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Originally Posted by rmay635703
Not to mention most tools don't do lean.
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Obviously I wasn't clear above. The reason that the tools don't 'do' lean is that, aside from situations like coast down with injectors closed, a modern gasoline vehicle is running stoich, or richer.
Stoich is measured, with excellent precision in normal combustion, by the O2 sensors. So the ECU typically adds fuel relative to that measured point.
Quote:
Originally Posted by rmay635703
No offense but if it was easy...
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Well, "easy" for me is a matter of experience, not access to all the goodies I have.
You could do what I describe above with readily available performance aftermarket stuff now. For example, I happen to have an aftermarket wideband setup sitting on one end of my bench now. The UEGO sensor used would screw right into the same bung your pre-cat O2 sensor is screwed into now. This particular unit has two analog outputs built in, both programmable. By default, one is a wideband output (0-5V DC for .5 to 1.5 lambda) and the other is a simulated narrow band (1V output with 450 mV at lambda 1.0), but you can reprogram either one to whatever you want.
There are some gotchas, like having to put a load resistor on the heater circuit for the removed O2 sensor so you don't throw a check engine light or drop open loop. And you generally have to either mimic the signal with an offset from a small discrete circuit (or just program the 2nd analog output) so that the ECU sees a shift on the post cat sensor in the right direction (HC's being removed). But aside from maybe having to double things up (I can't remember if the 3800 V6 used independant banks or not), pretty straight forward stuff. Since the cat will be rendered ineffictive you can use a bypass (another readily available performance market piece) and pick up a little economy that way (less back pressure in the VE/RPM curve).
You generally would want to periodically reprogram the analog outputs slightly leaner in small steps because a big jump messes up your fuel trims. But the limit is generally not your ability to shift the lambda measurement, but the limits of the fuel delivery system. As you get leaner and leaner you typically hit a point where fuel is not evenly distributed and the engine runs rough. Some engines will actually get to theoretical best economy, some won't. Sometimes swapping around or changing injectors will help.
Quote:
Originally Posted by rmay635703
NoX may not be as much of a bad guy as the US government believes.
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I recently did instrumentation for an ag study, specifically regarding exhaust and possible positive impacts on soil for cultivation, but I'm not really going to go there. Even at technical conferences specifically in this area discussions tend to drift from what the science tells us (which is all I'm interested in) into people's political ideology.
Quote:
Originally Posted by rmay635703
Heck many Honda cars ran lean including the gen 1 insight and had EXCELLENT emissions. I don't doubt their technique would have been far superior to our pig rich and CAT approach.
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The problem is in scaling it up for a larger engine and higher powers. For power generated, modern engines are typically more efficient and cleaner, but we're dragging around much heavier vehicles loaded down with built in Barca Lounges and home entertainment systems.
There are two good SAE papers on the system your talking about, including a good one from Horii on the problems of scale encountered. They are fairly technical, but worth slogging through.
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