Understanding - Engine Builder Magazine


The light turns green and the truck bellows out a plume of black smoke and in a flash all you see are the taillights. You’re struck that diesel trucks have really made an improvement over the past fifteen years. It’s amazing when you realize that a Corvette would have a hard time keeping up with a modern pickup.

Diesel performance is awesome and continues to grow, but the biggest question that I get from customers is, “What can I do to get more power from my diesel truck?” That is not a simple answer because I know that most people are not looking to drag race. They simply want to feel more power from their work trucks.

Yes, we consider them “work” trucks because that is why we pay the price for diesel power. Think about it, would you purchase a diesel truck if you didn’t want the pulling power? Of course, when you give someone a little power they always want a little more.

To answer your diesel customers looking for more power, my first suggestion is to look for products from reliable sources. These would come from a manufacturer who has spent countless hours of dyno testing to prove their products are safe and reliable. Many of these companies can be found in the pages of this magazine. The emphasis is on performance and reliability.

To be sure, there are other things like exhaust systems, air/fuel separation, turbos and injectors that can improve performance, but if you really want to learn about diesel engines, you have to understand the fundamentals. In working with diesel engines, the best tool I have found before installing upgrades is an air/fuel ratio meter.

One thing that you have to understand is how “lean” the diesel engine operates. The diesel engine is dependent upon fuel to make power. The diesel engine has no throttle blade and is controlled strictly by the amount of fuel that is injected into each cylinder based on demands from the accelerator pedal. Gasoline engines are dependent on fuel, which will enter the cylinders from a carburetor or injector when the throttle blade is opened. So the gasoline engine is not going to run unless the engine sees more air and fuel whereas a diesel is not going to run unless you inject fuel only.

The purpose of an air/fuel ratio meter is to help you learn. Before installing programmers and other upgrades, you need to see just what is taking place. Under normal operating conditions, gasoline engines will produce an air/fuel ratio of around 14.7:1. This refers to 14.7 parts of air to one part of fuel. In a diesel engine under normal operating conditions, the air/fuel ratio can be extremely lean – sometimes as high as 80.1:1. Knowing the air/fuel ratio for a stock application might give a better understanding of exactly what is taking place inside the engine. This can be your “eyeballs” so when a programmer is added, you can see exactly what is going on.

The black smoke you often see is what is considered “charred” fuel. This occurs when the injectors add more fuel to the chamber that is being completely burned producing more power. Along with that comes higher exhaust gas temperatures, which can become dangerous if they become too high. Add-on diesel gauge packages usually include a pyrometer, also known as an exhaust gas temperature (EGT) gauge. This can be helpful to an owner in knowing when to back off the throttle. Yes, the black smoke is cool, but just because a little is good doesn’t mean that more is better.

There are a lot of “goodies” out there, but choose something appropriate for the application. I see owners adding everything from twin turbos to dual common rail pumps and ask myself exactly what are they doing. The manufacturer designed the engine for an application. A lot of times these add-ons take away from the integrity of the vehicle and other components – such as the transmission and rear differential – will begin to fail. The only time that these products would be really beneficial is when you were using it for racing.

Most of the power adder questions come from the younger generation. I think it is a good thing because they are creating a passion for what they drive. That is what keeps our aftermarket companies producing more products. I often will extend the invitation for a chassis dyno pull. This tends to put the facts on the pavement and gives the owner an idea of what is going on. Regardless of the generation, If anyone is intrigued about diesel performance then they have to be somewhat of a gear head anyway.

Your customers may have an understanding of how a diesel engine operates – they probably just don’t realize some of the fundamentals used in making an engine ignite on diesel fuel.

Robert McDonald is owner of Atlantic Engines in Granite Falls, NC, and specializes in high performance diesel and gasoline engines and cylinder heads for street, marine, dirt and drag racing. Robert can be reached at [email protected]. If you have a passion for diesel engines and want to learn more, purchase tools such as an air/fuel ratio meter to broaden your horizons.

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