20

Exhaust

By
q20v
1340
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Leaks and rust

Nov 11th 2014

When I started the car the other day it sounded louder than usual. I checked out the rear muffler and the connection to it was a bit hollow. At this point I figured I just needed to replace the S pipe going to the muffler.

But, as I was wiggling the rear muffler I noticed movement from the exhaust closer to the engine. It was coming from the flex pipe.

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The first picture is the flex pipe. Notice how it looks cracked and worn. Also, when pulling on the pipe to the left (back) of the flex pipe, the flex pipe was separating, see pic two. If I were to pull 1/4" more the pipe would just fall out.

At this point I was thinking I could just remove this down pipe, cut off the flex section and weld in a new one, and reinstall the down pipe.

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I checked the connection between the down pipe and catalytic converter and the fasteners weren't exactly recognizable as fasteners anymore!

The first picture is the catalytic converter in the engine bay, just after the turbo. Just out of view to the left is the connection to the down pipe, see pic two.

I figure there isn't much of this exhaust that's worth saving except the rear muffler, so everything else will need to be replaced from the turbo to the rear muffler.

I began searching the internet for options. The system seems readily available in 2 parts, the catalytic (or a test pipe, which is a straight pipe deleting the cat) and the rest of the system (down pipe, mid pipe, rear muffler):

Catalytic: - OEM or aftermarket - $250 and up. - Test pipe (literally just a straight pipe with a flange on either end and an O2 sensor bung - $150 and up. - Plus about $30-50 in hardware and gaskets.

Down pipe / Mid / Rear including muffler: - Stainless steel system, cat-back, from Borla, Billy Boat, etc, cost $700-1000. - Ebay special, low quality but stainless steel - $350.

The cheapest I could piece together a system is $5-600, and that's with an Ebay special (i.e. cheap quality, poor fittment, bad sound)

Then I started thinking about building my own system, deleting the catalytic converter and making my own 'test pipe'. Here's the list of parts I'd need: - Misc piping, 2.5" dia - O2 Sensor bungs - A few clamps - Flex pipe - A mid muffler / resonator of sorts (car currently doesn't have one)

I can buy the supplies listed above from Summit Racing and build the turbo-back system, using the current rear muffler, for about $200.

Everything should be here on Friday. (14-Nov-2014)

Weekend update.. Slight change in plans. After removing the old system I found the Remus muffler inlet diameter is only 2", so I found a Magnaflow 2.5" straight through muffler at Canadian Tire. Pushes the price up by $130 but I'll rest easy knowing the exhaust is 2.5" turbo to tail pipes.

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In anticipation of starting to work on the system this weekend, I managed to get the car on the ramps just before both Myah and Sarah started projectile vomiting in their beds.

While the car is up, I'll change the transmission fluid and the rear diff mount that's clunking.

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Removing the old system

Nov 13th 2014

First thing I did was remove the air box. This gave me access to the front (pre-cat) and rear (post-cat) O2 sensors, as well as the turbo outlet flange nuts.

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The front O2 sensor felt weird as I removed it. Figured out why as soon as it came out.. it's one of those new press-in type sensors that doesn't use threads :S

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The rear sensor proved to be impossible to remove, as in, I could just barely get an open-end wrench on it, and it wouldn't budge. Even if it did, there is about 1" of room to swing the wrench. I left it on and removed it after the catalytic was out.

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Next I removed the exhaust from the flex pipe - back. It literally just slid out of the flex pipe, and the rear muffler was already disconnected from the rust. Probably the easiest exhaust removal I've ever accomplished!

It looks like the muffler is in the garbage, but rest assured I will be reusing it!

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I am surprised that it was as quiet as it was when I drove it. By the looks of it, she should have been howling! - ripcurl November 15th 2014

What was left on the car was the catalytic converter and the down pipe. They were bonded together permanently. There is a spring loaded mounting bolt part way down the down pipe, and I thought for sure I'd be cutting it off or it would just snap. Sure enough it backed out with ease. Go figure!

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Here is the catalytic and down pipe. I had to cut the down pipe in half in order to contort the assembly out through the engine bay. I'm amazed it came out to be honest.

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These pipes have seen better days.

