Meeting 2011 EPA Tier 4 Interim & EU Stage IIIB Emissions

This Frequently Asked Question document is intended to help Cummins customers better understand the low emissions regulations commencing January 2012 which introduce clean diesel technology with exhaust aftertreatment to the off-highway industry.

Information is provided on performance and operational characteristics applicable to the latest generation of QSB6.7, QSB4.5, and QSB3.3 engines covering the 75 to 173 horsepower (56-129 kW) range.
This FAQ features the following sections:

Tier 4 Emissions Regulations

What is the Tier 4 Interim and Stage IIIB emissions standard in 2012?

The regulations commence in January 2012 across the 75 to 173 horsepower (56-129 kW) category, requiring diesel engines to reduce PM exhaust emissions by over 90% and NOx exhaust emissions by approximately 30% compared with the current Tier 3 and Stage IIIA emissions standards.

The emissions standards for this power category are: 3.4 g/kW-hr Oxides of Nitrogen (NOx) and 0.02 g/kW-hr Particulate Matter (PM).

Equivalent emissions regulations for Ministry of Land, Infrastructure, Transportation and Tourism (MLIT) in Japan will likely commence October 2013 or later for engines across the 75 to 751 hp (56-560 kW) powerband.

What is the Tier 4 Final and Stage IV emissions standard in 2015?

Beginning in 2015, EPA Tier 4 Final and EU Stage IV will require another major emissions reduction for diesel engines from 75 to 173 horsepower, both NOx and PM exhaust emissions will be reduced by 90% compared with current Tier 3 and Stage IIIA levels.

The emissions standards for this power category are: 0.4g/kW-hr Oxides of Nitrogen (NOx) and 0.02 g/kW-hr Particulate Matter (PM) effective January 2015. These extremely low levels can be described as ‘near zero’ emissions levels.

What are Oxides of Nitrogen (NOx) and Particulate Matter (PM)?

Oxides of nitrogen are a regulated gaseous emission which is a collective term for emissions composed of nitrogen and oxygen. Particulate matter is a regulated diesel emission composed primarily of carbon soot and other combustion by-products.

When will engines above 174 hp need to meet the low emissions regulations?

For engines within the 174-751 horsepower (130–560 kW) power category, Tier 4 Interim and Stage IIIB regulations will commence in January 2011. The Tier 4 Final and Stage IV regulations will be applied in January 2014.

Emissions reductions are more stringent for this 174-751 horsepower category at Tier 4 Interim and Stage IIIB, which require Cummins to use a different solution. Details on Cummins technology solution for this power category were issued on a separate FAQ covering the 6-cylinder QSB6.7 (above 174 horsepower), QSL9, QSX11.9 and QSX15  engines and is available on

Meeting Emissions With The Right Technology

How will Cummins meet the Tier 4 Interim emissions standards in 2012?

Cummins QSB6.7, QSB4.5, and QSB3.3 engines will meet the 2012 low emissions standards with an integrated Cummins Compact Catalyst exhaust aftertreatment and a cooled exhaust gas recirculation (EGR) system incorporated on the engine.

The cooled EGR system enables clean combustion with NOx reduced by over 30% compared to Tier 3, while the clean engine combustion and Cummins Compact Catalyst exhaust aftertreatment system reduces PM by over 90% from engine exhaust.

Will Cummins meet EU Stage IIIB and equivalent emissions regulations in Japan with the same technology used for North America?

Yes.  Cummins will offer the right technology and engine platforms to meet the low emissions standards with an integrated Cummins Compact Catalyst exhaust aftertreatment and a cooled EGR system incorporated on the engine for the EU.  For countries outside of these areas that will adopt equivalent low emissions regulations, Cummins will offer this same technology provided Ultra Low Sulfur Diesel Fuel is available.

Does Cummins design their own aftertreatment and other key systems?

Yes. We design the Cummins Compact Catalyst as an integrated system with the engine. Meeting Tier 4 Interim and Stage IIIB demands new levels of system integration in order to achieve very low emissions while improving performance.

Cummins has access to all the key enabling technologies within our design and manufacturing resources, from aftertreatment, fuel systems, filters and electronic control to turbocharging.  This forms the basis of our ‘Right Technology’ approach to Tier 4.

Why is Cummins Tier 4 approach better than others?

We believe Cummins has significant advantages over other engine manufacturers. We design, manufacture and integrate the complete Tier 4 package from air-intake to exhaust aftertreatment. Only Cummins has all the key enabling technologies in-house and can therefore realize more effective integration with packaging and performance advantages.

