epa_logoThe big daddy of all the reasons that the four strokes were forced upon us, was that the EPA was banning all two strokes. This is repeated often as one of the cornerstone reasons by proponents on either side of the debate.

I have not seen any written proof of this legislation in any of the mainstream media. So with the attitude that we must have hard facts before we can agree or disagree, its is time to find out the truth.

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The EPA vs. Motocross

by JohnNicholas on 04/08/2009

epa_logoThe big daddy of all the reasons that the four strokes were forced upon us, was that the EPA was banning all two strokes. This is repeated often as one of the cornerstone reasons by proponents on either side of the debate.

I have not seen any written proof of this legislation in any of the mainstream media. So with the attitude that we must have hard facts before we can agree or disagree, its is time to find out the truth.

On the official EPA website the legislation called the Clean Air Act can be found. This is the law that governs recreational vehicle emissions. This document is over 200 pages long and is written is a confusing  legal fashion. It is difficult to read at first, excerpts are included after this article.

First things first… the law as it pertains to motocross.

“Clean Air Act subsections 216 (10) and (11) exclude engines and vehicles “used solely for competition” from nonroad engine and nonroad vehicle regulations.”

So anyone that has said that the EPA has banned two strokes for racing is wrong. It is clearly stated in this one section of the law that vehicles used solely for competition are exempt.

It would be an easy job if that were the complete story. A very interesting statistic was revealed while researching this article. That unfortunate news is that as many as 55% of all motocross bikes are used for off-road recreational use and not competition.

And according to the EPA regulations the manufacturers would have to guarantee that the bikes sold would be used for competition only. Otherwise the manufacturers would face fines.

“Conventional competition two-stroke motorcycles generate extremely high levels of HC emissions, as noted above. For every conventional two-stroke competition machine replaced by a certified competition machine, HC emissions would be reduced by 80 percent, or more.”

So what else could the manufacturers have done?

Envirofit Direct Injection retrofit.

They could have looked into developing cleaner two stroke technology. Is this even possible?

I suppose it depends on who you ask. But in doing a little research you will find that there are quite a few different ideas that have been developed to clean up the emissions.

One company called Envirofit has made some huge advances in two stroke retro-fit kits for two strokes. They developed a kit for two stroke taxis in the Phillipines that does an amazing job of reducing emissions.

The Envirofit kit reduces carbon monoxide emissions by 76%, carbon dioxide emissions by 35%, and hydrocarbon emissions by 89%. In addition fuel use is reduced by 35% and oil by 50%.

To read more about the amazing Envirofit project please visit;

Aprilla SR50 DiTech Scooter

In Europe the Aprilla company has developed a system called DiTech, a Direct Injection Technology for two stroke engines. This was developed for their scooter line when the four stroke engines did not live up to performance nor emissions standards. Here again the performance and emissions of the direct injection two stroke out performed the four stroke.

To read more about the Aprilla DiTech system please visit;

While these projects were not developed for motocross, you can see that the technology exists to build clean two strokes. The technology just needs to be applied.

In fact news from KTM shows they already have a direct injection motocross bike ready to be released. Hopefully we will see this bike as part of the 2010 KTM line up.

Rotax 600 E-Tech engine.

There already have been many articles written about the snowmobile and outboard two stroke engines that already meet and exceed emission standards.

Informative article on how the Evinrude’s E-TEC engine works.

The EPA is not the bad guy that they have been portrayed to be. There is not one reference in any of the EPA Clean Air Act that says anything about banning two strokes! At one point they did not believe that the two stroke could ever meet or exceed their standards.

It has been proven that it is possible.

ktmWhat we need now is a motorcycle manufacturer to step up and build a clean two stroke. My money is on KTM to bring this to a reality.

What are your thoughts?


The complete EPA document is located at this url

Below are the excerpts from the EPA documents. Some sections of the legislation have been bolded.

I. Introduction Section – Under sub category B. How is this Document Organized?

Section II describes general provisions that are relevant to all of the nonroad engines covered by this rulemaking. Section III through VI present information specific to each of the affected nonroad applications, including standards, effective dates, testing information, and other specific requirements.

