IAT range

[Len Sabatine]

At 11:06 AM 6/3/00 -0500, you wrote:
> >On another list, we where talking about relocating the IAT on a colder area
> >(on the Quad4, the sensor is directly on the manifold). I'Ve heard about
> >this mod on F-bodies, I wanted to know if it was founded or not...
>
>Well, one of our LT1_Edit mailing list members set up a little engine sim
>(hooked to his PCM) and varied IAT only. In MAF mode (the mode our 94-97
>LT1's run in 99.999% of the time), he found that varying IAT made no
>difference. Turns out it's only used in speed density mode (when the MAF
>fails). Makes sense, since the MAF meter knows exactly how much air is
>moving through no matter what temperature, versus MAP which needs a
>calculation based on temperature to know the density of the air.
>
>Throw that in the FWIW pile. I've heard many "butt-o-meter" claims about the
>IAT relocation mod, and some folks saying their cars ran better, but never
>any documented proof (per Doc's last post), and I think the engine sim is a
>great way to test a mod like this.
>
>-Andrew
    The "General's" implementation of IAT appears, after study to be more 
emission , EVAP,
   cold start and Hot soak restart  related. Back to Back 1/4 mile passes 
indicate nil
performance change with sensor location in OEor in the K&N  air box. 
Emission related
Hot Soak restart gets fatter with sensor relocated to a cooler residence , 
if you happen
to be able to test with a Exhaust Gas Analizer. The Importance of IAT 
is  greater
on a Speed Density fuel management system, than with Mass Air Fuel Managment ,
when investigating the details as Speed Density infers Spark and Fueling as 
compared
to the MAF's direct approach. Suppose you could say , same thing , only 
different.
Simplisticly put , on a 100 df day and AC on ,  after a short lay 
over,  telling the PCM
it's 0 df air temp most  likely will cause a bit of cylinder wall fuel 
wash.  Engine rebuilders
  will love you for it.
  I'm sure General Motors spent much time and effort to find the best location
compromise for the IAT, especially on LT1 , LS1 and Vortec equipped 
vehicles, from
what I can measure. Avoiding the Hype and finding the truth takes vigilance 
on all
our parts . In the end , how does a change apply to a specific combination 
of parts.

Len.

Len

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