Tier 4 FAQ

This Frequently Asked Question document is intended to help Cummins customers better understand the low emissions regulations commencing January 2011 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, QSL9, QSX11.9 and QSX15 engines covering a 174-hp to 600-hp (130-447 kW) range.

To view the questions and answers online, please use the FAQ below.

Tier 4 Emission Regulations

What is the Tier 4 Interim and Stage IIIB emissions standard in 2011?

Tier 4 Interim is the U.S. Environmental Protection Agency (EPA) emissions regulations for off-highway diesel engines in North America. Stage IIIB is nearly the equivalent emissions regulations for the European Union (EU) member states. In terms of effect dates and emissions levels, the EPA and EU are closely aligned.

The regulations commence in January 2011 across the 174 to 751 hp (130-560 kW) power category, requiring diesel engines to reduce PM exhaust emissions by 90% and NOx exhaust emissions by 45% compared with the current Tier 3 and Stage IIIA emissions standards.

The emissions standardsfor this power category are: 2.0g/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 for engines across the 75 to 751 hp (56-560 kW) powerband.

What is the Tier 4 Final and Stage IV emissions standard in 2014?

Beginning in 2014, EPA Tier 4 Final and EU Stage IV will require another major emissions reduction for the industry. Off-highway diesel engines from 174-hp to 751-hp must reduce NOx emissions by a further 80% compared to the 2011 level. By 2014, both NOx and PM exhaust emissions will be reduced by 90% compared with current Tier 3 and Stage IIIA levels.

The emissions standardsfor this power category are: 0.4g/kW-hr Oxides of Nitrogen (NOx) and 0.02 g/kW-hr Particulate Matter (PM) effective January 2014. 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 below 174-hp need to meet the low emissions regulations?

For engines within the 75-hp to 173-hp (56 – 129 kW) power category, Tier 4 Interim and Stage IIIB regulations will commence in January 2012. The Tier 4 Final and Stage IV regulations will be applied in January 2015.

Emissions levels are less severe for this power category at Tier 4 Interim and Stage IIIB, enabling more simplified aftertreatment. Details on Cummins technology solution for this power category will be issued on a separate FAQ covering the 4-cylinder QSB3.3, QSB4.5 and 6-cylinder QSB6.7 (below 174-hp) engines.


Meeting Emissions With The Right Technology

How will Cummins meet the Tier 4 Interim emissions standards in 2011?

Cummins QSB6.7, QSL9. QSX11.9 and QSX15 engines will meet the 2011 low emissions standards with an integrated Cummins Particulate Filter 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 45% compared to Tier 3, while the Cummins Particulate Filter 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 Particulate Filter exhaust aftertreatment and a cooled EGR system incorporated on the engine for the EU and Japan.  For countries outside of these areas that will adopt equivalent low emissions regulations, Cummins will offer this same technology provided proper Ultra Low Sulfur Diesel Fuel is available.

Does Cummins design their own aftertreatment and other key systems?

Yes. We design the Cummins Particulate Filter 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.

Has the Cummins Particulate Filter aftertreatment been used before?

This technology is new to the off-highway equipment industry – but it is not new to Cummins. Cummins introduced on-highway engines in 2007 certified to EPA standards in North America using both cooled EGR and the Cummins Particulate Filter. Our experience of using EGR extends back to 2002.

Cummins capability with this technology is unmatched in the industry, reflected in these production figures by the start of 2010:
EGR engines produced: 750,000
Particulate filter aftertreatment systems produced: 450,000

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.

Plus, Cummins has acquired unrivalled experience of using this technology by successfully meeting EPA 2007 on-highway standards. High performance and reliable technology drove a major increase in our market share between 2007 and 2010.

Will Tier 4 engine performance be the same as Tier 3?

It will be better. Cummins Tier 4 Interim engines have demonstrated up to 5% improved 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 particulate filter cleaning at 5,000 hours.

