Exhaust too loud

[willemml]

I have a CTS Turbo 3" exhaust attached to a testpipe. While it sounds nice at idle it is just loud and annoying driving around. I noticed this even more after a long drive where even 6th was not enough to keep the RPMs low and avoid the drone that comes in at 2.4k RPM and onwards. I had to wear earplugs for the entire drive (luckily I found a pair I had left in the car last summer.)

Any advice on how I can fix this without majorly reducing performance potential and also minimum cost? Is there a resonator of some sort I can install where the test pipe is? I deleted my SAI because it broke, and I don't want to have to worry about melting a cat with EGTs from tuning. The goal is quiet and minimal cost, even if it doesn't sound "cool". I noticed CTS turbo sells what they call a high flow cat (although as far as I can tell it is just a test pipe that looks like a cat). It was mildly interesting as they ship from canada and sell in CAD, which significantly reduces costs for me, but I have my doubts that it would make anything quieter.

[egovreau]

I'm guessing you went with the non resonated exhaust. A resonated exhaust should have kept the drone to a minimum

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[willemml]

I guess that makes sense, the exhaust was already on the car when I bought it so I don't know for sure. That being said I don't see anything other than mufflers and a Y splitter under the car. I guess I should find an exhaust shop that can add a resonator?

[grayjay]

You could try adding a 1/4 wavelength J-bend or a helmholtz resonator to address drone at specific frequency without impacting flow;
https://wilhelmraceworks.com/blog/dr...%20the%20sound.

A strait-through glasspack muffler added into middle of the system might also be helpful with minimal flow reduction.

Add a boost controlled Y-valve splitter so that unboosted non-performance exhaust flow is all directed through a more restrictive muffler, then Y valve opens under boost to dump the additional flow to a less restrictive muffler on other side. You might be able to do this by adding a silencer tip (used with motorcycles) to quite down one of the existing mufflers?

[egovreau]

Or two depending on how much room there is before or after the y pipe.

Most, if not all, resonated exhaust systems you can buy as a kit have two resonators. The Borla I have on my car does as does the Miltek exhaust I plan to replace it with (shown).

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[willemml]

Thanks for all the advice!

The helmoholtz resonator idea sounds really cool. Kind of like the one on the intake side... Although I suspect it will be either very expensive to get right or difficult to assemble as I won't have access to a welder (or a space to use one) until I go back to uni in fall.

I will probably try to find either some resonators that I can clamp in or a boost controlled Y splitter. I might ask around local shops.

What I really need to do is get under the car and measure everything and draw it out so I know what I am working with.

egovreau: why are you switching to Miltek from Borla? I have heard the Miltek is good, but I doubt I could recoup enough of the costs if I sold the CTS exhaust to justify it.

[Gunnarrrrr]

Your problem is the lack of a cat. 90% of droning problems come from going catless. Get a HFC and I doubt you'll feel the need to modify your exhaust at all after.

[egovreau]

The Borla, while it claimed to be a cat back exhaust, it connects to the factory downpipe. My downpipe was toast so I replaced it with a techtonics tuning downpipe. Unfortunately it didn't fit well so I installed a Bosal downpipe.

Also, the Borla is known to have fitment issues because of the front bracket. It tends to come in contact with the rear drive shaft.

The Miltek is a true cat back and doesn't seem to have those issues unless they've fixed them.

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[willemml]

Hmmm, thats good to know about the Borla.

I have a hard time believing that just an HFC would solve drone and volume, not that I really know anything about exhausts. But if I were to get one would the 034 250 cell HFC be a good choice?

[Gunnarrrrr]

034 cat is great I ran one for many years. Every one of my cars has been catless at one point, and whenever I ended up getting an aftermarket exhaust I ended up swapping on a HFC. In all cases, after a few months the drone became too much to tolerate for daily driving. An HFC isn’t going to get the noise down to stock cat levels, but it will still dampen a lot of that drone.

and as far as that borla system for our cars, it’s always been the consensus that it’s the worst one. miltek being the best sounding but also the loudest. the magnaflow 16601 system being the quietest, but still sounds pretty good. I ran a 16601 with a stock downpipe and 034 hfc for about 8 years, it sounded nice but was still very quiet, and comfortable for long road trips.


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[willemml]

Just for fun I decided to try plugging one of the exhaust tips, with the bottom of a yoghurt container duct taped to the left tip. Drone is reduced significantly, volume is reduced slightly, but it still sounds good. Looks terrible though, so I won't be going with that.

Definitely considering the HFC. I would love to switch to a magnaflow, although I can't justify the expense when I can live without it.

[B6ayfour]

Just for fun I decided to try plugging one of the exhaust tips, with the bottom of a yoghurt container duct taped to the left tip. Drone is reduced significantly, volume is reduced slightly, but it still sounds good. Looks terrible though, so I won't be going with that.

Definitely considering the HFC. I would love to switch to a magnaflow, although I can't justify the expense when I can live without it.

I'd personally go the resonator or valved muffler option before putting a cat on the car if you're worried about performance. will be cheaper as well.