Will Tier 4 engine performance and fuel economy be the same as Tier 3?

It will be better. Cummins Tier 4 Interim engines will have up to 5% improve fuel efficiency compared to Tier 3, depending on rating and duty cycle. Tier 4 equipment productivity is also enhanced with faster engine response.

Operators will also notice that Cummins Tier 4 technology enables the equipment to work cleaner and quieter than before. And while CO2 emissions are not regulated by the EPA and EU, Cummins fuel efficiency improvement at Tier 4 Interim translates into reduced CO2 emissions, helping our customers reduce their carbon footprint at Tier 4 Interim.

How will equipment operating costs be impacted by Tier 4 Interim?

Overall operating costs for Cummins engines will be lower at Tier 4 Interim compared with Tier 3. Depending on duty cycle and application, up to 5% better fuel efficiency can be achieved which will more than offset the marginal cost increase associated with using ULSD fuel, low ash lube oil and our Cummins Compact Catalyst does not require a filter cleaning like competitive Diesel Particulate Filter technologies for this horsepower range.

How will Tier 4 impact the cost of equipment?

Achieving very low levels of emissions for Tier 4 Interim has required a major investment in engine technology and involves the addition of systems such as Cummins Compact Catalyst aftertreatment. The cost of the equipment will therefore reflect the incorporation of a Tier 4 Interim technology system and in some cases more advanced cooling packages.

While Tier 4 Interim powered equipment will be inherently more expensive than Tier 3 equipment, the cost of achieving compliance will be helped by the lower overall operating costs offered by Cummins Tier 4 Interim engines.  With improved engine response and fuel economy, operators can also expect improved equipment productivity together with the benefit of cleaner and quieter operation.

Why is Selective Catalytic Reduction (SCR) less effective than cooled EGR and Cummins Compact Catalyst for Tier 4 Interim?

As part of Cummins Tier 4 Interim evaluation program, various combinations of Cummins Particulate Filter or Cummins Compact Catalyst with cooled EGR and SCR were extensively tested as possible technology paths.  However, our development work proved that a Cummins Compact Catalyst in combination with cooled EGR provides the most effective Tier 4 Interim solution.

This solution will achieve the best operating value for our customers. It offers equivalent, or better fuel efficiency improvements compared with using an SCR system for off-highway applications.

An additional consideration was that SCR requires regular refilling of an on-board Diesel Exhaust Fluid (urea) tank. Operators of off-highway equipment have consistently expressed a preference to avoid the additional cost, supply and refilling of Diesel Exhaust Fluid for an SCR system. Cummins cooled EGR and Cummins Compact Catalyst does not require this additional fluid.

Is SCR a technology option for Tier 4 Final?

SCR does offer a potential route to achieve Tier 4 Final emissions standards in 2015 used as incremental technology to build on Tier 4 Interim technology. SCR and other options are part of Cummins technical evaluation work for Tier 4 Final.

Cummins knows SCR technology better than any other engine manufacturer. In 2006, Cummins launched its on-highway engines certified to the Euro 4 standard using SCR in Europe with over 300,000 of these systems in operation.

In addition to this, Cummins is utilizing SCR technology together with cooled EGR and the Cummins Particulate Filter to meet North America EPA 2010 emissions.

Cummins Compact Catalyst

Why does Cummins use the Cummins Compact Catalyst below 174 horsepower – but not for engines above 174 horsepower and above?

Cummins provides value by offering the right technology for the right equipment.  As a maintenance free, “fit and forget” system, the catalyst is ideally suited for compact equipment, typically used in the rental market.  The Cummins Compact Catalyst also provides a simplified and flexible system installation for Tier 4, a key requirement for space constrained compact machines and material handling equipment below 174 horsepower.

Equipment with engines above 173 horsepower have more installation space and also needs to meet more stringent emissions regulations, which makes the Cummins Particulate Filter an ideal solution.

Has the Cummins Compact Catalyst aftertreatment been used before?

This technology is new to the off-highway equipment industry – but it is not new to Cummins. Cummins has been manufacturing Diesel Oxidation Catalyst technology since 1994 for on-highway bus applications, representing over 15 years of experience and a very high volume population in North America.

How does the Cummins Compact Catalyst remove PM?

The catalyst removes PM by a process of simple, passive oxidation.

