Test Drive: Cummins X12 Diesel Engine Version 2.0

February 2018, - Department

by Jim Park, Equipment Editor - Also by this author

SHARING TOOLS        | Print Subscribe
We tested our X12 in a Cascadia daycab on Interstate and two-lane highways in Western New York, near Cummins’ Jamestown plant. Photos: Jim Park
We tested our X12 in a Cascadia daycab on Interstate and two-lane highways in Western New York, near Cummins’ Jamestown plant. Photos: Jim Park

Cummins’ new X12 engine is slated to hit the street sometime early this year, probably shortly after its formal launch in February or March. The engine was introduced in August 2016, and I had a short drive with it then around the 7-mile loop track at the Transportation Research Center in East Liberty, Ohio. It wasn’t much of an opportunity to get to know the engine, but it whet my appetite. Cummins invited me to drive the new X12 this past November on a longer real-world route, starting from the plant in Jamestown, New York, where the X12 is to be built.

The X12 has a displacement of 11.4 liters, which, according to conventional mathematical rounding principles, should have caused the engine to be named X11. However, the engine punches above its weight, and to call it X11 would have diminished some of its brightest attributes. Tipping the scales at just 2,050 pounds, it has the highest power-to-weight ratio of any heavy-duty engine from 10 liters to 16 liters in size. It’s lighter than any 11-liter block on the market (albeit subject to interpretation on how “dry weight” is determined). And its published ratings put it squarely in 13-liter to 15-liter territory for torque and horsepower.

The unpainted parts remind us that this is a pre-production, but production-ready, engine.
The unpainted parts remind us that this is a pre-production, but production-ready, engine.

Under the hood

Development on the X12 began in 2013 in close collaboration China’s Beiqi Foton Motor Co. There it was known as the ISG. The version of the engine we’ll see here in the next month or so has been almost completely re-engineered. Cummins tells me that close to 90% of the engine saw some re-engineering to ready it for North America.

We’ll learn more about it when it’s formally introduced, but based on what we know about the ISG, the X12 has about half the number of parts found on other diesel engines. It uses a sculpted block design for greater rigidity and less resonant noise. The block was engineered to remove as much metal as possible to reduce weight without sacrificing structural integrity. Several composite components, such as the rocker cover and oil pan, also help reduce overall weight. It features optimized intake and exhaust ports for easier breathing, and coolant and oil galleries were engineered for easier flow with less pumping effort. It uses the XPI high-pressure injection system and a Cummins-designed integrated engine brake that delivers up to 50% more engine braking horsepower than traditional engine brakes, the company says. 

I have also been told that the X12 will be available with Cummins’ full suite of electronic fuel efficiency and operational enhancements, such as Adept (SmartTorque2, SmartCoast, predictive cruise), Load Based Speed Control, and Connected Diagnostics. It will also use Cummins’ Single Module aftertreatment system.

The X12 fits snugly under the Cascadia’s hood.
The X12 fits snugly under the Cascadia’s hood.

On the road

For this test drive in a van trailer grossing 61,100 pounds, I ran about 90 miles on a nice mix of Interstate and flat and hilly two-lane roads. I headed west on I-86 from the plant in Lakewood to Northeast Pennsylvania, where I flipped back eastward on I-90. I got onto New York State Route 5 at Ripley, headed east to Westfield, and then back south to the plant on S.R. 394 and 430. It’s a great route to test an engine like this, because it’s exactly the kind of terrain on which it will operate in real life. 

The engine was installed in a Freightliner Cascadia daycab with a manual transmission. I opted for the manual because it gave me a better feel for what the engine could do, unaffected by an automated transmission with ideas of its own. It was a 10-speed Eaton manual with a 0.78:1 OD ratio, 3.58:1 rears and 11R22.5 tires — a typical spec for a regional/P&D operation where the X12 might find itself.


X12 Specifications

Displacement: 11.8 liters

Horsepower: 455 (1,400-1,900 rpm)

Peak Torque: 1,700 lb-ft (1,000-1,400 rpm)

Clutch Engagement Torque: 800 lb-ft

Number of Cylinders: 6

Dry Weight: 2,050 lbs.

