If air/fuel ratio were strictly mechanical at WOT, what's the point of having a mass air flow sensor? Clearly you must accept that the computer is metering fuel based on what the MAF is reporting. The ACT (air charge temperature) as well as ECT (engine coolant temperature) sensor is also active at WOT. Do you think the computer would care what temp the air or coolant was unless it was compensating for it?
You're right, the computer has no concept of peak horsepower or what the fuel pressure is.
EVER. It doesn't need to. The only thing it is capable of doing is controlling the length of time for which an injector stays open. It can also control air to the degree that the idle air bypass can, but that's unimportant for this discussion.
Let's say that the MAF reports a certain voltage based on the amount air moving through it. The computer looks up a value based on that voltage and the values reported by other sensors to determine how long to open the injectors at a given RPM. These values are predetermined by a test engine that is in perfect condition. The computer then checks the oxygen content of the exhaust to see how much oxygen is present to decide whether it's too lean or to rich a mixture. The computer then starts making corrections with the injector pulse duration until it achieves the desired O2 content in the exhaust. If it has to make this correction over time, the computer stores this correction in an adjustment table in KAM (Keep alive memory). What I just described is Closed loop control. It learns about the engine and works to maintain the best possible fuel economy and emissions output.
At WOT, or open loop control, the O2 sensor is no longer used to fine tune the air/fuel ratio. Instead, the computer simply looks up values in its WOT lookup table and adjusts them based on the adjustment tables that were updated during close loop control. The computer still measures air and dispenses fuel accordingly, but it won't do it as precisely as it does during closed loop control. The computer will compenstate for any injector throughput you may have added to, or removed from, the fuel injectors by changing the fuel pressure.
Saying it's been proven doesn't make it so any more than just proclaiming that you're right. I'm open to the fact that I may be wrong, but I know that my experience and what I have read support each other.
This is one of those things that being wrong could be fatal to your engine. That's why I'll jump on it every chance I get. If the computer has adapted to 24# injectors and then all of a sudden the fuel pressure was dropped to only make them put out fuel at the same rate as 19#ers and the driver then just started running it at WOT before it built new adjustment tables, it's possible that it would run seriously lean and cause serious damage. I'm not clear on how much the computer can do to prevent this, either. Maybe it does a lot or maybe it will do nothing.
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351W 89 Mustang GT Convertible