Behind closed doors in 2007, the key people at Nissan USA and Cummins, signed a deal to bring to market a diesel engine for the half-ton truck segment. At that time, a number of vehicle manufacturers were working on bringing to market the first half-ton diesel.
The new Nissan Titan.
Then the market dropped shortly after and quite a number of OEM’s canned their diesel programs. Not Nissan, they stayed true to their original goals and continued working with Cummins. On January 12, 2015, we finally get to see what that engine is all about in the redesigned Nissan Titan XD!
While not the first half-ton diesel to market (Ram’s 3.0-Liter V6 EcoDiesel entered the market just a short time ago) it does promise to be the most powerful. At 310 horsepower and 555 lb.-ft. of torque, the Titan is almost creating a new class of pick up. The Titan is a half-ton (meaning it weighs less than 8,500 GVWR) but with the powertrain of a three-quarter ton.
In fact, according to Cummins, “The new TITAN XD engine features over 70 percent parts commonality with the commercial variant of the Cummins ISV5.0 engine family – which includes vehicles with 30,000-pound gross vehicle weight ratings [GVWR].”
5.0-Liter Cummins Specs.
Configuration: 90 degree V-8
Head/Block Material: Aluminum cylinder head, Compacted Graphite Iron engine block
Displacement: 5.0 liters, 305 cubic inches
Compression Ratio: N/A
Bore: 3.7 inches
Stroke: 3.54 inches
Valvetrain: 32 valve, dual overhead cam
Injection: 29,000 psi common rail
Aspiration: Intercooled, Modulated two stage
Oil Capacity: N/A
Horsepower: 310 HP
Torque: 555 lb.-ft.
The 5.0-Liter Cummins is a 90 degree “V” eight that features dual overhead camshafts (DOHC). This engine is a common rail engine that has all of the normal emissions equipment to make it a very clean running engine. Thanks to the common rail injectors and the design of many components, the engine is a quiet diesel.
Unlike three quarter and one ton trucks that are really work trucks that people drive and use daily for their personal lives, a half ton is a personal daily driven truck that needs to work on weekends. This means that to compete in the half ton marketplace, the engine needs to be light weight (for a diesel), quiet, fuel efficient, clean and powerful.
For the engine to be light weight, everything needs to go on a diet. Traditionally, diesel engines are substantially heavier than their gas counter parts. When Cummins started designing the new engine, they knew they needed to use a Compacted Graphite Iron (CGI) block. The graphite that is added to the iron helps strengthen the structure. With a stronger structure, the thickness of the block can be reduced and optimized to produce a very strong structure but yet a relatively light weight block.
To trim even more weight off of the engine, Cummins opted to use aluminum cylinder heads. Aluminum is about 35 percent the weight of iron. By switching over to aluminum, Cummins was able to trim quite a bit of weight off the engine.
Nothing on the engine was ignored. Even something as light and simple as a valve cover was looked at to see if there was a way to reduce the weight. A composite material ended up being chosen for the valve covers (more on this later).
Unfortunately, only some of the weight savings that Cummins was able to get shows up in the final weight. The four camshafts, unique turbocharger system and the emissions systems that were added eat up some of the weight savings, but the engine still ends up quite a bit lighter than what an older V8 diesel of similar weight would be.
For those of us who own and drive diesels, we don’t mind the noise. In fact, many of us actually like the noise of our diesel engines. For Nissan to compete in the half ton market, they have to compete with very quiet gas engines. Not only are customers sensitive to the noise while inside of the vehicle, but they are sensitive to the cladder on the outside as well. Few people want to show up to a golf course or fancy hotel with a loud stinky diesel.
We have been working on this together for a period of time, we have had the time to really do it right — Ric Kleine, VP, Cummins, Inc.
The block design was not only optimized for strength, but for NVH (Noise, Vibration, and Harshness). To reduce the noise from the aluminum pistons hitting the cylinder wall, a Bosch piezo injection system was chosen for the Titan. The piezo injectors are able to fire five times per combustion event. This allowed Cummins to fire the injector with small bursts to gently move the piston over to the cylinder wall before the full fuel is delivered and the power is created.
The Bosch CP4.2 high pressure fuel pump is run off of a timing chain. Instead of just running the chain to the pump and calling it good, Cummins actually times the pump. “Timing of the pump hides any pump noise by sequencing it with the combustion cycle,” said Steve Sanders of Cummins Inc.
