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Understanding AFR: Step 3 - Tune The Engine

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Step 3 - Tune The Engine


00:00 Now that we have a target AFR to aim for, we can tune the fuel and ignition tables in the ECU.
00:07 The process I use follows what we learnt in the Practical Road Tuning and Practical Dyno Tuning courses and if you want to learn more I would recommend considering one of those courses.
00:19 To keep the tuning process simple, I prefer to start with a conservative or retarded ignition map and focus first on optimising the fuel table.
00:29 There is a myth that changing the ignition advance will effect the air fuel ratio so I want to deal with that now.
00:36 If we look at whats happening inside the engine, the air /fuel ratio is determined by the amount of fuel and air trapped inside the cylinder.
00:44 This ratio is fixed at the point when the intake valve closes as no further fuel or air can be introduced.
00:52 The ignition event may not occur for another 100-120 degrees of crankshaft rotation, hence understandably there is no way that the ignition timing can effect the air fuel ratio.
01:06 Once the fuel table has been set to meet our target, we can then optimise the ignition table.
01:12 Its important when you are optimising the ignition table to take note if the engine is knock limited.
01:18 By this I mean if you run into detonation before you reach MBT ignition timing.
01:24 Use of high quality knock detection equipment is key here.
01:29 By the end of this step we should have an engine that is tuned properly and driveable, and this is where many tuners will stop.
01:38 We want to go one step further though and see how the engine responds to changes in AFR.