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a. The relative mix of NO and NO2. The EPA defines NOx as a mix of 1.34 parts NO to 2.05 parts NO2.  Seldom are these values reported as constituents of NOx, with calculations of their impact upon the reported value of total NOx.  They require measurement by a gas analyzer for accurate NOx level.
b. The drive cycle of the vehicle being tested, which contains varying torque demands being placed upon the engine vs. time of measurement under varying factors such as loads, terrain of traverse, wind and other weather effects, transmission shifting, drive axle ratios, etc.

The SPIER System reduces NOx, meeting the EPA Clean Truck Proposal of 40% or better reduction by 2027

The SPIER Systems is new technology for diesel engines to assist in meeting the NOx limits required by EPA, including those for 2027 and 2045 for NEW trucks.  However, the invention is also a solution for EXISTING trucks, since it is an “upfit” of exhaust plumbing which does not interact with the vehicle OEM controls and requires no calibration.  It is called the SPIER SystemTM, an acronym for SPI Exhaust Reaction System.  It is based on new application of chemical engineering to eliminate NOx gases in the cylinder and prevent their escape.  Concurrently, its positive impact upon combustion saves fuel and increases power.

The following are measurements taken on an engine dynamometer testing of a Cummins ISX 15-liter engine, OEM vs. SPIER in EPA heavy work truck drive cycle NRTC-US.


Immediately evident is that NO2 was nearly eliminated. Secondly, the impending EPA limit for 2045 of 60% reduction was more than met. Thirdly, the proper EPA mix of gases was included in the calculations.


Not evident in the above table but included in the testing and diagnostics, the federal “City Cycle” programmed into the dynamometer produced a 75% improvement in NOx through the use of SPIER, because of the differences in torque excursions.  

The accurate measurement and reporting of NOx for heavy truck diesel engines is essential to understanding the impact of U.S. current and impending emission regulations on the environment.  The above analysis indicates that even the anticipated 2045 limits can be met NOW through the application of the SPIER System, so both current and future diesel trucks can be made “Already Green” with the added benefit of improved fuel economy and greater power.

Greenhouse Gases: What are they and how are they measured on heavy trucks?

Greenhouse Gases

The EPA defines NOx as a mix of two gases which cause the bulk of greenhouse effects. They are: Nitric Oxide (chemically NO) and Nitrogen Dioxide (NO2).

The NO2 is considered by the EPA to be the NOx gas of long-term concern, since it can linger in the atmosphere for hundreds of years.  The California Air Resources Board (CARB) states, “Nitrogen Dioxide (NO2) is a pungent gas that, along with fine airborne particulate matter, contributes to the reddish-brown haze characteristic of smoggy air in California.”

When considering the measurement of NOx in the exhaust emissions of diesel engines for heavy trucks, there are two factors of great importance:

NOx Reduction

SPIER System - Frequently Asked Questions:

1. What does SPIER mean?  

        It’s an acronym for SPI Exhaust Reaction.  It indicates that the product provides a new                              technology for diesel engines that promotes enhanced combustion by chemical reactions                    that occur right within the cylinder. It’s patented in U.S. 11,391,251.

2. How does SPIER work?

        It is an “upfit” added to the diesel plumbing that takes a portion of the exhaust gases at the end          of the Aftertreatment catalysts and blends the portion back into the engine intake.

3. Does SPIER interact with engine controls?

        No. SPIER operates completely separately from them and does not require calibration or                        maintenance.

4. How long does SPIER run?

        For the life of the installation per VIN and vehicle owner under a lifetime usage license.

5. Does it void warranty?

        No.  It has no interaction with OEM controls or calibrations.

6. How effective is it on a truck?    

        SPI measures SPIER effectiveness according to the torque demand on the engine.  So, all                      results are based on the drive cycle of the vehicle and the conditions of operation, such as                    loads, weather, terrains, winds and ambient temperatures.  Also, the frequency and degree of            transitions in torque are important. The following are some specific measurements and typical          values:

                    -Fuel usage by volume or by weight. Reduction 5-25%, conditions dependent.

                    -DEF usage in MPG. 10-30% reduction.

                    -Frequency of DPF Regenerations. 30-50% reduction.

                    -EGR valve opening. 10-35% reduction.

                    -Maintenance costs & downtime for filters, catalysts, sensors, turbos, etc. In 120K miles,                           reduced $5-10k.

                    -NOx at engine-out. Reduced up to 60%.

                    -CO2 at engine-out. Reduced about 1:1 with fuel % reduction.

7. How long has SPIER been in use? 

        Three years on U.S. nationwide long-haul.

8. What trucks and engines have been tested? 

        Mainly class 8 Kenworth, Freightliner, Navistar with Cummins 15 and 8.3 liter, Detroit 13-15 liter,          Navistar A26 13.4 liter.

9. What loads have been tested?

      Primarily 40-45,000 lbs., some 75-85,000 lbs. Some double trailers.

10. What’s the environmental operating range?  

       Currently calibrated for 10-95F ambient.

12. How is it purchased? 

       License fee and parts kit per VIN, one-time fee, buyers arrange installs at their cost.  SPI                       provides engineering guidance.

13. How long does installation take? 

      About 8 hours by a qualified shop, typically a fleet shop or a dealer.

14. What do drivers say about it? 

      They LOVE the increased power and reduced downshifting on hills.  Horsepower is typically                   increased by 5-15%.

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