On top of each cylinder head, there are two camshafts. By using individual bearing caps, NVH was further reduced. Then the composite valve covers help to dampen the NVH even more.
The two stage turbocharger system is mounted very low in the valley and intake manifold basically wraps around the turbochargers. The design of the two system further reduces NVH. In fact, like the weight, just about every single component was designed to reduce NVH.
“We have been working on this together for a period of time, we have had the time to really do it right,” said Ric Kleine, VP, Cummins, Inc.
Fuel efficiency can be broken down into two categories: engine efficiency and vehicle efficiency. While the majority of the factors that affect vehicle efficiency are outside the scope of this article, one aspect is the weight. The heavier the vehicle, the less efficient it is. All of the improvements mentioned earlier, help to pull hundreds of pounds off of the front end of the truck, reducing the rolling resistance and improving the vehicle efficiency.
As far as engine efficiency, it comes down to really two main categories: air and fuel. As mentioned earlier, the fuel system is able to fire five times per combustion event. This gives Cummins the ability to optimize the combustion in each cylinder which leads to increased fuel efficiency. In addition, the fuel timing and pressures can be varied to ensure that peak torque can be reached sooner and extended for a longer duration of time. The allows the six speed Aisin transmission to select the right gear for the load without having to downshift for more power.
Another key aspect of the fuel efficiency is air. With the unique M2 Two-Stage Turbocharger system from Holset, the 5.0-Liter Cummins is able to get on boost much sooner. By having the air necessary for more fuel, the engine can produce the power required much more efficient. In addition, the exhaust gas temperatures will be lower resulting in less thermal stress on the components.
Clean emissions starts with a clean startup. Unlike the 5.9 and 6.7 Cummins, the 5.0 uses ceramic glow plugs to reduce start times and emissions on cold start. Another benefit to the ceramic glow plugs is that they require less current draw and reduce the stress on the electric system. (According to Cummins, the ceramic glow plugs should last the life of the engine with no maintenance.)
Once the engine is running, the injectors are able to regulate the fuel enough to minimize the soot production. Soot is further reduced with the extra air generated by the M2 Two-Stage Turbocharger system. The first stage turbocharger is able to come on boost much quicker than a turbocharger sized for the 310 horsepower. This keep the engine running lean and results in a much cleaner combustion.
To keep the engine running cleaner, the 5.0-Liter Cummins does use EGR (Exhaust Gas Recirculation). The engine features a single cooler on the right side (passenger’s side). Once the exhaust has left the engine, the usual assortment of SCR (Selective Catalytic Reduction), DPF (Diesel Particulate Filter) and DEF (Diesel Exhaust Fluid) are used to further reduce the emissions down to an almost zero amount of NOx (Oxides of Nitrogen) and PM (Particulate Matter) cooler, but there is only one cooler.
310 Horsepower and 555 lb.-ft. of torque out of a 5.0-Liter engine is nothing to shake a stick at. The new diesel could very well turn some gas people into diesel people. Especially with the Aisin six speed transmission behind it. We have high hopes and believe it will be one of the best options for the half ton towing market.
All of that power is transmitted through the forged steel crankshaft and is harnessed by the cast aluminum pistons. To keep the pistons cool when under high loads, the engine not only uses oil squirters but runs lean thanks to the second stage of the M2 Two-State Turbocharger system. The Two-Stage system isn’t a compound system where the first stage feeds the second stage, but rather a sequential system where the first stage gets the system up and running then passes the load over to the second stage.
The Cummins ECM mounted to the chassis is able to keep an eye on EGT’s thanks to probes mounted pre and post turbo. This will certainly help to ensure the engine is not only running optimally but should ensure maximum engine life.
“Our strategy for our diesel engine is to not only center on better fuel economy, but we also have to deliver on the performance of a diesel engine. Where you get a lot of tenacity when you are accelerating or on a grade climb. It is that feeling that the engine always has more to give. You never run out and hit the top of the torque curve or top of the peek. It is always wanting to give you more than you ask for,” explained Rich Miller, Director of Product Planning and Titan Chief Product Specialist.
We are not only excited by the addition of another half ton diesel engine in the marketplace, but we are super excited it is another Cummins. Over the past two and a half decades, the Cummins B series engines have proven to be extremely durable, powerful and a go to engine for performance. Hopefully, this engine will follow in those tracks and encourage more manufacturers to introduce half ton diesel engines!