An extra edge

| April 01, 2006

Cetane improvers
Cetane rating refers to the fuel’s ability to ignite instantaneously. This helps you get faster starts at subfreezing temperatures. But it also affects the engine when warm. Diesels use mechanical control of burning, and the process doesn’t work well if the fuel doesn’t ignite right away. Have you ever heard your engine pop and crackle in an irregular way for a short time after a cold start? That is the sound of “ignition delay,” which can be a byproduct of low cetane even when the engine is warm. A “cetane improver” can help to give smooth and efficient running, especially when fuel is borderline.

Rossow generally supports the value of cetane improvers and mentioned that Advanced Fluid Solutions’ product includes one. But he cautions that with some of the latest injection systems, you should not overtreat because you can actually have too much cetane.

Some engines have something called “split injection,” and if your fuel is well above the required cetane rating, you could actually get pre-ignition. So compare the cetane rating of the fuel you are buying with the engine maker’s cetane recommendations and don’t add a cetane improver unless the fuel will still be within the recommended range.

Warns Stratton, “Many additive labels read ‘contains cetane,’ but unless the label specifically addresses how it affects the cetane number of the fuel, it probably contains only trace amounts of cetane.” Power Service has products that increase the cetane number four to six points, he says.

Lucas is a bit skeptical of the need for cetane. “The government requires a level of 43. That’s all you need,” he says. He believes you should avoid buying alcohol to mix with the fuel and get rid of moisture.

He recommends smelling a bottle of additive. If it smells exactly like kerosene or No. 1 fuel, it is likely to be little more than that.

Injectors distribute the fuel in the combustion chamber in a very precise way. It’s a tough job, especially since the nozzle holes are unbelievably small and can easily clog partially due to deposits. The tip is exposed to high heat because it sticks right down into the combustion chamber. This heat can cause the fuel to form varnish and carbon deposits. A detergent will dissolve deposits, keeping the holes open and the fuel sprays forming an even mixing pattern. This speeds up combustion and reduces engine deposits and oil deterioration.

Additive packages may also include corrosion inhibitors and dispersants or emulsifiers. Corrosion inhibitors keep fuel from rusting metal injector parts, while dispersants and emulsifiers keep small amounts of water dissolved in the fuel. Water that separates can blow the tip off an injector.

Many additives claim to improve fuel economy. Stratton says Power Service Diesel Kleen + Cetane Boost provides an 80 percent fuel injector cleanup in the first 50 hours of engine operation, as measured in the Cummins L10 Injector Depositing Test. He believes you should look for cetane and detergent packages on a year-round basis.

Rossow reports that Advanced Fluid Solutions offers an additive that the Bible of the industry – the TMC/SAE Type II fuel economy test – proves actually increases fuel economy as much as 4.8 percent. Part of the product’s secret is a compound that “burns hotter and cleaner” than the base fuel to accelerate combustion. However, it also includes a potent injector cleaner. This will also increase mileage by removing carbon deposits in injectors to “give a complete spray pattern.”

While it is hard for an additive to improve combustion by modifying the fuel, if your injectors are starting to get dirty and a quality detergent additive cleans them up, you’re likely to see the fuel economy improvement mentioned on the package. Also, a couple of companies have developed very high-tech additives that actually help fuel burn better. You may want to try these out. But watch out for empty claims!

Diesel fuel contains paraffin, a relative of candle wax. While the paraffin stays dissolved in the liquid fuel at normal temperatures, it will form solid particles at even moderate winter temperatures. These particles will form and glom together in the cold. The largest challenge is getting them through the filters, and this challenge is getting tougher. Filters today are much finer than they were even five years ago.

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