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July 2012 Top Tech Questions

How To Make Smoke

Text By Diesel Power Staff, Photography by Diesel Power Staff

Welcome to Top Tech Questions. Oftentimes, readers contact us with questions about articles, or to praise us on what a good job we are doing. But our favorite form of reader communication is tech questions. Our Top Tech section is a place where you ask what’s on your mind, and we answer it. Got a trouble code? Wondering how to get your engine to make more power? Send us an email at and we’ll do our best to answer it.

Question: My wife and I just purchased an ’00 Ford F-250 with the 7.3L Power Stroke diesel. We live near a large biodiesel manufacturer in northern Wisconsin and are interested in using biodiesel in our truck. In the short time I have been reading your magazine, I do not recall an in-depth article discussing biodiesel use in modern trucks—such as cetane ratings, differences in corn and soybean or other types of bio-origins, filtering, and vehicle compatibility.
Chris Drost
Haugen, Wisconsin

Answer: You know, it has been some time since we’ve had a biodiesel discussion, so we’re letting our resident biofuel expert, Feature Editor Jason Thompson handle this one. Here’s what he had to say about cetane, compatibility, and lubricity.

The cetane number for biodiesel is derived from a test ASTM D613 and measures the time it takes once ignition occurs in a fuel until it starts to make pressure. This test is quantified into a number that goes with a cetane index. High-speed diesel engines operate well with fuel that has a higher cetane number (46 to 55) because it has less ignition delay—this gives more time for the fuel to combust completely. Petroleum diesel here in the United States needs to have a minimum cetane number of 40. Biodiesel from soy typically has a cetane rating greater than 47, and canola-based biodiesel has a rating greater than 49. According to a paper called “Cetane Number Testing of Biodiesel” by Jon Van Gerpen, who is the Associate Professor of Mechanical Engineering at Iowa State University, biodiesel’s cetane rating varies by oil type and ranges from 48 to 67. Basically, low-cetane problems are not associated with biodiesel, and regardless of feedstock the final biodiesel product needs to conform to the standards.

Older diesel engines made before 2006 sometimes need new fuel lines but are otherwise generally compatible with biodiesel up to B100 blends. Since newer diesel engines sometimes go into fuel regeneration modes (allowing fuel to seep into the oil) and have sensitive exhaust aftertreatments, biodiesel blends between B5 and B20 are generally the rule. It’s important to check with your specific manufacturer to find the biodiesel blend rate. Biodiesel blends below B20 do not need any additional filtering requirements compared to straight petroleum diesel—even in cold weather. Block and filter heaters are recommended on blends above that. Renewable or synthetic diesel, on the other hand, can be formulated to have better cold flow and energy density properties, even compared to petroleum fuels. Also, since renewable diesel is molecularly the same compared to petroleum diesel, it is a 100 percent drop-in fuel—even in newer diesel engines.

According to a document from the National Biodiesel Board that shows biodiesel is the best solution for low-fuel lubricity, which causes injector and pump failures with use of ultra low sulfur diesel (ULSD):

“…we have tested biodiesel at Stanadyne and results indicate that the inclusion of 2 percent biodiesel into any conventional diesel fuel will be sufficient to address the lubricity concerns that we have with these existing diesel fuels.”

Biodiesel should not be confused with vegetable oil. Most companies that make biodiesel make sure it can pass the rigorous standards needed for an actual fuel, and then the biofuel is usually blended with regular diesel fuel. Biodiesel blends are definitely a benefit to modern engines in small doses and address many of the lubricity concerns diesel owners have with modern diesel fuel.

How to Make Smoke
Question: Is there any kind of adjustment that can be made to an ’05 Dodge to make it smoke without spending a lot of money? My truck currently has an AFE stage 2 intake and a 4-inch straight pipe.

Jacob Miles
Raleigh, North Carolina

Answer: We get this question over and over on the Internet, so we figured it’s about time we address it in the magazine. First of all, why do you want smoke? A lot of folks see the huge-horsepower sled pulling diesels and assume smoke means big horsepower. The fact is, sled pullers use fuel to cool combustion, spool enormous turbochargers, and for a variety of other reasons besides just horsepower. On a street truck, more than 1,000 hp can be produced with a minimal amount of smoke.

We’re noticing a lot of younger kids getting into diesels who want to blow smoke so they can irritate the convertible or bicycle in the lane next to them. If this is you, then shame on you. Sure, smoking out your friends can be fun sometimes, but try to leave rolling the coal to circumstances involving friends or practical jokes—or when someone really deserves it.

That being said, lots of fueling and little air is the key to chugging like an old steam engine, and lots of load. Get big injectors, lock your converter up early, and you’ll be well on your way. Nothing, and we mean NOTHING smokes like a set of big injectors. The downside here is that if you’re not careful, the over-rich condition can melt down your engine due to excessive EGT.

Excess fueling at low rpm when there isn’t enough exhaust energy to spool the turbo is a great way to make tons of smoke. Adding fuel via a programmer for your ’05 Dodge should get you some of the smoke you’re looking for, especially before the turbo lights.

OK, so there are a couple of ideas. Now, please don’t smoke out everyone you see at every intersection.

By Diesel Power Staff
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