Re: BPW and Cylinder Vol.?

[garwillis@msn.com (Garfield Willis)]

On Wed, 28 Jun 2000 12:38:49 -500, rrauscher@nni.com wrote:

>At low air flow, with the O2 sensor in the header
>collector, the transport delay can exceed one second.

On Wed, 28 Jun 2000 16:41:33 -0400, rr <RRauscher@nni.com> wrote:

>Transport delay is from the injector, (I mentioned from the
>exhaust port), to the O2 sensor. I didn't think much of it
>until I found ecm code that uses this delay. The ecm
>needs to know this,  in order to know how long to wait for the
>O2 sensor to react to a fueling change made earlier.

This "dead time" as the controller guys call transport delay, is one of
the reasons why a PID controller for a WBO2 sensor-based ECU is
sometimes not so easy to get stable. And BTW, to be bitchy (but of
course :), the transport delay is all the way from the injector driver
thru and back to the ECU O2 input, and includes all them dang delays,
injector opening/closing, induction transport delay and combustion
delay, transport delay down the exh pipe, AND the O2 sensor delay
itself. And yupper, it sure all adds up, don't it!?

Even at higher airflow rates at higher rpm, it's not so much the
absolute time delay, as it is the "phase lag" between the controller and
the feedback variable (in this case AFR), and becomes even more
significant. I know this isn't news and has been observed by others
onlist already, but it's something like you said, you don't think about
it much until it matters.

Gar


----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org