Stock downpipe catalyst removal

[m5james]

I've been running gutted factory pipes for almost two years now, not a single issue other than a CEL which was fixed with my Halim/HCP stage 2 flash. I've got a set of aftermarket catless downpipes I'm going to try for the hell of it to see if it feels any different having 3" of straight flow vs filling that large chamber before it flows out, but for the price, there's money better spent than on aftermarket downpipes. As mentioned above, ALL aftermarket options need to be wrapped and/or ceramic coated as it's been proven that the back two cylinders will suffer from their extreme heat otherwise.

[Used2be]

Originally Posted by m5james

I've been running gutted factory pipes for almost two years now, not a single issue other than a CEL which was fixed with my Halim/HCP stage 2 flash. I've got a set of aftermarket catless downpipes I'm going to try for the hell of it to see if it feels any different having 3" of straight flow vs filling that large chamber before it flows out

It must have been your post I read those years ago, thanks. From what little I've read regarding turbocharged engines, it seems turbos prefer as little restriction downstream as possible. I'm thinking there might even be a small advantage to the large chamber attached to the exit of the turbo. Unlike NA engines with the tuned headers that help extract exhaust, turbos want a large empty space.

I haven't seen a good picture of the exhaust of the racing M6, but they dump it out right behind the front wheel and I bet it's just a short, large pipe.

[m5james]

The actual outlet of the turbo isn't the same size as the diameter of the exhaust piping so we're filling an air cavity no matter what, but I'm still going to try a full 3" to see if it feels any different, but I doubt it will.

[Lerxst M4]

Just got my used OEM downpipes in yesterday and will be gutting them over the weekend.

Shoudl be the best $300 I have spent on the car and I'll still have my OEM's to put back on if need be.

[TheHouseWon]

Originally Posted by Lerxst M6

Just got my used OEM downpipes in yesterday and will be gutting them over the weekend.

Shoudl be the best $300 I have spent on the car and I'll still have my OEM's to put back on if need be.

Time to call Mike at BPM to get stage II

[Lerxst M4]

Originally Posted by TheHouseWon

Time to call Mike at BPM to get stage II

Roger that (and to delete the cold start and CEL when it pops)!

[m5james]

I kinda like still having the cold start ever though it's not needed...I can hear it from a good distance away while I'm walking to it from work (remote start works up to 1500' away) and it definitely turns heads otherwise when it fires up :-)

[Lerxst M4]

Originally Posted by m5james

I kinda like still having the cold start ever though it's not needed...I can hear it from a good distance away while I'm walking to it from work (remote start works up to 1500' away) and it definitely turns heads otherwise when it fires up :-)

haha I bet! I work in a parking garage and cold start with just the AWE is pretty loud and I get looks from some. I can only imagine what it'd be like with catless DP's. I'm sure it'd sound FANfriggenTASTIC but I also leave my house at 5:55 every morning and I don't want to be put on blast from my neighborhood FB page...and I like my neighbors. lol

[m5james]

Haha, I hear ya...I work second shift so the X5M isn't started at my house until early afternoon and at 1am work my truck is hardly the loudest thing going at Boeing lol. I recently bought M5 headers and M6Beast gave me some exhaust ideas, so straight-thru resonators and the biggest tips I could find are only going to make it louder

[TheHouseWon]

You're turning your X5M into a lifted M5 !

[m5james]

Hey now, it's lowered a bit :-) I'm just trying to keep up with you guys lol

[babyboss]

Any dyno done with before & after oem catless dp ?

[Lerxst M4]

Originally Posted by babyboss

Any dyno done with before & after oem catless dp ?

I plan to have my car dyno'd prior to installing my catless OEM DP's - hopefully in the next week. Will redyno again after some time for adaptation.

Baseline dyno was 545whp / 545wtq when car was 100% stock.

[apsuard]

Gutted an extra set of OEM downpipes I picked up and took me 45 minutes with the help of a friend.

Will get them installed this week and will report back.

