MicroSquirt.com read only forum (Jan.15,2018)

before I make the plunge I want to make sure I can adapt MS to work with stock Crank/cam hall sensors on the dodge

thinking about building a MSII computer setup that will share stock cam/crank sensors, the coolant sensor, but use its own O2/MAP/air tem sensor. that way I don't lose the OBDII sensors and if need be I'm only 1-2 hours from getting it back to stock for the dreaded dealer visits. goal is fuel first then ignition as the stock PCM just provides a ground to the ignition circuit letting the voltage flow thru a distributor cap for final pathway to engine (sounds like routerboard to the rescue)

I know it can probably be done but I'm trying to avoid being the guinea pig as my programming experience is between slim and none (mostly none as getting the blue screen of death doesn't count towards programming time)...... more experience with wiring and testing rather than development

In trying to desribe the trigger wheel it is easier with a picture because it is more of a notched wheel rather than a missing tooth design 1notch/2 notch/1 notch/2 notch1 notch /2 notch all the way around for the 6 positions

If i'm successful in this endeavor I'm sure there will be more...... as the dodge-chrysler folks have one of the most archaic and non-user friendly systems out their. Its like they took lessons from the lucas school of electronics. If MS is adaptable I can probably get this setup for less than a ship and program to the stock pcm(dodgespeak=scary because you don't even know if what you asked for will be programmed; to top it off v6 people are considered to be "not worthy"=not profitable ) really waiting for development for sequential injection(router board) as this is what the factory has installed..... I know i can tap into the engine sensors as the factory PCM supplies the 5 volts for the hall sensors.

sensor ring on the flywheel has alternating notches ( has a notch then a set of notches) every 60 degrees
notch is very close to 3.75 degrees wide(calibrated eyeball measurement) that hall sensor uses for signalling state of change to stock ECU

I was able to determine a ball park figure for the notches since the wheel reads events which are evenly spaced. bear with me as I think out-loud and explain my version of the wheel notches. I will have to find a way to emulate this code as that is the ultimate goal. If anyone know more about this please educate me as I am learning as I go. 4/8 cylinders are so much easier as so many have been converted and it is divisible by 2.

Looks like they are 3.75 degrees wide (gives potential for 96 positions around the wheel helps that it is divisible by 3 lol). 4/8 cylinders would use figures divisible by 2 or 4

Wide gap between double notches and single notch is approximately 60 degrees wide
narrow gap between double and single is approximately 45 degrees wide
45+60+45+60+45+60 =315 degrees 360-315= 45 degrees left unaccounted for

Total gaps + space between =12 45 remaining degrees 45 divided by 12 = 3.75 degrees for each notch/space

3 groups of 3 notches
with 60 degree spaces in between
1st group assuming cw degree of the photo starting with a single notch

I am describing each notch by degree position and number of positions around the wheel(total being 96)

1st group
360/0-3.75 degrees position1
12 blank positions
48.75-52.5 degrees position 14
1 blank space position 15
56.25-60 degrees position 16

2nd group
16 blank postions
120- 123.75 degrees position 33
12 blank positions
168.75-172.5 degrees position 46
blank position 47
176.25-180 degrees position 48

3rd group
16 blank positions
240-243.75 degrees position 65
12 blank positions
288.75-292.5 degrees position 78
blank position 79
296.25-300 degrees position 80
16 blank positions up to 96

Hopefully everyone is up to speed now
next is determining which position on the wheel is the 0 degree mark

I know that MS can use hall sensors to trigger events just wondering how hard this is going to be hoping that i won't be the one going thru the tunnel first telling everyone else to come to the light lol

again i haven't made the plunge yet but if it is do-able i will be getting MSII on a V3 board.

dodge definitions from their manual

"Crankshaft Position Sensor "

The Hall Effect type crankshaft position sensor is mounted on transaxle bellhousing.

The sensor reads slots on flywheel/flex plate. The signal generated provides engine speed and crankshaft position information to PCM.

The PCM uses this information to determine proper fuel injection and ignition timing.

"Camshaft Position Sensor "

Hall sensor located inside distributor housing-- When leading edge of pulse ring enters the sync signal generator on the camshaft position sensor, the resulting change in the magnetic field causes a 5-volt reference signal to be induced.

On 6-cylinder engine, it indicates that piston No. 6 will be next piston at TDC.

When trailing edge of pulse ring leaves the sync signal generator on the camshaft position sensor, the resulting collapse of the magnetic field causes reference signal to drop to zero volts.

On 6-cylinder engine, it indicates that piston No. 3 will be next piston at TDC."


"On 3.9L engine, the slotted flywheel/drive plate, rotating past the sensor, contains 3 groups of 3 slots located 120 degrees apart.
Each group of slots represents the position of 2 of the pistons.
Pistons No. 6 and 3 approach TDC at the same time and use the same flywheel slot.
Pistons No. 5 and 2 are matched, while piston No. 1 is matched with piston No. 4.

The PCM, through the crankshaft position sensor, knows that 2 pistons are approaching TDC and uses the sync signal generator on the camshaft position sensor to determine which injector/spark plug to fire."

in researching this i realized cam sensor outputs 2 pulses per cam revolution - ie one pulse per crankshaft revolution,
is it possible to used the cam sensor as a sync input?

As far as I know the MSD6A series of boxes is compatible with the 3.9 magnum engine, why not just use its tach output? That is what most 5.9 magnum owners are using for their tach signal.

I got my msd6al for like 113 on ebay. It might save you a lot of headache.