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MembersPage/PeteKrgr (2007-07-03 12:28:28)

Building a Porsche 3,0l 944 turbo

Now the details that affect VEMS specs and installation.

Trigger

primary (crank)

* toothcount ?

  • missing tooth ?

Porsche 944 turbo Trigger: 132teeth on flywheel, VR sensor and Crank home (1 pin on flywheel 58,5 dec BTD, if i remember right) VR sensor. No cam sensor) And no missing teeth!

Are You doing Plug and Play to motronic harness? Same project. Yes.

secondary (cam)

* VR / HALL ? Anyone knows this ?

There are doubts that both of them are VR, so investigation is needed.

For both sensor, measure all pairs of pins, in both direction (with a 3 pin connector this is 3*2=6 measurements). Write them here.

Measure sensor resistance and measure DC

This, is very important. Measure from the econoseal-wire connector (with ECU removed), so that you also verify the wiring.

Write your measurements above. Confirm that they measure approximately the same in both directions. Preferrably also measure (and publish) DC voltage (measure between same wires, but maybe easier in the engine bay before you insulate the trigger wires) when the ECU is connected. If there are problems, do the DC measurements and publish all firmware + config info as IssueReports

OK, what I now know is this. Info above about flyweel teeth count, pin on flywheel and sensors type are correct, that pin position has just to be confirmed. I bought yesterday a book "Bosch Fuel Injection & Engine Management" and it describes this system

" For the most accurate measure of engine timing and speed, Motronic systems read the position of the crankshaft directly. Special sensors pick up signals from the flywheel teeth."

"The rpm sensor ( also called the engine speed sensor ) is an inductive-pulse sender that picks up pulses from a toothed wheel, usually the flywheel. The rpm signal can be displayed on a scope just as it is sent to the control unit, one blip or spike for each tooth. It is so accurate it can sense an rpm chance while the crankshaft turns only a few degrees.

The TDC, or reference mark sensor ( reference from cylinder no1 TDC ),is triggered by a set screw on the flywheel. each time the srew passes the TDC sensor, the sensor signals one blip for each crankshaft revolution. Both ensors are magnetic, with a soft iron core that stores the magnetic field. When a tooth in the flywheel or the reference sensorpin moves though the magnetic field, the change induces an electrical voltage in the winding. This voltage is he input signal to the control unit. The sensor is known as a passive diffusionfield sensor, because it does not require a current supply."

I have these both new sensors, identical, at home, I will post their Bosch number here as I return home. I guess this makes the system what is called the Auditrigger.

Trigger measurement: If you have those Vr triggers on table, is it possible for you to measure the polarity of them? As you know they are quite difficult to get access while the engine is on car.

Measuring trigger Vr trigger polarity.

measure with DVM, 200mV DC mode. If your wheel has normal shape (missing tooth), than signel should be +few mV when you move ferrous metal (iron) towards the sensor, and -few mV when you move it away. The reading shows up for a very short time only (while the sensor actually sees the movement)

Shopping list

Assembled v3.3 controller

Update on the 29th of April.

While being busy with engine's installation I also did the wiring harness, modifying the old one for VEMS. I removed unnnecessary parts, reused some wires with new tasks and build completely new harness for fuel injction and ignition. I also replaced DME & KLR harness connectors with Econoseals and integrated Apexi AVC-R to this harness. I attached the VEMS box to the original installation plate at passenger's footwell. There was so much space that I managed to place fuses and AVC-R's own MAP sensor there. There's still some pins/wires unconnected ( see questions below ) and some finishing work to be done, but I thing that I can start configuring my system next week.

Unfortunately all my pictures are at the moment at page that needs password, but I try to change that later.

Questions with new ones

How shift light output is done? It is done using rpm triggered outputs

Any specific info on this one...eg. which pin? ...although I have now read the instruction manual and have some clue about this myself...

I want the original boost gauge in instrument panel to be functional. The problem here is that it is electronic, ie. the Motronic's KLR ( boost & knock control unit ) feeds it. So it needs output from Genboard. Other peoples obsevations how the signal is handled can be found here

http://forums.rennlist.com/rennforums/showthread.php?t=313463&page=2&pp=5&highlight=boost+signal

Is it possible to get such output, and scale it a bit differently? Now the gauge shows 1,0 when MAP is athmospheric, and I would like it to mean 1,0bar boost... Does anyone have anything on this, like proper pin number and possible configuration data...??

Related to previous question, how can I get rpm signal out of the VEMS? 12V or 5V logic level pin and how to configure it ??

More questions

Do I need PowerFlyback when using low-impedance injectors?? Yes, definitely

I managed to screw my order at this part and didn't get the bidirectional transient supression diode with my othre stuff. Instead of 30V I got 39V one from local electronics shop. Is it OK to use it?