WOT open loop/closed loop

[Shannen Durphey]

Ron Schroeder wrote:
> 
> Other than not getting max power is there any disadvantage of 14.7:1 at WOT
> with a mild non-turbo motor?  (assuming the A/F ratio swings don't go too
> lean)

Geez...

Since when did an engine run on numbers?  An engine runs on fuel and air, and
it's your goal as a tuner to determine how much of both.  Is there any
disadvantage of running 14.7:1?  Sure could be, if you have one cylinder that
gets a little hotter and tends to detonate more easily, or one piston that's
manufactured a little wrong and creates a tendency toward detonation, or carbon
buildup in a cylinder does the same, or poor manifold design actually directs
more air to some cylinders than others (heaven forbid), or non flow matched
injectors get a little dirty and cause one cylinder to run slightly lean, or ???

Tuning is still trial and error.  Most guys just want to get a tune to run
"ok".  The obsessive ones keep pushing the limits of error.  The WB sensors, ion
knock detection, modified code are all ways to better report on the error and
understand what's going on.  Sometimes the tuner uses the info directly,
sometimes the system is redesigned to use feedback without tuner intervention. 
But the GM system is designed to detect what's going wrong, not what's working
right!  

Food for thought:  Want to try to approach tuning from the other side?  Think
about making spark maps that change themselves, changing timing based on changes
in the amount of time a full throttle run requires to go from one rpm value to
another.  Then think of all the ways you can add more functionality to that.  I
should mention that I've ridden in a car that can make fuel changes based on
what's right, not just report on what's wrong.  It is very impressive in its own
quiet way.

You'll do well not to think of tuning as "I'm going to run my engine at 14.7:1"
but as "What will my engine tell me if I run at 14.7:1?  What do I need to
watch?  How will I detect any problems?  What are the conditions I want to
prevent?  Are my sensors fast and accurate enough?  Is my data collection
appropriate?  Are the mechanical aspects of the system consistent enough?"  For
every question you could develop a strategy to gather feedback and a way to
spend time testing.

You'll figure out what your own limits are fairly quickly, but you'll also gain
a better understanding of the method of tuning generally applied today.  When
trying something different, you'll want to watch for signs of problems and make
corrections as needed.  There is a point where you can get the most an engine
can give, but it may not agree with what you want.  It's the engine's decision,
not yours. ; )

Shannen
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