DP to Catback Flange - Donut Gasket

Can anyone show me a picture of what the DP to Catback flange should look like when assembled properly? I just put an SPT v2 exhaust on the car (stock DP right now), and didn't pay nearly enough attention to what it looked like before I pulled the old one off. Now I'm wondering if I have this thing sitting right. It looks a bit funny, and I'm wondering if I didn't get the gasket seated properly.

It's normally a factory donut gasket 2.5in. Depending on the exhaust you might have to use a 2.5in flat exhaust flange gasket to match the factory DP.

Yeah it's a donut, and I put a new one in. It's more just the fitment. The two flanges don't come all the way together, which I get -- it just seems like they maybe didn't come together enough in this case. There isn't much direction beyond a torque spec at 13 ft/lb, but it seems like the actual assembly process of that flange is a bit more involved.

 

Basically I was hoping someone had a picture of what it looks like "properly" assembled so I can use that as reference. I'd also take "here's how to do the spring bolts & donut flange properly" as a step by step.

Nobody? Seems like someone must know how these things fit together.

I can snap a pic of mine tomorrow for you. When I bolted up my exhaust, i just tore the old gasket apart to get it off, cleaned up the flange, and then tapped the new one on with the butt of a screw driver. I started both bolts and then just evenly tightened the bolts all the way down snug, didn't use a torque wrench. It was pretty simple, the mid-pipe pretty much aligned and seated itself as I tightened the bolts. I can't feel any leaks with my hand around the gasket.

Right on, that is what I did -- it was more a visual thing -- when I looked at it, it was just kind of "huh, that's a lot of gasket visible". I'd still love to see a picture of a "properly seated" one. I wasn't sure if you had to do anything funny like compress the springs before you torque the bolts or anything, or compress the joint to some sort of torque before setting the bolts.

If its not sitting flush with donut gasket and there is a significant gap then you'll need to get a 2.5in flat flange gasket more than likely. The flanges must sit flush against each other. I almost guarantee the new exhaust tapers down to a 2.5in flange with a 3in inlet which won't mate with the donut gasket like my Greddy Evo2. It's been covered before.

It's an SPT v2, so it should be the proper inlet size.

As stated (IIRC) the SPT v2 is a 3in and tapers down to a 2.5in at the DP flange which would require a flat gasket and not a donut.

Hm -- OK, that's interesting. I couldn't find a clear answer on here anywhere. I still can't. Looking at the pipe, it certainly looks like it's intended to accept a donut (it's a rounded inlet on the flange). I suppose it could still be rounded that way and use a flat flange though.

It still may work with the donut. Measure the inlet of the mid-pipe. If the inlet is 2.5in then yes you would use donut. If the inlet is 3in then a flat gasket. You may have to clean the DP thoroughly to make new donut fit better. Either way the flanges should sit flush.

I'm pretty sure it's a 3" OD pipe with a 2.5" inlet for a donut flange where it mates to the DP. It's designed to mate to a stock DP, so it would be odd for them to use a 3" inlet. I've been searching all up and down the forums here, and there's some much back and forth/conflicting on this it's really annoying.

 

The best photo I've seen is http://legacygt.com/forums/attachment.php?attachmentid=72628&d=1251399039

 

You can kind of see the tapered inlet there that is kind of 'ball jointed' for the donut.

 

Obviously mine is mated on the car right now, so putting a caliper on the inlet is a bit tricky.

I have a Greddy Evo2 which tapers down to a 2.5in flange with a 3in inlet. Which uses a flat gasket (it's a bit odd.)

 

Yours definatley tapers to a 2.5in and should use the donut from what I can see. You'll just need to massage the donut on there and make sure the bolts you have are long and strong enough.

Yeah the SPT definitely takes the factory donut gasket. Before I took it off to sell to you, that's how it was installed. You'll see a lot of the gasket even after you're got it bolted down, as the flange faces won't come all the way together (which as far as I can tell is the whole point of a donut gasket...it stays sealed while allowing the pipes move relative to one another).

 

Pic of my HKS, which should look just like yours:

http://i268.photobucket.com/albums/jj11/Dbl_D718/2011-10-25_15-13-51_424.jpg

That is perfect -- and almost exactly how mine sits. I didn't look at the stock before I pulled it off, but I feel it was MUCH more compressed - the springs were pretty well fully compressed, and of course one of the bolts snapped in half when I removed it. So I just wanted to make sure having that maybe 1/8 to 1/4 inch gap of gasket was normal.

Both of my bolts snapped when I removed the SPT, and they were the only ones that were rusted on the cat-back. The rest looked almost new.

 

I couldn't tighten mine down more if I wanted to though. Like I said...it doesn't leak so it must be good. I've never looked at a factory exhaust, but the SPT looked just like this on mine, except that the gasket was a rusted mess that probably didn't seal at all.

The donut gasket has a flat shiny side and a rounded side, which direction does the flat surface of the donut gasket face?

 

Thanks.

The flat surface goes towards the DP/front of the car. The rounded side mates with the cat-back, towards the rear.

Thank you.

I'm pretty sure I was tellin myself it looked like the opposite, haha, so thanks again.