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      05-11-2021, 09:50 AM   #1
Bay23
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Downpipe with no tune??

Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
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      05-11-2021, 10:11 AM   #2
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Quote:
Originally Posted by Bay23 View Post
Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
Before I got a bm3 license and tune, I ran a VRSF catless downpipe and chargepipe for awhile. Got a CEL but it won't harm anything. You'll hear the turbo spool compression and decompression sound, faster throttle response, and a tiny bit more power.
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      05-11-2021, 10:47 AM   #3
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difference between stock map catted or catless is pretty significant on a b58 .
my car makes 330whp catless stock tune ,
100-200km/h went down from 11.4 to 10.22 .
i had an opf too
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      05-11-2021, 12:54 PM   #4
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Quote:
Originally Posted by Bay23 View Post
Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
catless without a tune is possible, but you win the most with a tune , turbo is less restricted with a catless downpipe, so stage 1 would be better.

Catless with a O2 spacer would not avoid a Cel, for that you need at least a 300 cell or more Downpipe from a good brand also !!
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      05-11-2021, 02:01 PM   #5
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Quote:
Originally Posted by kriszty View Post
Quote:
Originally Posted by Bay23 View Post
Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
catless without a tune is possible, but you win the most with a tune , turbo is less restricted with a catless downpipe, so stage 1 would be better.

Catless with a O2 spacer would not avoid a Cel, for that you need at least a 300 cell or more Downpipe from a good brand also !!
The cell count isn't really the issue but rather the cat used. Fabspeed which is CEL guaranteed uses a 200cell cat and is sold for $2K. AA is a 400cell cat and is sold for ~$1500. Almost every other catted downpipe on the market is also 200cell but they all throw a code, have no guarantee, but are 75% less than the Fabspeed.
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      05-11-2021, 03:05 PM   #6
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From reading other posts some people have had good experience with the O2 spacer avoiding the CEL, Im not sure about longevity of keeping it off though.
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      05-11-2021, 04:13 PM   #7
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Quote:
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From reading other posts some people have had good experience with the O2 spacer avoiding the CEL, Im not sure about longevity of keeping it off though.
I had an elbow O2 and never got a CEL catless.
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      05-11-2021, 08:12 PM   #8
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Those elbows definitely fck with the AFR. It's one thing to make the DME not throw a code for the lambda out of wack. It's another to move the secondary sensor farther away from what it should be measuring. The DME also uses those values to change the AFR
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      05-12-2021, 09:14 AM   #9
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Quote:
Originally Posted by Bay23 View Post
Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
The downpipe will add noticeable power even without a tune.
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      05-12-2021, 09:24 AM   #10
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Quote:
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The downpipe will add noticeable power even without a tune.
That. I can confirm.
I wouldn't go completely catless for so many reasons, but that's a personal choice/responsibility.
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      05-12-2021, 09:28 AM   #11
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Quote:
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That. I can confirm.
I wouldn't go completely catless for so many reasons, but that's a personal choice/responsibility.
I prefer catted as well
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      05-12-2021, 06:46 PM   #12
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Quote:
Originally Posted by mike@x-ph.com View Post
Quote:
Originally Posted by Bay23 View Post
Curious as to everyone's thoughts on installing a catless downpipe without a tune and if its worth it? Im looking at either Vrsf or Evolution Raceworks. I saw the ER downpipe on the dyno added a decent amount of HP with nothing else added to the car. My 340i is still under warranty so i do not want to add a tune but i figured i could put a downpipe on and add a little extra power that way. Worse case if i needed to bring the car in for repair i could always put the stock downpipe back on. Also my plan would be to add a O2 spacer to avoid a CEL.
The downpipe will add noticeable power even without a tune.
Couple days so far on this boat (catted). Car does feel nice.
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      05-12-2021, 08:15 PM   #13
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Originally Posted by Logicoeur View Post
Couple days so far on this boat (catted). Car does feel nice.
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      05-13-2021, 09:34 PM   #14
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If I were to take an aftermarket DP off and put the stock one back on. Would the dealership have a way of knowing about it? I wouldn't want any reason to be denied a claim by warranty over a downpipe
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      05-14-2021, 03:48 AM   #15
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Quote:
Originally Posted by Bay23 View Post
If I were to take an aftermarket DP off and put the stock one back on. Would the dealership have a way of knowing about it? I wouldn't want any reason to be denied a claim by warranty over a downpipe
No.
Unless you damage something by doing it
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      05-14-2021, 09:22 AM   #16
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Quote:
Originally Posted by Skyhigh View Post
Quote:
Originally Posted by Bay23 View Post
If I were to take an aftermarket DP off and put the stock one back on. Would the dealership have a way of knowing about it? I wouldn't want any reason to be denied a claim by warranty over a downpipe
No.
Unless you damage something by doing it
So the car doesn't store O2 info at all?
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      05-14-2021, 09:31 AM   #17
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If you are planning to drive catless and NOT fool
the Lambda sensor, that's a different story.

