Z06EATER

OK GUYS my buddy has a C36 with stock cats, a reso and no muffler, he has horrible back pressure, car's RPM's dip a lot, especially when he's at 60mph n he hits the gas softly the rpms go up n back down, really bad accel too, funny thing is my car has a magnaflow cat, after market running to stock reso and no muffler, my accel is awesome..no rpms probs...you think he should install like a magnaflow muffler? is back pressure good? is it like the more the better? or no? how much would be good? are there good power gains from this? his WOT is great tho, car tops at 155MPH very quick

silence

there is definitely something else wrong with his car

why in the world would your car have the resonator and no muffler?

Z06EATER

well he was lookin or sound, so he chopped out the muffler, but he's getting bad back pressure, as where i have one magnaflow cat, with reso, my cars back pressure is great...

Z06EATER

how should he go about fixing this? c'mon guys!!

RBYCC

With all due respect, stop talking about back pressure like it's something that you know about...

There is more wrong with the car then the lack of the rear silencer.

What else has he done to cobble the car up...???

Condition of O2 sensor, stock cat, fuel delivery system, ignition, many, many things that could cause this.

Driving at 155 mph doesn't help....

AMG140.6

Simple.

HAve your friend put the stock exhaust back in. AMG engineers spent a lot of time and $$$$$ designing the exhaust flow dynamics. There's a lot more to it than one thinks.

For one thing its high grade stainless.......so why replace it w/ some Magnablow generic installed @ a Midas or Meineke ?

These C36's are fine the way they are. The car is as fast as its going to get w/0 spending a ton of money and creating poor driveability issues .

The best mods are getting the car to proper stock specs via service and tune up.

It is what it is.

Buy a faster AMG if you want more.

silence

honestly, putting stock exhaust on isn't likely to solve his problems either.

like i said- something else is wrong with the car

splinter

How did you quantify that condition?

E55 PWR

Stock resonator does not have any backpressure, its free flowing. The stock catback does have backpressure because it is a baffle design and the inlet is only 2.25 even though piping is larger.

To me it sounds like maybe he went wrong when he installed the cat, did he change O2 sensor location? there may be airleaks, OR it could be something else totally unrelated, maybe bad wiring harness, or vacuum leak. who knows, he needs to take it to a shop to get diagnosed.

Either way, doing a straight pipe muffler is a stupid idea.

Z06EATER

ah yea, lol i don't know about back pressure too much that is why i'm asking, also the car only started doing this after he did the exhuast work, before then the acceleration was great...putting the stock exhuast back on sounds good lol....maybe juss a reso delete is betteer

Z06EATER

well we swapped out both 02 sensors and car runs great now!

bagelsjustbagel

did u do your own 02 sensor fix? and how much did it cost?whered u get the parts? all that good stuff

Z06EATER

the 02's are expensive about 140 a pop, i got mine from my buddy moe cuz his mom works at wolfpack, they are a warehouse that actually carry mercedes parts... i got both got 140 70 each, they did a great job on the car... runs runs very nice now, much better throttle as well, and to mentions MPG it is SOO much better

KJI3jflarryfe93

hey bud does his car only have 2 front O2 sensors, not the rear ones=?


euro cars like my c43, only have the front ones.

btw is our original exhaust system made of stainless steel all the way, from engine to rear end.
thanks

Z06EATER

i believe it is all stainless steel, and no we have only 2 sensors on the US models, one before the cats and one after i believe.

MarcusF

Why didn't you use the Bosch universal 4-wire O2 sensor? They're about half the price you quoted.

Z06EATER

realy now? where would i find these? are they as good as the ones i am using now?

MarcusF

The difference between a Bosch universal 4-wire sensor and an OEM MB Bosch 4-wire sensor is the plug.

You're in No Cal, so if you fall into one of the five million Kragens, Pep Boys, NAPA's, or Auto Zones, they'll probably fix you up. If those aren't near by, Advance Auto, Checker, and Schuck's sell them too. If you’re really in the middle of no where, just order them on der Interweb.

If you're wondering how tough it is, at Signal to Noise, under "Bosch Universal Oxygen Sensor", there's short blurb - but there’s really nothing to it. Just DON'T try to solder the connections.

Z06EATER

very interesting thanks for the tip marcus, i appreciate your advice and help

MarcusF

Glad to be of help. A set of OEM sensors list for just under $1K ($238 for my car). Universals put $700 back in my pocket - where I can flush it down the toilet on Google stock which dropped from $416 to $330 during the last 12 minutes the market was open today. Yes, down $86 in TWELVE MINUTES. Oh well, retirement is a long ways off.

suicidal4life

Why no solder?

MarcusF

Bosch uses stainless steel wire and it is very hard to get it permanently soldered. Bosch 4-wire universal O2 sensors come with a wire crimping kit because they know the solder never seems to hold. The crimping kit is really good. Take a look at Signal to Noise and you'll see what comes in the kit.

suicidal4life

Thanks. Lots of interesting reading on your site.

kinghais

i don't think that's from the exhaust

KJI3jflarryfe93

Hey bud.
I was thinking about the front o2 sensors, I only have these on my car for left and rite side front.
No rear sensors
The stealership say I have 4 sensors on their carparts catalogue, When I changed them the mechanic said I have only 2 of them, stupid mercedes dealers.
thanks