Buldawg76
Well-Known Member
- Joined
- Jan 11, 2022
- Threads
- 3
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- 757
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- Location
- Alabama,USA
- First Name
- Mike
- Vehicle(s)
- 2020 Mustang Ecoboost, Rapid Red Premium
Correct, the ECU is adjusting the AFR based on the upstream O2 reading from spent exhaust gases but the issue I see is that the O2 reading is not capable of accounting for any backpressure/reversion that is occurring in the combustion chamber or turbo housing before the exhaust turbine wheel that could lead to momentary a rich or lean condition. Since the fuel is direct injected into the cylinder and there is no mass air flow sensor on our ecos the fuel ratio being injected is based on the signals from the TPS desired/actual positions, RPM, MAP and O2, inferred EMAP readings to determine the AFR the cylinders are operating in at each combustion event.You make some good points! Especially concerning air fuel mixture. Exhaust back pressure will affect your AFR, as well as your fuel trims. Your ECU may interpret received data to indicate rich conditions, when you're actually running lean. Our ECUs will make the nessary corrections, but it takes time to react, and when I'm running at wide open thottle... the last thing I'm thinking about is what that ECU needs!
Most motors are blown up and very few blow up!
There is some lag between the actual and desired AFR possible if the Backpressure ratio gets over 1.5 to 1 for an extended amount of time. The ECU does react in milliseconds worth of time but at 5/6K rpm that could still be too late. I would not want to be close to 2.0 to 1 if at all possible.
Thats why a bigger turbo gives some more lead way in controlling the AFR and backpressure since its flows the exhaust more freely and reduces backpressure while increasing power at lower boost levels. Installing an actual EMAP gauge instead of relying on an inferred value to log the EMAP to MAP ratio is the best means to be able to tune and adjust accordingly IMO.
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