...sorta kinda.
It actually works BY swinging wildly from rich to lean at the DMEs command.
There are a few different parts to your catalyst, that take care of different pollutants and work in different ways. Simply put, one part works better with a higher concentration of oxygen in the exhaust, and the other works better with less oxygen in the exhaust.
Given that stoitch is NOT the optimum mixture for a few different scenarios, the DME also needs to know an approximation of what the mixture is when it is adding fuel for say a cold start. It also needs to tend to the catalyst.
How it does this is by varying the mixture a small amount multiple times a second. If you had a graphing scope, the oxygen sensors output would resemble a sine wave. That way both parts of the cat are happy and able to work efficiently by alternating between rich and lean, and it allows the computer to plot where it's corrections have placed it by allowing it to time the peak to peak intervals between the sine waves. Longer interval above stoich, richer mixture.
Enter the gauge in question, and this goes for a digital multi meter without a graphing feature too. A momentary display is crap for reading any damn thing unless you sit there with a stop watch, have incredible reaction time,
and plot a graph to notice the peak to peak differences. The peaks themselves do not change, its the timing between them, and before passing the stoitch line that changes. A digital multimeter with an averaging function and decent response is useful for this however.
Now, say you for some reason think your running rich (using lots of gas, we'll go with that one) When the DME is adjusting the mixture based on the o2 sensor values, it stores correction factors called fuel trim in its RAM. These values are immensely helpful in diagnosis, as it takes all of the computers interpret of the numbers, and shows what the computer decided to do based on that information. That value is based on a complete picture of the DMEs operation parameters, including the times when it decides to resort to hard coded tables (open loop) for engine operation, for say a cold start (when the o2 data is inaccurate) or for WOT (where the o2 data is inaccurate, too slow response time, and the DME already knows what it wants to do for maximum output) Interestingly, in a way, the o2 does still affect open loop, as the fuel trim values learned from the sensor are still applied to the final calculation.
Oh, and "tuning" your AFM is stupid. Don't make me explain that one too. Put it back to where Bosch had it, they guy that put it there knew a bit more than you and me. Work on finding your REAL problem.
It actually works BY swinging wildly from rich to lean at the DMEs command.
There are a few different parts to your catalyst, that take care of different pollutants and work in different ways. Simply put, one part works better with a higher concentration of oxygen in the exhaust, and the other works better with less oxygen in the exhaust.
Given that stoitch is NOT the optimum mixture for a few different scenarios, the DME also needs to know an approximation of what the mixture is when it is adding fuel for say a cold start. It also needs to tend to the catalyst.
How it does this is by varying the mixture a small amount multiple times a second. If you had a graphing scope, the oxygen sensors output would resemble a sine wave. That way both parts of the cat are happy and able to work efficiently by alternating between rich and lean, and it allows the computer to plot where it's corrections have placed it by allowing it to time the peak to peak intervals between the sine waves. Longer interval above stoich, richer mixture.
Enter the gauge in question, and this goes for a digital multi meter without a graphing feature too. A momentary display is crap for reading any damn thing unless you sit there with a stop watch, have incredible reaction time,
and plot a graph to notice the peak to peak differences. The peaks themselves do not change, its the timing between them, and before passing the stoitch line that changes. A digital multimeter with an averaging function and decent response is useful for this however.
Now, say you for some reason think your running rich (using lots of gas, we'll go with that one) When the DME is adjusting the mixture based on the o2 sensor values, it stores correction factors called fuel trim in its RAM. These values are immensely helpful in diagnosis, as it takes all of the computers interpret of the numbers, and shows what the computer decided to do based on that information. That value is based on a complete picture of the DMEs operation parameters, including the times when it decides to resort to hard coded tables (open loop) for engine operation, for say a cold start (when the o2 data is inaccurate) or for WOT (where the o2 data is inaccurate, too slow response time, and the DME already knows what it wants to do for maximum output) Interestingly, in a way, the o2 does still affect open loop, as the fuel trim values learned from the sensor are still applied to the final calculation.
Oh, and "tuning" your AFM is stupid. Don't make me explain that one too. Put it back to where Bosch had it, they guy that put it there knew a bit more than you and me. Work on finding your REAL problem.
Comment