AEM EMS Guidebook/Injector Phase

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This howto is sort of a combination of two very helpful posts, both by SA regarding finding where an engine is generally happy.

(injector phasing) (optimum AFR)

Ideally this test should be run on a dyno under a constant load but you can still get pretty good results without one.

Steps (all performed at closed throttle):

  1. Disable Idle FB
  2. Use the idle tables to force the idle speed up to ~1000 RPM
  3. Log parameters Engine Speed, Engine Load, Fuel Inj #01 Open, and optionally AFR at the fastest rate.
  4. Open injector phasing, set the 3 RPM breakpoints nearest 1000 RPM to 0 degrees in the advance table (typically 500, 1000, and 1500) for all loads
  5. View the parameter Fuel Inj #01 Open so you see roughly how it corresponds to Injector Phase
  6. Set the injector phase below what your basemap indicates by a few teeth
  7. Start logging data
  8. Increase the Injector Phase teeth step by step (I started with .25 increments) until you're well above the basemap's phase setting (I went from 5 to 9 teeth on my 24 tooth, base was 7). Remember to hit <enter> after specifying the next increment.
  9. While you change the phase, the engine RPM should first start to increase. It will hit a peak then it will start to fall off again. It may be very slight and almost imperceptible, but the logs should make it obvious.
  10. Stop logging.

Look at the data. Now there's a lot of assumptions that have to made here...there's nothing wrong with the engine, the ignition system is functioning correctly, etc., etc.

In general, with no influence from the IAC system, your engine RPM should peak and your manifold pressure (Engine Load) should drop at the best Injector Phase. In order to see the fine detail you'll probably have to set your logging view to a smaller scale -- like 900 min / 1200 max for RPM, and -11psi min / -9psi max for engine load for example. The two should peak and dip (respectively) near the same place. Note the Fuel Inj #01 Open setting at this spot and set the injector phase to achieve this same number.

You can repeat this process with a smaller tooth window for finer detail. I did from 8-9 teeth at .1 increments and then 8.8 to 9.2 in .05 increments.

This will give you a baseline injector phase for 1000RPM at 0 degrees and give you room in both directions for injector advance and retard, although you'll probably just be retarding only for 500 rpm and advancing from here up the RPM range.

Next do the same process at ~2000 RPM and instead of adjusting the Injector Phase teeth, adjust the injector phase table values for 2000 RPM (along with the nearest RPM breakpoints -- usually 1500 and 2500). You'll also need to change your logging parameters to watch Inj Advance rather than Fuel Inj #01 Open. You don't need to test more than 0-100 degrees of advance for the 2000RPM mark.

Once these two points are adequate you can extrapolate up and down from the 1000 and 2000 RPM breakpoints to get a good advance map according to what the engine has told you it wants. Keep in mind, phasing makes little difference in high RPMs because of increased duty cycle. But I mostly did this to help with low RPM throttle response. It's additional side effects include easier starting and smoother idle.

I did cheat a little on additionally sloping advance upward as engine load increases (to compensate for longer injector pulsewidth) by using some math and a spreadsheet because I don't have an easy way of loading the engine at those test speeds standing still (besides turning on my A/C) tongue Most of that stuff can be found in the Injector Phasing sticky at the top of this forum.