Is a ban on 2-stroke motorcycles an effective option to deal with air pollution?

There were times when a considerable amount of the basic utility motorcycles, such as the Yamaha RD 135, relied on 2-stroke engines due to their low manufacturing cost and perceived ease of maintenance. Even though the lack of a valvetrain and the lube method based on oil consumption along the fuel have led to the perception of an easier maintenance compared to some 4-stroke engines with a chain-driven overhead cam, prompting Honda to respond with the CG 125 with a gear-driven overhead-valve layout which stood better to longer-than-recommended intervals between oil changes. Unlike other third-world countries where 2-strokes remained widely accepted among a broader public in the small-displacement segments, the Honda CG 125 quickly became a market leader in Brazil where it was launched in '76.

While the 4-stroke layout would ultimately become more widely accepted from an utilitarian standpoint and become mainstream, truth be said much for influence of the Honda CG 125 and in recent years all the unlicensed copies from China, the 2-stroke still retained a foothold among users who perceived it as a somewhat sportier alternative for those who value a more spirited riding experience, be it in a basic model such as the Yamaha RD 135 or in a real beast like the RD 350 LC. Tightening emission laws are often pointed out to have pulled the plug on the 2-stroke engine option for conventional motorcycles, in times when carburettors were still the rule instead of an exception, and the nature of 2-strokes which rely on the overlap of the intake and exhaust flows for scavenging renders it even more difficult to deal with. Even with the fitment of expansion chambers on the exhaust pipe, an attempt to retain more of the intake charge for a complete combustion through pressure differences as a makeshift to compensate for the lack of exhaust valves, the porting overlap is even more critical than the valve overlap on 4-strokes.

What may be considered relevant when it comes to the emissions concern as a reason for the phaseout of 2-stroke motorcycles is the Piaggio Vespa PX 150 having been available brand-new until 2016 while being certified into the Euro-3 emission standards and still carburettor-fed, meanwhile electronic fuel injection was already mainstream among its 4-stroke contenders. Sure it would not be rocket-science to fit it with EFI too, either a direct-injection setup which would require a different cylinder head cast or a port-injection layout now used by KTM in some of its 2-stroke enduro motorcycles that are even Euro-4 compliant. Considering the Vespa, naturally a more restrictive porting in order to decrease the loss of unburnt air/fuel mixture through the port overlap was as relevant as the catalytic converter to achieve an emissions compliance, despite being clearly detuned compared to previous model-years not subjected to this very same level of environmental scrutiny.

While any explicit ban on 2-stroke motorcycles has not been enforced in Brazil, and I do hope it never happens, neighboring countries such as Colombia already have such measures in some cities, including Bogotá, sparking controversies not only among many people who used old and beaten-down Japanese motorcycles but also enthusiasts of classic models such as the Vespa who nowadays have a much more leisure-oriented profile in contrast to its utilitarian origins when the austerity of the immediate post-war years called for affordable transportation. Probably some random brain-dead leftie would claim a Vespa owner who could rely on any modern 4-stroke scooter should eventually become liable to extra taxation as some supposed compensation for a claimed environmental damage and eventually fund subsidies for a replacement of 2-stroke motorcycles with newer 4-stroke ones or eventually engine retrofits allowing older models to remain allowed on the streets, but it's an oversimplifying approach which ignores some technical aspects. Besides an eventual usage of synthetic lube oils which decrease noticeably that thick blue cloud often seen from the exhaust pipe of a 2-stroke ride, models not fitted with an automatic lube system through oil injection from a separate reservoir also work with vegetable-based lube oils which even blend more effectively with the ethanol added to the gasoline in so many countries nowadays for example, already leading to a noticeable decrease on particulate matter emissions due to an incomplete combustion of oil and spark plug fouling.

Even though it may seem quite obvious that a 2-stroke carburettor-fed Vespa would consume more fuel and have higher emissions than, lets's say, a Brazilian Honda Pop 110i, and looking at it from a merely economic standpoint the 4-stroke fuel-injected Honda would seem to be better for those who look for a simple and utilitarian approach, but it should be taken with a grain of salt when a so-called emissions enforcement becomes a threat to individual freedoms. Just like recently enacted stricter restrictions on Diesel vehicles in some European cities are technically objectionable somehow, comparable attempts toward spark-ignited 2-stroke engines in Latin America and Asia ignore other measures which could be more reasonable. So, even though it may seem quite simple, a ban on 2-stroke motorcycles is not really an effective option to deal with air pollution as it might seem at a first glance.

