Looking to eliminate stock 2.5" midpipe

[aclosedmind]

I may have a slightly different situation than most that I'd like some feedback on. I have a Roush phase 2 setup on my 2017 GT with BBK shorty headers which bolt up to the stock catted midpipe which then goes to my 3" magnaflow catback with x pipe. I'd like to eliminate the 2.5" midpipe section and have 3" exhaust from the rear of the cats through the rest of the system. I've looked at catless midpipes but all seem to be set up for long tube headers versus bolting up to the stock locations, likely because of the one piece manifold/cat design on the one side. Since I have shorties, those wouldn't work without modification. I've similarly looked at catted midpipes with essentially the same issue plus the concern about CELs from "high flow" cats. I feel like the best solution may be just to have an exhaust shop make custom pipes to weld directly to the rear of the cats and then lop off the stepdowns at the beginning of the catback thus making a full 3" connection from the header collector through the cats and then out the rest of the system. Thoughts?

A couple of points:

1. I don't want to modify the Roush Phase 2 stock tune. Not willing to budge on this for my own reasons
2. I don't want to install long tubes. That ship has sailed and the investment at this point would be significant and also require me to change my tune which I don't want to do as noted above
3. I don't want to change my catback system but I am willing to modify it to eliminate the 3" to 2.5" stepdown at the front of the X pipe
4. I'm willing to consider going catless or high flow catted provided I can avoid CELs or changing to LTs or changing my tune

Thanks for your feedback

Sponsored

 

[BmacIL]

The cat outlet is 2.25" all the way to the catback. You'd have to do something like MAK cat delete pipes and get green cats welded into them to make it full 3" after the collector.

 

[aclosedmind]

The cat outlet is 2.25" all the way to the catback. You'd have to do something like MAK cat delete pipes and get green cats welded into them to make it full 3" after the collector.

As in the interior of the cat is 2.25/2.5"? When you say green cats I assume you're not referring to the ones MAK sells. If these won't cause CELs and are 3" all the way through that might be a good way to go

 

[BmacIL]

As in the interior of the cat is 2.25/2.5"? When you say green cats I assume you're not referring to the ones MAK sells. If these won't cause CELs and are 3" all the way through that might be a good way to go

The entire pipe from the exit of the cat to the catback is 2.25", not 2.5".

You'd kinda have to piece it together custom. Not sure if MAK sells them.

 

[aclosedmind]

I guess it doesn’t matter much what size it is as I aim to replace it all. Are there better flowing/larger cats that won’t trigger a CEL?

Or eliminators on a catless setup that won’t cause issues?

 

[Furious18]

Buy o2 sensor bung extenders. Won’t throw a code without cats.

Don’t need a retune for headers (cat or catless) if you don’t want.

I think you might have to have an exhaust shop make the piece you want in 3”

 

[aclosedmind]

Big thanks to all for your replies and PMs. Sounds like the way to go is the catless 3” midpipe with O2 eliminators or some measure of custom catted midpipe

 

[GregO]

Big thanks to all for your replies and PMs. Sounds like the way to go is the catless 3” midpipe with O2 eliminators or some measure of custom catted midpipe

If your retaining the OEM converters be sure the rear O2 is the same distance from converter outlet core as designed by Ford. No need for spacers or eliminators.

 

[aclosedmind]

If your retaining the OEM converters be sure the rear O2 is the same distance from converter outlet core as designed by Ford. No need for spacers or eliminators.

A good point. Ideally I would like to retain converters but it seems all the aftermarket ones trip CELs. My only concern with the deletes would be if there are any CEL or other issues plus the volume. I know I am weird but I love the way it sounds now with cats. That small midpipe is really grinding on my OCD though

 

[aclosedmind]

Just to close the loop here, I decided to go with the Mak 3" catted midpipe. I'll modify it as necessary to hook up to my BBK shorties and my 3" magnaflow catback. I'll also run defoulers to make sure I don't get a CEL and don't have to change the tune. This keeps me at least mostly emissions friendly with the benefits to the exhaust sound from having a cat (for my personal tastes). Once its all done I'll let you all know how it goes and thanks much for all the great feedback

 

[aclosedmind]

Just wanted to follow up on this. I did order the MAK Performance catted 3" midpipe kit with the connection for a 3" catback and O2 defoulers. Had it installed today. With my BBK shorties we did have to cut off one of the flanges and reorient it a bit. Lopped off the stepdown section from my magnaflow 3" catback so now its a full true 3" system. The difference in volume is considerable. I think it sounds great. Here's some pictures

Sponsored