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The development of combustion system using a cast head normally takes quite a long time and quite an amount of money even if a single cylinder facility is used. The application of rapid prototyping technology to the combustion system development can reduce the time and cost of the development due to the elimination of a wooden pattern and casting process. The aim of combustion system development (specially port development) is to impart proper turbulence intensity around the spark plug at the right time. There are large body of data correlating the results of steady state flow rig test with engine performance. From port and combustion chamber CAD data, a resin model was made using stereo lithography apparatus(SLA). Flow rate and swirl strength were measured with the steady flow test rig, and the resin model was modified using file and clay until the satisfactory flow and swirl characteristics for the specific engine performance are obtained.

Natural gas vehicle's (NGV's) hydrocarbon (HC) emission is mostly methane, and it is very hard to get rid of methane using conventional Pt/Rh based three-way catalytic converter since methane(CH4) is one of the most stable hydrocarbon species. In countries where HC is regulated in non-methane hydrocarbon (NMHC), CH4 emission is not a problem, but in other countries where HC is regulated in total hydrocarbon (THC), more effort is needed to meet the HC emission level of a NGV. In addition, methane is known to be responsible for global worming, and there is a movement to regulate CH4 emission in North America. Recent research showed that Pd/Rh based catalyst is an effective means of reducing CH4. Other research showed that the dispersion of noble metals instead of crystalization on substrate is also an effective means of reducing CH4.