Craig:

That all sounds pretty reasonable to me. I would only respond to two items. 1) There have been several installations where the coils were placed near the plugs. They have always worked fairly well, but that also presents some of it's own difficulties--mostly maintenance issues. Several recent, new electronic ignition systems have considered that as a possibility, but have found that there are significant disadvantages. It's not a problem-free concept. 2) In the overly rich condition you expressed concern over (which I agree would be a major problem during a go-around), if the mixture were so overly rich that it had rich misfire, NO AMOUNT of spark intensity would make it burn. That's not an ignition issue, it's a flammable mixture issue. Ignition differences would have no effect. Lightening could strike a bucket of gasoline and as long as it's too rich to burn, it won't. In the example you presented, the problem was one of fuel distribution, not too little ignition.

Most of what you said in this post, I am in agreement over. Interestingly enough, I find no disagreement with what you posted below and what George posted that you originally seemed to have disagreed with. ?????

Walter


On Feb 15, 2005, at 6:58 PM, Craig Berland wrote:

Walter,
 
My point is... with a lot of general aviation aircraft there is a very short distance from a "new" part to non-conforming (as you put it) and that a prudent pilot may want to investigate ways to increase that distance....such as a better ignition.  A second point is...engines can exhibit reduced exhaust temps because of poor performing components, and those components may be nearly new.  The reason I use extremes to make a point (such as .080 plug gap) is because a wise old engineer told me...."Affect the system, don't get confused with a bunch of tiny steps".  You are correct, there were many trick engine developments in the early military aircraft engines.  Unfortunately...general aviation has been stuck with a very high percentage of non-crossflow heads, magnetos and carburetors. I suspect you know how bad the cylinder to cylinder A/F distribution is on some of these engines. I guess there wouldn't be much of a market for Gami injectors if even the higher end crossflow and fuel injected engines were done a little better. I know I want my TSIO550 engine improved over what Cont had in mind. I had an engine on a dyne years ago that had a 7 A/F spread from lean to rich at part throttle and a 4.0 A/F spread at WOT. At RBT the rich cylinder was near rich misfire.  The engine was new. If you were flying one of these bad boys and had to do an emergency go around after loading up one or two cylinders, then I would want an ignition that would fire all cylinders and some won't. It all makes since to me, but then that alone may be scary.
Craig Berland