[medphysdave]

I added the catless DPs this weekend. I used a set of quickjacks and did everything from below the car. This was difficult. The O2 sensor on the short downpipe is in a difficult to reach spot. If there is any chance the sensor is going to be tough to remove, I'd suggest using the posted method where you go through to top. Remove the charge pipes, and unplug the sensors. Honestly, if I did this again I think I would use that method. Working above the engine is much easier and forgiving than working below. Plenty of YouTube videos on removing the brace and chargepipes. I probably spent over an hour trying to get to, and loosen, that single sensor from below the car. I was quoted $600 to replace the pipes at a quality local shop. That was twice what I was willing to spend. After doing the work I can't say that it would be crazy to pay for it. Includes install, the gaskets, and guarantee. It took me 8hrs not knowing what the hell I was doing. An hour was spent just collecting tools, which required crawling out from under the car, fetching, and crawling back under. I didn't drop the midpipe, but I think it may have been quicker to drop it as well. All in all there are a couple of things like going in through the top of the car to avoid removing the O2 sensors while on the car and dropping the exhaust that seems like lots of extra effort, but probably save time and make the job less stressful overall. Knowing exactly what tools I need and following the regular instructions I could probably do it in 4hrs.

Remember to use copper anti seize. The silver stuff has a much lower temp rating. My DP to turbo gaskets still looked good, but I replaced them anyway. It looked like I could have reused my DP to midpipe gaskets. They still looked brand new. I replaced those too.

Sound. Uh oh, what did I do? I wanted it louder and yep, it's louder. Normal operation is louder unless really low load on the engine. Depending on speed and gear you can have it near silent if you want. There is now a pronounced drone around 2800 rpm that was not there with stock DPs. I have to drive through my neighborhood in 2nd gear now. A slight change in driving style avoids it. No drone present at highway speeds. Under load it sounds amazing. Valves open is just bonkers loud. Super fun, but not neighborhood friendly. Overall when getting on the throttle it sounds really good. The only noise I don't like is if you quickly get out of throttle it can make a weird resonance sound. Tough to describe. Happens infrequently, but it's there. Not all sounds with the catless dp are pleasant.

Exhaust smell doesn't bother me. Occasionally notice it. I drove with windows down this morning and got a whiff only once. Windows up there is nothing.

Burbles. A lot more burbles. I'm not a burble fan and I quite like the CSs minimal burbles. Well, the new dps don't mute any of those. Lots of rumbling. Not bad, but sometimes I feel like it doesn't go with my gray hair.

[OG Shark]

I try to stick with catted dps until the power level and/or usage dictates it. Like you said there is a lot of good with catless but for me the bad outweighs it unless it is a track car. I find catted is the sweet spot except for the cost bump.

I would recommend investing in a set of these - I sport them when I'm out in my straight piped M4...

[mike@x-ph.com]

Thank you for your review

The installation process certainly shouldn't take up to 8 hours. Given the appropriate tools and installation experience, it should only take a few hours.

This is, of course, assuming you received a good downpipe.

[medphysdave]

Originally Posted by mike@x-ph.com

Thank you for your review

The installation process certainly shouldn't take up to 8 hours. Given the appropriate tools and installation experience, it should only take a few hours.

This is, of course, assuming you received a good downpipe.

Akra downpipe. It boils down to my lack of experience. I think I could cut the time in half if I were doing it again. I wouldn't do everything from under the car next time. I'd unclip the upper O2 sensors from above. Pull everything out, swap o2s off car and put back in.

Oh, that little effing pin that holds the lower part of the long dp to the bracket. (With the wire washers) that SOB took me 1.5hrs to get on. I have a technique now though.

Another suggestion is to do yourself a favor and get a creeper.

This was very handy, buti should have followed it completely.

https://f80.bimmerpost.com/forums/sh....php?t=1096302

[mike@x-ph.com]

Originally Posted by medphysdave

Akra downpipe. It boils down to my lack of experience. I think I could cut the time in half if I were doing it again. I wouldn't do everything from under the car next time. I'd unclip the upper O2 sensors from above. Pull everything out, swap o2s off car and put back in.

Oh, that little effing pin that holds the lower part of the long dp to the bracket. (With the wire washers) that SOB took me 1.5hrs to get on. I have a technique now though.

Another suggestion is to do yourself a favor and get a creeper.