This engine was rated at 455 hp/1,700 lb-ft. The power curves indicate peak torque extends from 1,000 rpm all the way up to 1,400, while the peak horsepower of 455 is available from 1,400 to 1,900 rpm, which is a dream configuration. You have a 400-rpm range for peak torque, which gave me a 15 mph range on the Interstate in top gear where I was cruising at peak torque, from 50 to 65 mph. At 65, I was running 1,400 rpm. I was down to 1,000 at 50 mph, which is a bit low for a hilly road, but okay on flat ground. At 55 mph, the engine was rolling along happily at 1,200 rpm, which gave me a 200-rpm margin before I’d have to think about downshifting.

I can’t say how an automated transmission would have handled it, but my inclination is to run the engine down as low as possible before downshifting without trapping myself at too low an engine speed. I suspect an Eaton automated would have opted for higher shift points, and so might have spent more time in 9th gear on the two-lane sections than I did.

The sculpted block has a very narrow profile, indicative of all the excess material that was engineered out to reduce weight without sacrificing structural integrity.
The sculpted block has a very narrow profile, indicative of all the excess material that was engineered out to reduce weight without sacrificing structural integrity.

I did cruise along in 9th for a while on a hilly section of S.R. 394 and was quite pleased with the very spry performance of the engine between 1,500 and 1,700 rpm. Ninth gear gave me a speed range from 45-65 mph at a usable engine speed, so I could have happily left it in that gear the whole time I was in the hills.

The engine responds very nicely to low-rpm operation in the bottom five gears, when I usually shift between 800 and 1,000 rpm. Startability is great with that gear combination. In the higher gears, shifts were comfortably made at 1,200-1,400 rpm.

The engine brake was fantastic for such a small-displacement engine, and when the revs get up to 2,100 or so, you can really feel it digging in. With today’s low-rpm operation, it’s easy to forget about the top 500 rpm in the engine range, but that’s where the engine brake works best.

On a less technical level, I found the engine to be very quiet, and it has a very pleasant low growling sound. It won’t bother anybody. Because the engine is so light, I’m sure it will be a hit in weight-sensitive applications. The variety of ratings is astounding; they go up in roughly 25-rpm increments from 325 to 500. The 500-rpm rating is vocational only; on-highway goes as high as 475. Torque ratings run from 1,350 to 1,700, and there are several multi-torque ratings in there as well, 1,550/1,700 and 1,450/1,650.

I think the X12 is exactly the right engine for the emerging regional haul market, and Cummins has nailed the performance curves. There’s nothing missing on this engine except a few hundred surplus pounds of engine block.


  1. 1. Gary Pipenger [ February 21, 2018 @ 06:46AM ]

    I would like to dyno test this new X-12 engine in the Cummins dyno in Fort Wayne, Indiana. Is that possible?
    I also would like to know if the new X-12 engine has an exhaust sensor on it to reduce fuel flow to the engine if the exhaust temperature increases.

  2. 2. Rcupp [ February 22, 2018 @ 12:45AM ]

    And to think, I bitched about the stuffed underhood of a Century Class when it first came out!!

  3. 3. Mike Lopes [ February 22, 2018 @ 10:23AM ]

    Does anyone know when, if ever, Paccar engineers plan to accommodate the X12 in Kenworth T860s?

  4. 4. John Baxter [ February 23, 2018 @ 12:19PM ]

    As usual, a great road test, Jim. That is a lot of torque for an engine of that size. that is for sure! Sounds like it's a great engine in spite of its light weight with more power than you'd expect, and also more torque. Sounds like the noise level is quite pleasurable as well, and it's not as if the engine dies at low rpm, either. Thanks for some great reading!

  5. 5. Richard Rogers [ February 24, 2018 @ 10:09AM ]

    Just looking at it makes me shiver. A "Mechanics Nightmare".
    All nice when new.
    If I had my way, I'd have all Detroit Series 60's at 430-HP made exactly like the ones we ran from 1992 thru 1996. Million mile virtually trouble free engines save for a head gasket replacement at 500,000 miles. And their fuel economy was and is better than the leased Penske new trucks that replaced most of the old trucks. Al Gore took the trucking industry backwards. Sorry, {:>) I speak as a "Bill Payer $$$$


Comment On This Story

Comment: (Maximum 2000 characters)  
Leave this field empty:
* Please note that every comment is moderated.


We offer e-newsletters that deliver targeted news and information for the entire fleet industry.


ELDs and Telematics

sponsored by
sponsor logo

Scott Sutarik from Geotab will answer your questions and challenges

View All

Sleeper Cab Power

Steve Carlson from Xantrex will answer your questions and challenges

View All