This is how you make an S55 engine sound good!

[ntg44]

Originally Posted by Alan l.

Tone is good but def sounds quieter than stock at this point. I think it could sound amazing with a much smaller resonator type muffler.

Alan

Yep. It is. I was worried about drone with a single exit so we played it safe this iteration. I'm going to need a smaller muffler in order to fit a resonator in most likely, so that's the next step.

Still, very promising results so far. This version is definitely the wife approved one.

[spool twice]

Originally Posted by ntgarage44

Ok so I was able to get to some standing revs of my exhaust. I need to work on the small bit of rasp around 3500 RPM - I think it might be my single walled tip resonating at that rpm, but after hearing it outside of the car, honestly I think it sounds like it's naturally aspirated haha. Here you go:

Sounds good! So smooth!

[ntg44]

Had a chance for some mediocre recordings. My external microphone sucks, even with the wind guard, so looks like I need to find someone to just record a pull from the street. But here's what I have so far. Headphones encouraged to hear lower frequencies better:

- A standing rev video but from a different angle. This is closer to the exhaust and gets less of the engine sound in the mix. Not perfect, but better than before:

- Here's a pull through 2 gears with the crappy external mic - It distorts in 2nd gear, but you can get the gist of it with headphones and first gear:

https://drive.google.com/open?id=1MV...E3-71ZAP37Twap

I'll try to get a video of some pulls with someone standing outside the car sometime this week.

[yayaya]

Originally Posted by ntgarage44

Had a chance for some mediocre recordings. My external microphone sucks, even with the wind guard, so looks like I need to find someone to just record a pull from the street. But here's what I have so far. Headphones encouraged to hear lower frequencies better:

- A standing rev video but from a different angle. This is closer to the exhaust and gets less of the engine sound in the mix. Not perfect, but better than before:

- Here's a pull through 2 gears with the crappy external mic - It distorts in 2nd gear, but you can get the gist of it with headphones and first gear:

https://drive.google.com/open?id=1MV...E3-71ZAP37Twap

I'll try to get a video of some pulls with someone standing outside the car sometime this week.

Holy shit that sounds awesome!

[ntg44]

Originally Posted by yayaya

Holy shit that sounds awesome!

Thanks

The last step is to get rid of the rasp aroud 3500 RPM... Will most likely need to make the muffler smaller to fit a resonator in right before it.

At least it's not a terrible rasp that persists across all RPMs. My hunch is it's the single walled tip resonating, but if I'm going to take it back to the fabricator, may as well use it as an opportunity to make it a little louder as well. I'm going to keep this muffler as-is because it can pass for a stock muffler - super livable for day to day. Then, I can make the 2nd muffler just for the experiment, and clamp on either one depending on my needs.

[GT_Juls]

Originally Posted by ntgarage44

Had a chance for some mediocre recordings. My external microphone sucks, even with the wind guard, so looks like I need to find someone to just record a pull from the street. But here's what I have so far. Headphones encouraged to hear lower frequencies better:

- A standing rev video but from a different angle. This is closer to the exhaust and gets less of the engine sound in the mix. Not perfect, but better than before:

- Here's a pull through 2 gears with the crappy external mic - It distorts in 2nd gear, but you can get the gist of it with headphones and first gear:

https://drive.google.com/open?id=1MV...E3-71ZAP37Twap

I'll try to get a video of some pulls with someone standing outside the car sometime this week.

ohhhh myyyy lorrrrrdddddyyyyyyyy. Game changing noises are happening.

[Kilabyte]

That literally sounds NA, wow.

[spool twice]

Originally Posted by ntgarage44

Had a chance for some mediocre recordings. My external microphone sucks, even with the wind guard, so looks like I need to find someone to just record a pull from the street. But here's what I have so far. Headphones encouraged to hear lower frequencies better:

- A standing rev video but from a different angle. This is closer to the exhaust and gets less of the engine sound in the mix. Not perfect, but better than before:

- Here's a pull through 2 gears with the crappy external mic - It distorts in 2nd gear, but you can get the gist of it with headphones and first gear:

https://drive.google.com/open?id=1MV...E3-71ZAP37Twap

I'll try to get a video of some pulls with someone standing outside the car sometime this week.

