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Understanding AFR: Step 2 - Target AFR MAP

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Step 2 - Target AFR MAP

02.26

00:00 Now that we have dealt with the operating specifics of the car, we need to develop a starting point for our AFR target.
00:07 In the last section we looked at the AFR target MAP in some detail and discussed some reasonable starting values to use in this table.
00:15 Now that we have looked at the operating specifics of the particular engine, we can decide if it is necessary to modify these starting values.
00:24 Its easy to do this before you jump on the dyno where you can do it with a clear head and with the required amount of attention devoted to the job.
00:34 Often once you are running the engine on the dyno, there is so much going on that it can be hard to remember where you wanted the AFR set.
00:43 Now we will discuss what to do with the AFR Target MAP.
00:48 On some ECUs, particularly those that use a VE based tuning model, this target MAP is critical to the operation of the fuel model as it actually changes the pulsewidth the ECU delivers to the injectors.
01:02 With these ECUs, we need to actually enter the target AFR map into the ECU.
01:08 Failing to do this can compromise how effective the ECU is and give poor results.
01:15 With ECUs that have no built in AFR target map, it is useful to just draw up a Target table manually, even if its just written on a piece of paper or an excel spread sheet.
01:27 When you are on the dyno tuning, there is a lot of information to take in and its handy to have a quick reference so you don’t forget what AFR numbers you are aiming for in a particular area.
01:38 I suggest sticking this to the windscreen or somewhere you can glance at it in an instant.
01:44 If you are using an ECU which has a target AFR table, you will usually be able to display your target in real time as you track around the load and RPM zones.
01:55 Better still if you have an onboard wideband connected to the ECU you will be able to see the target and measured AFR at the same time, making it very easy to decide what correction to apply to get to your target.
02:09 Remember that this target map doesn’t have to be the final AFR that your engine will run.