[matthewcassity]

I had a '14 m235 RWD 8AT with the following mods
MPE
ER Catless DP
JB4

I now have a '16 m235 xDrive 8AT with the following mods
MPE
ER Catless DP
ER Charge Pipe
Bootmod3 Stage 2 93 Octane

When I had my '14 m235, my cold starts were very loud, loud to the point that the neighbors didn't care for it and it felt like the exhaust just breathed as free as could be.

I just installed the ER catless DP on my '16 m235 and this morning when I woke up and started my car there was no difference in the exhaust sound from when I started it the prior day before the catless DP was installed. Additionally, it also does not feel like the exhaust is breathing(as I call it) as freely as my '14 m235 when I had it.

I called my shop who installed it to confirm that they were sent the correct DP and it was in fact a catless version which they confirmed 100% it was. I asked them if they had any idea why this may be considering it's the same engine with the same mods besides the tune, and they were stumped. He said he could make a wild guess and a shot in the dark that maybe a piece of the old cat broke off and is lodged somewhere in the exhaust or maybe BMW changed how the car heats up when started between the '14 and '16. I also asked them if the difference in tunes would have any effect and they said no, I also asked the person from the forums who I bought my '14 from who has good knowledge of these cars and he also said the tune should have absolutely nothing to do with that.

I went into my bootmod3 tune config and put the burble settings to OEM and put the cold start start settings to OEM thinking it may have something to do with that, but nothing changed.


Hopefully this made even the smallest bit of sense and somebody out there can advise me or help me figure out why the same car (except the year, rwd/8AT & tune) with the same mods has a completely difference sound when first starting and a difference in the feel.

Thanks in advance for any comments, suggestions, etc!

[mike@x-ph.com]

Not sure what is going on, it's impossible to change from the stock downpipe to catless and not have any difference in sound.

[matthewcassity]

Originally Posted by mike@x-ph.com

Not sure what is going on, it's impossible to change from the stock downpipe to catless and not have any difference in sound.

Originally Posted by mike@x-ph.com

Not sure what is going on, it's impossible to change from the stock downpipe to catless and not have any difference in sound.

That's also my understanding of it and just the physics of it. I will try and remember to take a video in the morning when I start t my car and leave for work. it's literally the same sound as the stock downpipe. I was thinking of flashing my tune back to stock to see if there's ANYTHING in the map settings that's causing this problem/issue

[designatedposter]

what's exhaust smell like? it's very significantly different between catted and not catted.

also, by default, bm3 stage 2 tunes disable cold start, so it's much quieter. if you want cold start, then after you make those changes in the bm3 software, you have to flash again. finally, if your car is already warm, cold start does not go into effect.

[matthewcassity]

Originally Posted by designatedposter

what's exhaust smell like? it's very significantly different between catted and not catted.

also, by default, bm3 stage 2 tunes disable cold start, so it's much quieter. if you want cold start, then after you make those changes in the bm3 software, you have to flash again. finally, if your car is already warm, cold start does not go into effect.

Originally Posted by designatedposter

what's exhaust smell like? it's very significantly different between catted and not catted.

also, by default, bm3 stage 2 tunes disable cold start, so it's much quieter. if you want cold start, then after you make those changes in the bm3 software, you have to flash again. finally, if your car is already warm, cold start does not go into effect.

I can smell the fuel, it's not over whelming but neither was it on my '14 car.

in my bm3 software i turned cold start off before i started it this morning and no change, i'm going to post a video to this thread. yesterday when i started the car for the first time the cold start setting was "oem" so i've tried both options within bm3.

see the video i post in thread

[matthewcassity]

Sorry here is the video embedded

[matthewcassity]

For comparison, here is a video of my '14 after the car has already warmed up and in comfort mode.

[MLJR235]

matthewcassity Some maybe dumb questions but are you sure the valve is opening up on your exhaust? Peek in there to see. Also, you are 100% sure you have the M perf axle back?

If it's closed, you wont get much volume vs if it were fully open. Do you have a way to set it to open on command to see if it is functional? Like BimmerLink or MHD wheel control?

As a last resort you can physically check if you have a catless downpipe. They may have mixed something up, you never know.

To do so, unbolt the flex pipe that connects to the downpipe and move it enough just to peek in there. If you see any catalytic material you found your issue..

I'm just brainstorming out loud here trying to help you out buddy.

[MLJR235]

https://youtube.com/shorts/ExRIR3tAqgY?feature=share

Here's a semi cold start on catless , no resonator, remus axle back with valve open.

matthewcassity

[matthewcassity]

Originally Posted by MLJR235

https://youtube.com/shorts/ExRIR3tAqgY?feature=share

Here's a semi cold start on catless , no resonator, remus axle back with valve open.

matthewcassity

Originally Posted by MLJR235

https://youtube.com/shorts/ExRIR3tAqgY?feature=share

Here's a semi cold start on catless , no resonator, remus axle back with valve open.

matthewcassity

Video is private BUT, the guy i bought my previous one from and I were brainstorming too and i think you also brainstormed the cause, i think I may have have the exhaust flaps set to open 😭 it's been storming all day so i haven't been able to check my settings but i'm gonna check either later tonight or in the morning. I have a feeling that is it because i 100% have the mpe and the catless downpipe, i called my shop to confirm they were sent the correct one.

[MLJR235]

https://youtube.com/shorts/ExRIR3tAqgY?feature=share matthewcassity

should be available to view. Iphone doesn't capture loudness well but yeah you should be pretty loud with your current setup.

[matthewcassity]

Originally Posted by MLJR235

https://youtube.com/shorts/ExRIR3tAqgY?feature=share matthewcassity

should be available to view. Iphone doesn't capture loudness well but yeah you should be pretty loud with your current setup.

That's probably about how loud if not louder my '14 was.

Also, I haven't coded the flaps to be open 24/7 so i'm not sure what is going on lol