Emissions monitors to ready for track

[F80manz]

Say that a friend theoretically wanted to have a catless down pipe on their car for the track but they didn't want to use the CEL fix in bm3 or mhd. But they want to get rid of the cel and have emissions monitors say ready, again for the track so they know if anything is wrong. Has anyone in a similar situation found a work around? Again, for the track. Off-road use

[Jbonly21]

Not possible, your only options are O2 spacers or tune.

[M3SQRD]

You may/may not (doesn’t work for everyone) get the cel to turn off with either one of these: (1) post-O2 extenders (straight and/or 90 deg, some people stack two of them) or (2) a mini cat for each post-O2 sensor that mounts between the O2 sensor and exhaust. BM3 has stated leaving either of these devices attached long term will throw off fuel trims.

The f8x stock cats flow well enough that you can run a stage 2 tune with them. So why do you want to remove them? IMO, removing stock cats may increase the loudness of a stock exhaust but the sound is horrible with significant rasp and drone.

[ByeFelicia]

Originally Posted by M3SQRD

You may/may not (doesn’t work for everyone) get the cel to turn off with either one of these: (1) post-O2 extenders (straight and/or 90 deg, some people stack two of them) or (2) a mini cat for each post-O2 sensor that mounts between the O2 sensor and exhaust. BM3 has stated leaving either of these devices attached long term will throw off fuel trims.

The f8x stock cats flow well enough that you can run a stage 2 tune with them.

Has this been documented somewhere? Your opinion? and actually run stock cats with stage 2?

[theweebabySeamus]

Originally Posted by ByeFelicia

Has this been documented somewhere? Your opinion? and actually run stock cats with stage 2?

Yeah. Plenty do, including myself. There's a few threads about it.

[ByeFelicia]

Originally Posted by theweebabySeamus

Yeah. Plenty do, including myself. There's a few threads about it.

Good to know, I'll do it after smog

[theweebabySeamus]

You should, it's a nice difference. Not a big difference in peak numbers, but makes the car feel more....big block-ey?

[M3SQRD]

Originally Posted by ByeFelicia

Has this been documented somewhere? Your opinion? and actually run stock cats with stage 2?

Not my opinion. Talk to most of tuners including BM3. BW also developed their f8x GT4-based ecu tune using stock cats.

[ByeFelicia]

Originally Posted by theweebabySeamus

You should, it's a nice difference. Not a big difference in peak numbers, but makes the car feel more....big block-ey?

Did you mess with your boost reduction like this guy?

https://f80.bimmerpost.com/forums/sh...2&postcount=18

Considering trying as this Swede seems to have run this method for 3 years +

Full thread:
https://f80.bimmerpost.com/forums/sh...e+2+stock+cats

[theweebabySeamus]

Originally Posted by ByeFelicia

Did you mess with your boost reduction like this guy?

https://f80.bimmerpost.com/forums/sh...2&postcount=18

Considering trying as this Swede seems to have run this method for 3 years +

Full thread:
https://f80.bimmerpost.com/forums/sh...e+2+stock+cats

I did. To be fair, I'm only a couple weeks on stage 2, but after a few days I tried 1st gear at 30% and 2-6 at 20%. It's an interesting effect, the boost still feels like it comes on earlier than stage 1 but pulls better up top. It's a mind game, sure, but that's fine by me for now.

[F80manz]

Originally Posted by ByeFelicia

Has this been documented somewhere? Your opinion? and actually run stock cats with stage 2?

Difference between bm3 stage 1 and 2 is like 1-2psi. Not much of a change. Down pipe is recommended just cause the burbles are more aggressive.

[F80manz]

Originally Posted by M3SQRD

You may/may not (doesn’t work for everyone) get the cel to turn off with either one of these: (1) post-O2 extenders (straight and/or 90 deg, some people stack two of them) or (2) a mini cat for each post-O2 sensor that mounts between the O2 sensor and exhaust. BM3 has stated leaving either of these devices attached long term will throw off fuel trims.

The f8x stock cats flow well enough that you can run a stage 2 tune with them. So why do you want to remove them? IMO, removing stock cats may increase the loudness of a stock exhaust but the sound is horrible with significant rasp and drone.

Wanted to push out a little more sound but you do make a good point about rasp. Down pipes would need to be resonated.