I. Introduction Section – Under sub category C. What Categories of Vehicles and Engines are covered in this Final Rule?

For recreational vehicles, we are adopting separate emission standards for snowmobiles, off-highway motorcycles, and all-terrain vehicles. For snowmobiles, we are adopting a first phase of standards for HC and CO emissions based on a mixture of technologies ranging from clean carburetion and engine modifications to direct fuel injection two-stroke technology and some conversion to four-stroke engines, and second and third phases of emission standards for snowmobiles that will involve significant use of direct fuel injection two-stroke technology and conversion to four-stroke engines. For off highway motorcycles and all-terrain vehicles, we are adopting standards based mainly on moving these engines from two-stroke to four-stroke technology with the use of some secondary air injection. We are also adopting requirements to address permeation emissions from all three types of recreational vehicles.

I. Introduction Section – Under sub category E. Why is the EPA Taking this Action?

We believe technology can be applied to these engines that will reduce emissions of these harmful pollutants. Manufacturers can reduce two-stroke engine emissions by improving fuel management and calibration. This can be achieved by making improvements to carbureted
fuel systems and/or converting to electronic and direct fuel injection. In addition, many of the existing two-stroke engines in these categories can be converted to four-stroke technology. Finally, there are modifications that can be made to four-stroke engines, often short of requiring catalysts, that can reduce emissions even further.

II. Nonroad: General Provisions – Under sub category A. Scope of Application #4.

In addition, the Clean Air Act does not consider stationary engines or engines used solely for competition to be nonroad engines, so the emission standards do not apply to them. Refer to the program discussions below for a description of how these exclusions or exemptions apply for different categories of engines.

III. Recreational Vehicles and Engines – Under sub category B. Engines Covered by this Rule

5. Competition Exemptions
a. Off-Highway motorcycles. Currently, a large portion of off-highway motorcycles are designed as competition/racing motorcycles. These models often represent a manufacturer’s high-performance
offerings in the off-highway market. Most such motorcycles are of the motocross variety, although some high-performance enduro models are marketed for competition use.49 50 These high-performance
motorcycles are largely powered by two-stroke engines, though some four-stroke models have been introduced in recent years.

Competition events for motocross motorcycles mostly involve closed-course or track racing. Other types of off-highway motorcycles, such as enduros and trials bikes, are usually marketed for trail or open-area use. When used for competition, these models are likely to be involved in point-to-point competition events over trails or stretches of open land. There are also specialized off-highway motorcycles that are designed for competitions such as ice racing, drag racing, and observed trials competition. A few races involve professional manufacturer-sponsored racing teams. Amateur competition events for off-highway motorcycles are also held frequently in many areas of the U.S.

Clean Air Act subsections 216 (10) and (11) exclude engines and vehicles “used solely for competition” from nonroad engine and nonroad vehicle regulations. In the proposal we stated that in previous nonroad engine emission-control programs, we have generally defined the term as follows:
Used solely for competition means exhibiting features that are not easily removed and that would render its use other than in competition unsafe, impractical, or highly unlikely.

Most motorcycles marketed for competition do not appear to have obvious physical characteristics that constrain their use solely to competition. In fact, they are usually sold by dealers from the showroom floor. Upon closer inspection, however, there are several features and characteristics for many competition motorcycles that make recreational use unlikely. For example, motocross bikes are not equipped with lights or a spark arrester, which prohibits them from legally operating on public lands (such as roads, parks, state land, and federal land).51 Vehicle performance of modern motocross bikes is so advanced (for example, with extremely high power-to-weight ratios and advanced suspension systems) that it is highly unlikely that these machines will be used for recreational purposes. In addition, motocross and other competition off-highway motorcycles typically do not come
with a warranty, which further deters purchasing and using competition bikes for recreational operation.52 We believe these features are sufficient in distinguishing competition motorcycles from recreational motorcycles. Therefore, we are specifically adopting the following features as indicative of motorcycles used solely for competition: absence of a headlight or other lights; the absence of a spark
arrester; suspension travel greater than 10 inches; an engine displacement greater than 50 cc; absence of a manufacturer warranty; and the absence of a functional seat.

Manufacturers must specifically request and receive an exemption from EPA to sell off-highway motorcycles without a certificate under the competition exemption. Vehicles not meeting the applicable criteria listed above will be exempted only in cases where the manufacturer has clear and convincing evidence that the vehicles for which the exemption is being sought will be used solely for competition. Examples of this type of evidence may be technical rationale explaining the differences between a competition and non-competition motorcycle, marketing and sales information indicating the intent of the motorcycle for competition purposes, and survey data from users indicating the competitive nature of the motorcycle.

