Fish,
good Q... Pure speculation based on various observations but heres an
attempt to describe and explain:
The O2 sensors control mixture settings by teling the computer if the engine
is rich or lean. If they go lean, the pulse width to the injectors is
increased. If they go rich it is decreased. add more air, and youd expect
more gas, right??? wellll, you get the additional pulse width below a
certain RPM, but by looking at the Pulse width on during WOT, no matter what
air you put in, the pulse width appears to be "fixed" at the higher (4600+)
rpm ranges and caps right at about 80% duty cycle of the injectors. Big
injectors you say? well, it still caps the pulse width changes, but thats
after it has reduced the pulse width to get the right mixture in closed loop
No more fuel = no more power gains...Think of it in an EPA way: This engine
will make no more than x ppm of these pollutants... clogged airfilter, no
airfilter, clogged muffler, no muffler etc,etc. all normal situations but
equivalent to making "modifications" in the way they require the engine to
respond. This may be/is way to simple since many other factors come into
play too! Manifold vacuum signal should be lower due to better Volumetric
efficiency, signalling more gas and air...BUttt etc.etc. wondering how the
computer will make up for 1.7 rockers and a R/T package camshaft...
Bruce
-----Original Message-----
From: David Fishman [mailto:fish@chips.Eng.Sun.COM]
Sent: Tuesday, January 19, 1999 2:52 PM
To: dakota-truck@buffnet.net
Subject: DML: Computer cancels out mods (was: New Member Intro)
Mssrs. Bridges and Short state that the '99 computer cancels out the
effects of bolt-on mods.
At the risk of sounding dense, how would the computer (specifically)
cancel out the increased exhaust flow from headers and catback exhaust?
Slow down air intake? increase fuel injection rate or volume? Please
'splain.
fish
David Fishman, San Jose, CA
fish@ihot.com
97 BMW R1100RT
99 Dodge Dakota SLT+ CC 5.2 4x4
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