Hey guys. I've been brewing up my next project but I have some questions and I'm also looking for some feedback and advice on it. I currently have an E350 which as we know doesn't make a whole lot of power. It is currently fitted with a Brabus cat-back exhaust which gives it a nice note. The rest of my E class is also Brabus and I looked into what type of power packages they offer for my engine. They only have two, the B7 package, and the 4.0 package which strokes the engine to 4.0 and couples it with the B7 package. I can't afford the 4.0 nor do I think it makes much sense but the B7 is somewhat reasonable.

The B7 package consists of 4 300 cell cats to replace all 4 stock cats in the exhaust system and it also includes the brabus cat-back exhaust. The problem I guess is that Brabus asks 10k for the 4 300 cell cats and the exhaust together. Like I said, I already have the exhaust so I figured why not purchase my own 300 cell cats and install them myself, I should have a B7 package right? So my question is, my car dyno'd at 191whp with the exhaust. The Brabus sites claims the car will make an even 200 whp so thats approx 9 whp from changning the stock cats to the 300 cells.

Is this a reasonable claim? Can I expect 9whp out of this mod? Also, do you think there is any other type of R&D reason that Brabus offers this package for so much, or is it just marketing hype as others have told me? Brabus claims there is no CEL's and that the interior of the 300 cells are gel coated for heat. If I do this on my own with 300 cells, should I expect to get any CELs? Does anyone have 1st hand experience w/ replacing all 4 cats with higher flow cats? Should I have any emissions trouble being as these are higher flow vs people who replace them with straight pipes? The final question I have is what do you guys think this will sound like? I do not want a whole lot more volume than I have now. I plan to keep the stock resonator. Does anyone maybe have a sound clip of a v6 with all cats replaced and cat-back exhaust? Probably not but doesn't hurt to ask. What do you guys think of this idea? Worth while? There aren't a whole lot of power mods available for the car but I want it to atleast be little quicker than everyone elses E350 so I'll take even minimal power gains where they are available. Thanks for your input!

Here is Brabus's numbers for this package.
BRABUS B7
Base:
E350 (W211)
Power enhancement by back pressure lowering metal-catalytic converter (four monoliths with a full
OBD II suitability). The kit is completed by a matching stainless-steel end-muffler.

Technical data:
Displacement cm³ 3498
Compression ratio 10,7 : 1
Torque Nm 360 (350)
at min-1 2400 - 5000
Power output kW/PS 211 / 287 (200 / 272)
at min-1 6000

Thanks again for any inputs/thoughts you might have.

 

9rwhp is not unreasonable for replacing all 4 cats with high flows. Have you considered just removing the later 2 and running straight pipes there or hollowing the later 2 cats out? I believe there are no after cat O2 sensors there, so you won't get a check engine light...and here in TX they don't check emissions until the vehicle is older. They just give it a quick look over. I suggest youtube for sound clips of louder versions of your car. IMHO 3.2L sound ricey when they are louder, but I would still do it for the added HP.

The primary cats would be more difficult to replace with high flows because they are mounted close to the manifolds. If I did it on my car I would buy some pre-bent mandrel exhaust tubing and O2 sensor bungs from summitracing.com and cut it myself to get the bends I would need. I would run the high flows somewhere straight (closer to where the secondary cats are). Welders aren't that expensive and if you use a mig welder with argon gas it is actually pretty easy to get a good weld on exhaust tubing. Just my 2 cents! HAVE FUN!

 

Have you looked at a pair of headers for the M272? Kleemann and Renntech each make a set of headers. They claim they at about 20hp/tq by themselves and if you add their ECU tune you can get closer to 35-40hp/tq. I think Renntech advertises it as 40HP for $4000.

I found a post on (i think) slkworld where a guy had it done to his SLK350 really liked the improvement. He said it was night and day difference. Just his butt-dyno though.