[Dawgsfootball42]

Just had the FI Valvetronic Catback Exhaust installed on my new 2023 BMW M8 GC. Definitely sounds better from stock but not ~$8k-$9k louder. Downshifts are louder and tone is more aggressive but still not quite meeting expectations. The downshifts in anything higher than 3rd gear are silent (3rd to 2nd and 2nd to 1st are crazy loud). Upshifts aren’t much louder than stock. Also, the car is pretty quiet in slow speeds but once you give it gas in Sport Plus w/ valve open, it sounds wonderful. Still quieter than what I was used to with my prior car (C63 AMG S with RennTech Exhaust Valve Module). Any recommendations on how to maximize volume with this current set up? I think a challenge is this car is so well insulated, it’s tough to tell how loud it actually is when driving. I’m sure it’s much louder out of the car. My prior AMG was louder inside the car but I think that’s due to lesser quality insulation as a main factor.

Aesthetically, the FI exhaust w/ the carbon tips is A+. Below are pictures. I have a ton of videos but am unable to attach from my phone due to size. Happy to post them as well if someone lets me know how to.

Overall I’m happy with the FI purchase but need a bit more sound!

In addition to the FI catback exhaust, should I do 1) ER secondary catless downpipes or 2) ER secondary catless downpipes + catted primary downpipes (not looking to do catless primaries due to CEL), or 3) any other suggestions?

[ed4]

I have a similar setup as yours, plus in addition, ER secondary downpipes. Not only do I highly recommend adding these, the increased aggressive sound can be managed by closing the exhaust valves in any throttle mode - if there are any reservations about the sound being too much.

With the car in full-on mode, plus secondary downpipes, the sound seemly increases by a factor of about +0.7 (~ +70%).

Two other benefits I personally like are that, for one, in Comfort mode the car backfires very, very softly & very subtle. The other is that I like the increased, soft turbo spool noise in Sports Plus mode.

I hope you'll this helpful.

[Dawgsfootball42]

Thanks, very helpful. I want it as loud as possible 24/7 - will probably never shut the valves lol.

I had the ER secondary DP installed last week in addition to the catback Fi and holy s**t! You weren’t lying - game changer. Sounds extremely aggressive and mean now. A few cars have almost wrecked from how loud the down and upshifts are haha. It legit scares people.

Still pretty quiet in idle about 20-30 seconds after starting it. I don’t think you can fix that though. Just the way BMW is.

I’m probably done with performance/sound mods for now. Only other things I’m considering are intakes and a JB4. Are either worth it? Intakes aren’t cheap - do they make a significant enough impact on sound that justifies the couple Gs you’re spending? Also, will the intakes put your factory warranty at risk? And I would have already done a JB4 but am nervous about blowing warranty as well - especially since I still have over 3 years left on it. I drive aggressively 99% of the time and am always in Sport Plus/pushing the car every chance I get. I’m scared my style of driving plus increased power from the tune may be a little harsh on the car. Am I overthinking it?

[Powerwhee]

I had a JB4 on my 435i and am thinking of putting one on the M8. I never had an issue with the JB4 and drove that car decently aggressive, as well as filled E30. I think the JB4 may actually be safer than flash tunes in that it allows the stock safety parameters to remain in place.

As for warranty, I had numerous things fixed under warranty without an issue. But ultimately if your engine blows I think you’ll be SOL. I would think the chances of that happening are almost zero as long as you keep the JB4 on Map 5, the autotune map that is always changing the parameters to ensure the car is not running dangerously.

I’ve been researching tune options, and the JB4 just seems like the best bang for the buck.

[Justao]

If you wanna go super loud, you have to go fully catless… but you need a tune because of CEL… try catless secondaries first and see if it’s enough for your liking, secondaries are not monitored hence no CEL… I went fully catless on my M8 a while ago but it was too loud ( especially cold start) and I couldn’t live with the smell hence I put back stock primaries and just left secondaries catless… very satisfied with the outcome