Ask The Experts: Why Did Caterpillar Stop Manufacturing On-Highway Diesel Engines?

Caterpillar has a long history of producing quality diesel engines. But as you probably know, they no longer make engines for on-highway applications. 

Diesel Engine Semi With Caterpillar EngineIn this post, we're going through the SDP engine and why, after its creation, CAT stopped building class-eight truck engines.

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Why Caterpillar Stopped Manufacturing On-Highway Diesel Engines

Like a lot of changes in the diesel industry, the changes Caterpillar made to its engines and business were driven by the continuous changes to emissions regulations.

The amendments made in 1990 to the Clean Air Act required lower emissions from diesel engines beginning with the 1994 models.

Later, new emission standards put increased restrictions on engines manufactured after 2004. In 2000, new measures that would affect engines built after 2007, with further, stricter requirements on engines manufactured in 2010.

It became increasingly difficult and costly to keep up with these restrictions.

What These Changes Meant for Caterpillar

When these emissions changes happened, Caterpillar was the only manufacturer who went with ACERT (Advanced Combustion Emission Reduction Technology). 

But, after building a few ACERT engines, Caterpillar decided that on-highway applications were a race to the bottom, and would require a larger investment upfront to remain in compliance. 

That, combined with being tired of trying to keep up with the constant changes to emission regulations, led to Caterpillar stopping the production of new on-highway engines. 

They stopped manufacturing on-highway engines in 2010, making the SDP engine the last C15 and the last class-eight truck engine they built.

So, instead, they decided to focus on their successful off-highway applications where they saw more money.

Despite some rumors that they would make "on-highway vocational vehicles," CAT has not produced an on-highway engine since the SDP in 2010.


Differences Between Caterpillar Engines

Looking at the late Caterpillar E models, your 10W and 2WS, you'll notice that they physically look the same as earlier engines, and they contain the same hard parts as the first C15. 

A lot of changes, though, were made to the engine's calibrations, along with almost all the hard parts. It's really the first engine they made a lot of changes to. 

The next version of that engine would be the first ACERT.

ACERTs and Caterpillar's Newer Engines

So, with the ACERT, the BXS, they made big changes, including adding valve actuators to control the combustion temperature, adding twin turbos, and free coolers. 

The MXS and NXS are the next two engines, and they are nearly identical. They take the same turbos, injectors, and pistons, so these engines are very similar to each other. 

Next is the SDP. This engine includes huge changes from the previous version, including a complete redesign of the turbochargers. It also changed the injector set up and a big redesign on the oil coolers. They also added the EGR or clean gas induction.

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Piston Numbers by Serial Number

Pistons in the Earlier Engines

The first engine was the 5EK. A lot of the low horsepower engines or really early engines were a one piece aluminum piston. In the higher horsepower engines, they moved to a two-piece system that has a steel crown and aluminum skirt.

Changes to the Pistons in Later Engines

Pistons were very similar on the 5EK 6TS. When they went to the 1LW and 2WS, they changed the piston to what is probably the most popular piston of any of them: the 1807352, which is a 2 piece piston as well, with a steel aluminum skirt.

That's when they went to the forged steel model, and they used that through the VXS, MXS, NXS, and SDP, using the same system through all those engines.


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