Ah, but you can get them close. I tuned a stock port 13B on an MS3X with sequential injection that last year that would idle all day long at around 14:0 once the optimum injector timing was figured out. That's probably close enough not to be too much of a detriment to cat life.

true. its been my experience that the cats actually work better a little rich, ie the emissions numbers are lower when its just a tad rich vs a tad lean.

i have extend port and idle all day at 15.4 :1.. ( lambda 1 for LPG )
and cruise around at 0.95 or better lambda

it is all in how well it stays atomised .. dry gas fuels do not re-condense

would suggest in the petrol rotary it is mostly about getting the angle of injection timing right for you injector positions and airflows


luckily,, i also have a december 85 FC.... and as such it scopes below the law as for the absolute cut off date for manufacture requiring a cat.. which is in oz,, 1st of feb 86
( in those states stipulating build and not compliance dating )

but if i did , i would be fairly confident my lambda feedback system and tune is pretty close to what the cat desires
my biggest worry is having seen 1000 c under load on my EGT , and this would suggest i need to push mine further back

and if doing a test ( im240 or 5 gas ) it would pay to have pre-warmed the engine

btw,, in 2005 during testing with LPG
mine passed the equivalent 5 gas test as would have been expected from a euro 2 standard
- well beyond what a new FC is expected to do

in California we rate the emissions differently, and we're also given a visual check, as we are mandated to use OEM or specially approved parts only.

in an IM240 county (they are not all), we need to be under .6% CO, about 90 HC's, in parts per million, and about 450 nox's.

somehow these are not absolute numbers, as it varies by weight and something.

our system is basically a lesson in how not to govern. we have a 5 member panel that is only concerned with cleaning the air, and they will poison the water to do it....