intake plenum size & reversion

[Roger Heflin]

Chris Capowski wrote:
> 
> It is more complicated than that.  The number of cylinders you have makes a
> huge difference as well.  Three cylinder engines tend to have (or they
> should at least) the largest plenum/engine size ratio.  Reversion is bad...
> 
> Chris "Mighty Mouse" Capowski

What exactly is reversion?

The situation I have is the motor is a chevy V8 small block 6.6l engine, with
what someone else measured to be a 3L intake, with 3-4" runners.   This motor
is a late model chevy LT1 motor, and the intake has IAC passages built
into it (basically a separate plenum/runner setup going to each cylinders
runner, and this air is separately controlled with a idle air hole-much like
you would drill in a carbed motor, and a iac motor setup).

At idle (without using the special IAC passages in the intake, or without
using them enough) the motor runs consistantly different side to side 
(one side runs with say a blm of 110 or so and the other side run 160, 
basically -15% fuel on one side, and +25% on the other side), as the 
throttle increases things even out. The above was determined by averaging 
a large number of samples (10-15,000).

Now increasing air routing into the IAC passages evens out the above numbers
at low throttle and has minimal affect at higher throttles (it has some,
but in areas the engine does not often run, and the differences are much
less significant).  When this is done the TB blades are adjusted down
such that the total air in the motor should be about the same, and the
idle is about the same speed.

Several others have noticed exactly this same behavior and that upping
the air into the IAC passages fixes the inconsistancy.

Would reversion exhibit this sort of behavior, and would the IAC passage
setup be a way of fixing the part throttle issues?

				Roger
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