OVER 20 YEARS EXPERIENCE TUNING TWO STROKE ENGINES
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OVER 20 YEARS EXPERIENCE TUNING TWO STROKE ENGINES |
 Ported & Polished Liner
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This page illustrates the work I carry out and the reasons I tune engines to the stages shown. You can see from the images that the porting work I carry out does not appear as radical as many seen on other engine tuner sites. There are several reasons for this mainly brought about after many years of tuning full size two stroke engines, most of the same rules apply to nitro r/c engines. I build my engines not only for improved performance but also for utmost reliability and ease of tuning, something I believe is very important to most racers. Nobody wants an engine that goes like stink but goes out of tune and cuts halfway through a fifteen minute final. You have probably seen some of the very aggressive looking porting carried out by some very well known engine mod companies. This work looks impressive but often does little to improve the fuel flow through the transfer porting. As nearly all nitro engines with the exception of model boat engines are air cooled they require a reasonably constant running temperature to maintain tune and performance. The more metal taken away from the liner, especially when deep fuel transfer grooves are cut into the ports, the thinner the liner becomes. This creates very uneven wall thickness leading to poor heat transfer and hot spots. This in turn causes liner distortion and premature engine wear with liners often splitting. Not desirable unless you can afford to buy a new engine every few races. Manufacturers such as RB, Nova rossi, Sirio etc . spend many thousands developing incredibly powerful and reliable engines, but they are not perfect as it would not be cost effective to hand finish these units. Look inside them and you will never see porting anything like some engine mod company’s liners. However look at a liner in a Rody Roem’s edition RB or a Kanai spec Sirio and you will see work very similar to my own and these are very quick engines. “They’ve got it right” no question. All my engines see very good power gains and will have improved reliability. It is very easy to ruin an engine by over enlarging and altering port timing in an engine which has already had a fortune spent in R&D before it reaches the customer. I have included an image of a used Rossi P5 liner to illustrate fuel transfer which can be seen from the staining leading to the ports. You can clearly see how even this is. Uniform is the key to clean combustion. I can do the more extreme work on request but prefer not to attract a reputation of poor reliability just to give the customer an undriveable screamer. I hope this helps to shed some light on my way of modifying R/C engines. Dean Harmes |
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