5 reasons why Volkswagen's attempts to get rid of naturally-aspirated engines haven't been so effective

At least since May 2003 I remember speculations about Volkswagen eventually getting rid of natural aspiration at its entire range, with some progress on that matter becoming more achievable in the United States and Canada 10 years later in 2013. It's been a while, and some models such as the 6th-generation Volkswagen Polo are now highlighted in some markets such as Europe and Brazil for its 1.0 TSI engine available, but it turned out to not replace some naturally-aspirated counterparts so effectively. It might seem quite easy to justify the comparatively higher cost of a turbocharged engine with direct injection in Brazil and Europe due to the displacement-biased taxation, also highlighting an easier cold start with the direct injection while using ethanol as the 1.0 TSI is offered in Brazil as a flexfuel, but even in these markets the naturally-aspirated 1.0 MSI remains available as a base engine while in Brazil and regional export markets the 1.6 MSI is available as a flexfuel in the local market while in other countries such as Mexico its gasoline-powered non-flexfuel trim is the only engine offered. At least 5 reasons can explain the failure to the all-turbo strategy.

1 - cost: even though in Brazil the Polo has a more prestigious approach than in Europe where it's seen as an entry-level model (disconsidering smaller vehicles which may not be suitable to serve as a family car), both markets are inviting to the 1.0 MSI, while in Brazil a recent increase in demand for automatic transmissions is also favoring the 1.6 MSI which is more affordable to manufacture than the 1.0 TSI. In some countries supplied by the Brazilian-made Polo, not even the hi-tech approach could favor the TSI, as the absence or non-applicability of displacement-biased taxations render it somehow cost-prohibitive compared to the 1.6 MSI;

2 - suitability to alternate fuels: while the direct injection may benefit the usage of ethanol, as it not only increases cold starting ability but also allows a higher compression ratio which otherwise could be troublesome while using gasoline, it becomes more expensive to convert to gaseous fuels. Even though LPG can be injected at the liquid phase through the stock fuel rail and injectors of the TSI engine when fitted with a suitable conversion kit, CNG requires either specifically-designed injectors which allow liquid-phase injection for gasoline and vapor-phase injection for natural gas replacing the stock ones or mounting the CNG injectors bridge at the intake manifold for port injection while a smaller volume of gasoline direct injection is still required in order to keep the stock injectors cooling and lube as they are directly exposed to the flame spread. When it comes to ethanol, the electric pre-heating of fuel became a standard for port-injection flexfuel cars in Brazil as a cold starting aid, somewhat analogue to what has already been done on Diesel engines which relied either on glowplugs located at the cylinder head or grid heaters at the intake manifold;

3 - maintenance: turbocharged engines are still perceived to be more sensitive to factors such as lube oil quality, even though using a lower-grade oil in a modern naturally-aspirated engine is not exactly a good idea too. And even though turbocharging technology also had to evolve at a high pace due to the prevalence of start-stop on newer cars in order to address tighter fuel-economy regulations in Europe and Japan also leading to more demanding conditions for the lubrication system, the higher thermal loads to which a turbocharged engine is submitted are undeniable. A lower cost of replacement parts for the fuel system of a port-injection engine is also valued by budget-conscious buyers;

4 - turbo-lag: nowadays it's not so critical as it used to be when downsizing started to be more closely observed as a step toward a future that didn't materialise, but the turbo-lag is still often pointed out as a determining factor for turbocharging to not become so widespread on entry-level compact cars. On the other hand, models above the Polo and its derivatives now feature only turbocharged engines which may be smaller in displacement than the 1.6 MSI such as the 1.4 TSI yet the low-end performance is not so bad even though it still takes longer to reach full boost in Mexico City than in Cancún due to the lower atmospheric pressure inherent to a higher altitude;

5 - a conservative public: in the markets where Volkswagen failed to promote downsizing throughout its entire range, the acceptance of turbocharged engines remaining more concentrated around models and versions within classes above the Polo, which renders it easier to find out the appeal of natural aspiration for conservative buyers who look at Volkswagen for an all-around commuter instead of some sportier model which would be supposed to require a more specialized maintenance.

Volkswagen Up taxi: a highlight to some controversial aspects of most taxi regulations in a worldwide basis

Even though the extent of the success of Volkswagen's approach to feature the Up as a replacement for the Beetle is quite arguable, the few times I saw one in taxi livery it obviously reminded me the story of the so-called "táxi mirim" role the Beetle played in some Brazilian cities until it eventually took over a considerable amount of the market share for taxis to ultimately setting a new standard. Sure I would not hold my breath for the same happening with the Up, but its city-oriented design and small size may be a good asset for some taxi operators looking for better maneuverability on tight spaces and fuel economy. The small cabin and limited luggage capacity might become an issue, to which a more conventional taxi usually with a sedan bodystyle addresses more effectively, but it's not totally pointless to consider some minimalist approach which can also be related to the "autorickshaw" or "tuk-tuk" popularity throughout Asia providing some competition to taxis. Under some circumstances, a downsizing may turn into the most effective way to keep operating costs reasonable once the competition becomes fierce from Uber and other new modes of transport service, even though not reaching the same extent of compactness of a "tuk-tuk" for example. So, while it may not defeat a conventional taxi, a smaller car such as the Volkswagen Up might still have its effectiveness for both operator and customer depending on their priorities.

