I'm writing this to help out guys that are doing COP and sequential injector conversions with AEM ECU's.

On AEM ECU's, the injectors can be wired to the injector outputs in any order you want as the firing order is fully configurable in software. Same thing goes for ignition although in a wastedspark setup, the coils that are 360 crank degrees apart must be wired to the same output.

The way it works is that the ECU just keeps count of the crank teeth and fires the inj/coil when it gets to the output's tooth value set in the inj/ign phasing options. The option "Ignition Sync" and Injector Phase" options adjust overall base timing in relation to TDC #1 firing. These are also in "teeth" with smaller values meaning more advance and larger values meaning more retard,

For example, the 1UZ has 24 crank teeth so 24 teeth is one cycle. (for later model engines with the 36-2 crank wheel, the EMS only counts the 12 teeth that are even spaced so you still have 24 per cycle) For V8 sequential, the fuel and ign teeth should be space out every 24/8=3 teeth.

So for sequential injectors wired per cyl number you'd have:

fuel tooth 1 = 0 teeth
fuel tooth 2 = 21 teeth
fuel tooth 3 = 9 teeth
fuel tooth 4 = 6 teeth
fuel tooth 5 = 15 teeth
fuel tooth 6 = 12 teeth
fuel tooth 7 = 18 teeth
fuel tooth 8 = 3 teeth

So, if you follow the count, you get 1-8-4-3-6-7-2.

If you wired the injectors in the firing order inj 1 to cyl 1, inj 2 to cyl 8, etc... than you fuel teeth will be 0,3,6,9,12,15,18,21

On the eariler 1UZ's that are batch injection off four injector outputs (like my '91 SC400) you must change the option "Fuel Teeth" from 24 to 12 to tell the ECU to restart the injector count every 12 crank teeth or one engine rotation. You'd then use 0,3,6 & 9 for your fuel teeth and setup your firing order. (you also must check box the "Eng Cycle = 1 Rev" so the ECU know that 12 teeth is one engine rotation and not one engine cycle. (RPM would other wise read 1/2 actual)

Ignition is the same way with one little trick to it. On the first gen ECU's there are physically only 5 coil outputs but there are 10 outputs in the software. Coils 6-10 are aliases of coils 1-5 so when the tooth count for Coil 1 or Coil 6 comes up it will fire the coil 1 output, 2 & 7 will fire coil 2 output, etc... It is done this way so that the ECU can trim timing for each cylinder independantly even if they are on the same coil output. On the 2nd gen boxes have 8 coil outputs but still have the aliasing but have them as Coil 1 & Coil 1B which makes things a bit easier. Alternatively, you could change the option "Spark Teeth" from 24 to 12 and leave coils 6-10 off. and then set your firing order but you lose the independent cyl ignition trims.

For 1UZ's that still have the stock distributors (like my '91 SC400) You'll need to change "Spark Teeth" from 24 to 6 so that it will fire one output every 180 crank degrees. Using coils 1 & 2, you tooth values would be 0 & 3.

Now, if you were running a 6 cylinider, like a 2JZ, the spacing on the teeth values will change because you still have 24 teeth per cycle but 6 cylinders, so 24/6=4 and your values would be 0,4,8,12,16,20.

The big thing to remember is that what is important is the tooth value spacing. On a 1UZ you could use values of 1.5,4.5,7.5,10.5,13.5,16.5,19.5,22.5 and it would still work as they are still spaced out 3 teeth apart. (90 degrees)

Ok, so it kinda complicated to setup, so why in the F did AEM do it that way? it's because not all engines are even fire - Dodge Viper, some Buick V6's, Harley V-Twin, etc... So, to accommodate an odd fire engine, you can just change the tooth numbers so they are not evenly spaced. Some ECU's cannot even run odd fire engines and most of the other ones that do, need special software to be setup for specific engine. This way they don't have to write any special software and a user that understands how it works can just set it up on their own.

For example, let's look at the Viper. It's basically two 5 cylinders joined at the hip with an alternating 54/90 degree firing interval. (that's why they sound so funny)

So, in crank degrees, it fires as follows:

0
54
144 (+90)
198 (+54)
252 (+90)
342 (+54)
432 (+90)
486 (+54)
576 (+90)
630 (+54)
- plus another 90 degrees gets you back to 720.

So, let's do some math here. The Viper has 10 teeth per cycle which is 72 crank degrees per one tooth. Therefore out injector tooth numbers would be as follows:

0/72 is undefined but we'll say 0
54/72 = 0.75
144/72 = 2
2.75
4
4.75
6
6.75
8
8.75

You'd still have to assign these values to the correct injector output but I think you get the idea. You can check the AEM startup calibration for the Viper and see these same values.