Although there are several features that generally distinguish competition motorcycles from recreational motorcycles, several parties have commented that they believe motorcycles designed for competition use are also used for recreational purposes, rather than solely for competition. This is of particular concern because competition motorcycles represent about 29 percent of total off-highway motorcycle sales or approximately 43,000 units per year. However, a study on the characterization of off-highway motorcycle usage found that there are numerous–and increasingly popular–amateur off-highway motorcycle competitions across the country, especially motocross.53 The estimated number of off-highway motorcycle competitors is as high as 80,000. Since it is very common for competitive riders to replace their machines every one to two years, the sale of 43,000 off-highway competition motorcycles appears to be a reasonable number, considering the number of competitive participants. We are therefore confident that, although we are excluding a high percentage of off-highway motorcycles as being competition machines, the criteria laid out above are indicative of motorcycles used solely for competition.

However, we do recognize that it is possible that some competition motorcycles will be used for recreational purposes. We are therefore adopting a provision within the regulations that allows the Agency to deny a manufacturer’s claim for exemption from the standards for any models, including models that meet the six specified criteria, where other information is available that indicates these off-highway motorcycle models are not used solely for competition. This same provision allows the Agency to deny claims for exemptions in later years even if they had been granted previously. Examples of this type of information can be state registration data that indicate a significant number of competition exempt models being registered to operate on public lands. Off-highway competition motorcycles designed for motocross competition are not typically required to be registered with states, since most motocross competitions occur on closed-circuit courses on private, not public land, and motocross machines lack spark arresters which are required to operate on public land. We believe the
possibility of losing an exemption for competition motorcycles will encourage manufacturers to take proper actions in promoting, marketing, and guaranteeing that competition machines are sold to those
individuals who will use them solely for competition.

C. Emission Standards

1. What Are the Emission Standards and Compliance Dates?
a. Off-highway motorcycles. We are adopting HC plus NOX and CO standards for off-highway motorcycles. We expect the largest benefit to come from reducing HC emissions from two-stroke engines. Two-stroke engines have very high HC emission levels. Baseline NOX levels are relatively low for engines used in these applications and therefore including NOX in the standard serves only to cap NOX emissions for these engines.

Comparable CO reductions can be expected from both two-stroke and four-stroke engines, as CO levels are similar for the two engine types. We are also adopting averaging, banking and trading provisions for off-highway motorcycles, as discussed below.

In the current off-highway motorcycle market, consumers can choose between two-stroke and four-stroke models in most sizes. Each engine type offers unique performance characteristics. Some manufacturers specialize in two-stroke or four-stroke models, while others offer a mix of models. The HC standard is likely to be a primary determining factor for what technology manufacturers choose to employ to meet emission standards overall. HC emissions can be reduced substantially by switching from two-stroke to four-stroke engines. Four-stroke engines are very common in off-highway motorcycle applications.

Approximately 55 percent of non-competition off-highway motorcycles are four-stroke. Certification results from California ARB’s emission-control program for off-highway motorcycles, combined with our own baseline emission testing, provides ample data on the emission-control capability of four-stroke engines in off-highway motorcycles. Off-highway motorcycles certified to California ARB standards for the 2000 model year have HC certification levels ranging from 0.4 to 1.0 g/km. These motorcycles have engines ranging in size from 48 to 650 cc; none of these use catalysts.

The emission standards for off-highway motorcycles take effect beginning in the 2006 model year. We will allow a phase-in of 50-percent implementation in the 2006 model year with full implementation
in 2007. These standards apply to testing with the highway motorcycle Federal Test Procedure (FTP) test cycle. For HC+NOX emissions, the standard is 2.0 g/km (3.2 g/mi). For CO emissions, the standard is 25.0 g/km (40.5 g/mi). Both of these standards are based on averaging with a cap on the Family Emission Limit (FEL) of 20 g/km for HC+NOX and 50 g/km for CO. Banking and trading provisions are also included in the program, as described in Section III.C.2.

These emission standards allow us to set near-term requirements to introduce the low-emission technologies for substantial emission reductions with minimal lead time. We expect manufacturers to meet these standards using four-stroke engines with some low-level modifications to fuel-system calibrations. These systems are similar to those used for many years in highway motorcycle applications, but with less overall sophistication for off-highway applications.

