Diesel Performance Trucks - Crude Combustion

Diesel Performance

Gary Blount
Dec 1, 2005
Photographers: The Manufacturers, Gary Blount, Auto Imagery
Photo 2/25   |   diesel Performance Trucks truck
With today's inflated gas prices and emission-sensitive state, the idea of building a high-power hot rod is a rather drab concept-the dawning of a new era has crept up on us.
The diesel engine has come to bring a new name to hot rods-enter the sport truck. Truck consumers have realized the value of the diesel powerplant. Its ability to sip fuel for economy or burn loads of fuel to deliver remarkable power has made the oil-burning powerplant a must for many truck enthusiasts.
Of course, there are those who refuse to take off the hater vision, when it comes to diesel, but there are some facts that may change their mind. The refinement of solid state powerplant management has changed the stinking, black smoke-bellowing slug into a viable option as a replacement powerplant over gas-powered engines.
Photo 3/25   |   The diesel is here. Three-hundred thousand diesel vehicles were purchased in 2000, and by 2004, that figure changed to 500,000. In 2004, 60 percent of the medium-duty truck market chose diesel as the powerplant of choice.
This can be not only seen in the sheer numbers of diesel trucks on the road but by sanctioning bodies dedicating entire divisions to diesel racing in pulling competitions and quarter-mile drags.
What Is Diesel?
Diesel is an extract of crude oil. It consists of heavier hydrocarbons than gas. This basically means that diesel has more substance in its makeup, and its boiling point is higher than gasoline. Here's how diesel and gas is made.
Crude oil is cracked or refined by a distilling process. The crude is heated till it starts to vaporize in the distillation column. The column is like a tall cylinder that has extraction points at different heights along its side. The oil is super heated to about 1,100 degrees Fahrenheit, which allows the crude to release its hydrocarbons. The hydrocarbons are collected and made into different products.
The distilling process separates the carbons according to their hydrocarbon chain. A hydrocarbon chain is how many carbons are bonded together. The longer the hydrocarbon chain the higher the boiling point. The vaporization process allows these hydrocarbons to separate from the crude and coagulate at their cooling temperature, so they can be extracted and used.
Photo 4/25   |   Oil-burners put out high torque at low rpm, providing way better fuel economy and pulling power over gas.
The top portion of the distillation column is cooled to about 70 degrees Fahrenheit. Hydrocarbons at this level share a four-carbon bond, called a hydrocarbon chain, that forms lightweight, low-boiling-point gases. Gas is extracted from the column, just below the upper portion of the column at about 150 degrees Fahrenheit. Farther down the column-much farther-you will find diesel extraction at about 400 degrees Fahrenheit. This shows that gasoline is more of a flashing agent and burns significantly different from diesel.
How Is Diesel Different From Gas?
In order to compare diesel to gasoline, it's important to understand how power is made from fuel in the combustion cycle, and the mechanical differences between gasoline and diesel. Power is made in a combustion engine by an explosion of fuel on top of the piston, which pushes the rotating assembly through to the next combustion cycle. What makes gas and diesel different is how the fuel burns and the power displaced by the explosion.
Photo 5/25   |   There are a ton of products available to enable diesel powerplants to make a third more power than stock.
The power produced in the combustion is relative to the amount of heat that is generated by the burning fuel. Fuels have what's known as a British Thermal Unit (BTU) rating. A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at its maximum density, which occurs at a temperature of 39.1 degrees Fahrenheit.
It takes about half of a drop (0.002194 fluid ounce) of gasoline to provide enough power to achieve 1.028264 BTUs, which is about the same amount of heat generated by a sulfur match. One drop of gas holds enough energy to effectively produce 2.056527 BTUs. Of course, moving a 7,000-pound mass is significantly more work than changing the temperature of a pound of water. The power output of one drop of gas is also equal to 0.010282635 horsepower. Of course, a fuel's BTU rating is measured by the amount of output produced by one U.S. gallon.
There are 455.865637 drops in a U.S. fluid ounce, 128 ounces to one U.S. gallon, which equates to 58,350.8 drops in one gallon. So, if one drop of gas makes 2.056527 BTUs, then 58,350.8 droplets produce 120,000 BTUs. The energy put out by a drop of gas can also be measured in horsepower. One drop of gas produces 0.010282635 horsepower, so the same math will conclude a U.S. gallon of gasoline can produce 600 horsepower for one minute or 36,000 horsepower in a second.
Photo 8/25   |   The Dodge may not be first as the choice in trucks, but its Cummins inline six-cylinder engine seems to be the powerplant of choice on the track. The 5.9L engine makes 325 hp at 2,900 rpm and 610 lb-ft of torque at 1,600 rpm.
Gas is constructed of eight carbons bonded together making the molecular structure light. This makes gas have a flash point of -40 degrees Fahrenheit. Diesel No. 2 (average pump fuel), which is constructed of a 16-carbon bond is obviously heavier, and it has a flash point of 125 degrees Fahrenheit. This means it takes 165 degrees Fahrenheit more heat to ignite diesel than gas. The added density and makeup of diesel fuel increases the temperature it produces, giving diesels a 145,000 BTU rating. Even if the Brake Specific Fuel Consumption between gas and diesel was equal, the diesel would have a 17.2 percent increase in power. This would mean that a gallon of diesel fuel would make 703 horsepower for 1 minute or 42,180 horsepower in one second.