Does the catalyst impact the operation of the machine or require any user intervention?

No. The catalyst operates automatically and is transparent to the operator and does not impact equipment performance.

Does the catalyst create more noise or heat compared to a muffler?

The catalyst will not create additional noise or heat compared with a standard muffler. The maximum skin temperature of the catalyst will be no higher than that of today’s muffler.

Is an exhaust muffler also required?

Yes. Noise attenuation is still required. There will be options to purchase a Cummins Compact Catalyst without a muffler or with an integrated acoustic catalytic muffler. An integrated acoustic catalytic muffler would be somewhat smaller than a Diesel Particulate Filter.

Does the catalyst need to regenerate, like a Diesel Particulate Filter (DPF)?  Does it ever need to inject fuel in the exhaust to function?

No. The catalyst does not require active regeneration, which is typical of a Diesel Particulate Filter.

The catalyst works by a simpler process of continuous passive oxidation of the PM as it flows through the system. This oxidation is initiated by the normal temperature of the exhaust. No additional fuel injection is needed to increase this temperature.

How flexible are the installation requirements?

Based on our experience with this technology, oxidation catalysts are far more flexible in installation than a DPF due to sizing and positioning.

Is it really a “fit and forget” device?

Yes. Once installed the catalyst requires no user intervention or maintenance.

Why doesn’t the Compact Catalyst require ash cleaning?

Because it is a flow through device that does not capture ash or PM soot. A DPF does require ash cleaning because it is trapping carbon in a wall flow filter.

Will fuel sulfur content higher than 15-ppm damage the catalyst?

An oxidation catalyst and EGR system can tolerate diesel fuel sulfur up to 500-ppm. However, using 15-ppm fuel is the legal requirement for meeting EPA Tier 4 and EU emission regulations.

How does the Cummins Compact Catalyst differ from a typical Diesel Oxidation Catalyst (DOC)?

Cummins Compact Catalyst represents the latest evolution of diesel oxidation technology specifically designed for Tier 4 emissions and off-highway applications. The catalytic coating and substrate is unique to the QSB3.3, QSB4.5 and QSB6.7 to provide optimum performance.

Will the compact catalyst be used for the 3.3-liter engine below 75 horsepower?

Our technical evaluation work on ratings below 75 hp is ongoing, but we are not yet ready to announce our direction. Engines below 75 hp are not required to meet aftertreatment regulations until 2013.

Will the compact catalyst be used for engines above 160 horsepower and for all QSB6.7 engines?

The 6-cylinder QSB6.7 engine below 174 horsepower will utilize the Cummins Compact Catalyst and the QSB6.7 above 173 horsepower will utilize a Cummins Particulate Filter. All other components for the QSB6.7 will be common.

What will the catalyst cost?

We supply the catalyst as part of a fully integrated system with the engine, leading to a competitive system price that offers superior value to the end customer and OEM.

Cummins Cooled Exhaust Gas Recirculation (EGR) System

How does cooled EGR reduce NOx emissions?

Cummins utilizes cooled EGR to effectively control NOx emissions. Cooled EGR works by re-circulating a varying proportion of the exhaust gas back to the cylinder. This reduces the oxygen content to a lower combustion temperature resulting in a reduction of NOx formation.

The exhaust gas is cooled as it flows through an EGR cooler, and then is mixed with the compressed fresh air from the turbocharger before entering the intake manifold. As the EGR moves through the intake, the EGR reduces the amount of in-cylinder oxygen available for combustion while maintaining the same amount of air flowing through the engine. Exhaust gases present during the start of combustion are very stable and have a very slow reaction rate. They absorb heat during combustion, resulting in lower in-cylinder peak flame temperatures, and therefore, lower NOx emissions.

What are the key components of the EGR system?

The key components to the Cummins cooled EGR system are: EGR Valve, EGR cooler and either a Variable Geometry Turbocharger (VGT™) or Variable Flow Turbocharger depending on the horsepower. A schematic of the system is shown below:

VGT™ and VFT Turbocharger

How does Cummins VGT improve performance?

Cummins will use a VGT Turbocharger for our Tier 4 Interim QSB6.7 engine both above and below 174 horsepower and a Variable Flow Turbocharger for our Tier 4 Interim QSB4.5 and QSB3.3 products.

Cummins VGT Turbocharger has a patented one-piece sliding nozzle design that provides exact boost across the operating range. The sliding nozzle varies the exhaust gas flow into the turbine wheel to provide rapid boost at low engine rpm and then maintain high boost at higher rpm.

