C18 to be Cat's first off-highway ACERT diesel: Shown at Intermat in May, 18.1 L diesel foreshadows full ACERT off-highway launch next year - Diesel Engines

Diesel Progress North American Edition, July, 2003 by Mike Osenga

With the official launch of its ACERT technologies for the on-highway markets behind it, Caterpillar Inc. is now turning its attention to Tier 3 and Tier 4 off-highway uses for its combustion emissions reduction technology package.

Cat has announced a mid-2004 availability date for its model C18 ACERT off-road diesel. This move to production comes two years after the initial showing of the off-highway ACERT technologies at ConExpo-Con/Agg 2002.

The 18.1 L, C18 diesel, which debuted at the Inrermat equipment show in Paris in mid--May, is also the largest Cat engine thus far to be fitted with the ACERT package. It is expected the complete ACERT off-highway line will be introduced in spring of 2004.

The C18, to be built at Cat's Mossville, Ill., complex, will be available in five ratings from 575 hp to 765 hp. Expected applications listed by Cat for the engine includes blasthole drill rigs, four-wheel drive agricultural tractors, forage harvesters, payers, other types of construction equipment, mining equipment, as well as irrigation, petroleum drill rigs, chippers and shredders.

Cat has always hung the "solutions" label on ACERT, but now, more subtly, is starting to talk about the "building blocks" of ACERT. It can be speculated that at least a couple of generations of the technologies that make up ACERT -- fuel systems, electronics, air systems; variable valve actuation and aftertreatment -- are available or near availability.

It has also become increasingly apparent, that Cat, or any engine manufacturer, will not apply the latest generation of a specific technology until the applicable emissions regulation requires its use. And why would they?

That is part of the reason for both the MEUT and HEUT fuel systems showing up on various ACERT on-highway diesels, as well as the use of Cat's current generation ADEM-3 electronics on those truck engines.

Each successive introduction of ACERT engines thus brings new surprises as to what is included on a particular engine and what isn't. The surprise with the off-highway C18 is that it will be the debut engine for Cat's latest generation of engine management electronics, ADEM-4.

Calling it "the most sophisticated ECM ever produced by Cat" ADEM-4 has 32-bit architecture, with a 120-pin engine connector and a 70-pin OEM connector, key elements in creating an electronic driveline that will integrate engine operations, as well as hydraulics, transmissions and other system components. The ADEM-4 microprocessor operates at 40 MHz, 66 percent faster than ADEM-3. Flash ROM has been doubled to 2 MB.

These heavy-duty electronics will control Cat's MEUI (mechanically actuated, electronically controlled unit Injection) system, which also features multiple injection and rate shaping capabilities.

The retention of the MEUI system, in what had been expected to be an all-HEUI on-highway engine launch, was one of the surprises of the truck engine introduction.

It's now obvious Caterpillar was able to develop new software for MEUI to add multiple injection and rate shaping capabilities when it developed its so-called "bridge" engines. The bridge engines were developed for post-October, 2002 sales to lower the amount of noncompliance fines Cat had to pay, bridging the gap until the ACERT engines began production.

Developing this capability, it is thought, allowed Cat to keep current generations of HEUI and MEUI fuel systems in production until more stringent exhaust emissions regulations require a new generation of fuel systems, both on-highway and off-highway.

Like the truck engines, the new C18 has a new cross-flow cylinder head design and four valves per cylinder. Cat has said all Tier 3/Stage 3 off-highway diesels using ACERT will have this cylinder head design and most will have four valves per cylinder.

The new C18 off-highway ACERT diesel will not use aftertreatment and will use wastegated turbochargers similar to the units introduced in the C7 and C9 ACERT truck diesels.

While most of the off-highway ACERT models will use wastegated turbos, in most cases the turbocharger will be larger than those currently in use and some will feature titanium compressor wheels. Series turbocharging will not be used on off-highway ACERT engines for Tier 3, but may be used on Tier 4/Stage 4 engines.

Variable valve actuation is one of the "building blocks" Cat is also considering for Tier 4 ACERT off-highway engines. Likewise adding a diesel oxidation catalyst is likely for Tier 4.

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