downpipe to cat question
 

Hey everyone, just got a 94 Montego Blue. Previous owner had a downpipe installed, just noticed something that really bothered me. Between the downpipe and the cat there is a small 4" long piece of thin aluminum that is a little loose - I can rotate it with my hand. Before I start taking things apart, is this supposed to be there, maybe a clamp has come off?

Not sure what you're describing. Could be a heat shield?? Can you post a photo?

There is a u-shaped spacer on the downpipe side of the cat-downpipe joint, and there is a heat shield on the cat between the cat-downpipe joint and the main cat body. Neither is essential.

My heat shield was loose, and I suspected it for a rattle.
Get a big steel band with the screw-type tightener. Wrap it the whole way around this heat shield and tighten it until the pressure on the side seams squeezes it against the pipe. That should take care of it.

Dave

It's definitely not the heat shield, it is a small piece of pipe (I think the joint you are talking about, it's more like an 'S'). When I 'adjusted' the joint by moving it 1/4-1/2" away from the main downpipe bolts, my exhaust didn't sound right so I moved it back flush with the pipe it is covering to connect to the downpipe. I can't find my camera, this is what it is like:

CAT - thin joint covering portion of stock piping - | | - downpipe

The two | are the front end of the cat pipe and the downpipe bolted together. It seems like thin joint was used to maybe cover a hole in short piping from DP to converter?

That piece/part doesn't sound like it's part of the original exhaust system. May be a piece of pipe that was rigged to "patch" an exhaust leak on the DP??

Here is a picture of it. On the right is where the CAT pipe and DP connect (purplish). The joint is flush with this right now and is orangish in the picture. I had a flashlight on it.

I'm not familar with the stock FD main-cat. I bought my FD with an MP already installed. But the piece to the left of the flanges looks like a heat shield. Maybe the Main-Cat developed an exhaust leak (small hole) that can't be seen because the shield is covering it??

Sorry, I know I'm not being much help.

Weird question, but are you sure that isn't the gasket that's supposed to seal the DP to the cat? And maybe it's all broken up, and sort of swiveling on one of the bolts?

I don't think he's referring to the DP / Main-Cat exhaust gasket. The piece he's concerned about is the piece of aluminum that's located on the Main-Cat exhaust pipe side just before the flanges mate.

Ahhh, I get it. So the heat shield on the front pipe of the cat is moving around. And this is a problem because... ;)

Yep orange part looks like a heatshield piece to me. This piece should not really change the exhaust note at all though. It does sound more like a gasket is what your describing by the fact that exaust note varies when you move it though. Outside of the gasket between the downpipe and maincats' pipe right in the flange I can't think of anything that would affect exhaust note in that picture.
It does look like your pipes arent really set together very well either....

Indeed, the exhaust note was what had me thinking gasket. I do notice a fair amount of black soot at the bottom of the DP flange where it's mating to the cat, which indicates exhaust leak to me. Certainly what mine looked like when I had a similar leak. Anyway, maybe by pushing the heat shield around he jostled the DP to cat interface, resulting in the different exhaust note?

My thoughts exactly Spurvo....

Yeah sorry a newb question there. The primary heat sheild was taken off, that 'joint' was just a small heat sheild. I didn't realize the RX7 has 3 heat sheilds by the cat. I'm going to get the car up on jacks and check out the whole exhaust more closely, check for possible problem spots. The exhaust note is fine now but I am a little paranoid as a new owner :)