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 new systems such as Cummins Particulate Filter 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, operators can also expect improved equipment productivity together with the benefit of cleaner and quieter operation.

Why is SCR less effective than cooled EGR and Particulate Filter for Tier 4 Interim?

As part of Cummins Tier 4 Interim evaluation program, various combinations of Cummins Particulate Filter, cooled EGR and SCR were extensively tested as possible technology paths.  However, our development work proved that a Cummins Particulate Filter 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 as needed for an SCR system. Cummins cooled EGR and Particulate Filter 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 2014 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.

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 Cooled EGR & VGT™ Turbocharger

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.  EGR is introduced to reduce the amount of in-cylinder oxygen available forcombustion while maintaining the same amount of flow 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 Variable Geometry Turbocharger (VGT™). A schematic of the system is shown below:

How does Cummins VGT™ Turbocharger improve performance?

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™ 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 increasing engine performance and improving fuel efficiency. Introduced with Cummins on-highway EGR engines in 2002, total VGT™ production is approaching three million units, demonstrating outstanding in-service reliability.

Cummins Particulate Filter Aftertreatment

How does the Cummins Particulate Filter remove PM?

Cummins Particulate Filter in most cases replaces the Tier 3 muffler and provides equivalent or better sound reduction compared to Tier 3 mufflers.  The Cummins Particulate Filter consists of four sections: an inlet, a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF) and an outlet.

Exhaust flows out of the engine and into the Cummins Particulate Filter. It passes through the DOC and then into the DPF where PM is collected on the walls of the DPF. The carbon collected is then oxidized to remove it from the DPF. This is known as regeneration. 

When operating conditions maintain sufficient exhaust temperatures, the DPF is continually self-regenerating. This is known as passive regeneration and results in clean exhaust out of the tailpipe. On very infrequent occasions, an active self-regeneration is required to remove a build-up of PM in the DPF, due to insufficient exhaust temperatures.

What is passive regeneration?

Cummins engines are designed to maximize the use of passive self-regeneration. This occurs when operating conditions maintain sufficient exhaust temperature, therefore enabling continuous oxidation of the PM. Passive self-regeneration is completely transparent to the operator and does not affect the machine’s operation or performance.

Cummins field test results have shown that most off-highway equipment operates at a high enough engine load factor for the Cummins Particulate Filter to self-regenerate almost every time in passive mode.

What is active regeneration?

Active self-regeneration occurs when there is not sufficient heat in the exhaust to convert all the carbon being collected in the DPF. Exhaust temperatures are raised by injecting a small amount of fuel upstream of the Cummins Particulate Filter.  

The resulting chemical reaction over the DOC raises exhaust gas temperatures high enough to oxidize the carbon from the filter. This is all done without any operator intervention.  Cummins Tier 4 Interim system is designed to minimize the need for active self-regeneration.

The overall fuel consumption increase due to active regeneration of the particulate filter is barely measurable – approximately 0.1% for most applications.  Cummins field tests have proven the majority of active regenerations will be less than 1% of the total operating time. This minor increase resulting from active regeneration is included within Cummins overall Tier 4 fuel efficiency improvement of up to 5%.

What is a stationary regeneration?

Stationary, or parked, regeneration is the same as active regeneration but takes place while the equipment is not being operated. It offers the equipment operator the option, if needed, of performing regeneration outside the normal duty cycle. Using this option may only be required in a very limited number of applications. 

Does the Cummins Particulate Filter get hotter than a typical muffler during active regeneration?

Active self-regeneration takes place typically less than 1% of equipment operating time. The skin temperature of the Cummins Particulate Filter, which is double-thermally insulated, is actually lower than the muffler skin temperature of today’s Tier 3 powered machines.

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 by up to 35% 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 2,500 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 engine 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 the Cummins Particulate Filter aftertreatment.

Service Requirements

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

Yes. Cummins Tier 4 field test program 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 Particulate Filter require?

