How accurate the fitting of a trigger wheel should be?

[GGR]

Hi all,

I am planning to Megasquirt fuel and spark my euro 5.0 engine and go for EDIS wasted spark ignition. I am considering fitting the trigger wheel on the back of the crank damper, on the timing cover side. Space is limited, but it should fit. I saw that people use lathes and cold soldering to fit these trigger wheels. I do not have access to that kind of machinery so I am planning to go for a trigger wheel looking like the one on the picture below, drill four holes in the damper, thread them and fix the wheel with bolts and small cylindrical spacers between the wheel and the damper.
Here are some questions:

- How thick should these spacers be, knowing that the OD of the wheel is 5", which is smaller than the damper? In other words, how far should the wheel be from the damper to avoid any interference and allow the sensor to pick up a correct signal?

- I will do my best to center that wheel as accurately as possible, but it may not be as precise as with a lathe. Can that affect the quality of the signal pick up?

- I am planning to use the original sensor bracket on the timing cover to fix the sensor. How far from the wheel should the sensor be? Or what should be the space between the sensor and the wheel?

- Should the sensor be perfectly perpendicular to the wheel's tangent, i.e. perfectly oriented towards the center of the crankshaft?

- I read the missing tool should pass in front of the sensor 10° before TDC. Is this correct? If yes, is this the center of the missing tooth?

Thanks!

[cth350]

Gael, I beleive the sensor has to be rather close to the wheel, meaning if you don't get it fairly well centered, the excentricity of its orbit will be too great.

As for position of the wheel. I beleive that Ron said the wheel can be put on in any slap-dash fashion, as the megasquirt has a tuning parameter to control the baseline offset between when it senses the missing tooth and when it fires the ignition. ((after all the goal is to have a computer controlled advance)). Having said that, the "center" of the missing tooth is what you'd be trying to place.

HTH -CTH

[Tony H]

I think the VR sensor clearance to the wheel is .75 to 1.5MM so any eccentric movement and the wheel will hit the VR sensor. Why don't you go with the wheel I had made? I bought it from this seller:

http://cgi.ebay.com/ebaymotors/36-1-VR-Trigger-Wheel-Ford-EDIS-Megasquirt-Megajolt_W0QQitemZ230350969224QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item35a1fcd 988

I bought the 8.25" wheel and had the center bore machined to 94.75mm. The result is a press fit on the pulley. I was then going to use some Hi-temp RTV to hold the wheel against the harmonic balancer as extra insurance.
Hope this helps.

[GGR]

I may end up going your way. But would like first to study the possibility of hiding it behind the damper.

[Gurunutkins]

Hi GGR
first off sorry I didn't realize you were Gael! I may possibly be going senile?

Tony has it exactly, 0.75 to a max of 1.5mm. Do not exceed the 1.5mm max, I would not go past 1.25 myself. remember too that with the pulley set at TDC you line up the wheel with the sensor next to the 5th tooth after the gap. It doesnt matter where the wheel is in relation to the pulley but at TDC on the pulley the sensor has to be next to the 5th tooth.

cheers
Barri

[Tony H]

I have only had the wheel made-I did not mount the VR sensor yet. I was going to wait until the engine is in the car to see what hoses/belts/etc are in the way. I don't see that being too much of a challenge. I am still months/years from completing my project due to other demands on my time so any updates from others would be good.

[GGR]

I was looking at it again today and I noted that the damper on that 5.0 has a series of holes on the hedge. These must be for the original sensor to pick up some sort of signal. Then I thought why cant I use that original sensor to feed a signal to Magasquirt? I already asked that question time ago to a knowledgeable person who told me that this one wire sensor can't work with Megasquirt. But wouldn't there be a way to attach some kind of electronic set up behind that sensor wire so that Megasquirt understands it? I don't know how that 5.0 ignition system works as I am used to earlier systems. But I would surely prefer to use that original sensor setup if possible, as it is already in place... Any thought?

[Tony H]

There is a Megasquirt forum dedicated specifically to ignition.

http://www.megamanual.com/ms2/

I don't know if the link will work but you should be able to find it.

[cth350]

Gael, If the holes are small inverted cones, they are the spots drilled out to balance it. -CTH