OK, this is purely third hand information. Sorry for it not being a
definitive source. May or may not be interesting, and leaves a lot unsaid.
Maybe some of you can fill in some of the blanks. My brother work for DC,
(not in engine development), and this is what he has heard about the engine
calibration chips:
>>
Mopar's "performance" module is nothing more than a production controller
with 2 degrees of spark advance added to all the data tables (we use
flashable memory now instead of ROM chips). That's weak for $500! The
'hot' cals used to be done by engineers here in their spare time and given
to Mopar, we don't have the spare time anymore so they farmed out the work
to some company in California. Both spark and fuel curves can be adjusted
and can vary depending on what octane fuel you're targetting. The 4.7L
doesn't have a knock sensor (not until 2002) so the production cal is very
conservative. Not much spark advance, which needs lots of fuel to keep
exhaust gas temps (EGT) down. Also, there is a fair amount of variation in
the compression ratios of the engines. You can add a lot more spark
advance on a 'low spectrum' engine (which actually flows better at the
upper end). In general 10-15 degrees of spark advance can be added to the
curves, another 10 for premium fuel. Then 8-10% of the fuel can be taken
out because EGTs go down with spark advance (the flame front moves back
upstream). Believe it or not, these hot cals will actually improve the
fuel economy. NOx emissions go ballistic though because combustion
efficiency improves. The EPA wouldn't allow that in production, they
require emissions to be at stoichmetric (sp?), a compromise between
hydrocarbons (un-burnt fuel) and oxides (burnt fuel). My expert says if
you wanted to mill a little off your heads, with the new TB and intake and
cal, you'd leave any 5.9L in the dust. Yet still have high reliability and
better mileage.
<<
So who is this company in California?
- Rob
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