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My LX9 swap failed emissions miserably due to high NOX reading.
HC and CO were minimal, well under the limits.
NOX on the other hand was something like 50% OVER the limit. The car does have a high flow cat and I don't remember if it was a 2 or 3 way (3 way being the kind that reduces nox). But, the old dohc motor passed just fine with this same cat. I don't have an EGR either so that ain't helping.
I'll be installing a known 3 way cat. But, after a bit of research I found that some people (for some reason a lot of Miata guys) dial back their spark timing to reduce NOX and pass the e-test. From what I read a lot of the Miata cars that were doing this had NOX levels similarly high like mine. Some guys took out as much as 10* off their spark advance and others about 6* Making no other changes, that was enough to dramatically lower NOX emissions and allow for a emissions test pass.
Now, since my LX9 is installed in an OBD I car, I have an external crank trigger which is adjustable (see where I am going yet?). I can advance or retard by 6* (either direction). Since the injectors are batch fired anyway (not SFI) is that an acceptable way to temporarily retard spark timing? I know that reprogramming the chip is the correct way to manipulate spark but I don't have the know how.
The logic behind this is that excess NOX emissions are caused by high combustion temps. Retarding the spark timing allows the 'fire' event to occur later in the pistons stroke, leading to lower pressure and less heat and less NOX produced.
Would a lower temp thermostat help? I'm running the stock 195* now but I do have a 180* lying around.
HC and CO were minimal, well under the limits.
NOX on the other hand was something like 50% OVER the limit. The car does have a high flow cat and I don't remember if it was a 2 or 3 way (3 way being the kind that reduces nox). But, the old dohc motor passed just fine with this same cat. I don't have an EGR either so that ain't helping.
I'll be installing a known 3 way cat. But, after a bit of research I found that some people (for some reason a lot of Miata guys) dial back their spark timing to reduce NOX and pass the e-test. From what I read a lot of the Miata cars that were doing this had NOX levels similarly high like mine. Some guys took out as much as 10* off their spark advance and others about 6* Making no other changes, that was enough to dramatically lower NOX emissions and allow for a emissions test pass.
Now, since my LX9 is installed in an OBD I car, I have an external crank trigger which is adjustable (see where I am going yet?). I can advance or retard by 6* (either direction). Since the injectors are batch fired anyway (not SFI) is that an acceptable way to temporarily retard spark timing? I know that reprogramming the chip is the correct way to manipulate spark but I don't have the know how.
The logic behind this is that excess NOX emissions are caused by high combustion temps. Retarding the spark timing allows the 'fire' event to occur later in the pistons stroke, leading to lower pressure and less heat and less NOX produced.
Would a lower temp thermostat help? I'm running the stock 195* now but I do have a 180* lying around.
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