What is lean? Lean is an AFR in the mid 14's or higher. For emissions and fuel consumption, I suspect this is where the Z is when it leaves the factory. The cruising speed AFR's will be lean in the 1500-4000 rpm range. For tuning, Afr's will need to be brought down in the fuel maps down to the mid 13's which is not lean especially for cruising speed. The engine will run cooler but be a bit poorer on gas. There is always a trade-off when seeking more performance! Getting into the 11's is too rich and in the 12's it's starting to get rich but these low AFR's are for WOT operation only which is a margin of safety that you won't run lean. I also haven't read anywhere that getting into lower AFR's requires open loop operation. If the O2 sensors are not being changed out then I guess they are wide band and will work fine for all usable AFR's in conjunction with a sufficient flow of fuel through the injectors. MAF sensors measure the mass of air (from this and air temperature, volume of air can be calculated within the ecu to adjust AFR) but it's the feedback from the O2 sensors into the ecu to correct the amount of fuel and air required for the target AFR. I play with the map schedules on my Harley because I have the tuning software to do it. Chemistry is chemistry when it comes to burning fuel and the bike follows the same principles as a car. So when I read about adding a cai and cbe, the car will run fine at the target AFR unless the injectors can't flow the required fuel. I don't see anyone changing to high flow injectors by just changing to cai and cbe and hfc's unless making 400hp or better from FI. All the tuner is doing is adjusting timing and increasing fuel where needed using feedback from the dyno. This can be done by seat of the pants or a canned map (provided you have the tuning software/hardware) which should get you close to what the tuner will do on the dyno provided the tuner knows what he is doing. Just like dynos, all tuners are not the same.
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Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP
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