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Old 11-20-2012, 06:25 PM
oldbogie oldbogie is offline
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Quote:
Originally Posted by dilligaf View Post
I am getting a lot of liquid mixed with carbon from the exhaust pipes. It seems to be way to much for condensation. The inside of the pipes are coated with black soot. This problem was there with the old exhaust and the new exhaust that I just had done. It blows out when I first start the engine cold and after I have ran the engine for several miles. The temp after several miles was at 195. I am running a 650 Edelbrock on a small block with a mild cam. I mention this because all along I thought it might be raw gas mixing with the soot in the pipes.
A bit more than half of the exhaust is water vapor from the combustion of gasolne. The chemical formula looks something like this:

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

What this is saying in chemists shorthand is that 2 molecules of octane is reacting with 25 molecules of diatomic oxygen (the way oxygen is found in the atmosphere) to make 16 molecules of carbon dioxide and 18 molecules of water. This is perfect reaction of octane and oxygen from the air, in reality the chemistry of gasoline has other stuff in it like benzene, toluene, zylene all stuff best not gotten on your skin. Also, there isn't time inside a running engine for these reactions to complete so there's always some unburnt hydrocarbon left over and carbon monoxide that didn't have time or the free oxygen to burn to carbon dioxide. In addition the atmosphere is mostly made of nitrogen while this doesn't contribute to the reaction at high temperature it will combine with oxygen to make the many types of nitrogen oxides shown as NOx in the common press. Oxygenates are added to the gas to provide some extra oxygen without leaning the mixture to help the hydrocarbon and CO to CO2 burns to get at completion, today's love affair is with ethanol (grain alcohol) in the past they used methyl tert-butyl ether (MTBE) which is a throughly dangerous material you sure don't want on you and has mostly been banned, worked really good though.

The carbon can be from too much cold running to where it doesn't burn off. Or it can be from a rich mixture; this could be too much or too long on the choke, too much fuel pressure, too high a float setting, power valve (metering rod) comes on too early, the intake manifold is too cold, engine coolant and running temp is too cold, the ignition is not powerful enough resulting in miss and late fires, the air filter is dirty or in the case of K&N type oil wetted gauze being too oily.

Lots of choices to go look at.
Bogie
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