Ford 6.7 Powerstroke Firing Order

By Nick Marchenko, PhD

In the development phase, the 6.7-liter Scorpion Power Stroke engine emerged as Ford's in-house diesel powerhouse for the Super Duty lineup.

This marked a strategic shift with Ford taking full control of design, engineering, and manufacturing to maintain profitability and a competitive edge in the diesel market.

Notably, it is the first Power Stroke engine not developed in partnership with International Navistar. This independent approach has given Ford a unique advantage, allowing precise alignment with their requirements and customer needs while streamlining the warranty process that once strained their relationship with International.

Despite a nearly 3-decade partnership, Ford's self-reliance in diesel engine development appears to thrive. Explore more in the following sections.

6.7 Power Stroke Engine Features

Engine Architecture

The 6.7-liter Power Stroke diesel engine boasts a conventional 90-degree V8 configuration, featuring a compacted graphite iron (CGI) engine block and aluminum cylinder heads.

What sets its design apart is the unconventional arrangement of the exhaust and intake manifolds. In a unique twist, the intake ports are positioned on the outer deck of the cylinder head, closest to the fender wells, while the exhaust ports exit directly into the engine valley, where the turbocharger is situated.

This innovative design enhances thermal efficiency by establishing a shorter, direct path to the turbocharger's turbine. Consequently, it reduces total heat d`ipation and conserves exhaust gas energy.

Fuel System

The 6.7-liter Power Stroke diesel boasts a cutting-edge high-pressure common rail fuel injection system, featuring a Bosch CP4 injection pump reaching pressures up to 36,000 PSI, powered by piezoelectric fuel injectors.

To meet demands, an electric lift pump provides up to triple the required fuel flow, offering essential lubrication and cooling for the injection pump.

Excess fuel is continuously returned to the tank for efficiency. For protection, the system employs two fuel filters: one in the diesel fuel conditioning module (DFCM) capturing 10-micron particles, and another near the driver's side firewall trapping 4-micron particles.

While the engine can run on biodiesel blends up to B20, prolonged use of higher concentrations or pure biodiesel may risk fuel system damage.

Turbocharger System

In the 6.7-liter Power Stroke engine, various turbocharger setups have been used, all with core components like an air-to-water charge air cooler, intercooler, and variable geometry turbochargers.

The initial 6.7-liter engines (2011-2014) featured an innovative single sequential dual boost turbocharger. This setup had two compressors of different sizes mounted on a single shaft with one turbine, delivering twin-turbo-like performance in a single unit.

Later iterations switched to more conventional variable geometry turbochargers, likely due to cost and reliability concerns related to sequential turbos.

An air-to-water intercooler plays a key role by using engine coolant in the secondary cooling system, efficiently reducing intake air temperatures compared to traditional air-to-air intercoolers in earlier Power Stroke models, thanks to water's superior heat transfer properties.

Cooling System

The 6.7-liter Power Stroke diesel engine operates with two distinct cooling systems, each equipped with its radiator, degas bottle, thermostats, and belt-driven water pump.

The primary high-temperature cooling system radiator is positioned behind the secondary low-temperature cooling system radiator.

This arrangement is intentional, as the secondary system functions at notably lower temperatures, and thus it takes precedence in terms of airflow through the grille.

Emissions System

The 6.7l Power Stroke diesel engine incorporates a range of advanced emissions control systems, including cutting-edge exhaust after-treatment solutions.

This engine marks the first in the Power Stroke diesel family to require a selective catalytic reduction (SCR) system for the reduction of NOX emissions, ensuring compliance with both federal and state emissions regulations. Figure 3 below illustrates the configuration of each component within the exhaust after-treatment system.

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Exhaust Gas Recirculation (EGR)

The initial step in curtailing nitrous oxide (NOX) emissions involves exhaust gas recirculation (EGR). By cooling and reintroducing a precisely metered quantity of exhaust gases into the intake air charge, this process effectively reduces combustion temperatures and substantially lowers NOX emissions.

The EGR cooler is positioned above the passenger side valve cover and employs a 2-stage cooling circuit. In the earlier engines (2011-2014), the first stage of cooling relied on the primary cooling system, while the secondary cooling system handled the second stage.

However, all engines from 2015 and onwards utilize the primary cooling system for cooling both stages. To enhance EGR exhaust flow, a throttle body mounted at the intake manifold's lower inlet creates a differential pressure between the intake and EGR systems.

Diesel Oxidation Catalyst (DOC)

The exhaust after-treatment sequence initiates with the diesel oxidation catalyst (DOC) situated closest to the engine. As exhaust gases pass through the DOC, an oxidation reaction transforms selected hydrocarbons into carbon dioxide and water vapor.

Notably, the DOC plays a crucial role in generating and sustaining heat within the exhaust system, as the oxidation reaction is exothermic, generating heat as it progresses.

Selective Catalytic Reduction (SCR)

The selective catalytic reduction (SCR) system confronts NOX emissions through the application of a specially formulated exhaust fluid. Diesel exhaust fluid (DEF) consists of approximately 67.5 percent distilled water and 32.5 percent dissolved urea, serving as its active component.

DEF is introduced into the exhaust after-treatment system through a dosing nozzle positioned before the entry point of the SCR catalyst unit.

A spiral-shaped auger ensures thorough mixing of DEF with exhaust gases, leading to its thermal degradation into ammonia and carbon dioxide.

Prior to entering the catalyst within the SCR catalyst, a reduction reaction transforms NOX gases and ammonia into harmless nitrogen gas and water vapor.

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Diesel Particulate Filter (DPF)

The diesel particulate filter follows the SCR unit in pickup truck models, while it precedes the SCR system in all chassis cab trucks. This component is tasked with capturing particulate matter, primarily soot, suspended within the exhaust stream.

It stores these particles for eventual removal through incineration. The DPF undergoes cleaning through a process called regeneration.

Comprising two types: passive regeneration occurs whenever the exhaust gas temperature surpasses 572 degrees, the minimum temperature required to commence breaking down particulate matter in the DPF into smaller hydrocarbons that can pass through the filter.

This process occurs seamlessly and naturally, yet it may not be particularly efficient at rapidly cleaning the filter. Active regeneration, on the other hand, necessitates periodic cleaning of the diesel particulate filter.

Activation of this process occurs when exhaust system pressure reaches a predefined threshold. During active regeneration, raw fuel is injected into the exhaust stream to generate temperatures exceeding 1,000 degrees, incinerating particulate matter within the DPF while the vehicle is in motion.

The duration of active regeneration varies significantly based on driving conditions, typically requiring 10 to 20 miles of travel. Active regeneration temporarily pauses if vehicle speed falls below 35 MPH, with speeds above 35 MPH required to resume the process. Optimal highway speeds (55 MPH) expedite the regeneration procedure.

Nick Marchenko, PhD

Industrial Engineer & Automotive Content Specialist

Nick writes in-depth guides on car clubs, engine specs, vehicle ownership, and modifications, combining engineering knowledge with automotive passion.

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