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Old 04-17-2009, 08:52 AM   #119 (permalink)
NIZMOZ
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Actually one section of your post you are wrong.

Nissan ECU's do adjust for the type of driving you do. If you drove like a granny for a long time, then wanted to use the power out of your car for a road course or something your car would not feel like it has the power as it once did. I have seen this on many Nissans. Once you drive it aggressive after a while, it learns your driving again and makes the adjustments.

Quote:
Originally Posted by Jesse View Post
Cats are not oxygen storage devices. They convert carbon monoxide ( CO) Hydrocarbons (HC) and oxides of nitrogen (NOx), into more friendly Carbon Dioxide and water. The precious metals used in the manufacture of cats (platinum, rhodium and palladium) will clean themselves if the input gasses are in the correct ratios. that is why it is critical that a vehicles fuel management system and air injection system are working properly (going from slightly rich to slightly lean) and injecting air at the right places at the right time (if air equiped).

Both the 'dual bed' and 'monolith' cats need differing amounts of oxygen to perform the gas conversions. The platinum or palladium metals require high levels of O2 to convert CO (carbon monoxide) and HC (raw fuel 'hydrocarbons') into water (H2O) and carbon dioxide (CO2). The rhodium element however operates well in the absence of oxygen to convert NOx into NO and O2. By comparison, the single bed catalyst only works on CO and HC.

In no way does a computer adjust to accommodate different catalysts (hence cel). The computer is programmed to 'feed' the cat to make it as efficient as possible and watch its degradation over time setting a code once it gets below a certian efficiency.

Also, closed loop is not 'lean burn, steady cruse, or idling. Closed loop simply means the oxygen sensors are heated enough to control fuel. (some cars coolant temp needs to be up also).

all engines are different and degrade so a 'fuel trim' is incorporated. I believe the limits to set a cel are +/-13percent.....I think....been a while since I reviewed this basic stuff.

Your computer does NOT adjust to your driving habits it just learns what the MOTOR needs at different conditions. Your computer is not going to re-tune itself to a race setting just because you race it. Now it may feel better over time if your computer is still learning to adjust to something like intake and exhaust. if these items increase air flow, your computer will learn over time to adjust with more fuel....making more power. You guys should drive your vehicle a couple weeks before you dyno your new parts!!!

By the way...your basically saying your cats flow good, but are crap when it comes to doing the job a cat was meant to do....CONVERT!

and your quote "During driving situations where the engine sees load it will completely ignore the secondary O2 sensor and go off of it's pre-programs maps. " ----what are you talking about? when your driving the engine is always under load unless you take your foot off going downhill. Your computer uses pre-loaded maps when under HARD acceleration. Also, your computer wants to see you driving a certian way before it will even run a catalyst monitor. For example, it wont check the cat if you go over 65mph or if your throttle position sensor is all over the place, if there is a problem with another sensor or not under the right load.....ect.

Your race car runs pre-programmed cause you have tuned tuned tuned with a dyno and you know what you want the settings at. In the real world for everyday driving in a car that changes over time...this wont work well. you would have to have a computer that adapts to the changing engine or keep re-tuning it every so many years.

Sorry to rant and rave...I think I got a contact high from my roomate. And he wont shut up about his Vegas trip!
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