So I've got a new question I haven't seen asked before, and this is more of a fitment question than a "which cat" question.

So I'm getting ready to get the parts to finish up the front half of the system. I know with headders, the objective is to get the converter as close to the headder collector as possible. The Pacecetters have a 3" collector.

Well, was getting the 94136 based off all the obvious reasons around here. But then I got to thinking…Magnaflow has a 94139 which is the exact same converter except with 3" in/out. Then I really got to thinking…wouldn't this help my exhaust guy fit the converter closer easier if the dia of the converter was 3"?? If you use a cat with 2.5", he's going to have to make a small section of pipe to size that down between the collector and the cat, which is going to add some distance.

Seems to me, choking down the pipe from 3" to 2.5" after the converter is going to be easier and less critical than between there and the collectors; not to mention the discussed benefit of getting the cat as close as possible.

Thoughts???? Or am I waaaaaaaayyy over analyzing this??

**Side note…ever notice the word analyze starts with '****'??

 

Oh yea, one other…Do you guys have your exhaust guy add some type of feature where the exhaust can be taken apart between the collector and the cat, or do you just weld up the pipe straight to the collector and call it good with no concern about being able to disassemble it?

 

I would probably go to 2.5 right at the collector, then run 2.5 cats.

 

The easiest way that I dealt with this is to use a 3" maggie converter. The Pacesetter collector is 3" OD and the maggie converter is 3" ID so they will slip right over the collector its almost a perfect fit. The Maggie I used was a 94109 part# but has probably changed since then. I reduced the piping down to 2.5" immediately after the converter no problem.

 

And about taking the exhaust apart between the collector and converter just clamp it in case you need to remove the header cause it wont come out with the converter attached (at least not in my case). 3" SS walker band clamp is what I was using.

 

Don't think clamping in that area is a good idea; doesn't sound good to me anyways. Isn't a perfect weld/seal prior to the cat ideal for increased odds of not getting a CEL?

 

The headers should be female flanged to connect to some pipes with male flanged ends to connect for removal if ever needed in the future. You can buy ball flanged connection kits off mandrelbendsolutions.com to pt throughout your exhaust but they aren't very cheap.

I feel it is best to run 2.5" out the collector to begin with which is why I will go with the OBX kit. You can run 3" cats then reduce to mandrel 2.5" and it will perform just fine too.

 

Photo's that I've seen of the Pacesetters don't show any type of flange or connector at that point. They all just look like the headder collector comes to an end. I may be wrong, but I believe the OBX for my truck are 3" collectors also, making the difference moot. I'm already enough money into this project and don't personally see any real harm in welding the cat and/or any pipe segment straight up to the headder. This is the only reason I've ever had the exhaust apart don't foresee one in the future.

I would assume the decision between 2.5" vs 3" for the cat tubing size is irrelevant in regards to CEL likelihood? I mean one is not more likely to cause issues over the other?? Shoudl be a wash?

 

Have the weld flanges... That's why when I do headers full on kit so I don't have to deal with this crap. I'm not knocking anyone, but when you think about it, Dynatech's are around 1300 and autoanything sells them and offers discounts. To get a top quality system all mandrel bent and 304 ss like this and SW's system, you will be well over their asking prices. The beauty of these kits is everything is provided and it all fits and it top quality. My advice is to keep that same idea. Headers should have flanges welded on. Then flex pipe from header should be plaged then welded to the cat. Then the y-pipe should be another unit. Less of a hassle if something happens to a converter. Just thinking long term here.