2015 GTI problem child

[Zer0DazE]

The larger resonator means removing the Invidia one. I don’t think there will be a huge improvement. The UQ allows for a resonator in the downpipe. I took video on my way to work and will post them when I get home. I still haven’t made my final decision.

 

[Zer0DazE]

Probably needs a bigger round resonator.

Which badgeskin is that? too dark to see. matte or shiny? Got a better daylight pic?

I would have posted these last night, but I caught up with an old friend over a bottle of Colonel E.H. Taylor small batch. If anything in this post has misspellings and grammar issues, please chalk it up to the morning after.

Here are some videos. First of light to medium acceleration, and some of the fog horn drone at 2500 RPM.
https://youtu.be/aWkU2OPSpAY

This one is on the highway at 75 MPH on flat ground and with some load going uphill.
https://youtu.be/E4wrVEzWO3I

Watching these on my phone and computer don't do the drone justice. Watching them while playing the sound through the car speakers was a little closer. The low deep tone sounds like a fog horn.

So I read 1 thread where a guy with the same setup used the UQ in his B pipe (I think I mentioned this). He said it helped with the highway drone. Others here that are on different setups have said multiple times the UQ is not a good replacement for the OEM resonator. So I am left with a few options.

1. Replace the 20" bottle with the 17950 and hope that doesn't make me sound like a teenager driving a Honda with a Cherrybomb in place of the OEM muffler. (that was actually me about 22 years ago). This would allow for the addition of other components later if needed, but will require me cutting the flange off the B pipe.

2. Add a Vibrant UQ or other 14"ish resonator to the downpipe where the VW originally had one. It was probably there for a reason. This would leave the catback as is, but would require shortening the downpipe. It would then be a 2 piece and easier to get in and out.

3. Add the Vibrant UQ to the B pipe as mentioned by the person with the same setup on another forum, and hope his opinion of "fixed the drone" is the same as mine.

Currently I am leaning towards 1. This would allow for adding a resonator or race muffler to the downpipe later if need be, and I could even add a small muffler to the B pipe if I find things are too loud. It currently has a nice burble, sounds fine under 2200 RPM, sounds good when accelerating over 3k at WOT, and decel has nice pops (not obnoxious flaming belches).

Edit:
I picked option 1. Parts ordered, and I will post results.

 

[Diggs24]

Sounds bad on my iphone. Can't imagine it in person. Hope the vibrant solves it.

 

[Zer0DazE]

Sounds bad on my iphone. Can't imagine it in person. Hope the vibrant solves it.

Yeah, it's pretty bad. Almost as bad as my 40+ year old double chin in that video. Damn, I need to get to the gym.

 

[Jose_Gti]

Yeah, it's pretty bad. Almost as bad as my 40+ year old double chin in that video. Damn, I need to get to the gym.

Lol! Just grow a beard it easier

 

[Zer0DazE]

The resonator and clamps showed up today, but I am still waiting on the 3" pipe. So the resonator looks like it's OD is 1" larger than the Invidia one, but is only 2/3 the length. It does look like the resonator will fit in the downpipe in front of the Invidia resonator. Instead of replacing the resonator in the cat back I may hit a local shop and see if they can fit this on the downpipe. It will still need a reducer from 3" to 2.75" though. 2.75" isn't common, so they may not have it and I may be ordering more parts.

Thinking about it, I could actually fit 2 of these in place of the Invidia resonator by shortening the downpipe just a bit.

I also found this video here
https://www.youtube.com/watch?v=LwK7LkaeZ9k
and he just took Jake's advice and replaced the stock resonator with the Vibrant. I however am not running a OEM muffler, so my results will be different.

I have the parts on order to either replace it, or put it in front of the existing resonator. I am thinking I will try replacing it at first since I won't have to cut the down pipe and then work from there.

 

[Zer0DazE]

Fit the Vibrant 17950 in place of the Invidia resonator. I was able to use a section of 3" 304 SS and then cut the pipe exiting the resonator so I could use that section and flange. Ultimately the pipe and flange can be welded back to the resonator.

With the new resonator in place the car was much more quiet below 2500 rpm. Over 2700ish the same drone was there. So it looks like the 17950 just moved the drone up about 500 rpm.

I will need a plan "C". In the mean time I put the OEM exhaust back on the car. I may just sell off the Invidia parts. It should sound good on a car with an OEM downpipe, or be good for someone looking for a loud exhaust. I could also salvage the pipes and replace the suitcase muffler with something that has more baffles.

On the upside, I am now capable of dropping and replacing the exhaust on this car in less that an hour. The wasted time and money chaps my ass though.

 

[Zer0DazE]

Pulled the pics off my phone.

This is what I had come up with

Pleanty of room left here and on the downpipe to work with. I did have to flip the brace under the car around to clear the resonator.

Here it was on the car...
at the downpipe

and at the B pipe using the Invidia 3" ot 2.75" adaptor

I have the feeling that if I would have gone with my plan that placed the Vibrant resonator before the Invidia resonator I would have had better results, but it probably still would have been loud. The suit case Invidia uses isn't all that big, and appears to have little to no baffling. It has me wondering if a second small Vibrant baffled muffler in the B pipe would help. We used them in the past on other builds (non-VW). I also found the Vibrant 1119 Streetpower round muffler. I could move the resonator forward and the place this behind it.