The VGT Turbocharger design combines the benefit of both a small and large turbocharger in a single unit, enabling Cummins Tier 4 Interim to achieve significantly improved response compared to a Tier 3 engine demonstrated in customer field tests.

Manufactured by Cummins Turbo Technologies, the VGT™ Turbocharger is a key technology asset in not only meeting emissions but also in increasing engine performance and improving fuel efficiency. Introduced with Cummins on-highway EGR engines in 2002, the total VGT™ Turbocharger production is approaching three million units, demonstrating outstanding in-service reliability.

How does Cummins Variable Flow Turbocharger improve performance?

Cummins will use a VGT Turbocharger for our Tier 4 Interim QSB6.7 engine both above and below 174 horsepower and a Variable Flow Turbocharger for our Tier 4 Inteirm QSB4.5 and QSB3.3 products.

The Variable Flow Turbocharger drives cooled EGR and improves boost across a wider engine speed than our previous wastegate turbocharger to preserve transient response and low end torque. This turbo is proven with both high reliability and a simple mechanism variable turbine with both an inner and outer section. This simple turbine allows for lower complexity and fewer moving parts, which leads to higher durability.

The Variable Flow Turbocharger is integrated by Cummins and driven by Cummins electronics. At low speeds the valve is closed and exhaust gas flows into the inner section increasing boost pressure. At high speeds the turbo valve is modulated with integrated controls to allow exhaust gas to flow into both the inner and outer sections of the turbo.

Filtration Enhancements

What new filtration systems are used on Cummins Tier 4 engines?

Engine filtration enhancements include a new Cummins Direct Flow™ air cleaner and Cummins crankcase ventilation system with a highly-efficient coalescing filter, both manufactured by Cummins Filtration.

How is Cummins Direct Flow™ air cleaner different from other air-intake filters?

The new Cummins Direct Flow™ air cleaner was specifically developed for Tier 4 to provide more performance in less space. The rectangular, low profile design can reduce space claim compared with typical cylindrical filters used for Tier 3. Air flow to the engine is improved and the highest levels of protection are assured with virtually 100 percent efficiency over the filter life.

Can Direct Flow™ extend filter change intervals?

The increased air flow efficiency of the Direct Flow™ air cleaner offers operators the opportunity to extend air filter element service internals and potentially reduce air cleaner filter costs.

How does the crankcase ventilation filter improve the engine?

Tier 4 Interim requires that crankcase emissions, also known as blowby gasses, be included in the overall regulated engine emissions. To control blowby gas emissions, Cummins engines incorporate a highly efficient coalescing filter. The filter returns the oil to the crankcase and provides the added benefit of removing oil mist and tiny oil droplets, ensuring that the engine and powertrain remain cleaner than at Tier 3.

The crankcase filter requires a simple filter element change at 2,000 hour intervals.

Electronic Enhancements

How does the Electronic Control Module (ECM) differ from Tier 3?

The Tier 4 engine management system is significantly upgraded with the latest Cummins CM2250 electronic control module providing 3 times faster processing power and double memory capability compared to the Tier 3 module.

Cummins has a unique advantage in that we design the core programs and algorithms needed to precisely control the system from air-intake to exhaust aftertreatment as a single integrated system.

Does Cummins use the same electronic system for all engines?

Yes. Cummins latest generation CM2250 electronic control module will be incorporated on all Tier 4 Interim engines to ensure electronic commonality across equipment ranges.

Will electronic diagnostic tools change for Tier 4?

Cummins popular and easy-to-use electronic diagnostic tools such as InSite™ software and QuickCheck™ handheld device are already upgraded and available for use with Tier 4 engines and aftertreatment.

Service Requirements

Will Tier 4 equipment uptime remain the same as Tier 3?

Yes. Cummins testing has demonstrated that our Tier 4 Interim engines are able to achieve the same very high level of uptime availability as equipment powered with our current Tier 3 engines.

What service does the Cummins Compact Catalyst require?

Unlike a Diesel Particulate Filter, which has an EPA mandated ash cleaning interval of 3,000 hours for engines 75-173 horsepower (56-129 kW), the Cummins Compact Catalyst is a completely service-free, “fit and forget” aftertreatment system.

What is the life of the Cummins Compact Catalyst?

The Cummins Compact Catalyst is designed to last the life of the engine without maintenance. This “fit and forget” aftertreatment is specially strengthened against high levels of vibration and shock loading.

