Donwpipe

[autopiezasford]

If I install only the downpipe in my 2012 135i DCT ,I will see some benefits ?
It is advisable to do that? I know that the check engine went on.

[Jorgensen54]

If catless, yes you're reducing restriction of flow through the immediate hot side exit of the turbo.. but that CEL counters that unless you use some sort of DP fix(BMS products). Same applies for some downpipes with catalytic converters.

Do it right and you'll get some gains in hp/tq. Plenty of threads around here on the topic.

[Stewy_604]

I'd go with a tuner product (JB4, MHD, Cobb) at the same time to take full advantage of the DP upgrade and avoid CEL. All depends on what your overall goals are for the car and other mods you have planned. What have you done to the car? What else do you have planned?

[Tiron]

I data logged the results of my N54 catless downpipe install. These tests were all run in 3rd gear, with ambient outside temp around 70 degrees, and engine fully warm. Each test was done from a full coasting fuel cut condition, meaning the turbos had no load and minimal shaft speed in order to maximize lag time. I had a Cobb stage 1 tune.

I am high altitude with 100k miles, your results might be different. I honestly didn't "feel" much of a difference, I would get a tune first.

Stock downpipe results:
1000rpm start
6 psi time: 3.841s @ 2201rpm
12psi time: 5.194s @ 2798rpm

3000rpm start
6 psi time: 0.755s @ 3222rpm
12psi time: 1.200s @ 3415rpm

5000rpm start
6 psi time: 0.354s @ 5099rpm
12psi time: 0.655s @ 5275rpm



Catless downpipe results:
1000rpm start
6 psi time: 3.090s @ 1977rpm
12psi time: 4.150s @ 2500rpm

3000rpm start
6 psi time: 0.650s @ 3218rpm
12psi time: 0.959s @ 3356rpm

5000rpm start
6 psi time: 0.301s @ 5159rpm
12psi time: 0.555s @ 5265rpm

[autopiezasford]

Originally Posted by Stewy_604

I'd go with a tuner product (JB4, MHD, Cobb) at the same time to take full advantage of the DP upgrade and avoid CEL. All depends on what your overall goals are for the car and other mods you have planned. What have you done to the car? What else do you have planned?

My car is stock .Only the catless DP. I'm planning a JB4 and a K&N drop in filter

[Jeff@TopGearSolutions]

Originally Posted by autopiezasford

My car is stock .Only the catless DP. I'm planning a JB4 and a K&N drop in filter

Won't get much out of the K&N Filter, the stock intake box is just to restrictive once tuned- consider a different Intake. Cheapest intake is the BMS DCI. I prefer to recommend the AFE Momentum GT but it's not a budget friendly intake but is the better performing of the intake options.

[Stewy_604]

Originally Posted by autopiezasford

My car is stock .Only the catless DP. I'm planning a JB4 and a K&N drop in filter

You'll need the JB4 or a alternative tune to take advantage of the DP and defeat the CEL.