How much carbon residue on muffler is acceptable?

[detroiter]

Just a curious question that popped into my head earlier and though I'd ask. I know some cars (new ones), you couuld clean the exhaust tip clean and by the end of the days worth of driving, it's coated in carbon. Then other cars it seems, you could drive them hard and for a long period of time and they won't seem to have any sort of residue on their mufflers.

[ddongbap]

W/e the amount is that lets you pass smog.

[detroiter]

The beautiful thing is Michigan doesn't have emissions testing :D


I guess what I'm getting at is what is an acceptable amount of black carbon being left behind before you should be concerned something is wrong?

It's interesting to me that some cars you drive normal or romp sometimes, they have a ton of carbon residue yet other cars driven likewise are spotless. What is it that dictates it being like that?

[YAR1S]

i get quite a bit of carbon on my muffler tip....kinda lame.... but oh well.

[yaris-me]

Carbon build up doesn't mean something is wrong. In newer cars at start up the engine will run rich and the cat is not warmed, so you will tend to have unburned fuel out of the exhaust, carbon. After the engine is warmed and the cat is heated, the exhaust will have completely burned fuel. This will burn off some carbon build up because of the high heat produced by the cat. What will cause carbon build up is a lot of cold starts and short trips.

[Yaris Hilton]

When you stomp on the gas pedal and exceed around 70-80% of maximum engine load, the ECU goes into open loop mode and enriches the mixture, commonly enough to soot up the pipe. My Yaris never blackens the chrome tip during cold engine warmup, but does if I go to wide open throttle.

[RedRide]

Originally Posted by Yaris Hilton

When you stomp on the gas pedal and exceed around 70-80% of maximum engine load, the ECU goes into open loop mode and enriches the mixture, commonly enough to soot up the pipe. My Yaris never blackens the chrome tip during cold engine warmup, but does if I go to wide open throttle.

Yes, a little soot on the inside it the tail pipe is completerly normal if you don't drive like a '99 year old granny.

Personally, I always drive a bit agressively, frequently access WOT, and have always had some soot in the tail pipes on all my cars.

[RedRide]

Originally Posted by Yaris Hilton

When you stomp on the gas pedal and exceed around 70-80% of maximum engine load, the ECU goes into open loop mode and enriches the mixture, commonly enough to soot up the pipe. My Yaris never blackens the chrome tip during cold engine warmup, but does if I go to wide open throttle.

Yes, a little soot on the inside it the tail pipe is completerly normal if you don't drive like a '99 year old granny.
Personally, I always drive a bit agressively and have always had some soot in the tail pipes on all my cars.

Also, if you live is a colder area (or where there are cold winters) the engine runs richer for a short while when first started in cold weather.

[Vang]

i drive like a granny and my exhaust tip still looks new

[127.0.0.1]

the exhaust tip should be clean. constant soot indicates a problem.

my 12 year old 4runner only got soot once in a 2 month period when the a/f sensor went kaput. changed it and the tip went back to clean.