Re: VE stability

[Roger Heflin <rah@horizon.hit.net>]

On Fri, 10 Mar 2000, John S. Gwynne wrote:

> A few of my thought of what may be going on.... appreciate comment and 
> suggestions....
> 
> -- baro measurement screwed up because of sc 
> I'm collecting data on this now. The condition does seem more
> pronounce at partial throttle conditions.
> 
> -- EGR
> EGR partial pressure correction needs updated for exhaust system
> 
> -- inlet air temperature reading inaccuracy
> MAT sensor may be influenced by block/manifold temp
> 
> -- engine/cylinder conditions
> carbon in the cylinders changing the burn after highway driving
> 
> -- sensor temperature sensitivity
> MAP sensor may be somewhat temperature sensitive (1-2%)
> 
> -- limitation of the tuning procedure
> maybe, but it does look like it in the data.
> 
> -- O2 sensor
> temperature/accuracy sensitivity of the O2 sensor.
> 

humidity also will do it.  You get a parital pressure of say
.4psi(really hot and humid) and it does displace .4/15 % of oxygen
(2-3% overall).   That is probably part of it.   Also probably all of
the above, and any fuel inconsistancies (better or worse fuel), and
also how linear the temp sensors are.   THe MAT may be right a 70
(real temp is 70) and at 90 the real temp may be +- several degreees.
All of these together would make things much harder to get exactly
right. 

			Roger

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