DIY: OEM x-pipe secondary cat removal/gut

hmmm...i think i'm going to give this a go, looks easy enough. thanks!

Thanks a lot! That really helps .! I was thinking about replacing them
With just straight pipe.. Do you think that would change the sound at all ? or should I stick with just gutting the cats instead? P.s I'm having an exhaust shop do this . Thanks again !

great diy, any sound clips?

hey thanks a lot ! one more question i'm having an exhaust shop do this mod .. do you think it will make any difference in sound or anything thing in that nature if i just replace the cats with straight pipe.. ? once again thanks!

alpine92m3 wrote

hey thanks a lot ! one more question i'm having an exhaust shop do this mod .. do you think it will make any difference in sound or anything thing in that nature if i just replace the cats with straight pipe.. ? once again thanks!

You have to spend a little money for a tune if you want to see big power from this motor, along with deleting primary cats. Only reason for ONLY deleting secondary cats is boredom or tiny budget? It makes no hp...

This mod is actually quite pointless and does more harm than good in the long run, since the primary cats are the most restrictive, and you should retain your secondary cats to deal with the smell. The proper mod would be to delete the primary cats with TMS test pipes (cat delete kit ) and leave the secondary cats to take care of the smell that's common with deleting them. TMS test pipes are perfect, they slip over the stock exhaust and come with flanges and premium clamps to finish the job. You have 2 cuts and no welding. Then you get your tune from OETuning or ESS or AA, to take care of the CEL, you get 50-60hp. TMS sells them for $399. If you wanted to, you could retain the rest of the stock exhaust and it will be slightly louder than stock.

No problems with warranty and any company that I know of will always reflash your car for free in the event the dealer kills your tune.

STORM3 wrote

You have to spend a little money for a tune if you want to see big power from this motor, along with deleting primary cats. Only reason for ONLY deleting secondary cats is boredom or tiny budget? It makes no hp...

This mod is actually quite pointless and does more harm than good in the long run, since the primary cats are the most restrictive, and you should retain your secondary cats to deal with the smell. The proper mod would be to delete the primary cats with TMS test pipes (cat delete kit ) and leave the secondary cats to take care of the smell that's common with deleting them. TMS test pipes are perfect, they slip over the stock exhaust and come with flanges and premium clamps to finish the job. You have 2 cuts and no welding. Then you get your tune from OETuning or ESS or AA, to take care of the CEL, you get 50-60hp. TMS sells them for $399. If you wanted to, you could retain the rest of the stock exhaust and it will be slightly louder than stock.

No problems with warranty and any company that I know of will always reflash your car for free in the event the dealer kills your tune.

there is no smell from this mod. He is correct it is little hp with a stock setup and a small difference in sound. So if you are looking for the sound get and exhaust system.

STORM3 wrote

You have to spend a little money for a tune if you want to see big power from this motor, along with deleting primary cats. Only reason for ONLY deleting secondary cats is boredom or tiny budget? It makes no hp...

This mod is actually quite pointless and does more harm than good in the long run, since the primary cats are the most restrictive, and you should retain your secondary cats to deal with the smell. The proper mod would be to delete the primary cats with TMS test pipes (cat delete kit ) and leave the secondary cats to take care of the smell that's common with deleting them. TMS test pipes are perfect, they slip over the stock exhaust and come with flanges and premium clamps to finish the job. You have 2 cuts and no welding. Then you get your tune from OETuning or ESS or AA, to take care of the CEL, you get 50-60hp. TMS sells them for $399. If you wanted to, you could retain the rest of the stock exhaust and it will be slightly louder than stock.

No problems with warranty and any company that I know of will always reflash your car for free in the event the dealer kills your tune.

50-60hp. Are you serious:thumbdown

alpina527 wrote

50-60hp. Are you serious:thumbdown

even Turner say only 40hp gain from tune and test pipes, maybe 50-60 with high flow 2nd cats and exhaust (even catless), pulleys, scoops, cold air intake etc. to get 50-60 hp more you have to throw everything short of FI to get that.
no way to do it with just a tune and primary cat delete.

STORM3 wrote

You have to spend a little money for a tune if you want to see big power from this motor, along with deleting primary cats. Only reason for ONLY deleting secondary cats is boredom or tiny budget? It makes no hp...

