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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,563
The factory shop manual knows the answer. There are 4 engine type versions; USA, CA, Japan and ROW. From the manual:

" Cars in California version are equipped with a distributor having a double action pressure box. At idle speed the intake vacuum produces ignition toward retard, which is eliminated again when throttle is open just slightly. The charge air pressure is used for full throttle retard ignition control, to avoid coming into range of excessive advance ignition at full throttle with the ignition timing which is 5* earlier than the USA version."

It then goes on to tell you how to check for both vac and boost retard on the USA, CA and Japan versions only. The Euro distributor is completely different in both function and how it is set and tested. The timing for the Euro is set @ 4000rpm and ignition timing control is verified at idle with the vac hose attached. Timing for the twin port versions is set at idle and ignition control is verified @ 4000rpm with the vac hose removed. There is an ignition boost retard curve shown for the USA, CA, and Japan distributors. The Euro distributor only has a vac retard curve listed.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-30-2010, 08:50 PM
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