If you put a (emission compliant) catted DP you will be fine, nothing registered in the electronics, purely mechanical.

As I said - I would not put catless for so many reasons….
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      05-14-2021, 07:54 PM   #18
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Quote:
Originally Posted by Skyhigh View Post
If you are planning to drive catless and NOT fool
the Lambda sensor, that's a different story.

If you put a (emission compliant) catted DP you will be fine, nothing registered in the electronics, purely mechanical.

As I said - I would not put catless for so many reasons….
Okay thank you
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      05-17-2021, 01:46 AM   #19
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Quote:
Originally Posted by T_H_O_M_A_S View Post
difference between stock map catted or catless is pretty significant on a b58 .
Yeah The OTS tune adds five psi of boooooooooooooooooooost over stock. That's gonna make some power
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      06-04-2021, 07:40 AM   #20
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I am also thinking of going to a catted downpipe.

Does anyone know if a 400 or 300 cell would still be good for a stage 2 tune?
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      06-04-2021, 07:46 AM   #21
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Quote:
Originally Posted by steveindabmer View Post
I am also thinking of going to a catted downpipe.

Does anyone know if a 400 or 300 cell would still be good for a stage 2 tune?
Yes it is. It is not an exact science - a high flow catted DP is "higher flow" than stock either way. I have personally never heard of a 400 cell for B58, but the number of cells in reality tell nothing, without a cell size definition, as it is only the actual area/volume available which matters, together with the overall design.

Just like megapixels in digital cameras, the number of cells are primarily used for marketing as 200 is clearly less then 300 so it must be better 😊 The fact that each of the 200 cells might be half the size of the cell in a 300-cell cat is a "minor" detail a typical user would not even think about

Reality is - if you want no CEL and would still like to be somewhat environmentally friendly, you need a quality cat. HJS is one reputable manufacturer of high-flow cats, for example. Their B58 cats built into a number of various downpipes are 300 cell.
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      06-04-2021, 08:36 AM   #22
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Quote:
Originally Posted by Skyhigh View Post
Yes it is. It is not an exact science - a high flow catted DP is "higher flow" than stock either way. I have personally never heard of a 400 cell for B58, but the number of cells in reality tell nothing, without a cell size definition, as it is only the actual area/volume available which matters, together with the overall design.

Just like megapixels in digital cameras, the number of cells are primarily used for marketing as 200 is clearly less then 300 so it must be better 😊 The fact that each of the 200 cells might be half the size of the cell in a 300-cell cat is a "minor" detail a typical user would not even think about

Reality is - if you want no CEL and would still like to be somewhat environmentally friendly, you need a quality cat. HJS is one reputable manufacturer of high-flow cats, for example. Their B58 cats built into a number of various downpipes are 300 cell.
+1

HJS and GESI cats 200, 300, or 400 CEL all work with stage 2 stock turbo as they provide significantly better flow than stock
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