**New EPA Engine Standards: What Fire Departments Need to Know About the 2027 Transition

Chris Mc Loone
The upcoming EPA emissions standards slated for 2027 are set to reshape the landscape of fire apparatus engines. This article discusses what these new guidelines mean for engines, cab and chassis design, and apparatus bodies, drawing on expert insights to help fire service professionals navigate this transition.
WHY ARE THE EPA STANDARDS CHANGING?
For several decades, engine emissions standards have been steadily tightened to reduce pollutants, particularly nitrogen oxides (NOx). Since 1988, regulations cut NOx emissions by approximately 80%. In 2027, the EPA and California Air Resources Board (CARB) are aligning on a further 80% reduction target within just four years. Such a dramatic drop—from 200 mg to 35 mg of NOx emissions per horsepower-hour—represents a steep technical challenge.
Chris Crowel, Emergency Vehicles Lead at Cummins, explains the magnitude of this change. The first drop in emissions was costly but achievable. Now, pushing that second 80% reduction requires completely new engine designs. Additionally, these standards extend warranty periods for emissions components from five to ten years and impose stricter compliance requirements. Engines must meet emissions across the entire operating range rather than relying on emissions averaging.
ONE ENGINE MANUFACTURER’S APPROACH
Cummins is responding with a $2 billion investment in research, development, and manufacturing enhancements to deliver a new generation of fire apparatus engines. Existing engines like the B6.7, L9, X12, and X15 will be replaced with all-new platforms, including the AB7.2 (a 7.2-liter displacement engine) and the X10 (a 10-liter engine replacing the L9 and X12).
Several key technological innovations are driving these new engines:
Dual SCR Catalysts in One Module: To meet the low emissions thresholds, the after-treatment system will feature two Selective Catalytic Reduction (SCR) catalysts housed together, sometimes called a “snowman” or “infinity” design, increasing reaction surface area while managing packaging constraints.
Advanced After-Treatment Heaters: New heater elements before the Diesel Particulate Filter (DPF) and SCR catalysts will help engines meet emissions standards earlier after startup, but these require significant electrical power. Therefore, Cummins will add a belt-driven 48-volt alternator dedicated to generating this heat.
Clean-Sheet Engine Design: Leveraging computer-aided design (CAD), engineers have optimized material placement, improving cooling, oil flow, and block stiffness. For example, moving the gear train from the front to the rear reduces potential oil leaks and enhances durability.
Weight Management: Despite adding emissions hardware, the new X15 engine system will be roughly weight-neutral compared with current setups. The X10 engine will be about 300 pounds heavier than the L9 but similar to the current X12, which is itself lighter than most mid-bore engines in the market.
Improved Engine Performance: The X15 will maintain familiar horsepower and torque ratings, including the 605-hp/1,850 ft-lb rating popular in fire service applications. The X10 will cover all previous L9 ratings with a new high-torque family offering up to 1,650 ft-lb, close to the X12’s current capability.
Environmental Improvements: Moving to canister-style oil and fuel filters, replacing steel housing and elements separately, supports environmental sustainability through reduced waste.
Cummins plans to launch the new X15 as early as April 2026, ahead of the 2027 mandate, giving manufacturers time to prepare. However, the last date to build with the current L9 engine frame will be December 31, 2026.
Impact on Cab and Chassis Design
Jason Witmier, Director of Education and Technology for Safe Fleet, emphasizes that while every OEM will face unique challenges, the anticipated design impacts share some common themes:
Weight Considerations: The good news is that weight changes will be minimal. This is crucial since front steer axle weight limits are often more restrictive than the rear axle, and balance is a constant design concern.
Engine Footprint and Cooling: The new engines and aftertreatment systems, including larger radiators or additional cooling requirements, may slightly enlarge the engine “doghouse” (engine tunnel). Since cab width is heavily regulated by Department of Transportation standards (typically 96 to 102 inches), manufacturers have limited room to expand sideways, so any growth in engine or radiator size affects the available space inside the cab.
Seating and Ergonomics: Potentially lost cab space could slightly impact seating configuration, particularly rear-facing seats located beside the engine tunnel. The NFPA’s minimum requirements for seating width and operability remain protected, so OEMs will have to innovate around those constraints.
Crash Testing Considerations: OEMs are working diligently to avoid significant changes in the doghouse’s structural design, which would trigger costly and time-consuming crash testing.
Witmier observes that OEMs are already integrating prototype engines and computer-aided models to ensure the new powertrains fit into existing frames and doghouses as seamlessly as possible.
EFFECTS ON PUMP PANELS AND BODY COMPARTMENTS
Behind the cab, pump panel design and body configurations may face subtle but important changes due to aftertreatment placement and heat management considerations.
Pump Panel Location: Aftertreatment devices typically reside near the pump house, requiring plumbing and panel layouts to accommodate their size and heat output. This may result in relocation of auxiliary suction lines or changes in the size or door configuration of pump panels. While no fundamental changes to pumping capabilities are expected, departments might see slight reconfigurations of access or compartment arrangements.
Body Compartments: For aerials, rescues, or other apparatus without a pump house, the sizable aftertreatment devices may occupy space traditionally reserved for compartments. Consequently, front body compartments might be reduced or reshaped. Given the fire service’s familiarity with fitting equipment efficiently and creatively, these adjustments can be incorporated with minimal disruption.
Space Trade-offs and Wheelbase Length: In some cases, extending the apparatus wheelbase slightly can provide additional space to fit the engine and after-treatment package without sacrificing compartment volume. However, keeping wheelbases short often means stacking systems more tightly, so some compartment space might be sacrificed to accommodate emissions hardware.
Preparing for the 2027 Transition
The consensus from Cummins and Safe Fleet representatives is clear: fire departments and apparatus manufacturers need to stay informed and proactive. The timeline is set:
• Engines meeting the new EPA standards will be available in early 2026.
• The deadline for installing older-model engines on new apparatus is effectively March 2027, with only limited exceptions granted by the EPA.
• OEMs have been designing around these requirements for more than two years, leveraging CAD models, fuel and thermal testing, and prototype installations.
Apparatus purchasers should engage early with their manufacturers and ask detailed questions about engine selection, emissions equipment placement, and how these affect cab, chassis, and body design. Since differences between OEMs’ approaches will exist, direct communication ensures that departments avoid surprises.
WHAT DOES THIS MEAN FOR FIRE DEPARTMENTS?
The transition to cleaner engines comes with unavoidable costs and engineering complexities. The additional emissions hardware means careful packaging, potential minor sacrifices in compartment space or cab layout, and possible weight distribution adjustments. While no radical design changes are expected, departments should approach apparatus spec’ing with new engine technology in mind. This includes:
• Verifying engine options and emissions compliance timelines with manufacturers.
• Evaluating potential impacts on seating, compartment volume, and pump panel accessibility.
• Considering operational implications, such as heat management around aftertreatment components.
• Planning for potentially extended lead times due to new production requirements.
Advanced computer modeling and prototype testing at the OEM level reduces the risk of last-minute surprises, but the decision to specify and accept new engine models must be deliberate.
Fire departments should monitor developments, engage with suppliers, and prepare their purchasing processes accordingly.