From its start in 1932, the Model H diesel had been a prime mover and, by 1960, it had helped the Cummins Engine Company attain a leading industry position. It was one of those “just right” engines for many applications, but in an everchanging market, the Cummins engine lines also had to be ever-changing. The inherent flexibility of the core architecture would be tested by changes even Clessie Cummins might not have been able to imagine.
Speaking of Clessie, by 1960, he was long out of the managerial and manufacturing loop at Cummins Engine Company. For one thing, he was 72 years old at that point, and the pace of a modern company trying to stay at the top of a manufacturing peak is generally not for older men. The term, “creative differences,” also applies, and while those differences got heated at times—like relatives who argue politics at the Thanksgiving table—there was a deep core of friendship and respect. Clessie would transition to the “eternal machine shop” in August 1968, and he passed on during a high point for the company he helped create.
For 1960, a new variation of the original H design would debut. A simple bore change from 5.125 to 5.50 inches over the standard 6-inch stroke bumped the displacement from 743 to 855 cubic inches (most “dieselheads” will recognize that number). Ratings ran as high as 380 hp at the debut, making it a class-leading powerplant.
While the 855 helped Cummins own 60 percent of the heavy-duty truck engine market throughout much of the ’60s, it was also one of Cummins’ most challenging decades. Government regulations, a constant battle to fight off differential taxation on diesel fuel (to equalize gas and diesel prices), more competition, labor
issues and growing pains would all challenge Cummins’ leadership especially hard.
The ’70s would bring a heightened emissions awareness to the entire diesel industry. Cummins had long sought the least amount of smoke possible from all its engines, but smoke was just the visible part of the emissions issue. Noise regulations were also becoming part of the landscape.
To answer all these problems in the NH series engines (which dominated the 200 to 300 hp range), Cummins did two things—first by going from about 50 percent turbocharged on its automotive engine to nearly 100 percent. That included related upgrades such as aftercoolers. Industrial, marine and generator engines would eventually follow suit. Second, Cummins debuted the Big Cam engines for 1977.
As you recall from part 1 of this series, the PT fuel system used a camshaft-actuated injector. You also know that increased
injection pressure over a shorter period results in better atomization, combustion and less smoke. Cummins found the original cam didn’t have enough diameter to offer adequate surface area for the lobes to be optimally tuned to achieve this goal and still offer a durable lobe. The Big Cam engines solved that problem when the camshaft diameter was increased from 2.0 to 2.5 inches; that delivered the ability to more finely tune the lobe with more durability.
Over time, the Big Cam engines would come in four variations: Big Cams I through IV, each with a few upgrades designed to enhance power and economy. The Big Cam engines were stated to improve fuel economy by about 15 percent over a comparable Small Cam. The Big Cam III series are the best loved of the series. Other innovations were the Formula economy engines—which were an evolution of the NHE economy engines— that lowered the rpm peak and moved the torque curve to peak at a lower point.
The Big Cam era also had moments of technical faux pas. The 88NT was such a moment.
A 1984 EPA edict revealed stringent particulate emissions regulations upcoming for 1988. Cummins met the regulation challenges with the 88NT (a variant in the Big Cam IV series), but the engine fell on its face and took the company with it. The core problem was injector sooting, resulting in a remarkable drop in engine durability. The 88NT reportedly cost the company millions in warranty costs. But, most importantly, it significantly damaged the stellar Cummins reputation. Reportedly, customers left in droves, saying simply, “ABC” (“Anything but Cummins”).
The company knew it had flubbed—and why. The engine had been inadequately tested because the company had been lulled into complacency by product familiarity and a stellar record with the engine family. Cummins wasn’t used to going face first into the dirt, but it picked itself up and put its foundation-stone engine back to rights. So was born the N14, which was initially also a mechanically injected engine but with the faults of the 88NT eliminated.