We received comments from several states and environmental groups encouraging us to harmonize our off-highway motorcycle standards with California. The comments focused on the perceived difference in stringency between the two programs. For California, the standard is an HC-only standard of 1.2 g/km. Our standard is a HC+NOX standard of 2.0 g/km. We believe it is prudent to set a HC+NOX standard in lieu of a HC-only standard since the main emission-control strategy is expected to be the use of four-stroke engines in lieu of two-stroke engines. Two-stroke engines emit extremely low levels of NOX. Four-stroke engines, on the other hand, have higher NOX emission levels, in the range of 0.3 g/km on average. This is part of the reason why we proposed a somewhat higher numeric standard compared to California.

The California standards, which were adopted in 1994, were stringent enough that manufacturers were unable to certify several models of off-highway motorcycles, even some with four-stroke engine
technology. The result was a substantial shortage of products for dealers to sell in California. The shortage led California to change their program to allow manufacturers to sell noncompliant off-highway motorcycles under some circumstances. As a result, approximately a third of the off-highway motorcycles sold in California are compliant with the standards. The uncertified models being sold in California include both two-stroke and four-stroke machines.

EPA received comments from dealers and consumers concerned that a similar shortage could arise nationwide if EPA adopted the California standards. EPA shared this concern and proposed standards that were somewhat less stringent than that of California, based on test data from high-performance four-stroke machines. We are finalizing this approach to ensure the four-stroke technology can be implemented broadly across the product line in the 2006 time-frame. Although the approach we are finalizing contains somewhat less stringent standards than the California program, we believe it will achieve reductions beyond that of the California program because more products will be certified (even when the competition exemption is taken into account).

The vast majority of the HC reductions achieved by the program come from shifting away from conventional two-stroke engines which have HC emissions levels in the range of 35 g/km. The 2.0 g/km standard represents about a 95-percent reduction in emissions for these vehicles.
If we were to go beyond this level of reduction, manufacturers would need to employ on a widespread basis additional technology that presents significant technical issues concerning their application to off-highway motorcycles given their extreme usage patterns and issues such as safety, packaging, and weight. For example, technologies such as electronic fuel injection and secondary air injection raise concerns about their durability and reliability in the harsh operating environments to which off-highway motorcycles are sometimes exposed.

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The use of catalytic converters poses concerns over packaging, durability and safety. Off-highway motorcycles are very light and narrow. These attributes are necessary for operating through tight
forest trails and other harsh conditions. This leaves little room for packaging a catalyst so that it won’t be damaged from engine vibration, shock resulting from jumps and hopping logs, and falling over and
hitting objects, such as trees and rocks. These technologies may become compatible for off-highway motorcycles in the future, but we do not believe that it is appropriate to promulgate emission standards based on these technologies at this time, given the technical problems currently associated with their use. Four-stroke engine technology has advanced considerably since the California regulations went into effect. Manufacturers are now capable of offering four-stroke engines that provide excellent performance. This performance can be achieved only as long as manufacturers are allowed to operate four-stroke engines with a slightly rich air and fuel mixture, which can result in somewhat higher HC and CO emissions. Although the standards we are setting are higher than those in California, we believe they will require four-stroke engines that are well calibrated for emissions control without significantly sacrificing performance. For these reasons, we believe the standards we are establishing are appropriate.

As discussed above in Section III.B.5, the Clean Air Act requires us to exempt from emission standards off-highway motorcycles used for competition. We expect several competition two-stroke off-highway motorcycle models to continue to be available. We are concerned that setting standards as stringent as California’s would result in a performance penalty for some four-stroke engines that would be unacceptable to the consumers. This could encourage consumers who want performance-oriented off-highway motorcycles to purchase competition vehicles (and use them recreationally) in lieu of purchasing compliant machines that don’t provide the desired performance. We believe that our emission standards will allow the continued advancement of four-stroke technology and properly considers available emission-control technology while taking vehicle performance into consideration and avoiding significant adverse impacts on performance.

