[Corley]

Railcarmover, I think you may be confusing "Lean Burn", with normal cruise conditions. "Lean Burn" only became possible/practical with the introduction of Fuel Injection, when mixtures could be controlled more precisely. "Lean Burn" as implemented in many modern vehicles with EFI, is activated after a cruise situation has been detected and maintained for a few seconds, when mixtures are leaned out to as much as 18:1, which causes a much slower burn, and timing is further advanced to account for that. You might be surprised to find as much as 50 degrees of advance at cruise on some modern EFI controlled cars that have implimented "lean burn".


This is not the same situation at all as normal cruise, (and a model A at cruise), where we have not influenced the mixture at all, just increased the timing advance by a few degrees when not under heavy load. This does NOT increase combustion temperatures, in fact as the engine's optimal pressure vs the time when the pressure is needed (15 - 18 degrees after tdc) is more closely reached, when these times match more perfectly than without this advance, temps go down, and the engine isn't fighting itself, and is better able to expel the hot gasses. This is all win-win.




So, I don't agree with your premise that more advance creates more heat. However, In the case of the model A, the biggest benefit from the vacuum advance is probably at idle speeds and slower car speeds, when the excessive retard of the FSI distributor does in fact cause overheating in situations like parades. Excessive retard causes overheating, excessive advance causes detonation. Either one can be disastrous to your engine.






The biggest advantage I see in the Honda dizzy is it is a cheap way to get both centrifugal advance and vacuum advance. But like I've said, I'm a CAMO.