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Summit Racing Order

Nov 15th 2014

Box of goodies from Summit Racing!

4x 45* Bends (10" legs) 1x 180* Bend (5" Radius, 12" legs) 1x SS Flex Pipe 1x Summit Glasspack Muffler (for the mid muffler) 3x SS Butt clamps 5x O2 Sensor Bungs (will only use 2) 3x Hanging wires (will only use 2)

All pipe mandrel bent, 2.5" dia steel with aluminum coating.

$185 USD including shipping. Plan is to reuse the existing rear Remus muffler.

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Unfortunately she's gotta go.. I'm hoping the 2.5" piping, magnaflow, and cat-delete will keep some of the spirit! - q20v November 19th 2014
That Remus is half or more of the car's spirit. - booneylander November 19th 2014

Turbo outlet flange

The only part of the old system I want to reuse (excluding the rear muffler) is the turbo outlet flange. I cut it off the catalytic pipe and removed the old chunk of pipe.

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After removing the old pipe, there was a heft weld remaining. My new pipe fits in nice but welding it in would be difficult with the old weld in place. I figured I'd try to remove it on the lathe.

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It was quite difficult to machine considering the limited room I had. Also, the weld was pretty hard and didn't machine nicely. But I managed to turn it down enough to facilitate welding.

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I welded the pipe inside and out. A bit rough, but my pipe is stainless steel (found it in the scrap bin!) and the flange is cast iron. All the piping I ordered from Summit is 2.5" diameter, and it fit really loose in the flange. I managed to dig out a 2.75" piece of stainless, that tapered to 2.5", from the scrap bin. The odds of this ever happening again are impossible.

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Down Pipe

First picture is the old catalytic and down pipe. The down pipe I'm making replaces both of these.

The old down pipe had a little metal bracket that is used to bolt the down pipe to the transmission. I wanted this bracket on mine so I stole it by cutting it at the welds.

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After the down pipe was more or less finished, I positioned the transmission mounting braced on the pipe. Obviously it didn't fit exactly since my down pipe isn't in the same location as the old one. I cut one of the legs off and, using part of the old leg, re-welded it on. Lines up perfectly.

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Mid Pipe

The mid pipe connects from the down pipe to the rear muffler. Band clamps on either end for ease of installation / removal.

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After I finished the system with the glass pack center muffler, the car was waaay too loud on part throttle. Idle and cruise was okay, WOT was nice, but everything else was really annoying. So I ordered a Vibrant 1141 Ultra-Quiet Resonator to replace the glass pack.

Installation was pretty easy considering it was almost the same length as the glass pack. Cut out the old, weld in the new.

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Some before and after shots.

The result is a huge improvement. Quieted and smoothed the sound quite substantially, especially on part throttle. I'm glad I did this.

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Rear Muffler

I planned to reuse the Remus rear muffler, and got as far as finishing the entire system with it included. However, I regretted this decision because I found out too late that the inlet diameter is only 2", whereas the rest of the system is 2.5". I adapted my 2.5" pipe to mate up to the 2", along with a sharp bend into the muffler to clear the sway bar (see next section). I've been kicking myself since the weekend for going this route, knowing I'm chocking the system at the muffler like this. Last night I went into Canadian Tire for something else and took a look at their muffler selection, only expecting to find Cherry Bombs and Ractive 5" tips. I ended finding a Magnaflow with 2.5" inlet/outlet, straight through design, in Stainless Steel, and overall length shorter than the Remus. A win on all accounts. So I bought it and will re-do the rear end of the system.

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haha I figured you'd say that, I'll keep it safe until you're back. - q20v November 19th 2014
Boourns. Save the muffler, I want it for the Golf! - booneylander November 19th 2014
Nov 20th 2014

I got the Magnaflow rear muffler 90% installed. As I was finishing up welding the hangers I ran out of welding wire. Hope to have her finished this weekend..

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Got some welding wire and finished the rear muffler.

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I know, only because the muffler is a lot shorter. - q20v December 21st 2014
That bend is wayyyyyyyyy cleaner than the previous version. - ripcurl November 29th 2014

Tip

The outlet on the Magnaflow is a single 2.5" pipe. Ideally, I'd like to have 2x 3" pipes exit the bumper, but I don't have the materials or the desire at this stage to make a splitter. I do, however, have a 2.5" - 3" diameter adaptor, which is too short, AND another 3" dia pipe (about 3-4" long).

