MoTeC Global Forum

Hi
New to EFI, so may have a few dumb questions to start with !!
Looking at fitting A M800 to a early 90's 302 Windsor and have a few questions.
1. Whats the best number of teeth for the chopper wheel and why ? (there seems to be wheels from 4 to 36)
2. How big can the dia of the wheel be, looking at around 175mm ?
2. What type of sensor, hall or mag ? (std AU falcon of after market hall)
3. Thinking of using the std AU cam syc sensor, any problems with that ?
4. Whats the difference between a say, 36-1 and 36-2 wheel ?

Have access to full machine shop, so making all the bits is not a problem.
Been a points and carby man all my life, now I have to turn to the dark side.
thanks in advance
cheers

Clayton

I'd use/fabricate 36-1 wheel on the crank and read it with some fast hall sensor. 175mm is fine.

If wheel is made of at least 8mm steel plate and teeth are 10mm "long" then Hamlin 55075 is good sensor. With this kind of tooth design, sensor-to-tooth air gap should be 1.0 mm.

If cam sensor puts out one signal per engine cycle ie. two engine revolutions then it is very much ok. I assume signal is logic signal ie. "hall-type". Other signal counts are possible also, but one is simple.

Term "36-1" means that there actually is 35 teeth, and one missing which would be that 36th tooth. Same with "36-2", but two teeth are missing. Bosch invented 60-2 wheel many moons ago, I'd guess that's the first one used on commercially available cars.

Thanks mate,
I assume the missing tooth is to indicate TDC ??
Should I run the same width air gap as the tooth width, ie 10mm air gap ??
With the 10mm/10mm the disc will be around 230mm dia, is that too big ??
Or can I reduce the tooth width or the amount of teeth with the same tooth width ??

I'm pretty sure the cam sensor has only one trigger per / rev, but I don't have one at the moment.
Not sure if its hall or not.

So to make sure I'm on the same page, there would be a air gap of 30mm for the missing tooth if the teeth are 10mm and the air gap is 10mm ??.
thanks again

Clayton

See this: http://www.motec.com.au/filedownload.ph ... docid=1309

It explains a lot. Make "Gap" to 1,0mm, "Tooth Width" 10mm, "Tooth Height" also 10mm, and naturally "Tooth Spacing" depends on wheel diameter. Outer diameter of 175mm is okay, 180 is better if designing with some CAD drawing program. If Tooth Width becomes bigger than Tooth Spacing then you can make them the same, but not less than 8,0mm with Hamlin 55075.

Put missing tooth about 70 degrees before cyl 1 TDC so it is detected many degrees before where maximum ignition advance is supposed to be. Don't put it where some other cylinder is supposed to ignite at some needed ignition advance, if at all possible. This is to avoid any extra electrical noise.

Thanks again

otto69 wrote:Should I run the same width air gap as the tooth width, ie 10mm air gap ??

Sorry, I meant tooth spacing and not sensor to tooth air gap.

Now to work out how to adjust the ECU so it knows where TDC is, lots more reading I think

While looking for the cam sync sensor, AU 5.0 Litre. Found there were 2 types, an early model with 3 pins and a later model with 2 pins. Which one would be better ??
cheers

otto69 wrote:there were 2 types, an early model with 3 pins and a later model with 2 pins. Which one would be better ??

If three pin type gives out digital signal (ie. same as hall sensor) then it is easier to get right. Two pin model is probably magnetic ie. VR sensor. It can be used but it is not so easy.

PQatPIT wrote:Two pin model is probably magnetic ie. VR sensor. It can be used but it is not so easy.

Thats the one I ended up with, got it real cheap !! Is there any way to measure / confirm that its a magnetic one ??
What extra do you need to do to set it up in the M800 ??

I have an M800 on a stroked 302 (331) using a magnetic ref (crank position sensor) and a hall sync sensor (cam position). The crank trigger wheel is from electromotive, 60-2 teeth and 5" in diameter. It is mounted on an ATI damper hub via a shrink fit aluminum hub (0.006 interference) that is machined to be square to the crank axis. The trigger wheel is placed so that it easily clears the damper's offset weight. I also used the related electromotive 0.5" dia mag sensor with a 0.030 gap. The sync sensor was originally a gutted aftermarket distributor with just a single tooth left acting as a sync sensor (rest cut off). At that time I had only 1 coil so the distributor still distributed spark. When I went to individual coils I got a used Ford Explorer sync assy that used a Hall sensor.

The system achieves sync very quickly and has always operated well. The arrangement uses ref/sync mode 7.

Two pin sync sensors are magnetic. The Hall is a more straightforward arrangement and worth the trouble getting (IMHO).

Thanks mate

Is there a benefit in running the 60 tooth wheel over say a 36 tooth one ? Or just make sure that you have the correct sensor for the amount of teeth on the wheel ?

I also picked up a secondhand Explorer cam sensor, but it had a two pin connector.
Found out that the early AU's had a three pin sensor and the later models where two pin.
Why is a magnetic sensor harder to set up than the hall type ??
Sorry for my ignorance, but this is my first time with EFI.

I'm still along way off needing the finally parts (still building the car) but would like to get a handle on this.
Looks like I need to go back and read the manual again, couldn't find "ref/sync mode 7"
cheers

Clayton