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Present two stroke engines used for hand held power tools must confirm to prevailing emission legislation. A fact is that today the engines have to be run at leaner air fuel setting resulting in less amount of lubrication oil passing through the engine. This lean mixture combined with high mixture trapping efficiency also affects the combustion, raising the overall working temperature of the engine. So to gain more robustness out of these air-cooled power heads one viable route is to use different coatings to take control of tribology and heat management within the two stroke power head. In this paper a first discussion and description of the different coatings and their merits to the air cooled two stroke engine is conducted. Furthermore engine data for the test engine, in this case a 70cc professional chainsaw are presented. The outcome of engine dyno testing of the different coatings are presented and analyzed for further discussion.

Environmental concerns demand more stringent emission legislations concerning new power sources for handheld equipment like chainsaws and trimmers. Today the most common power source is the well-known two-stroke engine. This type of engine has been the natural choice due to low cost and high power density. The two-stroke engine, as we know it today is not able to comply with future emission demands due to its massive hydrocarbon pollutant. Future engine manufactures must come up with new cost efficient engine technologies that still deliver the same or improved performance for customer satisfaction. One of the solutions is the stratified scavenging two-stroke engine, which minimizes the unburnt hydrocarbon contents in the scavenging losses. An engine like this must have a dual feed system; one ordinary for air+fuel mixture and a second one that delivers pure air to the upper part of the scavenging channels.

Environmental concerns demand more stringent emission legislations concerning new power sources for handheld equipment, like chainsaws and trimmers. Today the most common power source is the well-known two-stroke engine. This type of engine has been the natural choice due to low cost and high power density. The two-stroke engine, as we know it today is not able to comply with future emission demands due to its massive hydrocarbon pollutant. To challenge the future engine manufactures must come up with new cost efficient engine technologies that still deliver the same or improved performance for customer satisfaction. Manufactures of handheld equipment are players on a very competitive market, where the cost is the main concern in choosing a feasible technology. This paper describes the development of a sequentially stratified scavenging 25cc trimmer engine.

To achieve realistic gas temperature and pressure in spray-study bombs, both precombustion and rapid-compression machines are used frequently. This paper describes an alternative concept for achieving the desired gas conditions. The gas intended for the spray study is pre-heated to 660°C in an external heated vessel made of a heat-resistant alloy. Prior to injection, the heated vessel is connected to the spray bomb via a new fast-opening valve located inside the bomb, and the hot gas fills the bomb rapidly. For convenient actuation of unit injectors in laboratory set-ups, a new hydraulic-based actuation system was developed. An eccentric drives a hydraulic piston. A second hydraulic piston actuates the unit injector. A range of injection pressure histories, i.e. rate shaping, can be obtained. The stiffness of the hydraulic system is compared with the normal cam - cam follower - pushrod - rocker arm assembly. The gas supply system was combined with the unit-injector on a spray-bomb.