X5M DIY cat gut

[Sylvan Lake V35]

I have been debating down pipes for awhile now my want list is long and expensive. My G35 turned into a never ending money pit and I promised myself the ///M would be kept simple. I decided to do DIY cat gut, I will follow this up with a custom tune from ECUProgram in Calgary. We will see how things go if I decide to do dynos, before, after the gutted cats and after a tune. Anyway I am not sure if anyone else has attempted this on an X5M so I thought I would document it.


My tools



About to start



The hole saw was my tool of choice



With the hole saw you can Tear up the cat material pretty quick.



The material turns to dust



On the edges there is some insulation that peels off pretty quick with the hole saw.





The issue with the hole saw is it's too short



After some pounding with a long flat head screw driver I broke through the first layer of the cat. Then there is about 1/2" of dead space and then another lay of the cat.



I pounded a hole through this layer





Just about done



Done...

[Sylvan Lake V35]

I am curious to dyno before and after to see what kind of gains if any this will give. It will certainly reduce a serious restriction.

Here is what came out.

[PrimoM3]

Any info you can provide after reinstalling? Check engine, O2 sensor lights? Any increase in sound? Does it feel quicker via butt-dyno?

Thanks!

[Sylvan Lake V35]

Originally Posted by PrimoM3

Any info you can provide after reinstalling? Check engine, O2 sensor lights? Any increase in sound? Does it feel quicker via butt-dyno?

Thanks!

I haven't installed them yet, I am debating getting them ceramic coated. I fully expect a CEL I will have my tuner turn it off. The noise will likely be louder as well....I hope it's not too loud. My eisenman race exhaust sounds about perfect.

I will report back as soon as I get them on.

[Phatcat]

Oh wow.........

[RichardH]

Thanks for doing this, please keep us posted.

[texvette]

Did that years ago on a truck. mechanic told me how. Not a big difference in
running or sound. Be interesting to read now with all the sensors how the
knock out still does. Its amazing how much stuff comes out of that little
box !!!!!!

[trev230]

Did that myself on a car back in 2000. All I got was loud popping between shifts and the ever so annoying hollow sound the exhaust produced afterwards.

I swapped it out for a performance race cat and it was much better. Each vehicle and cat are obviously different though.

[Sylvan Lake V35]

Originally Posted by texvette

Did that years ago on a truck. mechanic told me how. Not a big difference in
running or sound. Be interesting to read now with all the sensors how the
knock out still does. Its amazing how much stuff comes out of that little
box !!!!!!

Was it a turbo vehicle? I wouldn't expect much for gains on an NA vehicle especially without any tuning to accompany it.

Originally Posted by trev230

Did that myself on a car back in 2000. All I got was loud popping between shifts and the ever so annoying hollow sound the exhaust produced afterwards.

I swapped it out for a performance race cat and it was much better. Each vehicle and cat are obviously different though.

I do hope it doesn't give a hollow popping sound. It it does I will get a set of aftermarket down pipes. I guess until someone tries we won't know.

[Toneaero]

YES!!!!! Please give us some good news on this mod. I never could understand why aftermarket catless downpipes costs $1,600k+

[Sylvan Lake V35]

Originally Posted by Toneaero

YES!!!!! Please give us some good news on this mod. I never could understand why aftermarket catless downpipes costs $1,600k+

Me neither I have had lots of down pipes before I even had a wild set of 3.5" ones that were about 4' long custom built For my G35 and they didn't even cost $1,600. I have a couple friends that are fabricators that I was trying to get to build me a set but one guy designs and builds custom turbo kits for G35/350z G37/370z and he has 20 kits on order right now(it's his side buisness) so he said he was way too busy to do it the other guy owns a large speed shop and the only way he would take it on was if he built jigs and mass produced them. He figured he could have them built out of titanium and still have good profit margins at $1,500. However he is more int GTR, EVO, and STis where the volume is high. He said I am the first person that has ever even mentioned any thing about an X5M to him. I guess I don't blame him spend the time building jigs and sell maybe 50 sets for an X5M or go with a tuner platform and sell 100s....I guess that's why we get raped on down pipes. I feel if I was willing to leave my rig with the guy that does turbo kits he might build me a one off set. When I approached him about it I wanted to leave a set of OEM down pipes and have him built a jig off them and make the 3" DP from there...

