Air gap pipe?

[KChurch86]

I'm getting ready to order replacement secondary catalytic converters and came across something I was unfamiliar with.


Before anybody says "Just straight pipe it", don't. End of discussion.


I'm shopping around on RockAuto and I saw that each of the Walker brand rear cats they carry happen to have a $50 mail-in rebate on them as well. The Walker cats use their "air gap pipe", which is essentially one pipe sleeved inside of another, apparently for insulative purposes?

http://www.walkerexhaust.com/products/pipes-tubing/air-gap-pipe

Now, it seems to me as though eventually, the outer pipe is going to rust open and expose the inner pipe to the elements, with an added "bonus" of an outer pipe to hold on to dirt, sand, mud, snow, moisture, etc. and cause accelerated failure of one, or more-likely BOTH of the pipes. Makes sense, right? Then, to complicate matters, the double wall would make it difficult to clamp in a section of patch pipe to repair any holes...also make sense?

Does anybody have an experience in working with this "air gap pipe" double-walled exhaust pipe?

The $100 total mail-in rebate is mighty attractive, but if the air gap pipe is useless BS, then I'll just get the Eastern Industries catalytic converters for a few dollars less than the Walkers.

What would you do in this case? Keeping in mind:

1) Custom is not an option.
2) Straight pipe is not an option.
3) Cost is VERY important.
4) Straight pipe IS NOT AN OPTION.

 

[Silver dude]

It's been two winters and my Walker catback is still rust free, way better at holding up then other aftermarket exhaust I've had previously. Air gap pipe is likely better in design then the OEM style shields which promptly rust, rattle and fall off. However, no real experience with the double wall construction. I think it would likely hold up twice as good. Sure if rust got inside it could cause the layers to rust but it would have to eat through the outer layer first which would ruin any exhaust. As long as its fully welded there likely won't be any way to tell its double walled. Only thing that concerns me is if it starts to rattle how would you address it? But, overall I can say it sounds like a good idea and they seem pretty well reviewed overall on Amazon.

 

[KChurch86]

Thanks for the input. I want to believe that they'd hold up very well, given the double wall, but I can't help but feel like the air gap would hold moisture and cause accelerated failure.

Maybe the fact that it's a pair of cats as opposed to just tailpipe means the higher heat would keep everything dry? I dunno. As long as there is a warranty on them, maybe it's worth it regardless of how long they last.

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[Prime]

This is an interesting thought. How much are those cats? I still need to do mine as well.

 

[KChurch86]

This is an interesting thought. How much are those cats? I still need to do mine as well.

$165 each with a $50 rebate...so $115. That's for the Walkers. The Eastern Industries ones are like $158/$166 with no rebate.

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[Prime]

That's not too bad. From rockauto?

 

[KChurch86]

That's not too bad. From rockauto?

Yessir. I'm going to try and make a decision by the end of the day and put in an order on a set of one or the other.

Currently leaning towards the Walkers, but mostly for the rebate.

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[KChurch86]

Well I decided not to go with the Walkers. I remembered how close the passenger side cat pipe is to my transfer case shift linkage and got worried that the double wall pipe would mean a larger outer diameter, which wouldn't clear the linkage. I actually had to put a small dent in the pipe to clearance it.

Ordered the new parts (Eastern Industries) at 7:30 this morning, FedEx says I'll have them "by tomorrow". Didn't pay for faster shipping. #Winning

 

[KChurch86]

Prime, if you're interested or curious, the Eastern Catalytic units seem very well made. They come with a front crush gasket and a rear metal gasket, even though the Rock Auto listing only says one of them does.

The converter body is small, much smaller than the Pacesetter units. The heatshields seem nice and solid, too. Time will tell how well they perform and how long they last.

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