This is true only because the current commercially available computer advance systems do not have provisions for user-reprogramming. It is technically simple to build in an interface so one can tune the ignition timing map, just like the automotive world have been able to do for years now. I can certainly understand it from the ign system manuf's point of view. It's just like the RC TX makers not allowing user-reprogrammability - they are concerned about the support nightmares once they open up the pandora's box.

The mechanical advance systems work extremely well for simple small engines like our RC gassers, but I would not call it superior in any technical sense to an electronic advance sytem. Spark timing advance curve should be mapped to RPM - plain and simple. Mechanical TCSA system can get away with "mapping" it to the throttle position mostly because throttle position typically has a good correlation to RPM. That correlation, however, is neither linear nor invariant. TCSA is a rough approximation at best. For example, many of the high performance engines that sport big-bore carbs will have a very non-linear throttle vs. RPM curve, such that RPM builds quickly through the first half of throttle opening and the second half toward WOT produces relatively small gains in RPM. A simple TCSA system is incapable of compensating for such nonlinearity. Plus many engines have significant throttle reponse delays.

Mechanical advance systems are indeed "obsolete" in 1:1 automotive engines. When was the last time anybody has seen vaccum advance mechanism on a distributor? Hmm.. come to think of it, when was the last time anybody has seen a distributor on a late model car?

For the RC gassers, however, TCSA will continue to provide a very functional and cost-effective alternative for quite some time to come.