Re: Exhaust tuning??
Hi Ron,<br /> Hmmm, how to explain this simply....<br /> Exhaust tuning is a method of scavenging as much exhaust as possible out of the cylinder, while leaving as much of the next cycle's fuel charge in the cylinder. Most older outboards are quite inefficient in this regard, as a traditional 2-stroke design requires some unburnt fuel to exit with the exhaust to effectively empty the combustion chamber of exhaust gasses. <br /> The tuning itself involves pressure waves (essentially sound waves) and timing them so that an outbound wave sucks out exhaust and the echo wave effectively shuts the door at the exact time that the exhaust is out, but the next fuel charge has not yet left the combustion chamber. This is usually accomplished with a tube or baffle, or a combination of the two. As with all waves, the pressure waves vary in length and heighth, so the length and bredth of the tube and placement of baffles are what affect the timing of the tuning. Most tuners are fixed and are most efficient at a narrow range of engine RPMs. Some racing tuners, or stingers, are adjustible in length to handle different engine RPMs. <br /> My description assumes you know something of 2-stroke theory and how it works in regards to porting, timing, etc. A google search for 2-stroke tuning ought to turn up a lot of technical stuff if you want to look further. Tuning results in a more efficient motor that can make a good deal more power by taking advantage of more complete scavenging of exhaust out and fresh fuel in.<br />- Scott