This mod is actually quite pointless and does more harm than good in the long run, since the primary cats are the most restrictive, and you should retain your secondary cats to deal with the smell. The proper mod would be to delete the primary cats with TMS test pipes (cat delete kit ) and leave the secondary cats to take care of the smell that's common with deleting them. TMS test pipes are perfect, they slip over the stock exhaust and come with flanges and premium clamps to finish the job. You have 2 cuts and no welding. Then you get your tune from OETuning or ESS or AA, to take care of the CEL, you get 50-60hp. TMS sells them for $399. If you wanted to, you could retain the rest of the stock exhaust and it will be slightly louder than stock.

No problems with warranty and any company that I know of will always reflash your car for free in the event the dealer kills your tune.

How about not posting crap unless you know what your talking about! There is plenty of data backing up catless x-pipes and if you want to just repeat useless opinions from other threads, do it some were else. Obviously you believe everything you read and all the hype but have no real knowledge of how these changes actually change the flow, restriction and scavenging effects of the exhaust system.

Sorry.... I just hate useless crap that people seem entitled to spew on these boards!

alpine92m3 wrote

Thanks a lot! That really helps .! I was thinking about replacing them
With just straight pipe.. Do you think that would change the sound at all ? or should I stick with just gutting the cats instead? P.s I'm having an exhaust shop do this . Thanks again !

Alpine,

It will make no difference if you go strait pipe or gut the secondary cats. Actually you might get better performance out of strait pipes because there will be less turbulence from the gutted cat, but the difference would probably only be seen if you flow tested the x-pipe (no noticeable real hp/tq increase). So it up to you, but if you have a visual inspection in your area for emissions you will want to gut the secondary cat as it will look stock and there Will be no red flags as to what was modded.

mkPOTO wrote

great diy, any sound clips?

I'll try to get some up tomorrow.

video

RuthlessE90 wrote

video

Here are a couple of videos at the track of the exhaust, not very good videos. I will work on some up-close, in-car and drive-by videos and get them posted.

First video: This is Oregon's PIR front strait with UUC/corsa exhaust and secondary cat gut. This was full throttle in 4th gear at about 130mph and then letting off as going into braking zone.

Second video: This is at Bremerton raceway park with UUC/corsa exhaust and secondary cat gut. I was entering track from paddock at 1/2 throttle in 1st and 2nd.

Hi... I was wondering if you can just clear something up for me. In your second picture(post #1) can you tell me what is the left piece ( is it the secondary cat ) and the right pipe ( the one with slip joint, is that the pipe that goes to the front of the car towards primary cats) or is it the other way around?... Thanks (BTW getting this done tomorrow).

NECTAR wrote

Hi... I was wondering if you can just clear something up for me. In your second picture(post #1) can you tell me what is the left piece ( is it the secondary cat ) and the right pipe ( the one with slip joint, is that the pipe that goes to the front of the car towards primary cats) or is it the other way around?... Thanks (BTW getting this done tomorrow).

Pic #2 is showing secondary cat on left and exhaust pipe coming from main cats on right.

Probably a dead thread, just curious if the e92 m3 with aa exhaust and gutted sec cats could pass CA emissions? I currently have test pipes and need to pass smog and i obviously fail the visual inspection. I am opposed to taking out the pipes to put the cats back in to pass and then go back to the test pipes, too much back and forth. So i am now considering gutting the cats before i put them on but am hesitant in case i fail emissions then have to get new cats.....

Midpipe cats deleted: 335xdrive 2011

Will this make more drone to the car？

m3alabama wrote

if you are comfortable hacking up the exhaust than you should go a step further. Cut out the secondaries and cut out the primaries. Put the secondaries welded in to replace primaries and put it all back together. This should be enough to easily avoid the CEL and give you essentially a HFC setup

I was just thinking this since the secondary cats are 200 cells. i bet a good muffler shop could make quick work out of this. would it be much louder?

NELSON.MLGB wrote  

Will this make more drone to the car？

Same concern here if you might answer.

Quote:
Originally Posted by NELSON.MLGB
Will this make more drone to the car？

Linda_the_Cat wrote

Same concern here if you might answer.

I had my exhaust shop close to me take out the secondary cats and replace it with pipes with a small "crush" at the end so it would fit in the x pipe.

It does NOT drone, and it actually sounds very very good. Has more of a rumble and you can definitely hear its presence under load. I don't feel significant power gains, but it feels more "free."