Yet Another 3" Exhaust Problem: Stupid Donut Flange - Subaru WRX Forum
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post #1 of 26 Old 06-10-2016, 02:02 PM Thread Starter
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Yet Another 3" Exhaust Problem: Stupid Donut Flange

So im cleaning this 3" axleback and decided to clean up the flanges on my 3" midpipe too. Well one side has a stupid donut flange on it. Neither my 3" Perrin downpipe or my 3" axleback has this retarded donut flange. Why the hell did they make it like this? Both my downpipe and axleback have normal 2 bolt flanges on them. So I really dont want to trust so eone to cut off this stupid donut flange and weld a standard flat flange in its place. Do I have any other options here? Or am I screwed? I dont want to buy a new midpipe because its probably going to be built the same dumb way. I cant just use a standard flat gasket can I? Is there an adapter for a 3" donut flange to convert it i to a standard 2 bolt flange? This is really pissing me off. Thank you in advance.

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post #2 of 26 Old 06-10-2016, 03:02 PM Thread Starter
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So Ive called around and what Im looking for just doesnt exist. I took another look at this ignorant design and Im thinking that MAYBE a standard gasket will work? HEres pics of the 3" donut flange that is todays bane:






Heres some measurements and pics with a standard flat flange gasket on it:







I checked it out and on the gasket there is an inner ring made of metal thats probably supposed to basically get pushed and recessed inside the pipe a little bit, or is at least there to help keep the outer surface of the gasket from getting smashed totally flat. Its basically sitting in the empty cavity of the donut flange on one side and Im guessing would be flush against the flat flange on my DP.

It looks like it could still work though. I mean the majority of the surface area of the gasket has a decent seal on the surface area of this donut gasket. Maybe I just need to buy a thicker gasket and this will be fine? What do yall think? This entire catback basically cost me $20 and for good reason. Because I really dont have the money left in the budget to pay $200 for my tuner to weld on a new flange and install this catback for me. They are 1.5 hours away so they would have to install it because the next time Im there it will be to get my protune done and Im not making a special trip just for this, but I also need this catback installed before the protune. This is my dilemma. Thank you for your help and support.

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post #3 of 26 Old 06-10-2016, 04:05 PM
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Im pretty sure grimmspeed makes a gasket ( read : adapter ) that accepts the donut on one side and leaves you with a flat mating surface on the other.

As an alternate solution most exhaust shops will have donut ends with nothing else on them and Im sure they could weld the donut end onto your existing midpipe.

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post #4 of 26 Old 06-11-2016, 07:09 AM
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Stock DP>Aftermarket 3 in. Catback Adapter - Subaru - GrimmSpeed

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post #5 of 26 Old 06-11-2016, 11:43 PM Thread Starter
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Nah man thats for a 3" downpipe to a 2.5" catback. Not a 3" DP to a 3" catback which is what I have. I actually have that very same adapter already installed on my car. The Grimmspeed adapter is made to mount a 3" downpipe to the factory catback. Unfortunately nobody makes an adapter fro 3" exhausts with 2 different types of flanges like the donut to flat flange that I need.

Do you think by looking at my pictures that I can get away with just using a standard gasket? It might need to be thicker like the GS 3x gasket but at least it will be cheaper than cutting and welding a new flange. Thoughts?

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post #6 of 26 Old 06-13-2016, 07:24 AM
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Muffler shops weld these different adapters on and off every day.

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post #7 of 26 Old 06-13-2016, 08:23 AM
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oh you need 3" to 3"??

i know you can get one up here in canada. contact Lachute Performance. one was used with my full 3" turboback exhaust. it comes in the bag of hardware. they can probably ship you just the 3" donut gasket.

but yea, any competant muffler shop in your area should be able to solve your dilema by welding in new flanges. or find a buddy with a welder and DIY on the cheap.

you could always just try a thick gasket, i mean for the cost of the gasket its worth finding out right?

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Last edited by titter; 06-13-2016 at 09:31 AM.
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post #8 of 26 Old 06-14-2016, 12:09 AM Thread Starter
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Quote:
Originally Posted by titter View Post
oh you need 3" to 3"??

i know you can get one up here in canada. contact Lachute Performance. one was used with my full 3" turboback exhaust. it comes in the bag of hardware. they can probably ship you just the 3" donut gasket.

but yea, any competant muffler shop in your area should be able to solve your dilema by welding in new flanges. or find a buddy with a welder and DIY on the cheap.

you could always just try a thick gasket, i mean for the cost of the gasket its worth finding out right?

My sentiments exactly. I already called around and they want $100 for the job. Screw that noise. If it comes down to it Ill find a guy down on His luck with a good welder and pay Him to do it over letting those theives at the muffler and tire shops around here bend me over and make me their girlfriend. All the shops around here are HORRIBLE. So Ive got the flanges soaking in some excellent rust remover right now. Im gonna clean up that donut flange really good and try my luck with a thick gasket. Maybe even use both a donut gasket AND a flat flange gasket just to help fill in the void where the donut would go. Im thinking that pocket of air might start eating at the inside seal of the flat gasket over time but I cant say for sure. Thanks guys. Ill let you know what happens. It just might be a while. Oh and Ill check out that Canadian company too, thank you for that.

