Somewhere else it was mentioned to add shim(s) to an engine should the fuel contain high nitro levels. What does an engine sounds like without the shim - how do I recognize that this detonation is taking place?
TIA
Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:
The "typical" sound(s) are going to range from a sizzling, like a drop of water in a hot fry pan, up to and including a distinct knocking sound. The power of the engine may also be reduced. You can recognize the detonation by the damage to the top of the piston - it will be pockmarked (or worse ).
If you are running a fuel within the nitro range suggested by the manufacturer you should have no problems.
Detonation may cause your engine to make a crackling sound when running. It can also cause over heating. It can be noted by excessive "kick back" when trying to hand start it. Also, I have seen several engines throw the prop and spinner on idle due to detonation. This is very prevelent if you are near sea level and worse in cool weather. The first thing to do is use low nitro fuel. It makes no sense to pay big bucks to use 15% nitro that may cause detonation then add head shims to get ride of it. My 3 cents worth. Good Luck Gene
What do you mean by "high nitro levels"? Anything up to 15% is considered "normal" to most pilots.
Detonation can sometimes be seen as backfiring, especially while in the air, when the engine unloads. It will usually stop the engine, probably throw a prop, and possibly break the connecting rod.
Detonation sounds like water sizzling on a hot stove, only worse. A loud crackling sound.
Unless you really, really need slightly more power, don't use anything higher than 15% nitro. If you need more power than that, you might want to consider a larger engine.
Dr1
The only engines where detonation sounds like sizzling are small and turning a lot of RPM. On most engines it sounds like a rattel that disappears when throttled back.
Most engines needing head shims are FAI or overseas types designed for
0% nitro. I cannot find 0% nitro fuel in the stores here, even 5% is hard to find. Also it is fun to make an engine perform better than your buddies, to some that may require more nitro, the expense is not that great especially on smaller engines.PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.