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I wonder if relocating the sensor tubes from after the catalytic converter to before, will fool the electronics by reporting back a pressure reading?
For those that don't know, the OPF fitted cars have a pressure measuring sensor in each exhaust. The pressure sampling tube is placed after (downstream) of the primary CAT, but before the 2ndary CAT / OPF canister. So it effectively measures exhaust pressure just prior to the OPF /CAT2 system. I guess when it sees a high reading threshold, it triggers an active regeneration. But at all times it needs to see some kind of reading as a test. That's why a total OPF delete triggers CEL/LIMP.
My thinking about how to fool it is in three forms. And by the way, I'm looking at replacing the OPF canister mid pipe to earlier style 2nd CAT type, not a full delete. Some of the techniques below could work for full delete too.
1.) move the sensor to pre primary CAT. As long as the pressure isn't high enough normally in this area (between turbo outlet and CAT elements) to trigger active regen, we should be fine.
2.) Fit an elbow pointing upstream on the sensor tubes. Normally the sensor is Tee'd into the exhaust at 90 degrees. This measures static pressure only. If we added an elbow facing the exhaust gas stream, we get a dynamic pressure (static + gas velocity). So with OPF removed, the pressure reading will increase with revs (as it will with the OPF in situ). Different size elbow bores can be used to modify the dynamic part.
3.) fit some type of electronic gain chip to the sensor. Like a JB+. There will be some pressure in the exhaust even with 2ndary CATs only, we just need to amplify that signal into the right range. The sensor itself is a 0-5v analogue unit, much like the boost pressure sensors, hence the reference to JB+
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