Lean-Burn Dual P/U Distributors

Lean-Burn Dual P/U Distributors - Any Good?

AJ/FormS said
Mtrhed
I had thoughts like yours one time. I think the MS efi system can use that dizzy

Sure can. Honestly that's a good starter setup. I did a coil near plug/logic coil conversion with my MS3 EFI. really, really nice

KitCarlson said
About three years ago I purchased a NOS (new old stock) lean burn distributor for evaluation. I captured the waveforms using a dual channel scope. The results were not good. My understanding differs from RapidRobert, not to say I am correct.

The Mopar pickup coils are biased by a magnets, the reluctor tooth draws away magnetic flux resulting in change of voltage at pickup leads. The addition of the second sightly corrupts the primary pickup signal. Also note the deviation in signal magnitude for adjacent cycles.
View attachment 1714851947

My measurements suggest the second sensor leads the primary by about 40 degrees. I have a good guess why, but just a guess so keeping my mouth shut.

In general variable reluctance sensors are not used as position sensors. This is because the amplitude varies with angular velocity (RPM), this alters the reference position because it is sensed by an analog comparator of fixed amplitude.

Below are waveforms of a VR trigger circuit. The bottom digital signal going from high to low is the trigger point. With proper design of reluctor and trigger the second pickup could have been eliminated. Mopar was often economic driven in a way, disturbing rational development of electronics.
View attachment 1714851948
To make greater improvements the A Hall sensor could have been incorporated, and it was a few years later on the 2.2L mopar 4. I have heard of a Hall tab wheel for the V8, but have not confirmed that. I have seen the 1/2 circle used as phase sensor, use in conjunction with flexplate tone wheel and Hall sensor. That choice would let you do coil on plug, eliminating the rotor.

Right, they're typically speed sensors, HOWEVER, you can do position by having a known missing tooth when you have enough teeth. The MS3 System I installed uses basically a 1990's-2000's Ford 36-1 setup that uses a VR sensor. The angle between tooth #1 (first after the tooth) is known in the computer AND you have a second sensor (the dodge magnum distributor is a hall switch), which allows you to have positions for sequential injection. You wouldn't have to have a hall switch.

The VR sensors are far more reliable, and you really don't have to worry about adding extra parts like pull-up resistors.

You also can't use this as a dual sync distributor. If you want EFI, you can do spark timing with a distributor like this (I suggest an 80's electronic spark control single pickup over this one), or you do a 36-1 or 60-2 wheel with the 90's 3.9/5.2/5.9 distributor as a cam sensor.