By the end of the ’70s, it was very clear that mechanical injection wouldn’t be able to meet ever more stringent diesel emissions while maintaining competitive power levels. Electronics were taking over all parts of automotive technology, and Cummins started down that road in 1980 after an agreement with Bendix to co-develop an electronically actuated
diesel injector. Cummins ended up buying the Diesel Engine Control Division of Bendix in 1982, moving it to Columbus, Indiana, and deeply investing in the technology. The development of diesel electronics progressed rapidly, but Cummins management was cautious about jumping the shark again. Consequently, the introduction of electronics was a measured process.
An early system called ECI (electronically controlled injection) might have debuted in the 88NT, but instead, it appeared in an evolved form in the N14 for 1990. Electronics appeared first in a partial electronic system called PT PACER, in which line pressure was controlled electronically, or a fully electronic system then called CELECT.
The standard PT mechanical engines remained in production for industrial and marine applications. Electronic engines would represent an ever-increasing percentage of Cummins’ engine production, and the automotive N14 would be electronic only by 1994. Although the initial applications for the N14 with CELECT would be automotive, they would extend to industrial by ’96, generator by ’97 and marine by ’98.
By the late ’90s, the N series engine was in its declining years. With new Cummins designs, more stringent emissions regulations and a general drop in the heavyduty engine markets, sales were approaching a low point in the North American market.
Cummins management made the decision to curtail production of the N14 at the Number 1 Plant in Columbus, Indiana. The last engine was built in November 2002, and production was handed off to the Cummins India Plant in Pune, where it continues to be built in large numbers, along with NT engines. Later, the Chongqing Cummins Plant in China would begin manufacturing the N14; this continues as well.
As of 2019, that’s an amazing 87 years in production for this engine family. Will it make 100 years? Industry people think it’s possible, although perhaps not likely. In any event, 87 years is a milestone all by itself.
This exploded sculpture of a Big Cam III was erected in the Cummins headquarters lobby in 1983, and it looks like it will still be there after renovations are completed in 2019. The work was orchestrated by Cummins Applications Engineer John Walter and is considered a masterpiece of technical art. Walter, a B-24 pilot in World War II, has passed away, but his legacy lives on at Cummins. (Photo: Cummins Historical Collection)
Meet “Nettie.” The NT-380BI is the first high-power version of the 855, and it was cranked up to 380 gross hp at a maximum rpm of 2,300 versus the standard 2,100 rpm. A 380 hp engine was big news for 1960, and the rating was real, as you see. But it was marketing department inspired. Engineering had a low comfort level spinning the engine up that high, so sales were relatively low and directed to the most appropriate applications. A 335 hp rating was the “sweet spot,” and you could run those 855s full-out for decades at that output. The new generation of the N series involved more than just the displacement increase from 743 to 855 cubic inches: The block was extensively revised to enclose most of the lubrication system. Thicker liners were used, along with tapered connecting rods. The external fuel manifolds were replaced by drilled passages in the head. Valve sizes increased from 1.750 to 1.875 inches to increase airflow and the 855 retaining the four-valve configuration. Common base automotive ratings were 250 hp for the NH-250 naturally aspirated engine (code-named “Nellie”) and the NT-380-BI (code-named “Nettie”). (Photo: Cummins Historical Collection)
When 1964 rolled around, it brought a new feature to the N series diesels: the custom ratings. When you see a “C” in the designation, such as for this NHC-250, it’s a “custom” engine. That means the PT pump can easily be tuned to a selection of power ratings by replacing a small part in the pump. In the NHC engine line, which were naturally aspirated, you had the choice of a 220, 225 or 250 hp rating on the same basic engine. For the NTC turbocharged engines, you could see 240 to 335 hp ratings in the mid-’60s era. The actual power ratings changed often over the model years. However, the custom engines made Cummins’ work easier at the manufacturing end, and the end user had the means to bump power without a lot of major tweaks. The naturally aspirated engine applications were getting fewer for automotive applications at this point. (Photo: Cummins Historical Collection)
Although you could call 1960 and later the “855 era,” production of the 672 and 743 cubic inch engines did not cease. There were still markets for the previous-generation engines, and this 1960 NRTO6B was still a potent unit, making 335 hp at 2,100 rpm. It had reigned supreme in the ’50s and was the highest rating in the 743 cubic inch line. It remains legendary but was soon phased out of the early-’60s lineup for the lower-stressed 335 hp 855.
