Does anyone understand the ignition curves in the WSM?
I'm trying to figure out the centrifugal advance curve on pgs. 284d in vol1 of the turbo supplement WSM.
On pg 284d it shows a centrifugal advance curve for USA, Cali and Japan from model 78. At 2000 rpm dist. speed it shows 8* advance of dist shaft. It also shows at 500 rpm dizzy speed it has a +1* advance of dist shaft from TDC. So since dizzy turns 1/2 crank speed that means at 4k crank rpm the centrifugal advance is 16 crank*and at idle speed centrifugal advance effect is + 2 so essentially zero effect at idle as expected. On pg 284c for USA (not Cali) it says timing must be 26*+ 4* BTDC at 4k rpm with vac hose disconnected. Ok so max total timing for USA version could be 30* at 4 k rpm. So since centrifugal only gives 16* advance that means the timing at idle with vac hose disconnected would be 14* (30 total less 16 centrifugal), correct?
Of course then the vac pot pulls out 20 crank* at idle so that gives timing at idle of 4* ATDC (14 BTDC  10 = 4* ATDC). That agrees with the sticker on my engine lid that shows timing of 5* ATDC.
I'm assuming this retarded timing crap at low rpm was to keep the exhaust hot for the reactors to work?
