Running rich?

[Tripp Mcnealy]

so what the deal why they are running so rich? Lots of build up on the exhaust tips, starting to think about a MBC just to lean it out a bit.. lol
Or is this just how it runs while the motor is still breaking in?

 

[Rican219]

Runs rich by factory period

 

[forrestang]

so what the deal why they are running so rich? Lots of build up on the exhaust tips, starting to think about a MBC just to lean it out a bit.. lol
Or is this just how it runs while the motor is still breaking in?

Runs rich, but it's very likely the soot on your tailpipes is actually oil.

At least that was my situation.

 

[Tripp Mcnealy]

Runs rich by factory period

do we know why so rich... and how long does this last..

 

[dc82]

do we know why so rich... and how long does this last..

...it runs rich from the factory. That is how it was made to run unfortunately. It lasts as long as you have your car.

 

[Raynman]

If I had to guess, the reason the car runs rich is to meet stringent EPA Tier II regulations. EPA Tier II regs state that a car must meet be able to meet specific emissions targets within a certain number of miles in its life.

It's somewhere between 100K and 120K miles - I don't remember the exact figure.

The point is, everything in the car has to operate in such a way to meet those emissions targets for that number of prescribed miles - including the engine and catalytic converter. Running rich accomplishes two things:

1. A richer running engine has a cooler combustion chamber as compared to a leaner running engine. As a result, running rich extends engine longevity and therefore helps an engine meet the 120K mile life span.
2. An engine that runs rich produces exhaust gases that are cooler as supposed to an leaner burning engine. Cooler exhaust gases mean that catalytic converters are not degraded as quickly as supposed to when much warmer exhaust gases run through them. As a result, running rich extends catalytic converter life which means the car can catalyze exhaust gases to meet the emissions targets within the prescribed mileage lifespan as dictated by the EPA.


For more info on EPA Tier II:
http://www.epa.gov/tier2/
white papers: http://www.epa.gov/oms/tr2study.htm

 

[Raynman]

Forgot to mention. As mentioned and simply put: A richer AFR means a cooler combustion temperature which is what you'd want to meet NOx emission targets. You get higher production of NOx from a high temperature environment.

So there you have it, the EPA has chosen air quality and greater dependence on oil over efficiency. That's how I see it.