George Marsh said: (quoted from post at 16:56:59 07/26/14) There have been a lot of posts about adjusting carbs and engine dieseling, so I decided to look up how the old single engine airplanes adjust their carbs in flight using exhaust temp. So, If you can find a better source, I would like to read it.
It basically goes with what I've been saying that going lean will cool engine. My defination for lean is going past 14.7:1. However what I've learned is that getting the max exhaust temp, 14.7:1 fuel/air, will also create the max internal engine temps which could result in burnt exhaust valves and holes in pistons. Going too rich produces cooler engine temps, carbon build up on piston and spark plug, wet looking plugs, gas getting in to oil, and excessive engine wear.
Excessive internal engine temps will show up on spark plug. The electrode and tip will be rounded off. Cermanic will appear to have bubbles. NO carbon build up, gray or white power on plug. Perhaps that's why many years ago at Indy, cars would run a few test laps, then they pulled the plugs and checked them over.
The article I'm posting states that leaning past the max exhaust temp will cool things down inside the engine, loss of a little hp, and it saves gas.
I have seen pistons with a nice round hole in the top. What caused the hole? Too hot plug? Carb adjustment set at 14.7:1 (ideal)? Carb adjustment set at 12:1(rich)? Carb adjustment set at 16:1(lean)? I know that Chrysler in the 70's experimented a short time with lean burn to produce cleaner air, 16:1-17:1, before fuel injuection, oxygen sensors in exhaust and better computers came along. Don't think Chryslers had holes in pisons by going lean.
Hole in center of piston is caused from detonation/knock. A too hot plug can act like a model airplane engine's glow plug and light the mixture too soon.
Two strokes in particular with broken rings, cracked pistons and holed pistons. All too often a lack of lube oil is considered the prime suspect. When the problem was detonation from too much lube oil, a sooted up combustion chamber, too lean of a mixture or too low of fuel octane.
This post was edited by buickanddeere at 14:41:00 07/26/14.
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Today's Featured Article - Hydraulics - Cylinder Anatomy - by Curtis von Fange. Let’s make one more addition to our series on hydraulics. I’ve noticed a few questions in the comment section that could pertain to hydraulic cylinders so I thought we could take a short look at this real workhorse of the circuit. Cylinders are the reason for the hydraulic circuit. They take the fluid power delivered from the pump and magically change it into mechanical power. There are many types of cylinders that one might run across on a farm scenario. Each one could take a chapter in
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