Find compatible uprated injectors, and establish if mods to ecu will be required to run low impedance aka "low-z" injectors.

References

Rennlist procjet thread and discussion

964 55 pin DME Motronic pin out here

and here:

further information (some for 993 specifically)

Injector info

Injector flow vs pressure calculation

Standard DME coil dwell time table