Understanding AFR: Step 3 - Tune the Engine
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Step 3 - Tune the Engine
01.50
| 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. |
| 01:44 | This will make sure we are using the best AFR for our specific engine. |