This was very handy, buti should have followed it completely.

https://f80.bimmerpost.com/forums/sh....php?t=1096302

[medphysdave]

Drove around more today. Loving this change. Had my 4yo laughing in the back seat. He likes the valves open. Equates the loud exhaust with speed. It's fun. Thank goodness it's a valved exhaust. No way in heck could I handle an open valved system like this waaaayyyy too much. Normal valve operation is plenty.. I'm certain I won't be using the valve controller as much to open the valves. I did an open valve cold start in the parking deck today and admittedly felt a little embarrassed. Valves open is straight up a**hole mode, but sometimes I'm feeling it. It's kinda therapeutic after a long day

[(K)]

I'm hesitant to do the downpipes because of exactly what you mentioned regarding rasp/drone. Many clips of downpiped cars evidences the rasp which I'm wary of.

I find the factory valve behavior to be pretty good also but if I could make changes to the factory valve operation I'd have it open from 1st-3rd instead of 1st and 2nd only and also on downshifts. Having the valve controller is still great though for the occasional "rowdy mode."

[medphysdave]

Originally Posted by (K)

I'm hesitant to do the downpipes because of exactly what you mentioned regarding rasp/drone. Many clips of downpiped cars evidences the rasp which I'm wary of.

I find the factory valve behavior to be pretty good also but if I could make changes to the factory valve operation I'd have it open from 1st-3rd instead of 1st and 2nd only and also on downshifts. Having the valve controller is still great though for the occasional "rowdy mode."

It has created drone with the normal valve logic in one area that there was previously no drone. My guess is it has to do with the extra flow and the valves might be partially open. I'm really anti drone. I don't tolerate it well. When it first occurred I thought I might have to go back to stock. I then realized I can shift to a higher gear and problem solved. No drone at highway speed. It's funny because when the valves are closed at low rpm it's almost silent. So far the juice is worth the squeeze. All exhausts are different, so it's probably hard to tell how yours would behave and whether it would be tolerable. I suspect a catted downpipe would be less risk and still increase volume.

[MyM2See]

Originally Posted by (K)

I'm hesitant to do the downpipes because of exactly what you mentioned regarding rasp/drone. Many clips of downpiped cars evidences the rasp which I'm wary of.

I find the factory valve behavior to be pretty good also but if I could make changes to the factory valve operation I'd have it open from 1st-3rd instead of 1st and 2nd only and also on downshifts. Having the valve controller is still great though for the occasional "rowdy mode."

Im running catless DPs and have no drone. There is all around drone/loudness in the AMs when the engine is cold and i drive in Sport/Sport+, but that goes away after a few minutes.

[(K)]

I have the Akra evo system so I'd likely stick with the same branded downpipe if I were to continue down that rabbit hole. This is my "everyday" car so downpipes aren't high on the list, I'm not (currently) planning to pursue [too] much power or sound. I'm finding that even a minor, temporary drone/rasp would probably drive me nuts.

[medphysdave]

Originally Posted by (K)

I have the Akra evo system so I'd likely stick with the same branded downpipe if I were to continue down that rabbit hole. This is my "everyday" car so downpipes aren't high on the list, I'm not (currently) planning to pursue [too] much power or sound. I'm finding that even a minor, temporary drone/rasp would probably drive me nuts.

I feel like I've landed where I want to be sound wise. Loud or obnoxious. Those are relative to the audience. I liked the sound of stock, but wanted it a bit amplified. The akra midpipe and exhaust really added to the sound, and increased the volume a little. If you think you are sensitive to the volume, then I would not to this. Interestingly enough the soundkit is supposed to provide two modes. Open or stock logic, but I'm finding the "stock logic" mode behaves a bit differently than stock. Unsure if the valves are just being opened over a longer period of time or stay closed more. The sound kit seems quieter when setting it to "stock logic".

[medphysdave]

Interesting finding. I thought the factory valve behavior was a function of comfort, sport, and sport+. Changing between those didn't really do anything. There was a big change between switching MDM on and off. That surprised me. The Akra valve controller seems to mimic the factory MDM off logic. MDM on seems to keep the valves open more below 3k rpm. Anyone else experience similar between MDM on/off?

[Shax182]

What back box do you have? Still enjoying the catless life?

[medphysdave]

Originally Posted by Shax182

What back box do you have? Still enjoying the catless life?

Yep. I've got a full Akra system DP, mid, and backbox. Still loving it. The stock logic is now plenty loud. Occasionally I'll go full open, but it's kinda too much. It's loud. It doesn't sound too loud until you roll the windows down.