Quote:
Originally Posted by psalt
Sal,
The 67 BTDC must be an error. There are plently of threads on twin plug ignition timing to read. Most published info suggests that you need 7-10 degree less max timing for optimum power with twin plugs. However, if you look at the ignition timing curves from the 911SC to the 993, this is not what the factory did. The 993 curve I saw showed a max advance above the 26 BTDC max used in almost all cases. Up until the 993, it almost looks like Porsche was married to a 26 BTDC max and altered the compression ratio to suit the fuel spec for different markets. Compression went from 8.5 to 9.8 to 10.3 to 11.3.
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Paul,
It could be the chip bin I have if faulty. But if you look at the rest of the WOT timing it shows 30BTDC after 5500RPMs.
I'll double check the chip map by hand with a hex editor to see if those numbers make sense.