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?
In: 12
Ahhhh the Italian tune up. With fuel injected motored, the gasoline is either injecteddirectly into the combustion chamber, direct injection, or it is mixed with the intake air,
Carbon builds up on your valves of your intake manifold. The valves are just that, little spring loaded valves thay when open allow air to enter the combustion chamber. Well, above the valves is a crank system called the cambers, most motors have dual cambers, these campers have metal lobes built into the that when rotated, push down on the valves opening them. Anyway, this assembly is covered amd sealed by the valve cover and gasket. This is the top of the bottom you see when looking at your car, where you pour in the oil and draw the dip stick from.
One side has the valves for the intake, while the other controls the valves for the exhaust. Gases from the combustion chamber will invariably leak through the valves and build up in under the valve cover. For this, a blow back hose connect from the valve cover and hooks back into the air intake, to be recombusted and exhausted. This blow back has a mixture of gas, air, oil vapors, and water moisture.
Well, some kf this blow back ends up on the intake valves as carbon deposits. Left untreated, the efficiency of the intake valves decreases, meaning the engine must work harder to supply the same power, aka lower gas efficiency, plus less zip when hitting the accelerator.
The older air fuel injectors would spray gas into the air intake. Gas is a natural solvent meaning it will break down and clean oils, greases, and carbon deposits. The older fuel injected engines would have much less carbon build ups on the valves. The new direct fuel injected engines when new are more efficient and a better system, but because the gas is injected into the combustion chamber and not the air intake, the gas never has a chance to clean the valves. Hence a service should be performed to manually clean them every once in a while.
Back to the older air injection fuel injectors and the heart of your question. In slow city traffic, stop and go, short trips where the care doesn’t have a chance to warm up, etc. The older engines would be prone to carbon build up too. The term Italian tune up is exactly the same thing as the term blow the carbon off. Italian racers were stereotypically fast drivers who proffered the gas pedal over the brake. Like wise, blowing. The carbon off just means driving the car hard for a little bit, getting out on the free way and accelerating to 80mph as quickly as possible, hitting the hills and keeping the rims up for a little while. This forces more gas vapors in those older engines to be injected, effectively cleaning the carbon build up that occired from slower day to day city driving. It actually works in those older vehicles, to an extent at least. Better fuel economy, and power performance and be felt after
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