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      01-04-2013, 08:07 AM   #23
Artemis's Avatar

Drives: BMW M2 (MG 6MT)
Join Date: Jun 2011
Location: Belgium

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For a few hp and dB more

Originally Posted by ozinaldo View Post
Of course I have seen them, I like to be under the car whenever I can and yes they bend and so but if I would choose between changing them and mid pipes I would still change the mids instead and that's what I did exactly and am very happy with the result. I don't care if I would make 10 whp instead of 7 or 8, but that's just me. Counting ponies is not everything for me.
Mid change fixes the drone best, gives better flow and response (OK dps do that too) and it's relatively cheaper vs changing dps. Plus it also adds some hp/tq despite marginally less so than dps. It also doesn't cause any code/ECU issues. Thus, my vote is for the mids unless as I said in my previous post someone needs to change whole system that I understand better. I am not saying stock dps are perfect, I said opposite already in my first post, they are not, but every choice has its plus and minus and its own cost to be considered carefully.
In my case I don't want a car without any cats and too loud all the time so I kept the stock dps. If I would want max power and max noise I would change the dps too and justify myself the cost and certain issues that come as a result of my choice. Now I am very satisfied with the actual result and I have zero issues to live with.

Should also be part of the equation when opting for catless downpipes:
  • risk of trouble when pulled over by the cops (especially when catless in Cali) or when getting through vehicle control in the future. Emissions regulations for environmental care purposes, as we all know. With just the mids and axle back exhaust changed, you might get away with it (as the OEM DPs cats still do their job). With catless DPs you won't (except if the car is only used on race circuits). No hypocrisy about it (we're driving sports cars, so inevitably overshoot carbon dioxide levels of, say, a Prius) - that's just the way it is. And replacing each time the DPs and reprogram the ECU merely for passing the control is quite a hassle (regardless of the dishonesty aspect).
  • the fumes/fuel smell and CO2 (which DP cats normally filter), especially when idling with windows down.
Originally Posted by IancoleTX View Post
Yeah there is a smell, but I don't mind it.
My girl last week: "it smells like gas everywhere downtown"
Me: "yeah.. it.. ummmm.. yep, sure does"
See also: -

To each his own. For me, the cons of catless DPs outweigh the pros: the drone, the fumes/fuel smell and CO2, risks of trouble with the authorities (environment), neighbors (noise) and BMW warranty (ECU modification) are ingredients that might cause discomfort. Ain't worth it as quid pro quo or set-off for just a few hp and dB more (catless DPs). And sometimes you're simply not in the mood and/or area for having all parameters max'ed out. In my book another midpipe (for example N55) + a decent aftermarket axle back exhaust (for example Akra Slip-On) is the better alternative: badass, but no overkill.
“For ’tis the mind that makes the body rich” (W. Shakespeare, The Taming of the Shrew, Act 4, Scene 3)