(From the Archives – 11.19.04)
Diesel — The Performance Choice
Some old ideas about performance are slow to die.
The very idea that diesel engines could replace exotic gasoline engines as the top performing powerplants in cars, light trucks, and SUVs seems ludicrous to many automotive enthusiasts. How could a slow, smelly diesel ever hope to compete against an overhead cam, high-revving, high-compression, sophisticated gasoline engine? And the concept of a diesel as a racing engine seems to be pure heresy! What, enthusiasts ask, has the world come to?
There have been a lot of things that have led to the emergence of diesels as the performance engines of today, but most enthusiasts have missed this diesel evolution while it was going on right in front of them. No longer are diesels slow, sluggish, smoky, and smelly. They are quick and fast, and they have the potential to be a lot faster.
Consider what happened to gasoline engines. Big, high-revving, powerful gasoline engines were the norm in the ‘50s through the early ‘70s. Then the gas crunch hit and lead was removed from gasoline to permit the use of catalytic converters for reduced emissions. Overnight, most performance gasoline engines disappeared and it has taken 30 years of research and development to get back to the horsepower levels of the Muscle Car era. Unfortunately, development of the gasoline engine may have reached a plateau. Through these last three decades it has taken computerized engine management, electronic fuel injection, and a host of mechanical improvements to get performance along with low emissions and fuel economy. These are all good advances, but the one limiting factor has been the fuel. There’s only so far you can go with an air-throttled engine on 91-octane gasoline. In other words, it is the fuel, gasoline, that has become the limiting factor.
All the while the automotive industry was working to improve gasoline engines, the same effort was going on in diesels, but because a diesel doesn’t mix its fuel with intake air prior to compression, fuel octane (the ability to resist spontaneous ignition) and resultant detonation was not a problem. Consequently, all the things that technology brought to gasoline engines also benefited diesels, such as computerized engine management, electronic fuel injection, four valves per cylinder, and lighter, stronger engine components, were added without the necessity of reducing the compression ratio. In fact, because there were no compression limits, something else really catapulted diesels ahead of gasoline engines for performance – turbocharging.
While turbocharging has been applied to both gasoline and diesel engines, only limited boost can be added to a gasoline engine before the fuel octane level again becomes a problem. With a diesel, boost pressure is essentially unlimited. It is literally possible to run as much boost as the engine will physically stand before breaking apart. Consequently, engine designers have come to realize that diesels are capable of substantially more power and torque than any comparably sized gasoline engine. Equally impressive is the fact that development of performance diesels is just beginning. Diesels designed specifically for passenger cars are likely to be both more powerful and smaller than today’s gasoline engines. Look for light duty diesel crankshaft speed to increase, engine weight to decrease, and performance per liter to increase by another 50 percent or more! It’s all happening now.
What will these changes mean to performance? Diesels already equal gasoline engines in horsepower per liter. Diesels have twice the torque per liter, and diesels can deliver 20 to 40 percent better fuel economy than comparable gasoline engines. Suppose future diesels are lightened to increase crankshaft speed while reducing maximum torque output. Since a diesel already has so much torque, such a revision might only have 150 percent of the torque of a comparable gasoline engine while its horsepower would also rise to nearly 150 percent of the gasoline engine. The lighter weight would also let the diesel accelerate even more quickly and be just as desirable for vehicle handling characteristics … and all on ordinary No. 2 diesel fuel.
Because enthusiasts have been conditioned to think of gasoline engines when it comes to performance, the idea of diesels may still be difficult to accept, but consider a few facts. Most race cars use alcohol, not gasoline today. Those race cars that do use gasoline use special high-octane racing gas not available at ordinary gas stations. As long ago as 1952, the car that won the pole at the Indianapolis 500 was a turbocharged diesel. Diesels have since been rendered uncompetitive at Indy by rules changes. The fastest pickup truck in the world is diesel powered. The fastest gasoline-powered vehicle in the world (a streamliner) holds the record at 344 mph, and a diesel streamliner is being built to challenge that record. A diesel pickup is being built to challenge Corvettes and Porsches in endurance racing, and diesel-powered vehicles hold the world’s fuel economy records. Diesels are at the forefront of setting new records and of advanced vehicle development.
Is there a performance diesel in your future? Diesel development has come a long way, but the public perception of diesel is lagging 25 years behind. Maybe it would help to call them compression ignition engines instead of diesels, but the bottom line is still the same. Modern diesels are quick and powerful, quiet, easy to start even in cold weather, and don’t smoke. They’ve made incredible strides forward environmentally. They’re also surprisingly easy to upgrade for still more performance that simply embarrasses gasoline powered performance vehicles. If you want to be the fastest of the fast, or the quickest of the quick, or just plain economical, there just might be a diesel in your future. At least you should learn more about these exciting engines. Admittedly, it may take a while to get accustomed to things like a Corvette C6D, a Ford GTD, or a Viper RTD, when and if the car companies ever build them, but it won’t take long to get use to the power. For now you have to make do with a diesel pickup or diesel SUV, but even with these unlikely vehicles, imagine the fun of outperforming those other guys who are still asleep at the gas pump!