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M635 and CA Smog cert

Posted: Fri Aug 10, 2018 12:19 am
by philm635
Has anyone been able to pass the California Smog check with a stock federalized M635?
Just curious if it is possible before I throw a bunch of $ at it.
Thanks!
Phil

Re: M635 and CA Smog cert

Posted: Sat Aug 18, 2018 1:13 am
by philm635
I'm told to get an 079 ecu. I assume that would be one from a USA version M6??? Anyone have an extra or recommend a source?
Thx
Phil

Re: M635 and CA Smog cert

Posted: Sat Aug 18, 2018 1:59 pm
by motroman
Does "Federalized" cats were installed with corresponding software update to the ECU?

Re: M635 and CA Smog cert

Posted: Tue Aug 21, 2018 12:22 am
by philm635
The gray market Federalized M88/3 engines have a cat and O2 sensor installed. The ECU is not reprogrammed but there is an external "Johnson box" circuit installed that uses the O2 sensor input to try and keep the fuel mix at stochiometric level. I found it works poorly forcing the engine to respond to off idle transition with flat spots and lugs and surges at higher speeds. So now I'm trying to find an 079 ecu that has the O2 feedback loop built in.

Re: M635 and CA Smog cert

Posted: Sun Sep 16, 2018 6:32 am
by derrith
I’ve gotten several m88s through CA smog in the Bay Area using a resistor in line on the coolant temperature sensor. It richens up the mixture on the 055 enough that the NOx levels drop enough to pass on the rollers. Remove after smog, as vehicle will not run great. I have used the 560 ohm. Also works great on 061 10:1 m30s

“BMW Technical Service Bulletin # 13 07 86 Install an external resistor in the wire for the temperature sensor that feeds the Motronics (should be the one with the light grey connector) Resistor type is 270 ohm, 1/2 watt, "Gold Band" metal film resistor for Motronics Control Units with a Bosch code date of 342 or higher (production date after 9/83) and for Motronics 341 and lower (9/81-9/83 production dates), it is a 560 ohm, 1/2 watt "Gold Band" metal film resistor .”

Re: M635 and CA Smog cert

Posted: Fri Sep 21, 2018 2:41 pm
by smtguy
Derrith -
Will your temporary resistor mod work for my U.S. version '83 633csi that is having trouble passing smog? It's apparently too lean at speed when I had a pre-test done.. I know little about getting a car to pass smog other than changing the plugs, 02 sensor, oil, and cleaning the TB and ICV.
Thanks for the help.