Stock 964 chip versus upgrades and SMOGGING

[fadler1]

I am in California and one of the unfortunate things about that is our SMOGGING of cars. I think we have more strict regulations than the 1990 Clean Air Act and so, since I am buying a 1991 964 Cabriolet from the midwest and the description includes a statement of a EPROM DME upgrade (which one unknown for now until the car rolls in), what is going to happen when I try to smog the car to register it? Oh, it also has the conical air cleaner but the old one is included with the car. Information greatly appreciated on your experiences.

[Noah930]

Well, as you likely know being a California resident, you have two hurdles to overcome. The tech will do a visual test, to make sure the engine compartment looks like how it was when it left Stuttgart. So if that conical air cleaner doesn't have a CARB sticker on it, your car will fail. (Though, if the tech doesn't notice it/ignores it, you're good to go).

Then the car will have to pass the sniffer test. Not knowing what chip you have, not possible to predict if the car will pass or fail. But there's a chance you'll have to put back in a stock chip/tune.

Is the exhaust stock? Still have your cat?

[fadler1]

Thank you very much for the help. That makes me change it back to the original "air box" which is coming with it from the seller. I have to see on the PET diagram what parts may be missing and find them. I was waffling if I needed to change it back but since I need to use CRC Air Flow Sensor cleaner anyway on it, Ill just move that to the "old" air box and mount it.
On the sniffer and the Dyno test, I have read some sites saying that the new chips are "cleaner" than the stock so I guess if the old chip comes with the car (I doubt it), then I will put back the old one but if it is not with it, I may roll the dice since some chip makers claim the "cleaner".
On exhaust, I think it is original but again I guess will see that when it gets here and certainly hope the catalytic converter is there since the CarFax says it passed in Illinois and Indiana multiple times but I know how that goes sometimes.
Thanks again and any other advice appreciated.

[pdf17]

I’m in the same boat, and wonderful state of CA, as you. I haven’t yet read into it - CA has an upcoming ECU check @emissions test starting Monday, July 19th:

If you live in California and run an aftermarket tune on your car, you might want to think about flashing your ECU back to stock before heading out for your biennial Smog Check. Starting July 19, 2021, testing stations will begin to check whether cars are running OEM or California Air Resources Board (CARB)-approved tunes. If your car isn't, it'll fail the test.

[ischmitz]

First, the 964 DME is NOT OBD-II compliant and thus there is no way for a smog testing station to check what "tune" you are running unless they take the DME apart, remove the EPROM and read it out and compare it to a stock version. Not saying that this is impossible but I doubt that they would that route.

Also you cannot "flash" a new tune to these DME either. Changing mapping requires taking the old EPROM out and putting a new EPROM with modified content into the socket inside the DME.

Keep in mind that most if not all performance chips modify timing and then some change the fuel mapping a bit to suppress the onset of knocking. And these changes are done predominantly to the WOT maps and sometimes to the part-throttle maps as well. So this will not affect idle and low-load running. Depending on the type of sniffer test you have to pass (rolling dyno, simple sniffer test, etc.) chances are there isn't going to be a noticeable difference between the stock chip and a decent performance chip as long as the performance chip still uses the O2 sensor for closed-loop operation during part-throttle and you CAT is working fine.