On these forums speculating on what type of engine would power karts if and when tighter emission regulations are introduced is a popular past time. Wankels, four strokes and direct injected two strokes all have their champions. However could it be that even if, and its a big if, emissions regs are introduced into karting the carbureted two stroke, the mainstay of today’s karting, will still end up as the dominant power plant? I believe there are strong grounds for thinking that this might indeed be the case.
The carbureted two strokes well known Achilles heels are the fact that it spews out high levels of unburned HC and CO along with having poor fuel consumption. Frankly fuel consumption is not really of much concern to karters. If it became necessary to clean up karts it would appear the simplest way to do some would be to retrofit a simple oxiding catalyst(s) to the exhaust system of existing two strokes along with an autolube oil metering pump which is good enough to reduce HC and CO emissions by over 80%.
The 1984 Yamaha RZ (LC) 350 Powervalve model supplied to the Californian market was among the first to introduce this technology
http://www.rd350lc.net/pageCATA.htm
Today its is utilized on millions of small motorcycles, including the Aprilia 125 which uses a version of the Rotax Max engine, enabling them to meet even the stringent Euro 2 and Euro 3 standards for roadgoing vehicles. It is highly unlikely that emission standards for racing karts would ever be tighter than this.
http://www.aprilia.com/en-US/Model/40/RS+125/Overview.aspx
http://en.wikipedia.org/wiki/European_emission_standards
Simple two strokes could also run be run on alcohol based second generation biofuels if karting followed the lead of some of the Indy racing cars and the Australian V8 Supercars and took steps to reduce the sports carbon footprint.
In many ways catalysts on a kart would have a much easier time of it than on a small motorcycle operating in an urban environment. Karts are almost invariably well tuned, fed on nice clean synthetic oil and driven at consistently high throttle settings so the catalyst is kept LIGHT ON by being operated at high temperatures. The extra costs associated with providing a catalyst equipped exhaust system for a small two stroke motorcycle are typically estimated at less than $100.
It would appear that with today’s technology the introduction of catalysts does not badly affect the power output of the engine. However in any case karts could always take another leaf out of the RZ350s book and utilize 64mm dia. pistons to bring the power level back with the added bonus of considerably widening the power-band compared to a 125cc engine.
Compared to retrofitting a new exhaust and perhaps a couple of add-ons to current model kart engines such as the ROTAX MAX the other options to clean up karting would seem to significantly more disruptive.
I tend to agree that the carbureted Wankel is probably the most elegant technical solution for providing a karting power plant. It is light, smooth, relatively clean, very compact for its capacity and in 294cc guise has very smooth power-band. However it is expensive and Aixro at least appear to have concluded that the costs cannot be reduced significantly even if the engine is downsized. Relatively limited numbers of companies have the expertise to build reliable wankels and it is doubtful too many other companies would wish to gain the expertise given the tiny size of the karting market.
The direct injected (DFI) and Semi Direct Injection (SDI) two stroke is popular in watercraft and snowmobiling applications.
http://corp.brp.com/NR/rdonlyres/3F0275A3-1401-4042-8154-55CB76F60B74/0/2007_01_31_ETEC_backgrounder.pdf
Building a scaled down single cylinder version of a typical snowmobile engine would seem to certain to produce a great kart engine. Light, very powerful and very clean and there are grounds for thinking that the costs might not be too excessive. The trouble with the DFI & SDI two strokes in the kart racing arena, particularly the one make series, are that they achieve their cleanliness by limiting the magnitude and duration of the fuel injection pulses to prevent unburned fuel escaping out the exhaust port. More power could be achieved by increasing the magnitude and duration of the fuel injection event at the expense of cleanliness. To prevent cheating the scrutineers would be compelled to check the ECU unit hardware and software, injectors, fuel pumps and various sensors which is not a simple task.
Four strokes of course have virtually taken over from two strokes in motocross in recent years, aided in large part by a generous equivalence formula with two strokes, and many believe that they could do the same in karting. To date 250cc high performance four strokes, like the SwissAuto, have enjoyed limited success despite the fact that they are both powerful and torquey. They are undoubtedly more expensive to purchase and maintain than simple two strokes because of the much increased parts count which limited their adoption in karting and even sparked a bit of a backlash in MX circles.
There are many reasons why the bike manufacturers went for the 4 stroke solution for their MX bikes, many of which do not apply to the karting situation. The 250cc and 450cc MX bikes shared the same technology the manufacturers had perfected for their large road bikes.The very same technology could be used for their enduro and trail bikes which could be ridden on public lands and in some cases the street. They were also aware that many MX bikes are also used in non competition roles on public lands.
If four stroke kart engines were to follow the recent trend towards employing EFI then some of the problems associated with ensuring that the DFI injection systems were completely standard in the one make race series would also apply.
At the end of the day there are currently no pollutant emissions regulations for competition vehicles operating on closed circuits and this probably will not change. When you think about it tightening up the regulations in karting would make an infinitesmal difference to air quality on a local or global perspective.
From its inception over a decade ago the most popular kart engine of recent times, the 125cc Rotax Max, has sold over 70,000 units. Furthermore the average karter probably does not exceed 1,500-2,000km per year. Last year alone over 40 million motorcycles and 70 million cars were produced The average car and motorcycle probably travels 10x further than the average karter and also typically has a much larger engine so of course it is obviously far more important to limit the specific emission from these type of vehicles.
Food for thought?
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The carbureted two stroke - the future of Karting by 'Max14' << You are here!