The Cummins Particulate Filter is service-free up to 5,000 hours when low ash oil is used and the base engine is properly maintained. At that point, ash cleaning is required. The EPA has set minimum ash cleaning intervals of 4,500 hours for engines above 173 hp (129 kW). Cummins expects to reach 5,000 hours before ash cleaning is required.


What causes ash in the Particulate Filter?

Ash is incombustible material derived from the additive pack in the lube oil. All engines consume a small amount of oil as part of their normal operation. The oil is burned in the combustion chamber along with the fuel, and the resulting small amount of residual ash from the oil is trapped in the filter section of the aftertreatment system. During filter regeneration, the PM is oxidized and removed from the filter. However, ash from the lube oil cannot be oxidized and remains in the filter.

How is the Cummins Particulate Filter serviced?

The Cummins Particulate Filter must be removed and cleaned by a Cummins-approved cleaning method and authorized technician. The ash cleaning process typically takes 30 minutes, plus the time to remove the Cummins Particulate Filter from the equipment.

What is the life of the Cummins Particulate Filter?

The Cummins Particulate Filter is designed to last the life of the engine. The aftertreatment is specially strengthened against high levels of vibration and shock loading. 

Is low ash lube oil required for Tier 4?

Yes. To maintain regulated ash cleaning intervals it is strongly recommended to use API CJ-4 low ash lube oil in North America and equivalent ACEA-E9 lube oil in the EU.

Fuel Requirements

Is ULSD fuel legally required for Tier 4 Interim engines?

Yes. In North America, Ultra Low Sulfur Diesel (ULSD) is legally required for Tier 4 Interim 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 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?

A one time inadvertent tank of diesel fuel with greater than 15-ppm sulfur content will not damage the engine and aftertreatment system. The system will clean itself out when ULSD is re-introduced.

However, continued improper fuel use of sulfur levels greater than 15-ppm with Cummins Tier 4 Interim engines can permanently damage the engine and aftertreatment systems 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 backwards 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. Cummins anticipates that ULSD for off-highway applications will be widely available for Tier 4 Interim engines in 2011. Both the EPA and EU have a schedule in place with fuel producers and distributors to make ULSD available.

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

Cummins Tier 4 Interim 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 Particulate Filter aftertreatment and Direct Flow air cleaner housing. 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 not carry a warranty. The very low emissions levels for Tier 4 Interim require specific technology that is not appropriate for regions with less severe standards.

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 Tier 4 field test experience does Cummins have?

The first of our Tier 4 Interim field test engines started running in the field and earning revenue for the operator in June 2008. Tier 4 represents the most extensive development, concept installation and field test program that Cummins has ever undertaken with off-highway engines.

We have been deliberate in selecting specific customer field tests to cover the widest possible spectrum of machine types and duty cycles.

How are the Tier 4 engines performing?

The message from the operators is that Cummins Tier 4 Interim solution is dependable, reduces their operating costs and improves the performance of their machines.  Operators preferred the Tier 4 powered machine for its responsiveness and improved productivity.

The field test program surpassed an overall 20,000 hours of operation in January 2010 and continues to rapidly accelerate the total number of hours. The field test machines are remotely monitored over the cellular network which enables Cummins engineers to quickly fine tune engine calibrations to further enhance Tier 4 equipment productivity.

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 over 100 Tier 4 Interim installations with our equipment partners in the early part of 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.

What is the opinion of the Tier 4 field test operators?

Cummins field test installations are receiving excellence testimonial comments from equipment owners and operators who prefer the cleaner, more fuel efficient and responsive Tier 4 Interim engines compared with Tier 3 powered equipment. Some of these comments are shown below:

“...we prefer to use the Tier 4 because it is quieter, much more response, no downtime, no problems...”

“...our fuel efficiency has improved by at least 5% with this machine...”

“...it’s amazingly better, yes, a lot stronger, a lot faster, a lot quicker, everything...”

“...Tier 3 was nice - and now this one is a whole lot better engine...”.

“...the fact that you don’t have to do anything to make the Tier 4 system function is the best integration...”