Fuel Requirements

Is ULSD fuel legally required for Tier 4 Interim engines?

Yes. In North America and European Union, Ultra Low Sulfur Diesel fuel is legally required for Tier 4 Interim/Stage IIIB engines. The ULSD must contain 15 parts-per-millions (ppm) or less sulfur content.

Does the European Union have the same fuel requirements for Stage IIIB engines?

In the European Union, Ultra Low Sulfur Diesel (ULSD) must legally be 10-ppm at the point of manufacture and is expected to be 15-ppm at the point of use.

Will ULSD be available outside of North America and the European Union?

Availability of ULSD is very limited outside of North America and the European Union – so it is critical to not operate an engine requiring ULSD in a country without an available ULSD supply. Using high sulfur content fuel will damage the engine and aftertreatment system.

Could today’s fuel be used in Tier 4 Interim engines?

Tier 4 Interim engines must use ULSD. It is not possible to comply with the legally required PM emissions standard with today’s off-highway fuel which has a higher sulfur content.

What happens if higher sulfur fuel is inadvertently used?

An oxidation catalyst can tolerate diesel fuel sulfur up to 500-ppm.  However, using 15-ppm fuel is the legal requirement for meeting EPA Tier 4 Interim and EU emission regulations.

A one-time inadvertent tank of diesel fuel from over 500-ppm sulfur content will not damage the engine and aftertreatment system. The system will clean itself out when fuel below 500 ppm is re-introduced.

However, continued improper fuel use of high sulfur levels greater than 500-ppm with Cummins Tier 4 Interim engines can permanently damage the engine and Cummins Compact Catalyst within a short period of time. This damage could possibly cause the engine to be inoperable and cause unplanned downtime and expenses.

Is the engine warranty affected if ULSD is not used?

Yes. Improper fuel use of sulfur levels greater than 15-ppm with Cummins Tier 4 Interim engines can result in denial of warranty coverage for any damage caused by using fuel with sulfur content greater than 15-ppm.

Can ULSD be used in Tier 3 or other engines?

Yes. Current engines will work fine on ULSD. It is backward-compatible.

When will ULSD fuel be available?

ULSD is available today. ULSD was widely introduced in North America in 2006 and more recently in the European Union for emission compliant on-highway engines. ULSD for off-highway applications will be widely available for Tier 4 Interim 174 – 751 horsepower engines in 2011. Both the EPA and EU have a schedule in place with fuel producers and distributors to ensure ULSD will be available at this time.

Can biodiesel fuel be used with Cummins Tier 4 Interim engines?

Cummins Tier 4 Interim electronic engines are compatible with Biodiesel blends up to B20 as long as the fuel does not exceed 15-ppm sulfur content.


Does Cummins Tier 4 Interim technology change the current warranty coverage?

Cummins current engine warranty will become a broader engine and system warranty for Tier 4 Interim by incorporating the Cummins Compact Catalyst and Direct Flow™ air cleaner housing. The warranty hours, terms and conditions remain unchanged for Tier 4.

What happens if Tier 4 Interim engines are exported and operated outside of their intended emissions region?

Tier 4 engines and aftertreatment which are exported and operated outside of their intended emissions region will require the correct fuel to maintain the warranty.

Cummins is committed to manufacturing engines that provide optimal performance for their users as well as meeting emissions regulations. Since emissions standards vary across the world, Cummins designs its products to meet the standards of an individual country and/or emissions region. Equipment manufacturers, dealers and customers should carefully select the correct engine to meet the emissions requirements of their respective country.

Field Test Experience

What experience does Cummins have for the Tier 4 Interim 75-173 horsepower category?

Tier 4 represents the most extensive development, concept installation and field test program that Cummins has ever undertaken with off-highway engines. Cummins started our Tier 4 Interim field test program for this power category in 2009 for this category and we have been deliberate in selecting specific customer field tests to cover the widest possible spectrum of machine types and duty cycles.

To what extent are you working with equipment manufacturers?

Cummins is deeply involved with our OEM partners in the machine integration of Tier 4 Interim engines and aftertreatment in off-highway equipment. We will have hardware prototypes running in well over 100 Tier 4 Interim installations with our equipment partners starting in mid-2010. We have hundreds of OEMs engaged in virtual prototypes. Our OEM installations combined with concept and field test activity represents a broader range of equipment experience with Tier 4 than anyone else in the industry.