As proposed, we are also finalizing an option allowing off-highway motorcycles with an engine displacement of 50 cc or less to be certified using the Small SI emission standards for non-handheld Class I engines. These youth-oriented models may not be able to operate over the FTP due to the higher speeds of the test cycle. We did not receive comment on this provision.
Optional Standards

During the comment period, we received several comments expressing concern that our proposed standard of 2.0 g/km HC+NOX for off-highway motorcycles would effectively prohibit the use of two-stroke engines in non-competition applications. These engines currently have typical HC+NOX levels of about 35 g/km. The commenters argued that two-stroke engines possess several unique attributes, such as high power and light weight, that make two-stroke powered off-highway motorcycles more desirable to some operators, especially smaller, lighter riders, than heavier four-stroke powered off-highway motorcycles.

We also received comments from several states and environmental organizations expressing strong concern over the number of competition off-highway motorcycles that would be exempt from our regulations as a result of our competition exemption. They felt that people purchasing exempt competition motorcycles would use them for recreational purposes instead of solely for competition.
One manufacturer indicated that they were planning on building high-performance off-highway motorcycles equipped with direct fuel-injection two-stroke engines that would potentially be capable of meeting a HC+NOX standard of 4.0 g/km. To enable use of this technology, they suggested that we should adopt a standard of 4.0 g/km instead of the proposed standard of 2.0 g/km. The commenter believes that direct injection could be used to make clean competition machines and also argued that the technology is robust and not as susceptible to user modifications as other technologies such as catalysts. The commenter wanted an opportunity to develop and certify their product because it perceives a benefit to the purchaser not only in performance but also in the ability for the owner to resell the competition vehicle into the secondary market without concerns about potential misuse. In addition, the owner would be able to use the vehicle both for competition and recreation.

It is clear that if manufacturers were able to certify and bring to market clean competition machines as described by the commenter, significant reductions in emissions would be gained over conventional
two-stroke technology. Some competition models we tested had baseline HC and CO emissions in excess of 50 g/km and 40 g/km, respectively. We believe it is appropriate to provide an avenue for the development and voluntary certification of clean competition motorcycles. Therefore, we are finalizing an optional set of standards for off-highway motorcycles of 4.0 g/km HC+NOX and 35.0 g/km CO. For manufacturers to utilize this option, however, they must certify all of their models, including their competition models, to the optional standards. To qualify for this option, a manufacturer must show that ten percent or more of their sales would otherwise meet the competition definition.

The optional standard was derived from the fact that non-competition four-stroke engines can meet a 2.0 g/km level and competition two-stroke machines with advanced direct fuel-injection technology could meet a 8.0 g/km level. Since approximately one-third of the total off-highway motorcycle fleet are competition machines and the other two-thirds would be non-competition four-stroke recreational
machines, the weighting of the 2.0 g/km level by two-thirds and the 8.0 g/km level by one-third results in a weighted standard of 4.0 g/km. This presumes that emissions from four-stroke engines will not increase under this option and that non-competition engines will be almost exclusively four-stroke engines. These assumptions are discussed below.

The significant reductions in otherwise unregulated competition engines means that this option should produce even greater overall reductions than the base 2.0 g/km standard. We recognize that for some manufacturers this program will increase opportunities to make a limited number of non-competition recreational two-stroke machines; however, we believe that the number of two-stroke non-competition engines developed under this program will be limited by the fact that the required technology (direct fuel-injection) would be too expensive and complex for the recreational motorcycle market. The majority of non-competition recreational off-highway motorcycles that use two-stroke engines are entry-level and youth motorcycles, where cost and simplicity are important factors. There is also the fact that for every two stroke non-competition engine manufactured under this program, a manufacturer must make one less competition engine or must make more four-stroke engines. Further, we believe that any increase in the number of non-competition two-stroke engines is justified given the fact that this program will overall bring levels from off-highway engines down

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considerably and the fact that the technology needed to reduce emissions from competition machines will only be made available and used if, under this optional approach, manufacturers have an incentive
to use the technologies.

One major incentive in using this approach is the fact that once these machines are certified, a consumer will be able to use these machines legally for non-competition uses, which increases the value of the competition machines. This approach thus will also reduce the incentive for manufacturers to manufacturer all of their two-stroke machines as competition machines to avoid regulation, and thus reduce the incentive for users to circumvent the regulations. This may mean that any increase in two-stroke non-competition engines under this approach would not lead to an increase in total two-stroke sales, because manufacturers will not have an incentive to increase the number of two-stroke competition vehicles to avoid regulation.

