How does the ARC 2 "talk" to the ARM 1. I have both along with a MAF.
Since there is no O2 sensor what is the feedback source for the ARC 2 so it can adjust the mixture? When I drive my dithering gets less and less until it remains on the lean side. Then my temperature gauge starts rising. I have taken to shutting off the car (at first out of FEAR) which seems to reset something...the dithering resumes but then deteriorates again. Bad ARC2?Electrical problem?Problem with MAF? Also I notice that when I turn on a "peripheral" like my rear defogger or my PIAA running lights the ARM1 dithers much less.
Any feedback greatly appreciated.

Scott
'89 951 w/mods(obviously!)
'99 996C4 stock

 

The ARM1 and ARC2 do not talk to each other.

Your ARM1 gives you an A/F ratio from the stock narrow band O2 sensor, this set up is not very accurate but will give you an idea.

The ARC2 will adjust the fuel, if you are running lean then an ARC2 adjustment is needed.

You really need to get to a dyno with a wideband O2 sensor hookup, that way you can dial in a correct ratio.

Do you have an instruction sheet for the ARC2 ? if so study up and head to the dyno.

Check all grounds, make sure they are clean and tight.

 

Go to the 944 turbo forum and search under settings for the ARC2. This will give you a general idea. After that, please do what David recommends. Good luck.

 

I have the same set up. Is there a wideband O2 sensor that works with the arm1. While I'm at it. With the Arm1 and ARC2, does the O2 sensor still send readings to the computer?

 

Question 1, no
Question 2, yes