All that to say, I'll end up with 1x 3" pipe exiting the rear bumper.

To achieve this I'll have to improve the fit and finish of the adaptor and extension, considering they were cut a bit crooked.

I chucked them up in the lathe and trued their ends, so that when butted up together for welding they sit nice and square.

After I weld them together, I'll turn down the weld and clean up the pipe so that it looks a bit better. I might even paint it.

This is turning into a long chapter....

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I got it all buttoned up on the weekend, and there are a few issues.... I (Brad) installed a new rear diff mount to help eliminate a clunk in the driveline, which it did, but it amplified extremely worn transmission and motor mounts. Not a big deal, they just arrived today. However, I couldn't drive the car because the tranny/motor moving up and down during on/off throttle was yanking the exhaust loose at the first clamp. Plus, the clamps I bought are garbage and leak. I ordered better ones and they just arrived today. AND, the exhaust is just way too loud during part throttle. Idle / cruising is fine, WOT is BAAAAAAA, and everything in between is really annoying. So I have a Vibrant 1141 Ultra-Quiet resonator coming in on Monday, which I will install in place of the $20 el-cheapo glass pack muffler I installed in the middle of the system. IMO the tip I made looks pretty cool, but I don't have a picture of it. - q20v November 26th 2014
I love long chapters. How does it sound!? - ripcurl November 26th 2014

Instead of all the work I described in the last section, I decided to just buy a 2.5-3" adaptor that was long enough.

I cleaned up the end on the lathe to get rid of all the dents, and then brushed it with a scotch pad.

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I think it would have looked good with the brushed finish, but I primarily didn't want it to rust, so I painted it.

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O2 Sensor Bungs

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Painting

I finally caved and bought some proper degreaser in what seems like an impossibly small can for $15. Works surprisingly well. I loaded it into a spray bottle and wiped the entire exhaust down in minutes. Dried without residue in almost seconds.

After that I hit it with VHT Header paint, silver. Should have primed it first, but didn't have any.

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Installation

Using a new gasket and hardware, I installed the down and mid pipe. I still need to make the modifications for the Magnaflow rear muffler.

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Yup! I can't wait to open up the throttle when this is done. - q20v November 21st 2014
Looks like a whole lot of room in there without that cat! - ripcurl November 20th 2014

O2 Sensors

The A4 has 2 O2 sensors, front and back. I destroyed the front removing it from the old system, but the back sensor I managed to save. The seal washer was looking rough so I pried it off and installed a copper crush washer. I dug around on the net for a copper washer in this application and couldn't find anything that said not to. I'll keep an eye on it. (the stock gasket is steel)

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Since I'm deleting the cat, the rear O2 sensor needs to be tricked into thinking the cat is still there. Its purpose is to measure the emissions post-cat to ensure the cat is working properly. If the cat has failed a warning light on the dash is illuminated. To trick it, the O2 sensor must be positioned away from the direct flow of the exhaust. To accomplish this, I bought 2 spark plug spacers and attached them together, giving me about 3-4 inches of distance from the exhaust flow. However, the hole in these spacers is too small for the O2 sensor and must be enlarged slightly. (see photos above)

All three batteries for my cordless drill are dead so I sparked up the lathe to bore the hole.

I red locktite'd them together to prevent them from coming apart.

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First time I hear of it, too. I started the car last night (couldn't resist) while fitting up the rear muffler and I didn't have a warning light. Seems like it worked! I ran out of welding wire last night to finish the muffler tip :( - q20v November 21st 2014
Yeah this is legit I've seen this trick done on lots of cars. - booneylander November 21st 2014
Spark plug spacers?? I dont know if you are serious or not. Is that an actual thing? - ripcurl November 20th 2014

High temp Nickel anti-seize, use it or... just use it.

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Just need to add some pictures of the system installed on the car...

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I used an angle grinder and just went at it - q20v December 21st 2014
How did you get the bung to conform to the pipe radius? - ripcurl December 21st 2014
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