All the smaller engines I know of will not run happily on 0% nitromethane fuel at all [yeah yeah except diesels
]. A Cox .010 for example runs like crap below about 25%. Most .049's require about 15% to run smoothly, and run better on 25-30%. Increasing compression ratio won't help much - small engines suffer from excessive heat loss relative to their displacement, and run much more happily with a dose of nitromethane. Fuel economy is also much less of a concern in the smaller displacements so nobody complains too much. I doubt that any level of compression ratio increase will make the little guys behave well, but if it can well then live and learn.
Nitromethane noticably improves idle and throttle response and the effect is most noticable as the displacement gets smaller. I wouldn't run a .15 for example on less than 15% out of personal preference. I run my "North American" spec .40's on 15%, .61's on 10%, 1.20's on 5%. Never bothered with less. Nearly every review I have read on a large displacement engine designed for 0% nitro indicates that the motor was happy on 5% and the throttle response and idle were improved. It also broadens workable needle settings somewhat as well, though in small doses as in normal sport fuels you won't see that too much. You will in high doses such as for racing applications.
It is no surprise to me that as displacement increases, the "need" for nitromethane in order to realize the handling benefits diminishes to the point where in the larger engines they are happy with none. But as mentioned elsewhere, to run "nicely" on low or nitro the compression ratio needs to be increased in comparison. It is also quite true that the larger engines, if set up in terms of compression ratio and cooling area to use nitromethane, can of course generate more horsepower than on no nitro fuel. But at considerable operating cost. And since they generally are not set up to run on appreciable amounts of nitromethane, they will get very cranky when you feed them some, overheating and detonating and what else. Hence descriptions of large engines running better and making more power on zero nitro fuel are accurate, in that they are set up for them.
Now if you want some fun, run tetranitromethane
... apart from the high cost and it's nasty properties, the term "detonation" [preignition] when applied to engines will take on its more literal meaning.[X(]
So only newbies run nitromethane eh? I guess only newbies run small engines!
