Horrendous Sound Downpipes and Midpipes!!!

[Artemis]

Originally Posted by ozinaldo

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.

+1

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

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"

(source: http://www.1addicts.com/forums/showthread.php?t=639421)
See also: http://www.e90post.com/forums/showthread.php?t=560928 - http://www.1addicts.com/forums/showthread.php?t=359512

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.

[robertm]

Everyone has their own motivations, preconceptions and opinions as to why they do what they do to their own car. That’s what makes the modding experience great and it also provides a market for multiple vendors.

I will say from my experience (if I actually had them – which I don’t of course) that adding DPs will be the single biggest noticeable engine mod you can add outside of software. The turbo spool up response is noticeably quicker and the top end 'choke out' our engines experience is notably decreased. I assume there is some power gained too but I don't feel any mods before software add enough power to make 'that much' of a difference. You can definitely feel the difference in how quickly the turbo spools up with catless DPs.

Also, catless DPs with catless center section along with a free flowing intake makes great sounds without any drone that I’ve noticed. It’s by no means TOO loud and I’ve gotten lots of compliments. You can hear the motor a lot better now and there are all kinds of cool turbo spool up noises. This is in combination with the factory axle back mufflers. If you already have a free flowing axle back then adding catless DPs may very well become too loud.

With regards to the smell. I notice it when I pull into the garage but that’s really about it. I’ve never had issue with windows down driving and smell. I suppose if you are at a dead stop and windows down and wind is blowing at the perfect angle and you are reving the engine then you could get some exhaust smell but it’s never happened to me.

With regards to post cat O2 sensor. The BMS O2 simulator takes about 20 minutes to install and works perfect. As long as you don’t get an actual sniff test at State inspection it will never be an issue. All they do is plug into OBD II and scan for codes. Just as an aside to this, I am pretty certain a couple 2” O2 spacers would work just as well. I’ve had luck with them on other cars and they are used almost universally in the ricer scene. Someone could try them out if so inclined.

Someone said you might get in trouble with the police if you get pulled over. Never in all my life have I heard of someone getting pulled over and that turning into getting the car on a lift to see if it's equipped with cats. That's just way to far fetched. You should have your vehicle shut off long before the cop gets out of his car and reaches you anyways..

[MDORPHN]

I've been in 1Ms with catless downpipes -- once in combination with a N55 midpipe and another with the stock midpipe.

In both situations, the sound was fine. A little deeper than stock with bit of "gurgling" and significantly less drone.

The smell of gas was, of course, apparent with the fully catless set-up. However, with the stock (catted) midpipe, it was only detectable upon start-up.

Neil

[widbimmer]

Originally Posted by MDORPHN

I've been in 1Ms with catless downpipes -- once in combination with a N55 midpipe and another with the stock midpipe.

In both situations, the sound was fine. A little deeper than stock with bit of "gurgling" and significantly less drone.

The smell of gas was, of course, apparent with the fully catless set-up. However, with the stock (catted) midpipe, it was only detectable upon start-up.

Neil

With every post I get more and more confused!

I had the AR downpipes and the madDad mids installed with the original gaskets and the sound was horrible, pretty much like a rusty old car between 1500 rpm and 5000 rpm... after 5000 rpm it sounded deeper and cool

Now I only have the madDad midpipes with the stock gaskets and it sounds very good over 3000 rpm but when I'm in any gear at very low rpm it makes a very anoying noise...

I think I'll give the DPs a chance again but with the AR gaskets....

*Just for you guys to know... I don't have emissions or noise issues here in my country so DP's are allowed unless you are in a residential area and start drifting or making unecessesar noise....

[MDORPHN]

Originally Posted by widbimmer

With every post I get more and more confused!

I had the AR downpipes and the madDad mids installed with the original gaskets and the sound was horrible, pretty much like a rusty old car between 1500 rpm and 5000 rpm... after 5000 rpm it sounded deeper and cool

Now I only have the madDad midpipes with the stock gaskets and it sounds very good over 3000 rpm but when I'm in any gear at very low rpm it makes a very anoying noise...

I think I'll give the DPs a chance again but with the AR gaskets....

*Just for you guys to know... I don't have emissions or noise issues here in my country so DP's are allowed unless you are in a residential area and start drifting or making unecessesar noise....

I'd guess that there is an installation issue causing the nasty noise. Among other things, sounds like the downpipes may be coming into contact with the subframe.

Neil

[bdaddylo]

Sorry, but without a sound clip, this thread is pointless. Everyone has a different opinion of what sounds good.

Your issue below 3,000 rpm is probably drone if it's a low frequency bass sound that is annoying to your ears and head. Although I find it strange, some people actually like drone.

[widbimmer]

Originally Posted by bdaddylo

Sorry, but without a sound clip, this thread is pointless. Everyone has a different opinion of what sounds good.

Your issue below 3,000 rpm is probably drone if it's a low frequency bass sound that is annoying to your ears and head. Although I find it strange, some people actually like drone.

I understand that some people would like a sound clip.... So I will try to install the DP's again this week in another place an post a sound clip if the horrible sound comes out again... With mids the car sounds really good I hope that this time the DP's and Mids sound good together.....

[Chachirims]

If you want the install done right and have piece of mind, take it to the dealer. They installed a full Akra exhaust on Paolo Guerreo's 1M and retuned it.

[///1M]

Originally Posted by Chachirims

If you want the install done right and have piece of mind, take it to the dealer. They installed a full Akra exhaust on Paolo Guerreo's 1M and retuned it.

I'm confused... are you saying that the BMW dealer will install certain aftermarket exhaust systems?

[ozinaldo]

Originally Posted by ///1M

I'm confused... are you saying that the BMW dealer will install certain aftermarket exhaust systems?

Southern Hemisphere! Everything and everyone upside down around here

Seriously, my BMW dealer once even tried to warn me about the warranty risks of installing PSS tires outside the dealership and he got his answer of course.

[e82m_van]

Hey op, I know what sound you are talking about..
I just installed catless downpipes on my car, mated with n55 mids.
It sounds really bad.. around 2100 rpm. it goes like ehhhhnnnnngggggg hahahha lol

Also, I'm the type that likes to drive with my windows open as much as possible. But going completely catless, I don't think I can do it.. which is another reason why I'm planning on putting the oem dps back on.

But here is what I was wondering.
If smell or noise isn't the problem, would you go catless downpipes or catless midpipes?

[Alexim]

Originally Posted by e82m_van

Hey op, I know what sound you are talking about..
I just installed catless downpipes on my car, mated with n55 mids.
It sounds really bad.. around 2100 rpm. it goes like ehhhhnnnnngggggg hahahha lol

Also, I'm the type that likes to drive with my windows open as much as possible. But going completely catless, I don't think I can do it.. which is another reason why I'm planning on putting the oem dps back on.

But here is what I was wondering.
If smell or noise isn't the problem, would you go catless downpipes or catless midpipes?

I just did the same thing.. Kittyless DPs and removed the cats from the mids and welded on a straight pipe... The sound is exactly at around 2100rpm... and also when cold starting, it yells that weird sound for a few secs...
No way I'm getting the cats back on, so my bet is some resonated mids and aftermarket axleback...