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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N55 Turbo Engine / Drivetrain / Exhaust Modifications > Options if I remove my c4tless downpipe (F30 335i EWG JB4)
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      03-22-2018, 09:26 PM   #1
M-SP0RT
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Options if I remove my c4tless downpipe (F30 335i EWG JB4)

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I've had my 2014 F30 335i (EWG) for over 4 years and been running the following mods for almost 1.5 years:

JB4 with EWG & Flex connectors
BMS Intake
VRSF c4tless downpipe
VRSF chargepipe
E85 mix (~E25?)
Map 5 and hitting ~16+psi
Old JB4 firmware with no CEL

Car pulls hard and I really love it. I've surprised many other higher powered cars but I'm not trying to brag about kill stories here. But the c4tless dp has become a bit of a headache as it needs to be removed for emissions and the car stinks specially in my garage and in traffic with windows down.

I want to look into other mod options either with stock cats or good aftermarket cats with no CEL. I'm open to suggestions but I'm interested in similar power levels as my current setup. I'm flexible so let me know what you think. I'd like to keep this car for a couple more years!
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      03-23-2018, 04:50 AM   #2
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how much you think you will loose max hp (not midrange but max hp) installing stock dp on? probably 10hp, but not 20-30whp like downpipe sellers declare.

Quote:
Originally Posted by M-SP0RT View Post
I've had my 2014 F30 335i (EWG) for over 4 years and been running the following mods for almost 1.5 years:

JB4 with EWG & Flex connectors
BMS Intake
VRSF c4tless downpipe
VRSF chargepipe
E85 mix (~E25?)
Map 5 and hitting ~16+psi
Old JB4 firmware with no CEL

Car pulls hard and I really love it. I've surprised many other higher powered cars but I'm not trying to brag about kill stories here. But the c4tless dp has become a bit of a headache as it needs to be removed for emissions and the car stinks specially in my garage and in traffic with windows down.

I want to look into other mod options either with stock cats or good aftermarket cats with no CEL. I'm open to suggestions but I'm interested in similar power levels as my current setup. I'm flexible so let me know what you think. I'd like to keep this car for a couple more years!
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      03-23-2018, 05:38 AM   #3
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Maybe a catted downpipe bit its pricey
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      03-23-2018, 06:04 AM   #4
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Keep the catless downpipe, ditch the JB4 and get a proper flash tune. MHD or Bootmod3.
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      03-23-2018, 06:07 AM   #5
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300 Cell Sports Cat may be the answer.
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      03-23-2018, 07:44 AM   #6
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Quote:
Originally Posted by bradsm87 View Post
Keep the catless downpipe, ditch the JB4 and get a proper flash tune. MHD or Bootmod3.
How exactly will that help him with emissions checks or the smell?
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      03-23-2018, 12:24 PM   #7
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Quote:
Originally Posted by enemigo13 View Post
how much you think you will loose max hp (not midrange but max hp) installing stock dp on? probably 10hp, but not 20-30whp like downpipe sellers declare.
With stock DP I'll be back to JB4 Map 1 and that's a difference of 4-5psi which is a lot. There's a night & day difference between JB4 Map 1 and the way my car currently runs on Map 5. Not sure how much hp difference as I've never gone to the dyno but my butt dyno says torque difference is 100lb-ft!

Quote:
Originally Posted by bmwchue View Post
Maybe a catted downpipe bit its pricey
I'm worried a catted dp may not pass emissions and I've yet to find a catted dp that guarantees no CEL or emissions issues.

Quote:
Originally Posted by bradsm87 View Post
Keep the catless downpipe, ditch the JB4 and get a proper flash tune. MHD or Bootmod3.
But that's not going to solve my emissions or smell issues.

Quote:
Originally Posted by wibbles View Post
300 Cell Sports Cat may be the answer.
Any specific one you tried and does not trigger a CEL?

Quote:
Originally Posted by Whistlefist View Post
How exactly will that help him with emissions checks or the smell?
Exactly
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      03-23-2018, 12:28 PM   #8
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I'm thinking someone must have good experience with an aftermarket hi-flow catted dp or even another combination of mods on stock dp??

How about with more serious mods... Has anyone gone with aftermarket intercooler and seen measureable benefit on stock dp? How about fuel system upgrades etc? Or even aftermarket turbos?

