The 88 scirocco that I am modifying for the $2004 challenge race

has a little problem. The KE-Jetronic (CIS-E) system included the ignition circuit. And the 9A 2.0L block 4 clyn

does not have a CrankTrigger?. So Given that I have less the 50 days to get this thing running I need a improvised plan

to make sure that I have ignition. MS-AVR has an ignition output. The question is how do I hook it up.

Well with a little imagineering I came up with the following NO KNOCK solution.

Leaving the distributer in place in the 16v head provides the following inputs.

There is a 4 window hall sender in it. This sender can provide the basics input for MS-AVR until

I get the cranktrigger built.

Also leaving the distributer in provides a method for distributing the signal to each sparkplug. So

that 4 coils are not needed.

This application is for a 4 clyn car. The hall sender is on the camshaft therefore the angles between the windows is 720/4 = 180 degrees.


For the stock system a trigger event occurs at 6degrees Before Top Dead Center (6d btdc)

the transition is from high to low, because the stock bosch 008 igntion module is triggered by

a low level to fire the coil. This is a left over bit of engineering from the early CIS cars

where the points system was replaced with a pointless ignition, ie. the points were replaced by

the ignition module (IGBT with dwell control).

Since the hall sender depends on there being a window there is a rising edge as well. And from

my calculation ( ie. not measured on the car. the next even occurs approximately 96.3degress after

the normal bosch-008 trigger event. MS-AVR likes this very much so you have to change the

Ingition trigger to +ve vs. -ve for a normal

From #avrboard

Set Ignition trigger, to –ve or +ve.

[1] <Jorgen__> +ve = MSD CDI

[2] <Jorgen__> -ve = Autronic CDI

[3] <Jorgen__> -ve = Ignition modules e.g:- Bosch 008

This is the type of signal you can expect from this distributor.

or like this from a VW passat


and marcell responded :-)

[4] <GRMracer> mcell: how about the output?

[5] * GRMracer digs thru InitialConfig?

[6] <mcell> ign_out LSB

[7] <mcell> ign_out=70 or 71 is dummy, 00 or 01 is dummyign, FF is ign-off

[8] <mcell> see edis.c and (check Chris' config)

[9] <mcell> ign_out LSB tells output polarity (PORTB7 misc NPN IIRC)

[10] <mcell> Brian, even with bosch-008 selfdwell module, you can just set dwell (is higher or equal dwell needed than for the same coil with dummyignition? If it works with analog current limiting, than probably. If it is CDI, it shouldn't matter. So I'd set a high, like 4..7 msec dwell). The simple setups like MSNS does resetting the signal a few 100 usec _after_ spark (which is insufficient for DummyIgnition), MSAVR resets dwell time _before_ spark, which is good for any modules. If you set dwell too high (compared to available time according to RPM), msavr will ensure the signal is inactive for about 400 usec (decreasing dwell), which gets the reset _after_ spark behavior.

Basically, the plan is the following.

If possible later

NOTE: at this point problems will occur, but remember it is a racecar.. and we do have a spare motor.

The ignition module looks like


The pin-out is

The Bosch module 0 227 100 137 / 0 227 100 139 is designed to be used with Hall effect

and also takes care of the coil dwell period.

The module trigger when pin 6 is grounded, but the dwell control prevents

it to create a spark at the first trigger.

Pin layout

1) Coil -

2) Ground


4) 12V

5) Hall+

6) Hall-

7) Tach signal

Megasquirt-n-spark schematic is:



misc (small NPN) will be used, not fidle output.

additionally we'll be running the tach output p7 to a tach on the dash.

Another option might be to run one of these and 4 coils

Information on the hall sender in VW's

Taken from a VW repair manual.

6 Hall sender - testing

Note: A digital multi-meter should be used for testing.

Do not use a test lamp Release the lead connector from the Hall sender unit. Check the voltage supply to the sender unit by connecting a multi-meter between the outer contacts of the plug, then switch on the ignition (see illustration). A minimum reading of 5 volts should be indicated, if not check the FEI control unit and wiring.


To check the signal from the Hall sender unit, slide the rubber grommet away from the sender plug and with the plug connected,


attach the diode test light


brown/white are ground

to its centre and outer (brown/white) terminals (see illustration). Operate the starter motor and check that the LED is seen to flicker. If it does not, the Hall sender unit is at fault and must be renewed. which is available in kit form including a drive coupling, pin and circlip (see illustration).

2 If the rotor arm is defective, it must be removed by crushing with pliers as it is permanently fixed to the shaft with strong adhesive. Clean the shaft and secure the new grease.

The LED test light they are talking about is a +V clip -- +LED LED- 330 Ohm resistor – lead