Definitions needed

[Paul Taylor]

It is no secret that I am not very good at setting needles. I am not an engine man. I have started to use a Tach to assist me with getting good needle settings. And a lot help from my flying buddies.
I understand what a 4x2 break is. I can here that. I know what a screaming 2 cycle sound like. But I am not sure I know the difference between a rich 2 cycle and a lean 2 cycle.
Not sure if it can be done but can someone give definitions for some of the terms setting needles?

Wet 2:
Sloppy 2:
Fast 4:
And any more that you can think of.

Oh yea and besides the obvious…. Engine smoking and smelling burnt or locks up.
What is too hot?

Thanks!

[Jim Thomerson]

I don't know that there are defined definitions.  I'd say a wet two is just occasionally dropping into a 4-cycle and when you hold the nose up, the engine leans out, but does not sag.

[Randy Powell]

Generally, a rich 2 cycle is running in a 2 cycle just barely above the 4 cycle so that it will occasionally drop into a 4 cycle.

[L0U CRANE]

Paul,

Even on the half and half castor/synthetic oil fuels, there should be some visible exhaust "smoke" or vapor. There's less the leaner you go. The modern ABC, ABN, and AAC engines get plenty of lube from the popular 10%-11%-11% fuels, and should not fry.

Check with a tach for when you get into steady 2-cycle. Except for older style engines like the Fox 35, there should be well over a thousand RPM from that point until needling in doesn't increase RPM. On a light load prop and 10%nitro, 11%/11% castor/synth fuel, the range in steady 2-cycle may be a few thousand RPM .

The prop unloads as the model comes up to flight speed, and on 4/2 run engines, IMHO, it is that unload that sets the 4-cycle level flight mode. For engines designed, basically, to run primarily in 2-cycle, you might hear an occasional 4-cycle burp if you set it low in the 2-cycling range.

Anyhow, "wet" 2-cycling has ample visible exhaust, and is low in the engine's 2-cycling RPM range. "Wet' and "low" 2-cycling are pretty much the same.

You may need to train your ear a bit if you run mostly in 2-cycling. You will hear it strain a bit if you're set too high in the RPM range, particularly in the Overhead Eights and the upper loops of the Four Leaf Clover.

Since low-pitch prop, steady-2-cycling is pretty much like running in first or second gear in a sports car, there's plenty of power (higher RPM)  at reduced flying speed. There's no reason to use less than all the power you can get that way, short of hearing it strain more than rarely. In that case, richen a couple of clicks, check RPM, and see how that sounds.

[Joey Mathison 9806]

no expert here i am just a piddle flier but i have found an increase in head volume makes the needle range wider. add some head shims shorten your prop and pain in the but motor suddenly purrs like a kitten.