[Gunnarrrrr]

I'd personally go the resonator or valved muffler option before putting a cat on the car if you're worried about performance. will be cheaper as well.

in no way would that be cheaper nor would a high flow cat hinder performance at all at these power levels.


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[willemml]

I'm just going to go with one of those bolt in expanding plumbing plugs right before the tip on one side, given how well blocking off one side of the exhaust has worked (yeah I still haven't taken the yoghurt container off) with no noticeable power loss. 20$ solution, easy to remove. And I still have 3" exhaust all the way back.

I do like the idea of a valve before one of the mufflers. But I probably won't do it.

I am not making much power, noticeably a lot more than stock (well so says butt dyno), but not so much that a single 3" exhaust is a restriction.

[Kevin C]

My personal preference is to run a HFC, why be the stinky car? I know in traffic that I don't like being behind decatted cars. My pay it forward is to not stink out the guy behind me.

[willemml]

If it weren't for CAD to USD exchange rates and shipping costs, I would buy one. But they aren't exactly cheap (after shipping and tax and import fees it's overCA$850 for the 034 HFC).
Edit: I actually found a place in Canada where I could get it shipped for 700$ (Brox tuning). This is still more expensive than I'd like.

Also I can't smell it. I guess sensitivity to various smells varies person to person, but I also live in an area where straight piped diesel trucks are fairly common so I am probably desensitized by now, though I don't remember noticing when I originally bought the car.

I was actually about to buy the CTS Turbo HFC, but as far as I can tell it's just a test pipe that looks like a cat. Although they also sell a "plain" test pipe so I don't know.

If I bring the car to Vancouver I will likely cough up the cash for a HFC. But until then it seems too expensive.

[BumblebVR6]

If it weren't for CAD to USD exchange rates and shipping costs, I would buy one. But they aren't exactly cheap (after shipping and tax and import fees it's overCA$850 for the 034 HFC).
Edit: I actually found a place in Canada where I could get it shipped for 700$ (Brox tuning). This is still more expensive than I'd like.

Also I can't smell it. I guess sensitivity to various smells varies person to person, but I also live in an area where straight piped diesel trucks are fairly common so I am probably desensitized by now, though I don't remember noticing when I originally bought the car.

I was actually about to buy the CTS Turbo HFC, but as far as I can tell it's just a test pipe that looks like a cat. Although they also sell a "plain" test pipe so I don't know.

If I bring the car to Vancouver I will likely cough up the cash for a HFC. But until then it seems too expensive.

This is the high flow cat. I'd go w/ this in your situation:

https://www.ctsturbo.com/product/cts...flow-cat-pipe/

[willemml]

Wow I must be blind, I found many listings for a CTS Turbo HFC but didn't see any images of the inside/cells. Thanks for pointing that one out! Still have no idea how I didn't see that.

I will order have ordered one. Should arrive in a week or two.

Just putting this here for my own future reference, I already knew intuitively that back-pressure was bad, but this guy makes some interesting points about fluid flow mechanics that ties into some of my uni courses nicely. https://www.tercelreference.com/terc...st_theory.html

[B6ayfour]

in no way would that be cheaper nor would a high flow cat hinder performance at all at these power levels.


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did not see the CTS turbo link that's actually pretty cheap. most of the time HFCs are like 500+ though. yea you're right performance difference is negligible.

[willemml]

So the cat arrived. I went to install it and realized I had neglected to check if the test pipe was separate from the down pipe... It is not . Not really sure what the best route is from here, but first thing that comes to mind is getting a shop to cut it and weld on a flange. As far as I can tell the entire exhaust is one solid welded piece from the turbo to tips (the only detachable pieces).

[Gunnarrrrr]

time to bring the sawzall to the junkyard i guess


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[willemml]

Well I do have a cordless angle grinder... Would a stock downpipe be 3"? If not where can I get a 3" downpipe? Everything I have sen online so far is 2.5". I guess maybe I could just have the flange welded on to my existing DP? Only junkyard I know of within easy distance is already quite far, and only 2 or 3 B6s last I checked, all missing engines.

[willemml]

Haven't had any luck finding a wrecker with a downpipe, are there any options online? I see lots of 2.5" downpipes, but no 3". Another option I've been considering is just buying the flange and having it welded on to the existing downpipe, but I cannot figure out what type of flange the cat to downpipe is, although I have found lots of turbo to cat flanges.

Any ideas?

[BumblebVR6]

Haven't had any luck finding a wrecker with a downpipe, are there any options online? I see lots of 2.5" downpipes, but no 3". Another option I've been considering is just buying the flange and having it welded on to the existing downpipe, but I cannot figure out what type of flange the cat to downpipe is, although I have found lots of turbo to cat flanges.

Any ideas?

Only 3" downpipe I know of comes as part of the ECS turbo back exhaust. It starts out smaller though, then the rest is 3": https://www.ecstuning.com/b-ecs-part...dk/?pdk=AgAEAg

[willemml]

Hmm, it'll probably be easier to get someone to cut the existing downpipe and weld a flange on... I'd rather not purchase a whole exhaust.