Gary,

Here's my question:  With these engines the numbers should be very
consistent.  What compression ratio to assume - not sure, but pick one.
Given a manifold absolute pressure of, say, 20 inches, a fixed rpm of 2400
to 2500 and a fixed mixture of maybe 30 LOP, what is the optimum (MBT)
ignition timing with both ignitions at the same timing setting?  What is the
optimum timing for the second ignition if one ignition is set at 20 BTC?
What is the BSFC in each of the three conditions?  I'm sure there is someone
out there that has accurate data - and you know who you are!

Gary Casey
IO-540, 2 mags, but one might get exchanged for something else.



You rang ???

Regards,  George




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OK... seriously,  the problem with answering that question - - which we  could do - -  is that it leads to a lot of wrong assumptions about what is "good".  Other technologies would lead a lot of people to do some very wrong things with their ignition systems.  

Properly timed,   an IO-540 operating at WOT at high power (25 to 28"MP) can have a BFSC down around 0.39 to 395.  (with 8.7:1 pistons).  At lower MP (20")  the BSFC will not be as good.

A 520/550 class TCM engine will do about 0385 under the same scenario.

These are very good numbers that the automotive world does not  achieve.

Regards,  George


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