It must be clear: Only the cleanest of intake habits can assure an engine’s long and healthy life. That intake could be drawn in naturally or artificially induced, should this become necessary. But it needs to be free of unwanted elements, which tend to clog things up. 

And for today’s thoroughly modern off-road diesel engines, that means a sufficient volume of clean, filtered air on its way to the combustion chamber. That air is heated and serves as a foundation for another successful combustion event upon the injection of fuel at just the right time. Or multiple times, with today’s powerful electronic fuel systems quite capable of easily injecting fuel five times for each precious firing event. This moves the pistons downward, the crankshaft around, and businesses forward each and every day.

Fitted and Filtered

The need for combustion air that is as clean as possible was apparent with the very first engines used in off-road applications, and that need continues to this day. Any particle that makes its way into the engine is unwanted and likely to do some damage once it’s inside.

It depends, to some extent, on the overall size of the engine, but recall the old adage that it takes just a teaspoonful, tablespoonful or a metric equivalent to “dust” an engine — that is, to wear it out sufficiently so that rebuilding is required. Keep that adage in mind as you consider all the opportunities for dirt to get into an engine.

Rule number one in preventing this, of course, is to minimize those opportunities by not over-servicing the air cleaner system. If proper breathing is occurring, best to leave things alone. It is not necessary to poke about too much in the vicinity of the air cleaner if the engine is running properly. It never hurts to clean things around the air cleaner, but the element itself should be left in place. Every time the element is removed, there is the opportunity to — inadvertently perhaps — allow some dirt into the engine.

Rule number two is to fully understand and accept that an air filter actually improves in efficiency as it is used. That seems counterintuitive to many people, yet we still need to keep an eye on things. That said, it’s a warning sign if you’ve got someone trying to sell you more filters and encouraging you to change them more often to better protect your engine. 

The physics of this are simple. The filter companies produce media of various types that are able to capture the significant particles floating about and hold them in place so that they don’t become a part of the intake air. As these particles build up on the media surface, they provide further restriction and enable the capture of even smaller particles found in the air. While the “larger” particles might cause greater damage, anything hard and abrasive is going to cause some damage no matter the size.

A new filter starts at a 99-plus percent efficiency and then starts its march toward 100-percent efficiency. Once there, it’s “plugged” and must be replaced. Until that time arrives, let it do its job.

Something new about air filters these days is that the filter companies are finding better ways to increase media surface area for a filter of a given size. This allows for longer usage before it finally needs to be replaced. One might now be available for a particular product of yours that needs a little extra help in the breathing department. 

Befitted and Boosted

Another early realization in the world of engines was regarding the benefits of forcing more air into an engine if conditions warranted. This might be with a mechanically driven supercharger, using precious engine power for operation, but with a positive payback from the air pump spun at high speeds. Or it could come from a turbocharger, using essentially “free” exhaust gases to drive an air pump spinning at ridiculously high speeds — up to 250,000 rpm! Gasp! 

Actually no … not gasping at all when one of these precious, and initially expensive devices, was fitted.

While first of common usage for applications where the air supply might be lacking, like high altitude, turbochargers are seen more often these days on more engines than ever. They have become an integral part of producing a more complete combustion process. That would be for efficiency — reduced fuel usage, as well as for emissions — less production of the unwanted byproducts.

Most automotive diesels are fitted with at least one turbocharger, a testament to their importance in the world of modern diesel engines.

A turbo generating higher air flow is effective in making sure the two things needed for combustion, air and fuel, have a greater chance of matching up and resulting in combustion. Molecule to molecule.

Engines are often fitted these days with multiple turbochargers to address the dreaded “turbo lag.” Sometimes, a turbocharger doesn’t respond immediately when called upon for some added power. It takes some time to build up speed in the turbine wheel, so that the driven compressor wheel is actually pumping some volume of air. To address this, a smaller turbo responds first, followed by a second one operated either in conjunction with the first or solely on its own. The second one has a greater capacity for the high speed/high volume air needs of the engine. And a recent promising development is fitting an electric motor to the turbine wheel to get things spinning immediately — a little boost for the boost device itself.

The engineering behind these is straightforward and ongoing. Requirements of a proper one are such things as lightness, for responsiveness, along with strength for durability. These attributes are being fine-tuned and verified continually. That means more turbos available at ever higher performance levels and lower costs, used on more and more engines all the time. And something, perhaps, to seek out on new purchases. 

It’s likely that there will be an engine variation available at any horsepower level with a turbo in place. In fact, a recent engine introduced at a modest 24 horsepower is solely a turbocharged product. It’s a powerful little package, and potent under a wide range of operating parameters. Perfect.

As we wind things down, it should be clear at this point that these wonderful little turbos — subject to high temperatures and high speeds — rely on a steady diet of clean and fresh oil to continue spinning freely. And, unlike air cleaner elements, one is never punished for changing the required oil too often to keep these little wonders happy day after day.