The question, “Why do diesel engines smoke?” is loaded. The question assumes that diesel engines do, in fact, smoke. While, historically, black smoke was associated with diesel engines, that is simply no longer the case. Diesel engines do not smoke any more than gasoline engines. The reason being, catalytic converters for one. But also, the diesel engines of today burn fuel much more efficiently than they did 30 years ago. Why do diesel engines smoke? That is no longer a legitimate question. 

How? With improved injectors and aftermarket pre-combustion fuel catalysts like the Rentar. 

What Was the Black Smoke from?

Again, the black smoke associated with the combustion engines of the past was a product of engine inefficiency.  Black smoke was not the result of diesel fuel being dirty or more polluting than other fossil fuels. The diesel engines of the past blew black smoke out the exhaust because diesel engines were inherently inefficient. The diesel engines manufactured between 30 and 100 years ago simply were not capable of burning all the fuel fed into them. Neither were gasoline engines for that matter. 

As an aside, today’s diesel engines burn a higher percentage of the fuel fed into them than their gasoline counterparts. Gasoline engines, unfortunately, cannot run fuel-lean or they overheat and seize. They must always run fuel-rich meaning there is not enough air fed into a gasoline fuel mixture for the engine to fully combust it. 

In essence, gasoline engines are designed to blow black smoke out the exhaust. The reason black smoke does not appear from the tailpipe of gasoline engines is that the catalytic converter burns up the unburned and partially burned hydrocarbons shortly after they leave the exhaust manifold. 

Why Does Unburned Fuel Create Black Smoke?

The black smoke from combustion engines is (was) the same thing that blows out the smokestacks of a power plant and rises out of fireplace chimneys. Black smoke is nothing more than soot, ash. Soot and ash are simply unburned and partially burned hydrocarbons. Hydrocarbons are the molecules in fossil and biofuels that combust and burn. In doing so, they release heat, energy. But, if an engine is incapable of burning all the hydrocarbons fed into it, it simply blows them out the exhaust. 

In other words, black smoke is simply wasted hydrocarbons, wasted energy. Why do diesel engines smoke — or why did they — is as simple as combustion efficiency.

Again, today’s engines, especially today’s diesel engines, have a combustion efficiency that is much greater than the engines of the past. That is to say, today’s combustion engines burn a much greater percentage of the hydrocarbons fed into them than the engines of the past were capable of burning. There are still limitations with respect to what percentage of fuel an engine can burn off the total fed into it.

Why Engines Burn Fossil Fuels Inefficiently

All combustion engines allow a percentage of the fuel fed into them to pass through unburned or partially burned. Different types of engines burn different percentages of the fuels fed into them. And, they fail to do so for different secondary reasons. There is only one primary reason engines fail to burn all the fuel fed into them: a failure to oxygenate the hydrocarbons in the fuel.

Every fuel has an ideal oxygen-to-hydrocarbon ratio. It is called the stoichiometric ratio. According to Garrett, “For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel.” For diesel, the stoichiometric ratio is 14.5:1 for diesel. 

Reasons Diesel Compression Engines and Spark-Fired Gasoline Engines Produce Black Smoke

A diesel engine — which is a compression engine — fails to combust the entirety of the fuel fed into it because it fails to oxygenate the diesel fully. Poor oxygenation in a diesel engine is a consequence of the density of diesel. The hydrocarbon molecules in diesel are long and branched and often become entangled with one another which results in the formation of clusters. 

The structure of the hydrocarbon molecule clusters inherent in diesel does not allow oxygen to saturate the hydrocarbon molecules inside the cluster. The result is burned hydrocarbon molecules on the outside and partially or unburned hydrocarbon molecules on the inside of the cluster. When the partially burned hydrocarbon clusters blow out the exhaust — if they are not burned up by the catalytic converter — that is the soot and ash you see coming out the tailpipe and smokestacks of diesel engines. 

Because of catalytic converters, diesel engines rarely blow black smoke anymore. But, the partially burned and unburned hydrocarbon molecules still constitute a waste of energy. Wasted energy potential is what the unburned hydrocarbon molecules inside a fuel cluster amount to. Even though catalytic converters burnup the black smoke molecule clusters, molecules are lost energy. The only way to prevent energy loss is to break up the hydrocarbon clusters.

Dispersing the hydrocarbon molecules in a cluster allows the molecules that were inside the cluster to oxygenate. There are two means by which to minimize the clustering of hydrocarbon molecules in diesel. The first is the ultra-high-pressure injectors. The second is a pre-combustion fuel catalyst. 

How the Rentar Fuel Catalyst Prevents Unburned and Partially Burned Hydrocarbons from Escaping Out the Exhaust

The Rentar Fuel Catalyst is a pre-combustion diesel fuel catalyst. Made of the same noble metals found in a catalytic converter, the Rentar conditions diesel fuel before it enters the cylinders of a compression engine. By neutralizing the inherent charge found in fuel ions — the charge that produces clusters — the Rentar homogenizes diesel fuel. 

As opposed to the fuel being a heterogeneous mixture of hydrocarbon clusters, the Rentar makes the fuel an even mixture. This allows for the oxygenation of the individual fuel molecules. And, that allows a diesel engine to maximize the potential of the fuel. 

The Rentar can reduce black smoke by up to 44 percent on machinery and trucks both with or without a catalytic converter. Additionally, the Rentar can reduce fuel consumption by between 3 and 8 percent on off-road equipment; 7 to 12 percent on stationary equipment; and 2 to 5 percent on on-road equipment and trucks.