AMGC43

Hello board,

I would like to ask if any of you has deleted the CAT in your C43 (remove the ceramic stuff inside and reweld back the OEM pipes) and if the check engine doesn't turn ON or most important, if the 02 sensor doesn't sense the difference and start consuming more fuel?

My euro C43 AMG has one CAT per bank and as well only ONE 02 sensor per bank (not double, before-after as probably other market C43's could have) and my euro C43 doesn't come with check engine light either.

I would like to de-CAt my C43 to get a better flow of the exhaust.

Opinions?

Thanks

503C43 ////AMG

I don't have an answer for you but I do have a question, hopefully someone could answer.

How is it that the Euro C43 comes with only 1 set of o2 sensors? Are they pre cat or post cat? Is there some different programming in the ECU?

Sorry for the thread jack

KJI3jflarryfe93

simply, euro c43's are less complicated than US c43's, stupeed Californian law regulations requiers extra parts.

o2 sensors are mounted on front cats on euro c43's

AMGC43

Yes, the 02 sensor are mounted BEFORE the CAT and only one per bank, as well one CAT per bank as I think I have read that the US C43 has double CAT per bank? That would restrict some power!

Now I wonder if removing the inside CAT and leave empety the "Bottles" will have a negative consequence for the ECU programing or MPG

DRBC43AMG

If I recall an owner in Germany (Popeye24?) removed the innards from the secondary cats. That way visual inspection could not determine anything. Mine with secondary cats and resonator delete passes all emission controls in this country no problem.

AMGC43

I took some pics, sorry for such small and lightless photos, but this is how my car look like down under.

You can see the bung/tap for the 02 sensor in the last photo in the right side CAT which is not used.

nd4spd13

If the O2 sensors are PRE cat, I don't see how removing the cat would have any effect on them... But why just gut them? Seems like much more work than just cutting them out and welding in straight pipe. Don't know where you're located, but in most states I don't see how you can register a car newer than 96 without a CEL, so whether you have cats or look like you have cats shouldn't really matter.

AMGC43

I'm from Peru. Most BMW's and Merc's if not all, euro version pre or post 96' doesn't come with a CHECK ENGINE LIGHT unlike the US specs cars as we have those here as well (a mixed market). The BMW's come with some weird and different (if equipped withs such CELL INDICATOR) inidcator light of malfunction in the OBD system, not sure about Merc but I guess the same apply to it.

I will just go ahead and remvoe the inside CAT and wel back the "bottles" but before doing that, I will run into the dyno and see what I get first, then by removing the CAT will measure it again and see if there was a improve or nothing at all..just for fun

503C43 ////AMG

Are the ECU's different? How come mine would throw a CEL if I didn't hook up the rear o2 sensors?

nd4spd13

Have to be. Or at least maybe somewhere in STAR there's a way to set it up for Euro specs. now that would be interesting

AMGC43

Not sure about the Merc's but the 80's and 90's BMWs when are euro and 02 sensor less the ECU/DME is the same P/N as their counterpart US specs which use the 02 sensor from factory. They instead don't place relay and/or the connector plug is tapped with a plug and "bridged" and the ECU is programmed to run in "open loop" I think.

Some of these BMW's as well Merc's I bet, that doens't use 02 sensor, their MAF has a small screw to adjust the air mixture at idle and pass C02 emissions, etc or has the option through the oficial scanner to make fuel trim adjustment pre loaded in the ECU/DME.

I just visited the MB dealer, hooked up the STAR and got a fault of ONE 02 sensor (my cluster didn't show any light as it doesn't have the check engine or something similar)) and while in there, I asked the tech to check in what OCTANE FUEL program was my car at, and found it was in BASIC, which according to them is the highest/most agressive timing. I was hoping to find it in the middle or lowest position/setup...oh well!

speed43

I will just go ahead and remvoe the inside CAT and wel back the "bottles" but before doing that, I will run into the dyno and see what I get first, then by removing the CAT will measure it again and see if there was a improve or nothing at all..just for fun

And please post if it sounds louder or not.

MarcusF

The second set of O2 sensors in US spec cars are there to check the exhaust’s oxygen content after the primary cat on each side. The ECU compares that reading against the O2 levels recorded by the first sensor. That information is used to allow the ECU to determine whether the cat is in need of replacement. A STAR box can be used to turn off the second set of O2 sensors on a US spec car. Tuners do it all the time (not just on Mercedes). In that case, the STAR box tells the ECU to ignore signals from the secondary sensors (just like an ROW Benz).

There are (can be) three parts to a California smog test. The electronic OBDII test, the visual inspection, and the sniffer test. If the secondary sensors are turned off, the car will fail California’s electronic OBDII test. It is possible to pass the sniffer test and have the ECU indicate the primary cats are failing. This will also cause the car to fail a California smog test (if the CE light is illuminated during a smog test, the car fails). If someone has that problem, send me a PM and I’ll tell you how to get around it for about $5 in parts.

Lastly, hollowing out cats creates a low pressure zone in the exhaust. A straight pipe works much better. If the cat isn't clogged, the exhaust flow may be better with the cat than with the dead zone (though not as well as straight pipe).