[abenson91]

I’ve had my M4C since December and my build plans are coming together and I’m ready to start buying parts. I’ve settled on a single midpipe, stock muffler, and I already have the SST valve controller installed. I want to also get high flow catted downpipes that won’t produce a CEL but mostly so the car doesn’t smell like absolute ass at a red light or in my garage in the mornings. My question is, anyone who has high flow cats, did you get a tune or is it even necessary? Will the engine run lean with extra flow but no tune?

[forcefed]

The engine keeps an eye on the a/f ratio and tunes itself basically, if you don't want a cel make sure to get a high quality downpipe, most will throw a code even with a cat.

[81bear]

Install the mid pipe first and see how you like it. The DP’s are more geared toward power improvement when tuned.

Any Catted DP should reduce the smell but only gesi catted DP will be cell free as they are 400 CAT vs 200 CAT DP. They also cost substantially more.

I have ER 200 CAT DP paired with an MPE rear section and I love it. I’m also tuned so I don’t have a cell. I did experiment with adjusting the exhaust flaps to be open full time, in sports plus, and didn’t like it. I noticed it started to inject a degree of drone which I don’t want, no matter how minor the drone is.

[abenson91]

Originally Posted by 81bear

Install the mid pipe first and see how you like it. The DP’s are more geared toward power improvement when tuned.

Any Catted DP should reduce the smell but only gesi catted DP will be cell free as they are 400 CAT vs 200 CAT DP. They also cost substantially more.

I have ER 200 CAT DP paired with an MPE rear section and I love it. I’m also tuned so I don’t have a cell. I did experiment with adjusting the exhaust flaps to be open full time, in sports plus, and didn’t like it. I noticed it started to inject a degree of drone which I don’t want, no matter how minor the drone is.

What tune do you have? Something plug and play or custom?

[81bear]

Originally Posted by abenson91

What tune do you have? Something plug and play or custom?

I’ve had a Jb4 and now have the BM3 stage 2 custom rom flash tune. Will probably get a custom flex fuel tune later on just want to experiment with the Ots flex fuel map for now.

[mike@x-ph.com]

The car won't run lean due to the downpipes.

If your car is flash-tuned with bootmod3 and the check engine light is not a concern, get the MAD or CTS downpipes.

If your car is stock or tuned with a piggyback like the Jb4, you need the active autowerke downpipes to avoid the check engine light.

The smell, in either case, is almost unnoticeable.