Where were you able to mount your external mic? It's been a challenge for me too, my phone and external mic distorts and makes "crackles" that sound like rasp but isn't present in person.

[ntg44]

Originally Posted by spool twice

Where were you able to mount your external mic? It's been a challenge for me too, my phone and external mic distorts and makes "crackles" that sound like rasp but isn't present in person.

I've tried the diffuser and rear bumper. No luck so far. I think it's just my crappy microphone. My phone sounds better but I'm not about to mount my $800 phone to my bumper and hope it doesn't fall off haha. Maybe I'll get a GoPro or something. I just prefer the external mic approach because I can run a long cable to the front seat and control when to start and stop recording from there.

[spool twice]

My suction mount for my phone is terrible too, it falls off from the vibs.

This past weekend, I tried to do a fly-by using a business signage as my phone mount, but was limited to 1st and 2nd gears at like 2/3rds throttle, didn't want to fly by too quick and had to end it near 6,000rpm in 2nd gear.

But still doesn't capture everything, I don't think it ever will, there is a higher pitched howl that the camera picks up at the top of 1st gear, but the volume has to be louder to hear and is more apparent in person. It also amplifies rasp, which isn't as apparent in person

[ntg44]

On a side note, after looking under my car again, I'm pretty confident a dual exit can be achieved using 2 shorty mufflers. Only modifications required are:

- Delete existing muffler
- Shorten U pipe bend (get rid of extension in the middle)
- EITHER:

- Extend single pipe to the middle of the car, then add 90 degree pipe towards the rear, split to Y pipe, and route to both sides with shorty mufflers.
This is the more challenging implementation for packaging reasons

- Split single pipe into Y pipe on driver side, then put 1 exit to driver side, and extend other pipe to passenger side with shorty mufflers at both exits. This is easier to implement, but one side has a longer way to travel before exiting, so not ideal.

Either way, I won't be trying either solution, since the single exit suits me just fine. But to the most of you who are interested, you can roll with this most likely if you are interested in my tone but with the stock look.

[spool twice]

Actually looking at your pic, I would mount the muffler more towards the passenger side, and in the drivers side just do a straight pipe that's valved.. since it already crossed over at the Y-pipe section, itll have all the benefits of the equalized pulses and you can open the valve when needed.

[ntg44]

Originally Posted by spool twice

Actually looking at your pic, I would mount the muffler more towards the passenger side, and in the drivers side just do a straight pipe that's valved.. since it already crossed over at the Y-pipe section, itll have all the benefits of the equalized pulses and you can open the valve when needed.

That's a good point, and the next pioneer who wants to build on this design can attempt that at their own discretion (and budget ). Personally, I have no desire to attempt to integrate a custom 3.5-4 inch valve actuator to OEM harness, but I'd be happy to help however I can to whoever would.

Realistically, here's how I see this working out. I'm going to attempt 1 more iteration with a smaller muffler and resonator, and if it's successful, blow up Instagram and call out every manufacturer directly to pay attention to this design and implement the valved/dual exit design so we don't need to for them, hopefully gain enough traction/publicity with IG/Road & Track/Jalopnik until one company finally wakes up and releases the first product to market.

Who knows - maybe they already are. They've STILL been suspiciously quiet on this thread considering how active they are on the forums in general.

[spool twice]

No doubt! Your fabricators work is great! The bends, the welds, it looks legit compared to my work that was done.

[RMDZidane]

I wanted to update you guys about my midpipe prototype. I think there may be hope after all. It's just that my design seems to be really sensitive to changes. I made an adjustment this morning before driving to have warranty work done and there was a positive outcome. When I get it back I'll do more investigating and see if it comes out the way I want....i.e not sounding like an ATS-V

This is a design that keeps everything stock except for the space between the secondary cats and the oem muffler.

[Lifestyler]

Originally Posted by RMDZidane

I wanted to update you guys about my midpipe prototype. I think there may be hope after all. It's just that my design seems to be really sensitive to changes. I made an adjustment this morning before driving to have warranty work done and there was a positive outcome. When I get it back I'll do more investigating and see if it comes out the way I want....i.e not sounding like an ATS-V

This is a design that keeps everything stock except for the space between the secondary cats and the oem muffler.

Pictures?