Going with additional mufflers and/or resonators is going to get spendy, and is just going to be a mess under the car. My wife said "Hold on to it, maybe you will feel like working on it again later." This will be my in for purchasing and new welding machine, my old one is crap.

Also, I am still waiting on Stratified for a base map. It's been 10 days, and kinda sucks since I had time off this week and good weather. It would have been convenient for getting logging done.

The DKM clutch seems to be holding up well, and engagement continues to smooth out. So I have that going for me.

Edit:
Doing more digging found the Magnaflow 12641 and 14641. They use a 30" body and might tame the exhaust similar to the OEM cat back. With the OEM monster in there I don't have the drone. With the over all length of 36" I should just need to save a couple of inches off the down pipe. I would also need to make a couple of spacers for the brace since the 6" diameter won't fit past it.

Edit 2:
I was driving to the store and listening to the engine/exhaust noise with the OEM cat back, and it got me thinking. I could just replace the muffler section to get the more aggressive sound and look; however, the more I listened the more I noticed that the engine just seems to make an ugly note (call it the brown note) between 2200 and 3000 rpm. At 3000 rpm the note changes and is less doo doo brown. The OEM muffler seems to do a good job of keeping it quiet. My concern is that I would end up with the same complaint I had with the full Invidia cat back.

Edit 3:
The more I listen to videos of MK7 GTI's with turbo back exhausts, the more I realize they all just make that same ugly brown note.

 

[Twist1]

I know what you mean with the brown note. I've had 6+ exhaust config on my car by now. Right now a mf cb with cast dp. After everything I slowly am realizing it seems the best sounding was just the dp with the stock muffler and res delete.. lol.

 

[Jose_Gti]

Take a look at this thread https://www.golfmk7.com/forums/showthread.php?t=27305
I followed this path and I’m happy with the sound I got.

 

[Zer0DazE]

^
I may have to give that a try in the future.

Maybe in the future I will put it back on and determine what frequency the drone is. I could then build a Helmholtz chamber to deal with it. I'm not sure if there is actually enough room under the car for that though.

edit:
I had an idea. I fired up a spectrum analyzer and then played the videos in my car. The brown note on the highway appears to be 172Hz. The acceleration video shows it coming up from about 125Hz and moving up with revs. There is also a big hump around 65-75Hz.

I could probably add a J pipe to cancel out the 172Hz brown note.

 

[Jose_Gti]

This maybe also a solution? https://www.golfmk7.com/forums/showthread.php?t=45633

 

[Zer0DazE]

This maybe also a solution? https://www.golfmk7.com/forums/showthread.php?t=45633

I already tried that resonator. It only moved the issue so that it was obnoxious at 2800 rpm instead.

edit:
A J pipe like this should help, but I don't know how much, nor do I know if the recording is giving an accurate reproduction of the sound.
http://synapseengineering.com/synapseusa/products/nodrone/nodrone-18-ss-resonator.html
I still need to calculate the correct length for a 2" diameter pipe to cancel 172Hz.

edit 2:
it looks like I could use a 2" x 8" leading to a 3" section with a volume of just under 1 liter to help with the 172Hz drone. I think that could be fit just off the B pipe section.

 

[Zer0DazE]

A friend and I got bored today and decided to play with the exhaust some. I decided I wasn't going to solve the issue of 172Hz droning based on a recording. We cut some piping to move the Vibrant resonator back a little. The body was too close to the brace that runs under the exhaust, so I moved it about 3" back. When all was said and done I ended up with way too many clamps, but it's temporary and can all be welded up.

On the road in 3rd it begins to get loud at 2500 rpm, at 2700/2800 it's the brown note, and then at 3000 it quiets back down immediately. I am thinking about seeing if the tuner can adjust when the intake manifold flaps actuate. I figure it can't hurt to try.

At 60 mph the car is quiet. Between 65 and 70 you begin to hear it, and then at 75 it's pretty bad. The spectrometer says it's between 99Hz and 122Hz. The decibels are mid 70's at when you are at 75 mph. I am glad I decided to test it again, 172Hz is not the issue with the Vibrant installed.

I think I will start with the possible tuning solution. If the issue can't be solved that way then I will probably add a J pipe or similar solution.

 

[Zer0DazE]

Unlivable. That is how I would describe the catback with the downpipe. I made it almost 3 days before putting the OEM one back on. 45 min from wheels up to wheels down... I am getting beyond good at this.

I am wondering how the Invidia muffler would sound with the OEM resonator. I get the feeling that it would be like the Club Sport muffler that people say can be obnoxious with a downpipe; none the less, this is easily reversible like a muffler delete.

I need to rethink this exhaust...

Edit:
https://www.golfmk7.com/forums/showpost.php?p=372849&postcount=157

I have been thinking about a 1/4 wave resonator as a possible solution. It got me thinking about the above thread. Both the R and Club Sport have them built into the suitcase. Interestingly the stock GTI muffler doesn't have/need one. I think it is a safe assumption that the Invidia muffler does not have them in their design. It sucks that the user who posted that was banned, I would love to know the length of those tubes/branches in the suit cases of those 2 mufflers.