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Understanding AFR: Step 1 - Operation Specifics

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Step 1 - Operation Specifics

01.59

00:00 Our first step in the process is to consider the Operation Specifics of the engine.
00:05 Since the desired AFR we will want to run has a lot to do with the engine, the fuel and the way the engine is to be used, we really want to start by getting all of these parameters on paper and understood so we know exactly what we are dealing with and don’t overlook anything.
00:22 The very first details we need to know is pretty obviously the type of fuel we will be tuning on.
00:27 This will effect our stoichiometric AFR as well as potentially the target lambda we need to use to ensure a safe and reliable tune.
00:37 Its also important to have a good understanding of how the engine will be used.
00:42 Remember that when we are selecting a suitable air fuel ratio, we are firstly aiming to achieve maximum power by mixing with all of the available air with fuel beyond that though we are also using additional fuel to control combustion temperature.
00:58 The combustion temperature will depend on how much power the engine produces as well as how hard the engine can be driven.
01:06 What I mean by this is that we can safely tune a road car engine a little leaner than we would for a competition circuit car as it won’t see the extended high load running that we can expect to see on a racetrack.
01:19 An exception here might be for those parts of the world where you have access to motorways or autobahns with no speed limit.
01:27 At the extreme of engine usage is land speed racing where the engine can be at full load for minutes on end.
01:35 In this situation, controlling combustion temperature takes precedence over engine power, and we will end up settling on a very rich AFR.