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First, let me say I'm very excited about the numbers and the graph
you posted on the performance board - I can't wait to have mine
done. My only concern is with the A/F figures under boost.
My previous software, now owned by Bob Davis, never dropped
the A/F ratio below 12.5 under boost. Of course, the boost
never got much more than 21 psi, whereas Fredriks' consistently
gives me +23 psi (1.65 bar). And with the Volvo injectors, I'm not
really worried about running lean. Anyway, plug gaps......................
Bill, you might want to search through past posts by Karl and
Mathias concerning this matter. It was they who first brought to
my attention the matter of decreasing the spark gap with higher
boost pressures. Bob Davis, if you're reading this, take note!
What they told me was corroborated by Aeroguy, who was the
first on this board to note the correlation between wide plug
gaps and DI mortality. Although Dr. Boost cites studies in the
engine development labs to support the stock gap settings, Aeroguy
cited that Saab set up a test program to investigate the high
mortality rate of DI cassettes. They found that many failed cassettes
had plugs gapped over 1.1 mm and that 0.9 mm was an optimum
gap. The smaller gap resulted in lower cassette temperatures
because of the reduction in energy required to discharge the plug
under high cylinder pressures. On completing his doctoral thesis
for "Multi Cylinder-Individually Fired, Random Ignition Systems for High Performance Automobiles.(Published: Seigen University Press, Seigen-Weidenhaur, Germany,1962), Aeroguy and Porsche, for
whom he was employed, became well aware of the importance of
plug gaps for ignition systems that were the forerunners to Saabs'
design - actually, not just plug gaps but consistent resistance,
as anyone who has used a plug other than NGK, can attest is
critical for these ignition systems. So, to make a long story short,
I'm not surprised, at all by the results of your dyno run. It corroborates
what Aeroguy, Karl, and Mathias, have maintained all along - my
plugs are staying at 0.9 mm!
posted by 12.91.26...
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