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post #9 of 26 Old 06-14-2016, 01:19 PM Thread Starter
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UPDATE: So the last time I contacted my local muffler shop (rhymes with Feineke) they told me that theyd have to put the car on a lift, instect al the parts and blah blah blah and that it costs $100 per hour. So I just got back from driving up there and talking to a tech in person at the garage bay door(something that always seems to help in these situations. Its the universal sign for "Im not afraid to be in a garage and Im discreet about under the table side jobs". So the guy there tells me itll be $20 to cut off the old donit flange and weld up a new 2 bolt flat flange. We shook hands on it and here I am. I just ordered a Vibrant stainless 3" 2 bolt flange off Amazon for $20 shipped with free 2 day shipping. I believe its also billet cut but Im not sure. Anyways now at least I know my Vibrant gasket will have the best possible chance to seal up and $40 for a perfect fitting midpipe and a $20 axleback is something I can definitely live with. It's still cheaper than buying a brand new eBay catback lol. Ill post pics when its all done.

Now I have to get to Ace hardware and source some M10x1.25x50-75mm ISO 10.1 bolts...this should be easy. Wish me luck fellas! Thanks!

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post #10 of 26 Old 06-17-2016, 05:34 PM Thread Starter
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Well I just got back from the muffler shop. Actually I got back about a half hour ago but Ive been beating my head against the wall trying to save my ridiculously convoluted new password but I cant because of some stupid error with the forum. SO for now I have to spend 10 minutes typing in this retarded temp password. Anyways...I got my new flange welded on in pladce of that donut flange, but Im a bit worried about it. It doesnt look like the weld penetrated all the way through, I think He wire MIG welded it instead of TIG welding it like youre supposed to with stainless for a proper weld and I think theres a small chance this flange will just break off at the first sign of a pothole or speedbump. Heres some pics after I got the flange welded on, but theyre also before and after shots of when I had to clean up the inside of the pipe with a dremel tool and file:







What do yall think? Do you think I should have Him lay a bead around the inside of the flange as well to make sure it actually penetrated all the way through? Before I went in HE told me that welding stainless would be no problem there. I should of asked if they have a TIG welder because I dont think this is TIG'd. Thoughts?

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post #11 of 26 Old 06-20-2016, 10:46 AM
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No to harsh on your welds but those look like hell. I'm sure that ll hold but I agree that doesn't look TIGed to me, or if it was it was done by someone who didnt know what they were doing. Did he do it on rollers of was that just balanced and hit?

It also looks like there is some flashing that needs to be ground off on the inside edge. i would clean that up with a rotary tool or a long reach belt grinder and see if the weld looks good from the inside. If everything looks good i would clean up those angry looking blobs on the outside and hit it with come exhaust enamel just to keep the weld from oxidizing.

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post #12 of 26 Old 06-20-2016, 09:45 PM Thread Starter
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Hahaha dude it doesnt offend me in the least. I just realized that I didnt tell yall the end of the story. So here goes, its a good one...

So I get my old factory catback out. Go to install the midpipe. It doesnt fit. The flange doesnt line up. Then I realize that the other flange is even more off from the axleback. Staurday night. Open downpipe. Cant install the hew Frankenpipe. So I throw a hail mary and call my guy at Meineke. Hes actually there! So I haul ass throwing the exhaust and tools in my car, lower the jack and take a gamble by driving my open downpipe stage 2 wrx past 2 police stations, through a college campus and through Colonial Williamsburg. Somehow I didnt pass a single cop.

So 2 hours and $40 later the same guy that welded that flangr chopped, welded, chopped, welded and chopped and welded again. He did the absolute best He could given these bullshit cheap poorly fitting exhaust pieces. Now my Perrin downpipe has been chopped and reclocked at the flange and my midpipe ahd axleback? Well I wont need to worry about an exhaust leak because He cut the flanges off and welded them together. It makes my nervous how rigid it is, but it sounds pretty awesome. Pics coming right now.

By the way...open downpipe? I dont recommend it. Pedestrians were upset. Children cried. My car shook violently. My butthole puckered.

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post #13 of 26 Old 06-20-2016, 10:14 PM Thread Starter
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My Perrin DP with the flange chopped off. It was then welded on at a different angle.



The flange for the DP was bolted to the midpipe, then welded onto the DP to ensure the bolts lined up:



The midpipe or pipe section of the axleback was about 8" too long, so since one of my gaskets flew off the roof of my car after leaving it there in a panic and driving away, my options were limited. I can always have V bands welded in later!



Here it is with the midpipe and axleback welded together. He put a sleeve of pipe inside them:



I know its far from ideal and potentially problematic. It worries me. So please dont kick me while Im down. In fact, I could use some silver linings or words of encouragment here lol.
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post #14 of 26 Old 06-21-2016, 11:32 AM
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It's on. It's done. It'll probably outlast some far more problematic part. You got a nice butt massage?

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post #15 of 26 Old 06-21-2016, 01:26 PM
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Not to stress you out but it really helps to have some flexability in the system. Maybe take it by that shop and have them throw a flex pipe between the down pipe and the mid pipe just so things can move around a bit without torquing your turbo flange.

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