[Topfun99]

Went to set my timing today and noticed the timing was varying retarding 4-5 degrees as I revved the engine up. I'm using a basic Craftsman induction timing light, no retard knob.

My car has 2 MSD boxes (digital 7 and 6AL) on it and I can trigger it with either the MSD crank trigger (reluctor pickup) or the Accel Dual Sync Distributor (Hall effect). The variation seems approximately the same with any variation of pickup or MSD box. The MSD 6AL seems to have a little less variation (3-4 degrees) then the MSD Digital 7 (4-5 degrees) but basically both retard the timing from idle to 5000+ rpm where it seems to stop moving.

The trigger goes to my Haltech ECU which then sends a trigger signal to the MSD boxes and I can LOCK the timing in the ECU just for setting the timing like I'm trying to do.

Polarity is correct on the MSD crank trigger pickup, I check it twice. The only thing I haven't tried is reversing the wiring on the crank trigger but I don't expect that will do any good since using the Hall effect from the distributor as a trigger is doing the same thing.

The only thing I can think of is the MSD boxes are doing this.

Anyone else have this experience?

Thanks.

 

[Glenn.Payne]

Adjust the inductive delay in the Haltech to fix this.

 

[Topfun99]

Adjust the inductive delay in the Haltech to fix this.

I'm real good with the Haltech but I've never seen any "inductive delay" in the software. Could be you are simply using different terminology than Haltech uses.

Could you explain where in the software this adjustment is located?

 

[Glenn.Payne]

I know nothing about Haltech but for sure FAST, Holley, and Megasquirt all have this adjustment and when using them to fire an external ignition box this setting affects the timing wander with RPM.

From FAST instructions-

This parameter is used to compensate for the varying delays that occur with different types of crank sensors. These varying delays often cause ignition-timing error that will increase as engine RPM increases.

For inductive pickup ignition systems, leave this parameter set to 40 uS (microseconds). For other types of ignition systems, this value can be altered to reduce or eliminate ignition-timing error as a function of RPM. This error will show up as either unwanted timing advance as RPM increases or unwanted timing retard as RPM increases.

Increasing the value in this parameter will reduce unwanted timing retard.

Decreasing the value in this parameter will reduce unwanted timing advance.