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David Carter wrote:
A point I like to think of is that 50 or 80 degrees "from" "peak" on the rich side and on the lean side is, the same temperature. For piston engines, running 50 deg lean of peak is the same temp as running 50 deg rich of peak, so the valves are seeing the same temp - so why are some engine "gurus" so adament about cruising 50 deg rich of peak? It makes no sense to me.
So, I believe there is no such thing as "EGT too high". There is only "peak EGT", whatever it is for your installation.
David
The problem is with the delicate mechanical valves in the exhaust stream and the mangled fuel mix distribution that is necessitated by a carbeurated 4-banger.
The EGT as typically measured is an averaged value of the 4 cylinders. If you're lean on one, you may be rich on another, depending on how the fuel gets spread around in the intake. There's really no way to tell without measuring it. The valve in the first cylinder doesn't care about the temp in cylinder two. Since all the valves have to stay below that critical temp, the solution is to build in some headroom. Going lean of peak will increase the chance of detonation. The same rules apply. The mix will not be consistent, so you have to provide a large margin of detonation prevention by retarding the combustion process with extra fuel.
The rotary deftly sidesteps the first problem by eliminating valves. The second problem is eliminated by proper design (and by leaving the turbo in the hangar). As a side note, for maximum performance and economy, you want the engine to run as close to detonation without going over as you can get.
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