[STR8-6IX]

I took my car to a muffler shop the other day to have the secondary cats sawed off and replaced/welded with straight pipes - though i would share my experience with this. The engine note coming from underneath the passengers became much louder.. the inline 6 growl is just amazing. the engine overall feels like it has better pickup and it is making very good power above 4000rpm all the way to redline. i feel like its making 5 hp extra right now. keep in mind the ECU needs about 150km of no full throttle initially to adjust. after this period, the next 350km you can drive however you want but try as many different driving scenarios to let the ECU adjust. every 100km i am just getting a better and better engine note. just for your information, the exhaust note does not get much louder.

[cpie168]

Thanks for sharing. Any annoying drones on the highway?

[STR8-6IX]

Originally Posted by cpie168

Thanks for sharing. Any annoying drones on the highway?

not at all actually, under 2.5 except for some minor increase in engine response the exhaust sounds stock. theres some pleasant sounds coming from underneath the driver, but only once you wind out the engine past 3-4k rpm. sounds amazing and no drone!

[STR8-6IX]

thought i would also share a little update now that the ECU has almost finished the self-adjusting process.. the Exhaust note has gotten a much more developed tone, I dont even want to replace the muffler anymore. it did not sound this good when i first did the delete. its been 400km in so far and it sounds amazing... how it should have from the factory. like a proper inline 6. I strongly suggest anyone looking for more engine and exhaust noise do this..

[cpie168]

Wow very tempting. Does it affect emissions? Will it fail the test?

[STR8-6IX]

Originally Posted by cpie168

Wow very tempting. Does it affect emissions? Will it fail the test?

Ontario is more lenient with the emissions test. from what i've heard, only in california you would have problems with this mod because they actually do a visual inspection and you would fail just by not having them on your car. Being that these are just secondary cats, the primaries are not affected so i have heard of people passing the emission test with no issues... although i have not tried it myself, I am not concerned. If you do end up doing it, which i strongly suggest you do, I would take it to Asad muffler shop. the welds and overall job was excellent. when i was doing research someone was saying that their mechanic recommends you remove them for peak performance.. they were right. if you do it, dont forget to do every type of driving style you can possiblysubject your car to during the adjustment process: highway, city driving, revs to 2,3,4,5k, full throttle pulls, idle, literally everything you can within the 500km period. again, NO FULL THROTTLE FOR THE FIRST 150km. best of luck!!

[The Nightman]

Thanks for sharing. Is the rest of your exhaust stock? I've been on the fence but I think you just convinced me.

[STR8-6IX]

Originally Posted by freedomfries

Thanks for sharing. Is the rest of your exhaust stock? I've been on the fence but I think you just convinced me.

rest of the exhaust is dead stock and it sounds REALLY GOOD. I was debating on changing my muffler eventually, the the exhaust note sounds good with the sec. cats deleted. the stock BMW exhaust is actually quite good, the design and piping is well designed so a full catback is kind of a waste of money. you should definitely do it if you want to open up some exhaust gains. plus the engine note coming from underneath the driver (where the cats used to be) sounds awesome.

[Fundguy1]

Shouldn't do anything power wise as they aren't restrictive but it should sound mean. The down pipes are where the restrictions are. The sound is probably similar to catless dp but since its beneath the cockpit probably more drone.

[STR8-6IX]

The fact that they were fairly close to the primary cats (below the driver) I would say made them fairly restrictive. above 4000rpm, I feel a 6hp increase easy. engine response in general, at any rpm has improved considerably. if you thought your exhaust sounded somewhat wimpy and flat stock, this would be your first step lol.. to whoever is considering doing it, keep in mind you wont notice much of a difference until you are fully done the ECU adjusting process.. 500km in you will get the full sound and it is awesome.

[STR8-6IX]

Originally Posted by Fundguy1

Shouldn't do anything power wise as they aren't restrictive but it should sound mean. The down pipes are where the restrictions are. The sound is probably similar to catless dp but since its beneath the cockpit probably more drone.

I actually also thought there would be more drone - there was none. all you hear is just delicious inline 6 growl when you start to wind her out past 2700rpm.. no drone whatsoever which somewhat surprised me.

[Fundguy1]

Do the catless first would be my advice. Much more power gains and reversible.

[STR8-6IX]

Originally Posted by Fundguy1

Do the catless first would be my advice. Much more power gains and reversible.

I already deleted the sec. cats, next step for me is probably headers. which headers would you reccomend? I would also need a tune right?

[Fundguy1]

Idk the n52 setup.

[justpete]

Originally Posted by 6IX-F10-N52

I already deleted the sec. cats, next step for me is probably headers. which headers would you reccomend? I would also need a tune right?

Supersprint FTW. And be sure to have them ceramic coated at the very least, Kevlar wrapped if you can find someone competent to do it.

[STR8-6IX]

Originally Posted by justpete

Supersprint FTW. And be sure to have them ceramic coated at the very least, Kevlar wrapped if you can find someone competent to do it.

I want supersprint headers, but i cant justify that eyewatering price tag.. I will eventually do it though, no need to keep cats on a car that I will not sell.. lol.

[The Nightman]

Originally Posted by 6IX-F10-N52

I actually also thought there would be more drone - there was none. all you hear is just delicious inline 6 growl when you start to wind her out past 2700rpm.. no drone whatsoever which somewhat surprised me.

How about when cruising at highway speeds?

I'm not a fan of loud exhausts but wouldn't mind a small increase in noise for a subtle "factory sport" sound. The secondary cat delete seems perfect for me.

[STR8-6IX]

Originally Posted by freedomfries

How about when cruising at highway speeds?

I'm not a fan of loud exhausts but wouldn't mind a small increase in noise for a subtle "factory sport" sound. The secondary cat delete seems perfect for me.

no drone at any speeds. no unpleasant sounds at all. just engine and exhaust sound. if you're looking for a moderate increase in sound like i was, this is highly recommended.