AEM Trigger disc settings.

BlackBirdSR71
Posts: 44
Joined: Tue Jul 14, 2015 3:41 am

AEM Trigger disc settings.

Postby BlackBirdSR71 » Mon May 20, 2019 5:37 pm

Well, with the help of Matt and others I have my old E11 running quite nicely on my 1978 Datsun 280Z. Learning how to dial in Raw Injection Timing, Dead Time compensations and a few other things.

One problem still remains. I am using a 1983 Nissan Turbo Optical distributor. I can run this with the Stock 54mm L28 Trigger disc. This has 6 equal space slots on the inner disc, so I just run that as a " Standard No Home " . With a single coil distributor and Multi Point injection. Engine and timing are perfect.

However, I want to run Full Sequential injection with just a Single coil distributor for now. Later on down the road I may switch to Direct Fire COP. But at this point, Single Coil with Full sequential fuel will, Suffice.

I have an AEM 30-8762 54 mm trigger disc to use for Home Trigger. This has 24 equal spaced outer slots and one inner slot for Home signal. All mounted in Nissan distributor.

For the life of me I can't get this Trigger Disc to work properly. Engine will run, but with a lot of missing, backfiring and timing jumping all over the place. I have tried the following.

1: Tried Trigger settings configured as " Multi Tooth 24 + 1, Full Sync. This is what Toyota and Mazda run and I figured that logically, this should be the setup. Well, it doesn't seem to work. I have tried both Rising and Falling edge, Pull-up On and Off. I know the correct settings are Falling edge ( Hall sensor ) and Pull-up on ( Nissan CAS needs 12 volt pull up ). Changes were only for testing and only made things worse.

2: Tried Locked timing to 10 BTDC .Trigger angle was tried at 60 BTDC with Tooth offset to 10. Massive Miss firing and back firing. Tried evry offset between 0 and 11. Never ran correctly.

3. Tried locked Timing to 15 BTDC. Trigger Angle to 70 BTDC and Tooth offset of 9. Same misfiring and timing jumping all over the place.

4: Tried Multi Tooth General with Number of Teeth set to 24. Same problems as with " Multi Tooth 24 +1 Full Sync ". MTG I used same Trigger angles and Tooth Offset as above.

I'm wondering if I should be selecting Multi Tooth General with Number of Teeth set to 12? Some Ecu's seem to vary on this. Guess it depends on how the decoder works.

I have included a picture of the AEM disc. Rotation is CCW. TDC slot is maked and you can see that the Home slot is 14 teeth before TDC slot. I initially calculated 60 degrees BTDC at 4 teeth before TDC. 14 - 4 = 10 Tooth offset.

Butttt.... I'm thinking that may be wrong. Since crank turns 720 degrees for 360 degrees of Distributor rotation... I'm thinking that 60 BTDC would be 2 teeth. Tooth offset 12 and Number of Teeth = 12??? Does this make sense. Can someone help me with this please/ TIA.


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HaltechMatthew
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Re: AEM Trigger disc settings.

Postby HaltechMatthew » Tue May 21, 2019 11:50 am

It is a 24 and 1. On these old ECU (and new ones too) it is the number of teeth seen for the full engine cycle (2x crank rotations for a 4-stroke).
Make sure Trigger is connected to the 24x and Home connected to the 1x signals.

Phase check your distributor. Engine on 20BTDC Cyl1. Rotor button should point dead centre to the post for Cyl1. Lock down distributor and use Trigger Angle and Tooth Offet to make it run at the right timing.

BlackBirdSR71
Posts: 44
Joined: Tue Jul 14, 2015 3:41 am

Re: AEM Trigger disc settings.

Postby BlackBirdSR71 » Tue May 21, 2019 12:29 pm

HaltechMatthew wrote:It is a 24 and 1. On these old ECU (and new ones too) it is the number of teeth seen for the full engine cycle (2x crank rotations for a 4-stroke).
Make sure Trigger is connected to the 24x and Home connected to the 1x signals.

Phase check your distributor. Engine on 20BTDC Cyl1. Rotor button should point dead centre to the post for Cyl1. Lock down distributor and use Trigger Angle and Tooth Offet to make it run at the right timing.


Rotor Phasing is done. Quite familiar with that procedure. Have triple checked 24X and Home connections with Trigger Diagnostics . They are correct and I'm getting good solid readings. Just can't get the Timing stable. Can't seem to get the combination of Trigger Angle and Tooth Offset to work at ANY setting.

Have also tried Several different CAS modules, thinking they might be defective. They seem to be fine.

I don't have a proper VG31 wheel. I may try and get one to see if system will run using the Nissan 360 slot outer track.

BlackBirdSR71
Posts: 44
Joined: Tue Jul 14, 2015 3:41 am

Re: AEM Trigger disc settings.

Postby BlackBirdSR71 » Tue May 21, 2019 12:36 pm

I wonder if 60 Trigger angle and Tooth Offset of 12 or 13 might work. I do not think I tried a combo above 10 Tooth Offset. 65 Trigger angle and 12 Tooth Offset might work??? I sure hope so.


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