EDITOR’S NOTE

DIESEL 101

Around 2000 when the Duramax came out the diesel performance industry exploded. A couple years after that I got my first job in the industry, while I’ve bounced around in it I never once left it, and I don’t plan on leaving ever. After spending the last 16 years working professionally with diesel, and currently as a diesel magazine/brand manager I have to stop myself and think of what it was like when I was learning. There are so many things that I just consider general knowledge at this point in my life, but for those just getting into diesels, or even those who have been into them for years, many of these things might not be something everyone knows much about. So I figured I’d spend a bit of time quickly explaining what diesel performance is, in the short single page I have to get that done in. Wanna know more? Just keep picking up the mag. each month. You’ll be a pro soon enough.

HOW THEY WORK

Suck, squeeze, bang, blow, is how it was taught to me in school. No, I’m not insinuating anything here. That’s how a 4-stroke engine works. The piston drops within the cylinder pulling in fresh air through the intake valves (SUCK); after the piston makes its way to the bottom of its rotation it then comes back up compressing the air (SQUEEZE); next the injector sprays diesel into the combustion chamber atop the piston which due to the extremely high temperature of the compressed air it causes the fuel to ignite (BANG) pushing the piston back down the cylinder which creates the power to turn the rear wheels via the crankshaft, transmission, and axles; after the combustion event the piston travels back up the cylinder pushing all the spent air out the exhaust (BLOW); and the cycle repeats.

COMBUSTION IGNITION

If you know gassers, you know that a spark plug is used to start the fire in each cylinder. Timing is dictated by spark. Well for diesels it’s different. Diesels are much higher compression engines, so high that once the air is compressed it’s hot enough to start the fire on its own. Gassers have average 10:1 compression ratio while diesels are closer to 20:1. So while a gasser can inject fuel into the intake air, doing so with a diesel would mean somewhat random ignition. Timing would be uncontrollable and performance would suffer greatly leading to catastrophic damage. Diesel’s inject fuel into the cylinder to start the combustion process. Many don’t like me using this analogy but when thinking of timing, the injector is both an injector and the spark plug for a diesel. Timing is dictated by the injector as a spark plug would do for a gasser.

MORE AIR MORE FUEL

The combustion event (bang) is how power is made. So, increasing the intensity of this contained explosion is how to make more power. This is done by adding more fuel and more air. Adding fuel alone will only make power until there is not enough air to burn the fuel with. Fuel needs air to burn. The perfect mixture of fuel to air is known as the Stoichiometric Ratio. For diesel’s that’s around 14:1 (14 parts air, 1 part fuel) but they generally run at much higher a ratio of fuel to air during normal operation. When you see black smoke that’s caused by not enough air in the mix. That black smoke is just wasted fuel and power going out the tail pipe. Everything done to make more power with diesels (and gassers) is related to tuning, fuel delivery, air delivery, or keeping parts alive. We add fuel until we need more air, so a bigger turbo goes on, and then we need more fuel. That cycle continues until something breaks. That part gets strengthened, and the cycle begins again.

TORQUE

Diesel has more BTU’S (aka power making ability) per ounce than gasoline. But it also burns more slowly. For this reason diesels cannot make as many RPM as a gasser, and they make more power down low in the RPM range. What is generally accepted as the max RPM for diesel engines is around 7,000 RPM. Fuel will simply not burn any quicker than the time 7,000 RPM allows for, at least not with today’s technology. Somehow, someway, that will change, I promise you.

IN THE END…

Diesels aren’t much different than gassers. They’re physically stronger to handle the raised compression and torque, have different ways of delivering the fuel to the combustion chamber, rev a little less, are tuned a bit differently, but their basic operating principle is pretty much in the same as spark plug engines.

I assume I created more questions than answers here, and that’s ok. Send me an email at Dw-editor@engaged.media. We’ll get your question answered via email or in the Q&A section in the back of the magazine.