[northern2020]

Did this mod to my 2001.5 Audi B5 S4 downpipes...

They were named "piggie pipes" after the forum member whom first utilized gutting his cats...

Worked so well it was a phenomenon amongst those Audi owners!!

[SteveMD]

Originally Posted by Toneaero

YES!!!!! Please give us some good news on this mod. I never could understand why aftermarket catless downpipes costs $1,600k+

Because it's a BMW. In the 335 community we were getting raped with $1000-$1200 downpipes until the 'Godspeed/Raceland' eBay pipes came along for $200-$300. The established vendors tried to give all kinds of amusing reasons why they weren't as good as their product but of course they were.

[Orange fever]

Op, I hope you did baseline dyno .... So we can see if it gain any horsepower
And thanks for doing this... We all can save some money

[Toneaero]

This will be my winter project once the OP tells us his opinion after driving with it.

Seeing prices ranging from $1600-$2999 is ridiculous. Its just a metal pipe with a flex pipe right?

On a side note, how hard was it to pull out and install? It looks fairly straight forward from looking over akra's install manual. Any special tools/bits needed to take it out? Any tips you learned along the way? Skip the hole saw and just punch it with a screw driver right?

[Sylvan Lake V35]

The hole saw made it much quicker...I started with a flat head and a hammer but i had a hole saw and a drill so i thought i would give it a try and it cut the time in half. if you dont have a drill and hole saw it could be done with a flat head/hammer.

I have yet to swap them in so i will discuss a base line a little more in depth with my tuner. They say 4-5hours to swap the down pipes. i might just do it myself in my garage if i can find the time. It looks very straight forward, pull a couple O2 sensors a V band and two nuts...

I spent a pile of money this week on my wifes 10yr annaversary ring so cash is a little tight or I would pull the trigger on base line, gutted down pipe and gutted DP w/tune dynos. as it stands i might go with a base line now (my rig goes in for clear paint protection wrap this week) then on the week end i will install the gutted DP and re-dyno. After I recover from christmas do a tune with a final dyno...I just have a ton of crap going on in the next couple months (Nov/Dec)I am taking myself and 3 other guys to a Broncos game so I have to pay for tickets/hotel/flights for 4 guys (i do get rembursed) and my sister is getting married in mexico so I have to fly our family in for that coupled with christmas...just bad timing for expendable cash flow..

I do hope to have some results though, worst case scenario these lose power or sound crappy and I am buying a set of $1,600 aftermarket down pipes

[blaferty]

Have you installed the gutted pipes yet? Very interested in results.

[Sylvan Lake V35]

I am in Mexico on holidays right now but when I get back on the 25th of November I plan to have them installed. Unfortunately my tuner wants over $200 for dyno runs so it would be close to $500 to get before and after...it's just a little steep to satisfy a curiosity. I might work on him and see if he will cut me a deal, I have been getting a fair bit of work done there lately.

[Toneaero]

Is that price for a custom tune or just dyno runs? Just dyno runs shouldn't cost more than $75 for 3 pulls.

[theaudir8fan]

that is most likely just dyno runs, unlike you guys, here in canada, we get screwed on pricing for doing anything, that's just the way things go.

Sylvan, we should meet up after you put these in, i really want to hear the sound difference

[windsailor]

Originally Posted by theaudir8fan

that is most likely just dyno runs, unlike you guys, here in canada, we get screwed on pricing for doing anything, that's just the way things go.

Sylvan, we should meet up after you put these in, i really want to hear the sound difference

+1

[Sylvan Lake V35]

Just dyno runs....we don't have many options here so it's take what you can get most of the time.

Sounds good R8fan, I already have eisenman exhaust but we can meet up and you can have a listen. I should have got the pipes installed while I was on holidays but I keep telling myself I was going to install them in my garage when I get home. However my ambition is on the low side lately not to mention it would suck if it goes into limp mode when I was driving it from sylvan to Calgary.