Improvement

 It's a great fun for my life to compensate the gap between overlooking and under looking. Basically, I gathered necessary information by consulting papers and articles written by former researchers in specific field. It was so difficult to do that wasting time. Articles I wanted were floating in the Ocean of them. But, now, in the period of Internet, Web is scattered in every direction and very easy to do that in very short period of time.

In spite of golden condition, I have been in misunderstanding thought about combustion firing timing of VW Super Beetle for over tens of years. I knew about the double diaphragm vacuum advancer specifically equipped in '71 production and the fact that advancing and delaying functions performed done at the same time. Recognizing such a function with watching the scheme actually, I still believed in the necessity of vacuum advancing effect for smooth acceleration. The shape of mechanical distributor was that of equipped diaphragm(single) chamber aside, so printed in my Cortex. This is why I fed vacuum signal to distributer without doubt for long time until few days ago. I had some suspicion on the function of accelerator fuel pomp in the carburetor body, because of ill function while departing phase.

Watching up the graphic drawn the relation between vacuum advance and delay also mechanical centrifugal advance, I come to the conclusion that vacuum advancing is not always necessary for replacing distributor from double diaphragm to single or less chamber distributor! After adjusting the timing at zero degree under no vacuum condition, I was so surprised to feel completely different attitude of 1600 cc AD motor as if released from heavy burdens. In addition to lubrication on the steering gear box, these improvements changed it's character like different vehicles. Also, first idle phase with stall tendency was far improved without thermostat function.