Cat tuning

[myjadezxt]

is there built in tuning for a catylitic converter? I think the fuel should occolate at idle and cruise?

[boost junkie]

With a cat converter an air/fuel ratio of 14.7:1 is expected during closed loop operation...

[myjadezxt]

correct.. but when you are in closed loop, in order to be efficient, you want to have between 16-17 afr. If I remember correct, this throws way too much carbon at the cat, which is why factory computers occilate during cruise, in order to change the mixture in order to save carbon build up on the cat.

Does the megasquirt accomodate this occilation?

[efahl]

correct.. but when you are in closed loop, in order to be efficient, you want to have between 16-17 afr.

Actually 16:1 is good for efficiency irrespective of whether you are running closed loop or not.

If I remember correct, this throws way too much carbon at the cat, which is why factory computers occilate during cruise, in order to change the mixture in order to save carbon build up on the cat.

When lean you have excess O2 and NOxs, when you are rich then you have excess HCs. You aren't keeping the cat clean by changing mixture back and forth about stoich, you are making it work properly.

Does the megasquirt accomodate this occilation?

Yes, if you are using the standard bang-bang narrow band algorithm, and have the switch point set to stoich. If you are using the more sophisticated PID algorithms in MS-II with a wide band, then it will not be unstable at stoich, so it is not particularly suitable for use with most catalytic converters as the controller damps out the oscillations if properly tuned.

Eric

[Tjabo]

What exactly happens to the converter if you run a lean cruise, anything? GM must be doing some of that with their recent LS-1s and such, wouldn't you think?