5 French cars that could have been reasonably served by the Perkins 4-108 engine

It may sound quite strange to suggest an English engine as a good option for a French car due to all the rivalry between France and Great Britain, but it's not so pointless at all. Among the best British engines, the Perkins 4-108 deserves a special status even though automobile applications were not widespread, mostly concentrated on utility vehicles and light-duty vans. Since it was phased out in '92 it would not be available during the production run of some cars I believe it could've been a good fit, but I'm sure it could have lasted long enough to eventually find its way into at least 5 French cars from the '80s to early 2000s...

1 - Peugeot 309: this one had even been assembled in England, so a Perkins engine could not seem so outrageous at all. Sure the gear-driven cam-in-block and 3-bearing crankshaft design would be seen as too outdated compared to the 1769cc XUD7 engine which besides having more 9cc had a belt-driven overhead camshaft and a 5-bearing crankshaft, and also had a noticeably higher torque throughout all the RPM range, not to mention the 1905cc XUD9 which was offered in the 309 too, but when we take a look at the gasoline-powered engines the old Perkins may still fare better than both a 1118cc version of the Simca Poissy engine rechristened as PSA E1A that only started to get better torque than the Perkins after both engines surpassed 4200 RPM which is too close to the 4400 RPM rev limit of the Perkins and means any performance advantage would be negligible through most of the operating of both engines. Even the 1294cc Poissy rechristened as G1A would only beat the 1760cc Perkins 4-108 above 3200 RPM, so for most normal driving circumstances the "agricultural" nature of the Perkins would not be a problem at all;

2 - Citroën ZX: this model has been also made in Spain, where the Perkins 4-108 used to be a popular powerplant for taxis and light-duty utility vehicles, and assembled in Uruguay in a time when Diesel engines were more favored. The agrarian tradition of Uruguay, well-known for its high-quality beef, could be a good excuse to promote a higher acceptance of such a rugged engine which had been fitted to small farm tractors, while the reliance on imported parts would make it quite easy to assimilate the idea of a different engine for some Uruguayan-assembled versions of the Citroën ZX. And even though the Perkins 4-108 would eventually be outperformed by all the gasoline-powered and Diesel engines originally fitted to this model, it would not be absolutely underpowered;

3 - Citroën Xsara: the direct replacement of the Citroën ZX, which relied on the very same platform of its predecessor, among its engines the 1527cc PSA TUD5 was available in some countries where it was favored either due to a lower taxation for Diesel engines up to 1600cc while larger-displacement ones such as the XUD9 and its replacement the 1868cc PSA DW8 were subjected to a higher taxation and some budget-conscious international markets. Even though the TUD5 would need to surpass 4000 RPM in order to catch up to the old Perkins, the seemingly outdated technical features of the 4-108 could make it cost-competitive toward the TUD5 which not only had a 5-bearing crankshaft but also had its OHC head made out of aluminium instead of iron;

4 - Citroën C3 (2nd generation): it's not easy to compare the naturally-aspirated indirect-injection Perkins 4-108 to the turbocharged 1398cc PSA DV4 and the 1560cc DV6 which feature a common-rail electronic direct injection, also subjected to stricter emission requirements than the Perkins would have ever been. However, since both the TUD5 and DW8 engines remained compliant to Euro-3 retaining natural aspiration and indirect injection, it could seem reasonable to expect a slightly improved version of the 4-108 to have succeeded in the same target and still become a good option for countries with a less stringent emissions regulation through the production run of the 2nd-generation C3. Obviously it could not be a fair comparison in regard to performance with the Diesel engines fitted to it, but it would be reasonable to expect it to serve as a good option for those who would prefer a no-frills Diesel instead of both the 1124cc PSA TU1 and the 999cc PSA EB0 which would only overperform the 4-108 above 3800 RPM;

5 - Renault Kangoo (1st generation): with the lowest-grade gasoline-powered engine fitted to it being the 1149cc D7F and the entry-level Diesel option being the 1870cc F8Q with natural aspiration and indirect injection, the Perkins 4-108 could be eventually justifiable in countries such as Uruguay where it was assembled from CKD kits by Nordex under contract until 2002. While the D7F would only outperform the Perkins once it surpassed 4000 RPM, the F8Q actually does it at every RPM, even though the displacement which is 110cc greater and the OHC head clearly give it an advantage.

Brazilian Kombi of an intermediate model

Brazilian Volkswagens often have some differences from their German counterparts, and the Kombi is no exception. Instead of the split-window getting directly replaced by the T2, which is often refered to as "Clipper", there was a facelift made exclusively in Brazil between '76 and '96 with the front of the Clipper added to the same bodyshell of the split. Besides a handful of regional export markets in South America and Nigeria where it was assembled from CKD kits, a right-hand drive model with dual doors on the left side was developed for export to South Africa and Indonesia where it was sold along the Clipper as a lower-cost option. While in South Africa it's often referred to as "Fleetline" just like a last batch of splits which were assembled with Brazilian body panels after the Clipper started to be made in Uitenhage, it's often refered to in Indonesia as "Kombras" in order to differentiate from the German-supplied Kombis, even though it had been also refered to as a Clipper even in advertisements.