[hjernazian]

I'm running a JB3 with a DCI on my car. I was interested in purchasing some downpipes but quite honestly, not sure what they exactly do on the 335. I know I'd be able to run higher maps. Any info is appreciated, I've found lots of info on the threads but nothing really basic to give me a more conceptual understanding of the process. Thanks in advance.

[Drakos]

DP's will help your car breath better and remove the bottleneck in your exhaust. Factory DP's are the biggest restriction in a turbo charged vehicle regardless of the manufacturer. Your car will respond much quicker and will sound more aggressive. You will be able to run higher maps due to the bottleneck being removed. A catless downpipe will perform better than a catted one. Downside however are possible codes being thrown but can be solved by installing o2 sims which trick the computer by reading a proper proportion of oxygen (O2) in the gas being analyzed. You also risk a chance of not passing emissions testing which is probably a regular thing in California. There are many members here who have had no issues with this however. You can expect at least a 20whp increase with a good set of DP's on map 5. I have the exact same mods as yourself with the addition of AR Catless DP's and divider pipe and Forge DV's. I have a friend with a stock 335i and I can tell you that the difference is night and day.

[hjernazian]

Originally Posted by Drakos

DP's will help your car breath better and remove the bottleneck in your exhaust. Factory DP's are the biggest restriction in a turbo charged vehicle regardless of the manufacturer. Your car will respond much quicker and will sound more aggressive. You will be able to run higher maps due to the bottleneck being removed. A catless downpipe will perform better than a catted one. Downside however are possible codes being thrown but can be solved by installing o2 sims which trick the computer by reading a proper proportion of oxygen (O2) in the gas being analyzed. You also risk a chance of not passing emissions testing which is probably a regular thing in California. There are many members here who have had no issues with this however. You can expect at least a 20whp increase with a good set of DP's on map 5. I have the exact same mods as yourself with the addition of AR Catless DP's and divider pipe and Forge DV's. I have a friend with a stock 335i and I can tell you that the difference is night and day.

that was a downpipes 101 lesson for me, seriously, thank you. few follow up questions: What is the 'bottleneck' on the exhaust', these AR Catless DP's, can you link me? and also, what are Forge DV's? Not passing emissions is not an issue, and I have a BT cable to clear codes if ones are thrown. Also, I would imagine installing DP's isn't a DIY ordeal, so I would probably have to find a reputable shop as everything else on this car, and previous ones, I have done myself.

[Forcefed3]

Riss racing downpipes are catted, why are they better than the AR catless?

[vasillalov]

Originally Posted by gbreeE90

Riss racing downpipes are catted, why are they better than the AR catless?

Riss Racing is dead as a company and most of their products are not on par with AR products when it comes to quality.

[MKR_DmD]

Catless is always better then catted. When catted you are still trying to push air through a cat. High flow or not, it still has some restriction to it.


As far as bottlenecking. In turbo vehciles the goal is to the exhaust away from the turbo the fastest way possible. More air you move the more power you will produce. The stock DP have Restrictive Cats in them to make it so you can pass smog. Also the pipping is very small to make room for all this junk. The turbo is trying to push air through the exhaust and it is fighting all these things. When upgrading dp, you usually remove the cats and make the pipping bigger, 2.5"-3". When you put that with a free flowing exhaust, anything aftermarket, you are helping the turbo out big time. Now you can run more boost because the turbo now has a way to get ride of all that exhaust coming out.

Unlike NA cars, turbo cars hate back pressure. No back pressure is otimal, were as a NA car needs backpressure to create more torque.

Any questions.

[david @ eas]

Originally Posted by DrivinMissDaisy

Catless is always better then catted. When catted you are still trying to push air through a cat. High flow or not, it still has some restriction to it.


As far as bottlenecking. In turbo vehciles the goal is to the exhaust away from the turbo the fastest way possible. More air you move the more power you will produce. The stock DP have Restrictive Cats in them to make it so you can pass smog. Also the pipping is very small to make room for all this junk. The turbo is trying to push air through the exhaust and it is fighting all these things. When upgrading dp, you usually remove the cats and make the pipping bigger, 2.5"-3". When you put that with a free flowing exhaust, anything aftermarket, you are helping the turbo out big time. Now you can run more boost because the turbo now has a way to get ride of all that exhaust coming out.

Totally agree. We've seen great gains with the Macht Schnell Downpipe, and when added together with just a few other mods, we've achieved this:



Here is a list of modifications to the vehicle:

2008 BMW 135i 06/08 build

GIAC Stg. 2 beta calibration
Macht Schnell 3” Catless Downpipes
Macht Schnell Dual Cone intake kit
Macht Schnell Intake Scoops
Snow Performance S2 Boost Cooler
Evolution Racewerks Competition Intercooler
Forge Motorsport Adjustable Diverter Valves for N54 Turbo

[hjernazian]

thanks for all your help guys, got a lot of valuable information.

[Baldur Abendroth]

I enjoyed this as well

[garfi]

Originally Posted by Drakos

DP's will help your car breath better and remove the bottleneck in your exhaust. Factory DP's are the biggest restriction in a turbo charged vehicle regardless of the manufacturer. Your car will respond much quicker and will sound more aggressive. You will be able to run higher maps due to the bottleneck being removed. A catless downpipe will perform better than a catted one. Downside however are possible codes being thrown but can be solved by installing o2 sims which trick the computer by reading a proper proportion of oxygen (O2) in the gas being analyzed. You also risk a chance of not passing emissions testing which is probably a regular thing in California. There are many members here who have had no issues with this however. You can expect at least a 20whp increase with a good set of DP's on map 5. I have the exact same mods as yourself with the addition of AR Catless DP's and divider pipe and Forge DV's. I have a friend with a stock 335i and I can tell you that the difference is night and day.

Originally Posted by DrivinMissDaisy

Catless is always better then catted. When catted you are still trying to push air through a cat. High flow or not, it still has some restriction to it.


As far as bottlenecking. In turbo vehciles the goal is to the exhaust away from the turbo the fastest way possible. More air you move the more power you will produce. The stock DP have Restrictive Cats in them to make it so you can pass smog. Also the pipping is very small to make room for all this junk. The turbo is trying to push air through the exhaust and it is fighting all these things. When upgrading dp, you usually remove the cats and make the pipping bigger, 2.5"-3". When you put that with a free flowing exhaust, anything aftermarket, you are helping the turbo out big time. Now you can run more boost because the turbo now has a way to get ride of all that exhaust coming out.

Unlike NA cars, turbo cars hate back pressure. No back pressure is otimal, were as a NA car needs backpressure to create more torque.

Any questions.

i learned a lot things. thank you guys