pinoyk20

so do you think i will loose power with the diameter increase on the pipngs? from 2.225 stock to 2.5 ? thanks!

AMS Performance

not really, stock piping is dual 2.25" anyways. Any exhaust shop can expand the 2.25 or contract the 2.5" to make it fit, its nothing difficult, basic exhaust 101 stuff. Hope that helps.

saintz

The front O2 sensor is for determining AFR, i.e. correcting fuel trims. The rear O2 sensor is for emissions purposes. Knock sensing is done by a separate knock sensor. It is basically a microphone that listens for vibrations that are typical of pre-detonation (knock).

This sounds pretty reasonable. Pinoyk, I think you need to focus in more on what will actually make power and what your goals are.

Here are the things that are bad about the system:

• Primary tubes of the header are very small

Here are the things that are ok but not great about the system:

• Front cat is a restriction close to the engine, but it is relatively high flow (metallic) and so isn't that bad
• Rear cat is a restriction (ceramic), but it's downrange pretty far, so it isn't that bad
• Resonator is a little heavy

Here is what's good about the system:

• 2.25 inch pipe is matched to the flow needs of the system
• Dual 2.25 inch flows a lot (more than a single 3 inch)

From looking at this, we know we want to replace the headers, as they're a big restriction. We know we want to leave the stock exhaust piping as much as possible. Going too big will reduce velocity of the exhaust gas. We also know that we might consider removing cats (for restriction) or the resonator (for weight), but that these aren't as big gain areas and we don't really need (or want) to remove all three.

I think you have two options, the hard way and the easy way:

Hard way:

• Long tube headers (will require cutting and welding and will remove your primary cats)
• Replace resonator with X-pipe
• Leave 2nd cats in place, they're not going to hurt much with the primaries gone

Easy way:

• Shorty headers (bolt on)
• Replace resonator with X pipe
• Remove or replace rear cat with high flow/straight pipe as desired
• Leave primary cats, the cost benefit to remove them is not there

The easy way should be a lot cheaper and will probably get you very similar results.

saintz

Regarding running catless, this topic is complicated. Here's my short version:
Removing the rear cat has a major impact on performance, with only a minor impact on cost, drivability, and the environment. Removing the front cat as well has a minimal impact on performance, but a major impact on cost, drivability (smell/noise), and the environment. It's just not worth it for the tiny (2 hp?) gains.

pinoyk20

thanks for sharing good inputs saints! i guess i want the hardway hehe ...

Fabio D

Saintz, when i remove my cats the primarys are Ceramic & secondarys too (my car is an euro) are you sure the primarys in the Us spec are Metallic?? Thanks in advance bro

Fabio Daniel

Silver Logic

I also have a euro car. I too would like to know if my primaries are ceramic. I was going to go the easy route, but if they are ceramic and will eventually fail, I'll go the hard route. Please advice. Thanks.

Fabio D

Silver, i think your car is the same mine, if you are 99" Euro you only have 2 O2s sensors, no worry about cel & your primaries & secondaries are ceramic

Hope that help

Fabio Daniel

Silver Logic

Ok, thanks.

I want to put headers on, but plan on retaining my original resonator and muffler to keep the noise down. I will then put the x-pipe where my secondaries used to be. If both my cats are ceramic, I'll probably remove both. So what would be the recommended headers, long tube (i.e. Kleeman) or short tube (i.e. AMS)?

saintz

On the US spec, the ones that fail are most commonly the rears, not the primaries. I've seen the rears, and they appear to be ceramic. I've never actually seen the primaries. From what I've read, combined with common sense (the fact that the primaries don't fail as often and the fact that a ceramic cat that close to the exhaust valve should fail pretty rapidly) indicates that the primaries are metal.

In the US, there's an 8 year 80k mile federally mandated warranty on cats. So it's not in Mercedes' interest to put a cat in that's likely to fail in under 80k miles, or else they'd have to replace them all the time, even when the car is outside of its regular warranty.

On a non-US spec car, though, it's hard to say. Maybe they cut corners in some markets where the law doesn't penalize them as heavily. Ceramic cats are cheaper.

armaniE55

Saints - Dropping knowledge lately

+1 On the Easy Way

Easy way:

* AMS * Shorty headers (bolt on)
* Replace resonator with X pipe
* Remove or replace rear cat with high flow/straight pipe as desired
* Leave primary cats, the cost benefit to remove them is not there

To add to that... AMS Pulley and you will have yourself a nice light modded AMG

AMS Performance

I'd agree with that

It is the most headache free & cost effective setup you can run on these NA 55 AMGs, and the best part is you don't even have to touch the mufflers or primary cats or anything else. You don't even need software to run that setup (although it always helps, its not necessary). The AMG ECUs are highly adaptive and can adapt to most conditions (which is why we always recommend saving software until the end when you really approach the true limitations of the stock ECU software tune).

pinoyk20

can changing the exhaust system like headers, pipings xpipe and removing both primary and secondary cats make our car run lean?????

saintz

I think you're probably safe. Those are pretty minor and should be within the realm of the ECU's adaptation ability. You can always do the ECU update if you are worried.

Fabio D

No Pinoyk, the rich/lean mixture are controled directly by the knock sensors & O2 primary sets (only change your exhaust sound), any alteration in your exhaust system (increasing the gas flow) are corrected by the sensors mantaining your mixture, the only problem if you have 4 O2 sensors & you remove your cats you get your Check light up CEL

Fabio Daniel

pinoyk20

i only have 2 sensros. mine is a euro version e55. so i guess it will be safe.. how do you do the ecu update? thanks

do you need an ecu update even if you have a reflash ecu??? thanks

Fabio D

Saintz, the front cats really made a major impact in performance & cost, you will go to remove the secondaris, but really you can upgrade your primaris by 300cel metal hi flows if you want to go clean, but the primaris have the majr restriction near the exhaust manifold & this is no good

Regards friend

Pinoyk i do not reflash my ecu & no made any change,,if you have only 2 o2's yo will no have a CEL

Fabio Daniel

pinoyk20

thanks fabio!!!

Fabio D

U welcome buddy

Fabio Daniel

Silver Logic

Fabio, you are right. On the Euro cars, the primary cats are also ceramic. I just removed mine.

saintz

Wow, that's pretty bad. I'm guessing there's no EU requirement for a 8 year, 80k replacement on cats like there is in the US.

AMS Performance

Fabio is correct, I have confirmed they are 400 cell ceramic core cats, same exact core design as the secondaries, just much smaller. They are actually a better design than the secondaries b/c at least the air is force through in a conical shape. The secondaries are very oddly shaped and have large irregular cavities before & after the cat core which creates a great deal of turbulence. Getting rid of the primaries will help of course as well, but its best to start off with the secondaries. It is very rare for the primaries to fail even though they are ceramic cored. 9/10 times the secondaries are the ones that go bad which is why it is recommended to always replace those first anyways, they go bad anywhere from every 50-100k miles (some have failed even before 50k).

Fabio D

1+

pinoyk20

my primarys failed first. ehehhhhee

AMS Performance

Consider yourself the lucky lotto winner lol. I guess you are one of the "special" ones .