Discussion and questions related to the course Understand AFR
I Live in Finland and we have now winter here, 0 to even -30 celcius, I was thinking that should i target warm up enrichment so that AFR stays close to same than on warm engine? If we have say -10 ECT for start and should I target same 14,7 for cruise or little richer?
Hi, what's the engine, ECU, and vehicle? Is it direct injection or portion injection? What mods?
Car is stock 1998 Subaru Impreza GT 2.0 turbo, no mods yet. Ecu Link G4+ WRX 3-4, great ECU so far :)
In the first few seconds of cold start you may need to go richer, such as 12.0:1 , depending on spark timing. Then you can gradually lean it out as it warms up. You will have to test to see how lean it can tolerate. Spark timing plays a role too.
Arghx7, how does spark timing play a role on cold start? I'm in Indiana and no stranger to cold weather so this is a topic I'm really interested in.
I understand that a good portion of the injected fuel is not in a burnable state, but even if we can inject a quantity of fuel to give the ideal "vapor to air mass" why and how does that change ignition requirement? Is that much compression and fuel lost past rings and seals before we even have a chance to ignite it?
Another factor I wonder about is port injector timing during cranking. Does that play a large enough role to warrant a look at and if so, is there a method to test changes that's affordable outside of R&D test chambers?
Any help from the knowledge base here?
If you look at the way OEs deal with cold start, you'll often see that they advance the timing as part of their cold start strategy (Note that this is after any initial ignition retard that's used for cat light off). It's not something I've personally ever found the need to employ during my own tuning in the standalone world but I know some tuners find it beneficial.