We believe this approach is responsive to all of the above comments. It directly addresses the concerns of the manufacturer developing the new competition motorcycle and also helps address the concerns of users, states, and environmental groups. The successful development and certification of clean competition models increases the choices for consumers in the marketplace. Offered the option of a certified high-performance two-stroke off-highway motorcycle that can be used both for competition and recreation, consumers may not feel the need to purchase exempt competition motorcycles. This option has the potential to significantly decrease the number of conventional two-stroke competition machines sold under the competition exemption and is likely to decrease the potential for misuse of competition machines.

Conventional competition two-stroke motorcycles generate extremely high levels of HC emissions, as noted above. For every conventional two-stroke competition machine replaced by a certified competition machine, HC emissions would be reduced by 80 percent, or more.

While the 4.0 g/km standard is higher than the 2.0 g/km standard contained in the base program, we do not expect any loss in emissions reductions from four-stroke models. We continue to believe most off-highway motorcycles will continue to be powered by four-stroke engines. Most non-competition off-highway motorcycles are already four-stroke motorcycles, and the trend towards four-stroke is continuing even in the absence of these regulations. We are convinced that there will be no backsliding of emissions control for motorcycles using four-stroke engines, because the dirtiest of the four-stroke models tend to be competition machines, and our emissions testing indicates that
competition four-stroke off-highway motorcycles have HC+NOX emission levels below 2.0 g/km. Since these motorcycles are optimized for power and racing conditions, there is no incentive for manufacturers to increase HC+NOX emissions from their current levels. In fact, increasing the emission levels would mean increasing the air-to-fuel mixture, which would tend to reduce the engines performance.

As with the primary program, these optional standards would take effect in 2006 with 50-percent implementation and full implementation in 2007 and manufacturers could switch between the options from model year to model year. The HC+NOX standard can be met through averaging with some families certified above the standards and some below. If averaging is used, the FEL cap would be 8.0 g/km.

We are retaining the averaging approach for this option because it may be a critical flexibility for manufacturers pursuing clean competition products. The commenter based its recommendation for a 4.0 g/km standard on their projections for a single prototype model equipped with a medium sized engine. This engine is in the early stages of development and there is some uncertainty as to what emissions level the final product can achieve. Also, manufacturers may want to apply their approach to other engines that may not be able to achieve this same level of control. Manufacturers could find that they can produce competition products that are very clean relative to the baseline but with higher emissions than 4.0 g/km. For example, larger engine sizes could have emissions levels somewhat higher than the 4.0 g/km suggested by the commenter.

We are not satisfied at this time that two-stroke off-highway motorcycles, particularly those used in competition could meet the 4.0 g/km standard, especially considering the special performance needs of competition motorcycles. Therefore, rather than keeping a 2.0 g/km standard for four-stroke engines and having a standard higher than 4.0 g/km for two-stroke engines (a standard as high as 8.0 g/km might be appropriate), we are using a 4.0 g/km standard that permits averaging. Averaging provides flexibility for manufacturers to bring cleaner two-stroke, particularly cleaner competition two-stroke, engines to market without creating a disincentive to building four-stroke engines. One way of taking advantage of the averaging program in this way would be for a manufacturer to maximize its sales of four-stroke models as part of its sales mix, and average the emissions from these engines against the higher emissions of the two-stroke competition engines which still would need to be much cleaner than if they were unregulated.

This approach therefore requires the substantial use of cleaner four-stroke technologies while at the same time encouraging manufacturers to substantially reduce emissions from motorcycles that would otherwise be unregulated competition motorcycles. We have capped the emissions levels at 8.0 g/km HC+NOX because we want to ensure that products certified under this option provide large emissions reductions compared to baseline levels and that the option provides environmental benefits in all cases. Competition motorcycles certified to the 8.0 g/
km level would continue to provide over a 75-percent reduction in HC emissions over baseline levels.

One of the challenges facing manufacturers selecting this option is the potentially high CO emissions from competition machines. We tested competition models and found CO emissions to be in the range 25 to 50 g/km. Although this option contains a somewhat higher CO standard (35 g/km compared to 25 g/km) than the base program, manufacturers are still expected to need to control CO emissions through tight engine calibrations. We are not including averaging for the less stringent CO standard. As noted by the manufacturer supporting the 4.0 g/km option, direct injection technology is likely to reduce CO from two-stroke engines. We believe that through proper calibration, the 35 g/km standard will be achievable and will not significantly impede manufacturers in selecting this option.