What does “blow the carbon out” really do?
Occasionally, I will see a car in front of me, floor it (gas pedal), and when they do puffs of black smoke, come out the back of the car as the car hits full throttle. What gives?
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White-ish smoke at full throttle usually means either the vehicle is using more fuel than air during the combustion cycle (in a petrol engine) and what you’re seeing is excess fuel that has been heated, but not fully consumed.
The right “settings” on spark plugs and air/fuel ratios (usually set via software these days) helps alleviate this.
Some sports cars or cars that have been modified after purchase will intentionally run “rich”, meaning there is a certain level of waste (smoke you’re seeing) that is accepted. The general reason for this is a safety measure for the engine. When changes are made to increase power and torque in a car, if the aforementioned air/fuel ratio swings the other way (when there is more air than fuel), it can do thermal damage to the engine (and beyond).
However, black smoke can also be a sign of other issues. Sometimes oil leaks in various places can cause oil to enter the combustion chamber(s). Then the smoke is coming from oil burning (or more precisely, not burning up all the way). In all but very small cases, oil should not be entering the area where petrol and air are burning.
“Blowing the carbon out” would mean to run the engine up to its highest state of tune (usually high/peak RPMs for a somewhat sustained period of time (15-120 seconds depending on context and capabilities). Someone smarter than me will have to explain whether there is any real benefit to this in modern fuel management systems.
Hope that makes sense.
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