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Old 10-27-2011, 08:10 PM   #1652
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Quote:
Originally Posted by Gruesome View Post

Sorry if this has been answered before, I read quite a few pages (but not all 110 of them...), and followed a few links, but didn't find the answer:

Is this fooling of the air temperature sensor needed because oxygen sensors are too slow to keep the optimal (stoichiometric) fuel/air ratio during acceleration?
Good question, I'm surprised it hasn't been asked before.

First, the purpose of the O2 sensor is to allow the ECU to control the oxygen levels in the exhaust, in order to supply the catalyst. The catalyst creates a chemical reaction between the oxygen and hydrocarbons in the exhaust, and will not function without the correct oxygen supply. The primary purpose of the O2 sensor is control of Exhaust Gas Oxygen (EGO), not the control of combustion mixture. Read that sentence again.

The motor has different operational ranges, or modes let's say. Acceleration is one of those modes. The ECU controls the exhaust oxygen differently based on which mode the motor is operating in.

Motor acceleration is always preceded by another control mode called Transient Throttle Enrichment, sometimes known as Throttle Tip-in. These two modes, Throttle Tip-in followed by Acceleration, create a difficult control problem. Let me explain.

The ECU must serve many masters. The drivability master, the power master, and most importantly the efficiency and emissions masters. These masters, or operational goals if you will, are at cross purposes with one and other. You know, it's one of those situations where you can't meet all the objectives at the same time.

Mostly how it plays out is Drivability is first to get sacrificed. Then Power is offered up, followed by Efficiency. Emissions is always spared because at the end of the day we all must obey the same God. The Emissions Regulators.

I don't think Emissions Regulations are a bad thing, I support them. I think we need more and stricter regulations. Regulations force the development of better motor control equipment and algorithms. There's a lot of spirited debate as to which ECU control algorithm is best, but history has shown one thing. As emissions regulations get tighter, ECUs get better at motor management, while sparing Drivability. (Speaking of poor drivability, do you remember the first few generations of emissions carburetors? And the first couple of rounds of motorcycle fuel injection?)

Wait, where was I going with this? Oh yea, Acceleration and Throttle Tip-in. Those two events create the most amount of exhaust emissions. And are difficult to control in a way that feels smooth and makes good power.

This is what the IICE Air and upcoming IICE Cool are for. Smoothness and power.



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