[KaWi]

I have done the same with my M5 Katalysts but the power on the Dyno was 30Hp less down to 700HP. After this I put 400 cells inside and I get 30Hp plus to 760HP. I think they need a bit pressure after the twinchargers.

[Igor_M5]

Originally Posted by m5james

Haha, I hear ya...I work second shift so the X5M isn't started at my house until early afternoon and at 1am work my truck is hardly the loudest thing going at Boeing lol. I recently bought M5 headers and M6Beast gave me some exhaust ideas, so straight-thru resonators and the biggest tips I could find are only going to make it louder

Slightly off topic, but just noticed you're swapping the turbo mani's from a tu to non tu? Keep in mind that your factory manifolds are dedicated to each bank. On tu's, the manifold crosses banks, so the o2's are expecting to read specific cylinders and not just a row.

If you haven't proceeded with this yet, just keep in mind that you'll need an entire cast from Matrix to get it properly working. lol

[ice7]

Interested in this....Any updates on the dyno numbers and sound clips of the OEM gutted downpipes?

[apsuard]

Originally Posted by ice7

Interested in this....Any updates on the dyno numbers and sound clips of the OEM gutted downpipes?

I had mine installed this week. I don't have any thing to compare to but to me it sounds like all other catless downpipes. I had new gaskets installed and no waste gate rattle at all. This was the best mod I ever did besides tune. Sound is absolutely menacing paired with my Erace. Can't believe I debated going catless for so long. The power is insane paired with my tune.

The only benefit from dragging my feet was going OEM gutted option vs aftermarket. I only considered the gutted approach lately and was considering AMS or ER catless before then.

Now that I have gone catless doubt I will go back any time in the near future. Smell and other complaints I heard seem overdone to me.

[m5james]

Originally Posted by Igor_M5

Slightly off topic, but just noticed you're swapping the turbo mani's from a tu to non tu? Keep in mind that your factory manifolds are dedicated to each bank. On tu's, the manifold crosses banks, so the o2's are expecting to read specific cylinders and not just a row.

If you haven't proceeded with this yet, just keep in mind that you'll need an entire cast from Matrix to get it properly working. lol

Entire cast from Matrix? What's lol? Nonetheless, I'm not the first to install these onto the S63, I've just avoided an absurd markup for relabeled factory pieces.

http://www.xbimmers.com/forums/showthread.php?t=638340

[m5james]

Originally Posted by KaWi

I have done the same with my M5 Katalysts but the power on the Dyno was 30Hp less down to 700HP. After this I put 400 cells inside and I get 30Hp plus to 760HP. I think they need a bit pressure after the twinchargers.

Without tuning to match, it's expected to lose power when mods like this are done. At minimum you should have gotten a stage 2 tune. Google any article about back pressure on FI engines...they want to breath, period.

[apsuard]

Originally Posted by m5james

Without tuning to match, it's expected to lose power when mods like this are done. At minimum you should have gotten a stage 2 tune. Google any article about back pressure on FI engines...they want to breath, period.

After removing the primary and secondary cats both in the downpipes I can't believe my car made any power breathing through those. Talk about thick and restrictive.

[ice7]

Originally Posted by apsuard

I had mine installed this week. I don't have any thing to compare to but to me it sounds like all other catless downpipes. I had new gaskets installed and no waste gate rattle at all. This was the best mod I ever did besides tune. Sound is absolutely menacing paired with my Erace. Can't believe I debated going catless for so long. The power is insane paired with my tune.

The only benefit from dragging my feet was going OEM gutted option vs aftermarket. I only considered the gutted approach lately and was considering AMS or ER catless before then.

Now that I have gone catless doubt I will go back any time in the near future. Smell and other complaints I heard seem overdone to me.

Thanks for the feedback. Been debating about doing this since I was afraid of stock DPs wouldn't get smooth flow with the catalyst removed due to the change of diameters through the piping. I do have a E-Race as well and bet it sounds intoxicating