That's not where I was trying to go with this thread but it appears focus for modding an F30 N55 during the past 2 years is on tunes instead of piggy-backs, but from my research those tunes don't add much more value (power) with the restriction of a stock dp.
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      03-23-2018, 01:18 PM   #9
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unfortunately, as you've already noted, the stock downpipe is the bottleneck. if you go back to stock, no sense in going too crazy in front of it. an aftermarket FMIC is something missing and would be a good addition to your setup. imo wagner's competition evo I would be appropriate since it is lightweight and has a tube fin core but there are cheaper bar-plate stepped cores that would do almost as well if you didn't want to spend that much.

for high flow catted downpipes look into fabspeed's sport cat with HJS 300cell cores. it's not cheap, though.

EDIT: a GFB diverter valve is also another thing to add

Last edited by alohasurftoad; 03-24-2018 at 02:06 AM.
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      03-23-2018, 02:21 PM   #10
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Quote:
Originally Posted by alohasurftoad View Post
unfortunately, as you've already noted, the stock downpipe is the bottleneck. if you go back to stock, no sense in going to crazy in front of it. an aftermarket FMIC is something missing and would be a good addition to your setup. imo wagner's competition evo I would be appropriate since it is lightweight and has a tube fin core but there are cheaper bar-plate stepped cores that would do almost as well if you didn't want to spend that much.

for high flow catted downpipes look into fabspeed's sport cat with HJS 300cell cores. it's not cheap, though.

EDIT: a GFB diverter valve is also another thing to add
wagner comp 2 is bar and fin.
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      03-23-2018, 02:24 PM   #11
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Quote:
Originally Posted by M-SP0RT View Post
I'm thinking someone must have good experience with an aftermarket hi-flow catted dp or even another combination of mods on stock dp??

How about with more serious mods... Has anyone gone with aftermarket intercooler and seen measureable benefit on stock dp? How about fuel system upgrades etc? Or even aftermarket turbos?

That's not where I was trying to go with this thread but it appears focus for modding an F30 N55 during the past 2 years is on tunes instead of piggy-backs, but from my research those tunes don't add much more value (power) with the restriction of a stock dp.
Iím going stock dp,Wagner comp 2 or CTS fmic, AA flash tune stag 1 so I am anxious to see without raising boost how much difference a cat less dp will make. Key is without raising boost.
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      03-23-2018, 05:26 PM   #12
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Quote:
Originally Posted by alohasurftoad View Post
unfortunately, as you've already noted, the stock downpipe is the bottleneck. if you go back to stock, no sense in going to crazy in front of it. an aftermarket FMIC is something missing and would be a good addition to your setup. imo wagner's competition evo I would be appropriate since it is lightweight and has a tube fin core but there are cheaper bar-plate stepped cores that would do almost as well if you didn't want to spend that much.

for high flow catted downpipes look into fabspeed's sport cat with HJS 300cell cores. it's not cheap, though.

EDIT: a GFB diverter valve is also another thing to add
AA has a high flow catted DP just on the horizon, and I will be transitioning from my stock cat to that as soon as they can ship it. I also am doing the DV+ actually this sunday and will post the DIY on the forums.
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      03-23-2018, 07:54 PM   #13
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Quote:
Originally Posted by alohasurftoad View Post
unfortunately, as you've already noted, the stock downpipe is the bottleneck. if you go back to stock, no sense in going to crazy in front of it. an aftermarket FMIC is something missing and would be a good addition to your setup. imo wagner's competition evo I would be appropriate since it is lightweight and has a tube fin core but there are cheaper bar-plate stepped cores that would do almost as well if you didn't want to spend that much.

for high flow catted downpipes look into fabspeed's sport cat with HJS 300cell cores. it's not cheap, though.

EDIT: a GFB diverter valve is also another thing to add
I've been looking for a catted DP as well.

+1 Fabspeed. HJS cat is quoted 93% as much flow as catless.
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      03-23-2018, 10:28 PM   #14
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Quote:
Originally Posted by raichean View Post
AA has a high flow catted DP just on the horizon, and I will be transitioning from my stock cat to that as soon as they can ship it. I also am doing the DV+ actually this sunday and will post the DIY on the forums.
Hopefully the cost wonít be anywhere near crazy like fabspeed.
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