mstull
R.I.P.
I would like to increase the torque and efficiency of my MZ201 engine by machining a little off the bottom of the cylinders. I've read that this is a good way to improve low RPM performance. It increases the compression, and makes the ports open later. I'm running the engine direct drive up to only 3,500 RPM, where it produces just 29 Hp.
But I don't want to melt my engine from detonation (knock). Is there a way to determine whether or how much its compression can be increased without detonation? Engine designers know that maximizing compression, up to the octane limit of the fuel, is important for engine efficiency and power. So it would make sense if my engine's compression ratio was already at or very near the limit.
I can think of two ways to test that empirically. I could machine the bottom of the cylinders and see if the engine knocks. Or I could try running it on regular instead of premium. But either way, if it does knock, even momentarily, the engine could be damaged. I don't think the crankshaft main bearings are strong enough to withstand that overload. Other parts could be damaged too.
I was alarmed after reading a recent article in a magazine about removing the alcohol from gasohol, for use in a rotax 503 powered aircraft. Alcohol serves as an octane booster in gasoline. So removing the alcohol should make the remaining gasoline have a lower octane rating, by some unknown amount... which tells me his engine probably didn't need premium in the first place.
How can the first hint of detonation best be detected?.. a mechanics' stethoscope? There's so much prop and exhaust noise around my engine, it may not be easy to hear slight knock.
Would retarding the ignition a little, allow a higher compression without detonation? I haven't experimented with ignition timing to see if it can be retarded a little without losing power. You'd think that a few degrees retarded would be okay at my lower than normal RPMs. And it might even help smooth the idle, since this engine has a fixed (non-advancing) ignition system.
But I don't want to melt my engine from detonation (knock). Is there a way to determine whether or how much its compression can be increased without detonation? Engine designers know that maximizing compression, up to the octane limit of the fuel, is important for engine efficiency and power. So it would make sense if my engine's compression ratio was already at or very near the limit.
I can think of two ways to test that empirically. I could machine the bottom of the cylinders and see if the engine knocks. Or I could try running it on regular instead of premium. But either way, if it does knock, even momentarily, the engine could be damaged. I don't think the crankshaft main bearings are strong enough to withstand that overload. Other parts could be damaged too.
I was alarmed after reading a recent article in a magazine about removing the alcohol from gasohol, for use in a rotax 503 powered aircraft. Alcohol serves as an octane booster in gasoline. So removing the alcohol should make the remaining gasoline have a lower octane rating, by some unknown amount... which tells me his engine probably didn't need premium in the first place.
How can the first hint of detonation best be detected?.. a mechanics' stethoscope? There's so much prop and exhaust noise around my engine, it may not be easy to hear slight knock.
Would retarding the ignition a little, allow a higher compression without detonation? I haven't experimented with ignition timing to see if it can be retarded a little without losing power. You'd think that a few degrees retarded would be okay at my lower than normal RPMs. And it might even help smooth the idle, since this engine has a fixed (non-advancing) ignition system.
