Electronic Trigger Wheel placement

[SeriesVtime]

I'm seriously looking into moving away from the stock ignition system and to using an electronic trigger wheel but wanted to get some thoughts on where best to place the trigger wheel. There are two possibilities: in front of the harmonic balancer or behind it.

My preference is behind it, but my motor is out at the machine shop so I can't measure and assess whether there's adequate room to bolt a 1/4" thick plate with 36 teeth to the back of it and still clear the timing chain cover, and anything else that might be back there. I recall there's a standoff that comes through the cover and requires a nut to secure it, but I don't recall whether that's within the circumference of the pull, or not.

Thoughts? Thanks!

 

[Bill Blue]

Do you really need a 1/4" plate? The Duratec trigger wheel is about 1/16". Maybe 3/32" but definitely less than an eighth.

Bill

 

[RootesRacer]

whatever you do dont mount the trigger wheel onto the suspended portion of the harmonic balance itself.

It vibrates when spinning and causes the sensor gap to vary with the rotation of the crank.


I take it you are thinking of going ford EDIS?

 

[SeriesVtime]

Bill, you're right, it's not that thick - it may be 1/16th, not 1/4". As I'd mentioned earlier, I've just started looking into this option.

RR, I understand that the TW needs to be attached to the center portion of the HB, and it should have at least 1/16" distance from the outer portion of the HB.

Having addressed those issues, do either of you know whether there's space to mount this on the back or front of the balancer? As I'd mentioned, all of the pieces of my motor are out being machined.

Thanks RR, Bill for your time.

 

[RootesRacer]

On the rootes engine there is no room at the rear of the HB, and putting it up front makes road debris a serious liability since anything that gets between the sensor and the trigger wheel will knock the sensor to Valhalla.

You didnt answer my question, and my advice might be to trigger off the dizzy.

 

[SeriesVtime]

Sorry dude (RR), yup, what I'm considering is for the MegaJolt using the ford edis.

Your thoughts regarding road debris is a serious consideration.

I'd originally hoped there was space behind, but have also come to the realization that in front is really the only option.

Thanks all for your input.

Jeff

 

[puff4]

Re road debris, couldn't you easily make and mount a small shield on the timing cover to prevent stuff from hitting your trigger?

 

[SeriesVtime]

I would think so - there are a bunch of machines out there using this device with a trigger wheel. My plan though is to not remove the standard distributor in the event that something goes wacko. Then all I'd need to do is swap some hi-voltage cables, add the coil +12 and back to the races I'd go.

 

[twospeed]

If you using a crank trigger you still need the stock dist. You still have to have away to bring the spark to the plugs. You just need the cap and rotor.

 

[RootesRacer]

If you using a crank trigger you still need the stock dist. You still have to have away to bring the spark to the plugs. You just need the cap and rotor.

Not when you are using waste spark or individual coils per cyl.

Dizzy not needed for anything but perhaps as a cam phase signal if you wanted to run sequential coil on plug ignition.

 

[robertf]

interested to see your solution. I'm thinking alpine #2 is going to get efi on a "stock" 1725.

rootesracer - what are your thoughts on placing both the cam and crank sensor in a modified distributor? How important is the resolution?

 

[RootesRacer]

interested to see your solution. I'm thinking alpine #2 is going to get efi on a "stock" 1725.

rootesracer - what are your thoughts on placing both the cam and crank sensor in a modified distributor? How important is the resolution?

On one product I designed, the cam and crank sensor is the same, that is one sensor which allows normal crank decode along with cam phase synchronization for true sequential injection and ignition.

The slop you get on the cam/distributor cannot be ignored, it will reduce accuracy as compared to a true crank triggered arrangement, though it will still perform better that then best distributor and carburetors in existence.

Bill Blue is currently installing one of my ECUs into an alpine, though it is not a rootes engine and already has the crank wheel internally.
His will use waste spark but sequential injection.

 

[robertf]

good point on the timing slop. you figure a new timing chain and distributor gear is enough to combat this to within a degree or 2?

 

[RootesRacer]

good point on the timing slop. you figure a new timing chain and distributor gear is enough to combat this to within a degree or 2?

The slop is not random unless its really worn out, the chain is not the culprit, the cam/dizzy drive interface is, as is the chain rubbing block.
The slops effect is to retard timing on acceleration and advance on decel.

Speaking strictly for my own system, the software employs a digital phase locked loop on the trigger information which reduces somewhat the jitter errors you get as the result of mechanical hysteresis and backlash.

Crank triggering definitely is best, and quite often a pulley mounted target wheel is OK, though I have seen road debris like belts and tire pieces really screw things up.

I am facing this same issue on my own setup, my prior injection incarnation was off the dizzy with one trigger per ignition event and used the dizzy for ignition distribution.
My new setup obviously is going to be somewhat more advanced setup than the old one, if I go off the cam/dizzy it will use a 48-2 target wheel.
I am also considering finding a way to do it off the rear of the crank on the flywheel. Porsche has done this with a 60-2 wheel for some time.

 

[socorob]

Sorry dude (RR), yup, what I'm considering is for the MegaJolt using the ford edis.

Your thoughts regarding road debris is a serious consideration.

I'd originally hoped there was space behind, but have also come to the realization that in front is really the only option.

Thanks all for your input.

Jeff

Did you ever get around to doing this? and if so, how did it work out?