[mmmmQuattro]

Originally Posted by ntgarage44

So I just thought of something.

Looking under the car at different angles, that crossover idea got me thinking - why not just cross over the pipes before the stock resonator? Check out the attached photo. At least from that angle, seems like it would fit?

I actually want to try this.
It's a bit like the old V8 equal length headers concept.

Will there be enough room?

I would need to replace my secondary cats with smaller ones and move them back a bit. If there's enough room, I would like an additional couple of resonators and one more balance pipe.

Here's a link to the photos in the thread: https://f80.bimmerpost.com/forums/sh...&postcount=256
(I really need to learn how to quote stuff properly)

[judsonlct]

Originally Posted by spool twice

My suction mount for my phone is terrible too, it falls off from the vibs.

This past weekend, I tried to do a fly-by using a business signage as my phone mount, but was limited to 1st and 2nd gears at like 2/3rds throttle, didn't want to fly by too quick and had to end it near 6,000rpm in 2nd gear.

But still doesn't capture everything, I don't think it ever will, there is a higher pitched howl that the camera picks up at the top of 1st gear, but the volume has to be louder to hear and is more apparent in person. It also amplifies rasp, which isn't as apparent in person

Wow. I need to start looking for enthusiastic custom exhaust fabricators to take on this project. The tone is a world of a difference!

[spool twice]

Originally Posted by judsonlct

Wow. I need to start looking for enthusiastic custom exhaust fabricators to take on this project. The tone is a world of a difference!

It absolutely makes everything sound better.....well as much as the stock muffler can make for sound anyways.

The exhaust is so smooth at idle and at all rpm range, heres a part-throttle 1st gear up to 4,500rpm

[MR_X]

Originally Posted by spool twice

It absolutely makes everything sound better.....well as much as the stock muffler can make for sound anyways.

The exhaust is so smooth at idle and at all rpm range, heres a part-throttle 1st gear up to 4,500rpm

That's such a teaser....get a longer WOT video.

[beech_nuts]

Originally Posted by spool twice

It absolutely makes everything sound better.....well as much as the stock muffler can make for sound anyways.

The exhaust is so smooth at idle and at all rpm range, heres a part-throttle 1st gear up to 4,500rpm

Originally Posted by spool twice

It absolutely makes everything sound better.....well as much as the stock muffler can make for sound anyways.

The exhaust is so smooth at idle and at all rpm range, heres a part-throttle 1st gear up to 4,500rpm

Man you guys are doing awesome work. I have the AA mid pipe. With signature full exhaust. I'm looking to put my OE pipes back in and run your set up just for that sound man. Keep up the good work guys. And it is extremely weird none of the big name vendors have yet to say anything on here. Guarantee their R&D are running similar set ups or prepping their own as we speak because of what you all have done! 🤘🏼🤘🏼

[ntg44]

Originally Posted by mmmmQuattro

I actually want to try this.
It's a bit like the old V8 equal length headers concept.

Will there be enough room?

I would need to replace my secondary cats with smaller ones and move them back a bit. If there's enough room, I would like an additional couple of resonators and one more balance pipe.

Here's a link to the photos in the thread: https://f80.bimmerpost.com/forums/sh...&postcount=256
(I really need to learn how to quote stuff properly)

After getting under the car to check it out, unfortunately, there isn't enough room without lowering the red pipe in that picture to be fully below the yellow pipe, which decreases the ground clearance by about 3 inches at that position. If you look at the area where the pipes straighten out again, you'll notice that I failed to take into account how much space is added in that tunnel in the center of the car that isn't available when the pipes curve sideways. That's the problem.

Even if the concession is made to lower the red pipe to work around the yellow pipe, that's not even getting into the wonky bends needed to execute the crossover. Would be very costly, and far from ideal. We're probably better off increasing the diameter of the driver's side pipe for 1 meter before the stock resonator.



Also, as an update to all following my exhaust: I'm taking the car back to the fabricator today to brainstorm a new axle back section. Will figure out how to add a resonator after the merge, change to a smaller muffler, and change to double walled rolled tip to see if it addresses the rasp. After having the car for a week with this system, I've come to love the single walled single tip even more, but if it's the reason for the rasp, it needs to go. I'll post an update based on our conversation.