Just thought I'd share something I did trial and error on.

As you all know, putting an aftermarket DP on our cars WILL trigger a CEL. Most likely the P0420 code.
So after I installed the Akrapovic DP (100 cell cat) and ran the car for a little bit, the CEL came on (P0420). No surprise. I know a tune will get rid of the CEL, but I am holding off for now. So I was trying to figure out ways to get rid of the CEL without a tune. I researched using spacers and mini-cat spacers. 90% of the people found that spacers did NOT work for them.
But I wanted to see for myself if spacers worked or not. So I installed one spacer with the original O2 sensor. The spacer I used was a spark plug non-fouler that I drilled out. Anyways, I ran the car for a bit and it gave me O2 heater codes (P0136 and P0141), but no P0420 code. The spacer worked to get rid of the P0420 code, but now i had to deal with heater codes. So I searched around for a bit and found that i might have broken the O2 sensor. Then I bought a new O2 (OEM NTK). I installed it with one spacer. I cleared the codes with my reader after I installed it.
And then BAM, the heater codes came up again after about 100KM. I did NOT clear the codes with my reader. I ran the car more (about 500KM) and then the CEL cleared itself on the dash. I used my reader, and voila, no codes. I believe the ECU sensed that I completed one drive cycle without encountering any cat related codes and cleared the codes itself (no more permanent codes).
Then I noticed something else. The CEL would come back on whenever I engaged sport mode only when the engine was not up to operating temps. But when not in sport mode, the CEL would not light up. After the engine is at normal operating temps (170F+), I engage sport mode, the CEL does not come on. EDIT: Nvm. The light comes when not in sport mode, but only when the engine I cold and I am boost happy.

Remember, YMMV.

 

Hey GEMSTER,

I'm on my way down the path of the aftermarket downpipe soon. Couple questions:

1. In your post (which was a while ago), you indicate you weren't ready for a tune, but your sig indicates the Manic tune. Did you tune after your post? Did the tune affect your CEL?

2. More of a comment than Q. Your O2 heater code - did you get codes and a readiness indicator on your scan tool? I had to replace my pre-cat O2 sensor a while back. My scan tool (Innova) indicated an O2 heater problem (indicator not code), but more advanced tools at Mini dealer and my local shop didn't have the same readiness indicator which implied that my scan tool was wrong. BTW O2 sensors (and most emissions parts) have longer warranty than rest of your car - Mini doesn't advertise this though.

3. Tunes - do they actually prevent CEL codes from firing with aftermarket DP, or do they just hide it from the dash? I have a VR tune which supposedly opens the O2 sensor range preventing a CEL, but I don't understand how it works well enough to pull the chain and purchase a DP for fear of a CEL and failed emissions test (CA car). If the tune really prevents the CEL, then a O2 spacer should not be required right?

Thanks!

 

A few months after i posted that, the CEL came back on 24/7. I was getting tired of changing/swapper spacers and o2 sensors, so i just gave up. It was only recently that i uploaded the Manic tune. The CEL was gone afterwards.

My scan tool only showed the code. I did not bother checking readiness since there is no emissions testing here.

Im not entirely sure what the tunes do to the P04020 code. I have heard that it readjusts the parameters so the computer senses the extra flow as normal. Each tune is different, so better to check with your tuner to see what actually happens.
And yes, most tunes removes the CEL. No spacer will be needed.