Misc ?? EFI

[thergen at svn.net]

On Fri, 20 Nov 1998, Scot Sealander wrote:

> > WOT, is it only truely correct to call this PE, rather than even 
> > mentioning "open loop"?.
> 
> When in PE, the process is open loop, i.e., the feedback device is not
> being used.  It can be in open loop, and not in PE, like when the
> engine is first started.
>  
> 
> > Is it really closed loop, open loop, and PE?.
> 
> Well, PE has to be open loop for the systems mentioned.  When in closed 
> loop, it is not in PE.  When in open loop, it may or may not be in PE. 
> When in PE, it is open loop. 
> 
> Remember that this is just process control.  When a process is open
> loop, it is not using feedback.  When it is closed loop, this means that
> it is using some feedback to monitor and adjust the process.
> 
> As the feedback device used here is the O2 sensor, and it is only 
> accurate at 14.7 AFR, it is only used when the commanded AFR is 14.7.
> 

Your statements make sense to me.  Just to add a couple more cents... 
When an ECM is in PE and open loop, it can still be using the info it
learned about the engine during closed loop operation.  So, while it can't
use the O2 sensor to try to maintain an AFR of say 12.5 (PE and open
loop), it can extrapolate from what it learned during closed loop and make
adjustments to the fuel delivery that ECM programmer thought would result
in an AFR of 12.5.  Depending on how good the programmer was, the
asumptions made, and engine mods, the resulting AFR may end up close to
12.5.  

Comments?

Tom