The Big Cam III (BCIII) engines that debuted in 1982 are certainly the most popular of the Big Cams and might be the most popular of the 855 cubic-inch series when old truckers get to gabbing. The most immediately noticeable feature of a BC III engine is the stamped steep pan versus the cast-aluminum pan of previous models. A more efficient oil cooler was added, and the cooling system was improved. Injectors were updated to a Direct Fuel Feed type for increased flow. Internally, the piston skirts were improved. Along with the carried-over BCII updates, as well as turbo improvements, the BCIII was a potent addition to the Cummins family. Shown is an NTC-350 version—by far the most popular in the BCIII range That rating was one of those “sweet spots” for the industry and certainly one for Cummins. (Photo: Cummins Historical Collection)
Beyond the “Big Cam” cast into the left side of the block, there was little externally to distinguish a Big Cam I (BCI) engine when it debuted in 1977 ... unless you were familiar with the family. Performance- and emissions-wise, they could be easily distinguished. They also delivered a 4 percent fuel economy bonus versus the Formula Small Cam engines. Their designations did not change. This one is an NTC-250, and the ratings spread largely didn’t change. The big Cam II (BCII) engine debuted in 1979, offering another 6 percent economy boost over the Big Cam 1. The BCII was developed in Cummins’ Essen, Germany, tech center to help the 855 series engine better compete in Europe. The BCII added demand flow-cooling to reduce the parasitic load of the water pump, along with a pulse flow exhaust manifold with a new turbo to increase power. (Photo: Cummins Historical Collection)
X Which would you pick? On the left is a mid-’60s NH-180 (180 gross hp at 2,100 rpm and 504 gross lb-ft of torque at 1,500 rpm from 672 cubic inches). On the right is the NHE-180 (180 hp at 1,950 rpm and 533 lb-ft at 1,300 rpm from 743 cubic inches). Both were dyno-tested on the same day in 1964. Note the substantially better BSFC curve at the bottom of the NHE chart. Better economy from an engine with the same power, 71 additional cubic inches and 29 more lb-ft—what will they think of next? (Photo: Cummins Historical Collection)
X In 1963, the NHE (“E,” for economy) engines were introduced. They produced rated power at a lower 1,950 rpm, and their torque peaked at a lower rpm. With a truck properly geared for it, the economy engines delivered great performance with a boost in fuel economy. This concept was so popular that it was morphed into the ’75-up “Formula” series that continued into the Big Cam era. (Photo: Cummins Historical Collection)
What replaced the N14 in North America? The ISX, known initially as the Signature series engine, was a “clean sheet” engine with no design carryover from the N series. It was the 15L DOHC, later SOHC, inline-six that made from 435 to 650 hp and up to 1,950 lb-ft. It was a fully electronic engine using the Cummins Interact System (the “IS” in the designation), which allows communication with the transmission and other chassis systems. A variation was the QSX, which was a fully electronic engine. However, it was designed for industrial and marine use. As of 2017, the new X12 and X15 were replacing the ISX in heavy truck applications, but it looks as if the ISX and QSX will still be around in some applications. (Photo: Cummins Historical Collection)
T There are 70 years between these two engines, yet they share “DNA.” On the left is the last N14 to roll off the Cummins Plant Number 1 line in November 2002. On the right is the HA engine that was approximately the 25th engine to roll out of the same plant in September 1932 and is the earliest Model H engine known to survive. This year is Cummins’ 100th anniversary. Whether you are a “Cummins person” or not, you should be celebrating the centennial of an American company that has strongly supported the nation and its people.
The most current engine in the same class as the H and its progeny is the X15. There is virtually no “DNA” from the line we are celebrating. A wide range of applications and outputs is accommodated in the emissions-compliant automotive range—from 485 to 605 hp (1,650 to 2,050 lb-ft). It’s well on its way to a stellar reputation. (Photo: Cummins Historical Collection)