[AlpineG05]

Pros: faster/louder spool, hp gain
cons: money, pita to install.

[CBR335]

Pros: Amazingly fast turbo spool, louder exhaust note, more boost to redline.

Cons: Well they are a PITA to install. You had better have some skills with the wrench and patience plus a friend with a lift.

[Forcefed3]

Bad?

Originally Posted by Rotary Rasp

Catless cars stink.... literally.

[CBR335]

Originally Posted by gbreeE90

Bad?

I have ***less DPs and the stock rear section. No smell at all.

[MF80]

How is the MPG?

[JoshM813]

AA downpipes are out of stock...I won a set in a raffle and I've been waiting for 2 months...

Lutz Performance down here has been waiting for about 6 months...so get AR

[cn555ic]

Originally Posted by JoshM813

AA downpipes are out of stock...I won a set in a raffle and I've been waiting for 2 months...

Lutz Performance down here has been waiting for about 6 months...so get AR

Better off getting the ARs since they have a proven track record

[Belarus]

Macht Schnell DPs is another choice and get good reviews for your consideration. I've got AR and been happy with them.

http://www.e90post.com/forums/showthread.php?t=326644

[kenneth]

I have stock downpipes, but if you are looking for catted DP check out the CP-E. These are a thing of beauty!

[Ilma]

Originally Posted by CBR335

Pros: Amazingly fast turbo spool, louder exhaust note, more boost to redline.

It's the tunes that determine the boost targets to redline and they control the turbos to meet those targets by controlling the wastegate duty cycles.

So I am left wondering by your statement that downpipes give you MORE boost to redline.

They might get you to the boost target a bit sooner, but I don't see how they will enable you to make more boost.

[CBR335]

Originally Posted by Ilma

It's the tunes that determine the boost targets to redline and they control the turbos to meet those targets by controlling the wastegate duty cycles.

So I am left wondering by your statement that downpipes give you MORE boost to redline.

They might get you to the boost target a bit sooner, but I don't see how they will enable you to make more boost.

Sorry, you are correct, this was not the intended interpretation of my sloppy statement.

Of course any tune can command the wastegates to remain open to keep boost high to redline, but your just gonna generate a whole lot of even hotter air. Might as well help the situation by allowing the turbos to breathe. The downpipes alone will not allow you to make more boost, but allow you to make it more efficiently through the whole range. Because the turbos are less restricted (by the poorly flowing stock downpipes), less wastegate dutycyle is required to hold boost at higher rpms where exhaust gas flow is at its greatest and the turbos are less efficient.

[CBR335]

Originally Posted by JsTech

How is the MPG?

Terrible with or without DPs when you go WOT at every opportunity like I do.

Seriously though, there doesn't seem to be a difference when cruising.

[Ilma]

Originally Posted by CBR335

Sorry, you are correct, this was not the intended interpretation of my sloppy statement.

Of course any tune can command the wastegates to remain open to keep boost high to redline, but your just gonna generate a whole lot of even hotter air. Might as well help the situation by allowing the turbos to breathe. The downpipes alone will not allow you to make more boost, but allow you to make it more efficiently through the whole range. Because the turbos are less restricted (by the poorly flowing stock downpipes), less wastegate dutycyle is required to hold boost at higher rpms where exhaust gas flow is at its greatest and the turbos are less efficient.

Perhaps what you were trying to say is that downpipes will allow you to run higher boost via more powerful maps.

So in that sense, you would be getting more boost to redline......

[M3 Eater]

Originally Posted by gbreeE90

Who has installed DP's here? Are they a pain the the ass to take on and off for every service visit or state inspection??

talk about a pita to install!!! I could do it now by my self but only because I had a guy that built race cars try to put on pipes that didn't fit while I watched. I couldn't believe that they didn't fit so I tried my self. It took about a week for the guys at AR designs to convince me to send those back and get some that are proven to fit and perform time and time again. The guys at B and B finally got their act together and I think they are shipping pipes that fit. Basically a guy from AR started his own business and so the products are similar. CPe has a hell of set of pipes ... they dyno well but look kinda strange. They get smaller toward the back to make room to fit various exhaust systems Cat back...or no cat back. There are a few DIY's but if its your first time putting them on by yourself.... get a case of beer and start on Friday after work. You might make it to work on Monday without a ride. If you have someone that knows there way around Modified vehicles, It's a 3-4 hour job. In BMW talk thats $360.00 at $90/hr! If I had it to do over...I would have paid the money to have it done. They will be the last mod I give up because I love the sound of the turbos as they spool up much faster, of course you need an open intake to really hear whats going on.

[CBR335]

Originally Posted by Ilma

Perhaps what you were trying to say is that downpipes will allow you to run higher boost via more powerful maps.

So in that sense, you would be getting more boost to redline......

Yeah, but that is way too short and simple to say.

[335i-boy]

I too would like a definitive answer on this topic.

"Hotrod 182" has done on excellent job testing various different mods and there effect on 1/4 mile track times and traps. These include ambient temps, fuels, meth, DCI's -v- Stock intake, a variety of different maps and downpipes.

Search for his thread, "Testing Performance Mods On The 335i Steptronic Sedan"

His initial thoughts are that installation of Catless DP's do not result in faster ET's or traps.

He has Catless DP's installed on an E92 and is going to do some more testing on his E90 once the Catless DP's go on.

The limited research i have done on this forum suggests, that the most significant benefit of Catless DP's is a possible increase in service/life of the turbos when running higher boost levels. The turbos are able to spin more freely due to the lack of back pressure in a free flowing downpipe. The turbos have to work a lot harder to force hotter air, which is now at a higher pressure, through the more restrictive Stock DP's.

BIG NEGATIVE: Loss of powertrain warranty. You have to pay to play.

I have had both turbos replaced prior to installing tune. Would not want to pay even half of what BMW charges in Australia which is $14500USD ($16000AUD using exchange rate at time of turbo replacement).

[david @ eas]

Originally Posted by CBR335

Pros: Amazingly fast turbo spool, louder exhaust note, more boost to redline.

Cons: Well they are a PITA to install. You had better have some skills with the wrench and patience plus a friend with a lift.

+1

All downpipes weren't created equal though. We've had great success in installing the Macht Schnell downpipes on customer cars. I've heard terror stories of guys trying to fit other downpipes in their car that take hour after hour after hour, but the Macht Schnell ones seem to be a nice fit for the N54 motor

[Forcefed3]

Do you guys take the DP's off for service? If your still under warranty?

[ZombiE90]

anyone use or have opinions about the VK Motorwerks DPs? they're obviously among the cheapest out there, but how does the quality compare?

[IlChengis]

Does anybody wrap their downpipes before installing them? I understand that special coatings are offered with certain DPs, but I am still curious about wrapping...

Thanks,

-Walter

[k3silk]

can you post a sound clip because i have been thinking of doing this Exhaust cost so much for such little gains I would rather do a mod I will feel more then a mod I can just hear.

Originally Posted by CBR335

I have ***less DPs and the stock rear section. No smell at all.

[caliguy562]

I'm too running just catless downpipes and the stock exhaust w/golf tee mod. I also have an UR intake and I feel that I may be done on the exhaust side of things. At least three people have asked if I have an exhaust on the car and just the other day, my roommate said my car sounded "rough". That's code for loud from her. It doesn't sound that loud to me, but when compared to a stock 335i you know there's something going on from all the whistling under acceleration and pops on deceleration.