This factor doesn't include the fact that diesel also sustains power over a much wider rpm range. When gas ignites, it combusts quickly, which means it supplies all its power potential in a small window of the combustion stroke. Diesel is directly injected into the cylinder and is sprayed through an optimum duration in the combustion cycle. With the addition of super-high compression ratios, diesel makes much more torque. The high flash rate of diesel makes it predictable and stable. A diesel can operate within a wide range of air/fuel ratios, allowing it to sip fuel or burn gobs of fuel to make incredible power. This dramatically affects engine efficiency.
Photo 9/25   |   All three powerplants are turbodiesel engines with plenty of potential, but we'll be keeping our eye on the Duramax, which definitely has a lot on the table. The inside of the engine looks like a Pro Stock race engine with huge lifters and massive intake and exhaust runners.
Brake Specific Fuel Consumption (BSFC) is a measure of how many pounds of fuel it takes to make 1 hp for 1 hour. The BSFC coefficient is derived by the engine's efficiency. The known coefficient used for an internal combustion engine is as follows:
diesel engines
Fuel-injected four-stroke
gasoline engines
four-stroke engines
Engines don't maintain a fixed BSFC over their entire range. Typically, an engine achieves its highest BSFC rating when producing only a fraction of its rated power. This is due to thermodynamic factors which limit the engine's efficiency when it runs cold. BSFCs typically reach their lowest value for the engine in the 50-80 percent power range, then, begin to trend upward again as friction begins to play a dominant role, and the mixture must be enriched to provide for adequate engine cooling.
Why Don't Diesels Make High Horsepower?
Horsepower and torque are methods for measuring raw power. Measuring raw power is done by figuring the amount of work that can be done by the raw power. Horsepower is the speed at which a given load can be moved, while torque is how much that load weighs. Diesel engines don't spin high rpm, preventing them from making great horsepower, but allowing them to produce phenomenal amounts of torque. High rpm can also increase the wear on bearings and seals. Because diesel makes power at a lower rpm, it doesn't wear some of the components as fast as gas.
Diesel engines are modeled after tractors that were designed to have a long life expectancy. Many of the components are built heavy duty to sustain heavy work loads for long durations of time. A certain amount of the energy made by the combustion is used to work the engine. The heavier the rotating assembly, the greater the amount of energy is needed from the combustion cycle to move the assembly. Because of the laws of physics on this planet, as the rpm speed is increased, the rotating weight multiplies, requiring more power per rotating pound to accelerate the rotating mass.
Photo 12/25   |   The impressive part is that this 14-second run was made by a 7,300-pound truck. The stock run was 3 seconds slower.
Another factor that works against a diesel from spinning higher rpm is that diesel fuel has a slow burn rate. The fuel is injected into the cylinder on the compression cycle for a long duration as the piston moves down the bore. The slow-burning fuel provides a steady pressure on the piston producing high torque. Faster piston speed wouldn't reduce the amount of time the injection system had to pump the fuel into the cylinder. With gasoline, the combustion happens so fast the fuel is spent within a couple degrees of the compression cycle.
Enhancing Diesel Performance
With a diesel ignition, timing is controlled by fuel. Fuel is injected directly into the combustion chamber, which starts to burn immediately due to cylinder temperatures. A high-pressure high-volume (more like a hydraulic pump) fuel pump sprays the fuel out of the injector at a high rate. The pump is run anywhere from 17,000 to 27,000 psi, depending on the injection system. This moves the fuel so quick the fuel burn never touches the injector until the injector stops releasing fuel.
The ignition timing is established by how long and when the fuel is sprayed into the cylinder. The wide range of completion ratios that diesel will operate in means all you need to do is add fuel and air. With electronic-controlled fuel injection and wastages, adding air and fuel can be done with a plug-and-play piggyback computer. Of course, your air intakes and exhaust enhancers will allow you to move more air, providing the ability to burn more fuel. Propane and nitrous oxygenate the fuel again, allowing the ability to burn more fuel.
Diesel in Racing
The diesel era is here. What once was tractors pulling sleds has evolved into gathering of oil-burners pulling sleds and quarter-mile competition. In fact, sanctioning bodies such as Diesel Hot Rod Association (DHRA) have put together a series of drag races just for diesels.
Photo 15/25   |   Greg Hogue, driver of this diesel Dakota, has one of the fastest time slips we've seen for a diesel truck. Line up this truck with a Pro Street door-slammer and the experience could be pretty humbling. That's right, for those of you with doubts, this truck trips the 1320 in 8.724 at 154.44 mph.
Is Diesel the Answer to a Depleting Gas Resource?
What if we were to run out of crude oil? This leaves little provisions for implementing a new fuel resource and distribution channel to bring whatever fuel change into effect. So what's a nation to do when rotten dinosaur carcasses can no longer support the level of consumption in a modern age? Turn to a renewable source, that's what. Biodiesel is biodegradable, nontoxic, and is essentially free of sulfur and aromatics. It's a renewable resource, based on soybean and other oil crops that are grown domestically. In fact, most pump diesel already contains as much as 20 percent biodiesel.
A Glance at the Differences Between Gasoline and Diesel
Fuel Pressure: 40-{{{90}}} psi 17,000 to 27,000 pounds
of fuel pressure
Fuel Injection: Direct Port Injection Direct Cylinder Injection
Ignition Source: Spark Plug Compression Heat
Air/Fuel Ratio: 12.1:1 to 14.7:1 25.0:1 to 100.0:1
Compression Ratios: 8.0:1 to 11.0:1 (17.0:1 race gas) 17.0:1 to 20.0:1
Ignition Timing: Coil Spark Fuel Injection



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