«In the past we cut the fueling during shifts, because you don't want a load
of unburnt fuel being fired into the catalytic converters.
This reduces the final compression temperature in the combustion chamber, which also reduces the risk
of unburnt fuel and «engine knock».
By tow starting the car you could cause large amounts
of unburnt fuel to be pushed through the engine and into the catalytic converter.
When questioned about the fictitious sounding overrun, Porsche's engineers stated that, like the Jaguar F - Type and its maniacal exhaust, small droplets
of unburnt fuel are dropped into the exhaust system not only to engineer the 911's soundtrack, but also to keep the catalytic converters hot and emissions down.
But, to me, the presence of smoke equals the presence
of unburnt fuel.
A long silence follows, accompanied by the wafting of the strong smell
of unburnt fuel.
Not exact matches
And the idea that the tiny black specks
of unburnt diesel
fuel are lethal is not new.
For deep future survival, brown dwarfs represent a large resource
of unburnt fusion
fuel, either for harvesting slow use, or to light up a new star.
With this loss
of energy, you'll also see the large carbon buildup on the business end, due to
unburnt fuel deposits.
An old engine may spit more
unburnt / partially burnt
fuel, but that's negligible compared to the total amount
of burnt
fuel.
They say it is due to a small amount
of fuel left
unburnt when the engine is shut off.
To let the ECU cut
fuel if a spark plug stops firing, for the express purpose
of preventing
unburnt fuel from overheating the catalytic converter.
Although this would be a bad idea if the mildly intoxicating fug
of hydrocarbons and
unburnt fuel filling the interior is anything to go by...
Change down a few gears, and you'll hear some phlegmy overrun as it spits
unburnt fuel out
of the exhaust, let it hit the rev limiter and it'll bounce on it frustratingly.
Because the burning
of the
fuel is never 100 % efficient, trace amounts
of pollutants including
unburnt carbon are produced in the form
of fine particulates (soot), hydrocarbon gases and carbon monoxide.