EGT and O2 sensors time resolution

[Bruce]

But does it really matter, and to what degree?.
If your averaging the readings then who cares?.
If you want to do individual cylinders, and real time corrections (well
kinda of) then it can matter.   But again at higher rpm you'll start
averaging anyway, because the injector firing is overlapping the cylinder
events anyway.
All the feedback systems you can imagine are still less powerful then a
human brain.  In engineering they like to try and remove the art form from
activities, yet that is what can make things such as tuning unmatchable by
them.  The feedback of a mechanical/ electronic system is faster, but
weather doesn't change that fast.  the only true advantage to that is when
the tune is drastically off anywho.  You can split hairs finer then the
engine can appreciate.
Bruce







----- Original Message -----
From: "Diehl, Jeffrey" <jdiehl at sandia.gov>
To: "'Bernd Felsche '" <bernie at innovative.iinet.net.au>;
<diy_efi at diy-efi.org>
Sent: Thursday, September 13, 2001 2:43 PM
Subject: RE: EGT and O2 sensors time resolution


> I was jsut about to ask the VERY SAME QUESTION!  I can't believe that this
> isn't documented somewhere.  Perhapse on the spec sheet?
>
> Anyway, there were threats of doing the math... I guess I missed it, so
here
> is my attempt.
>
> At 7500 RPM, we have 125 revs per second, each lasting .008 seconds.  We
> have an exhaust stroke every other rev, or .016 seconds apart.  At this
> point, I'm assuming a probe on EACH exhaust runner.  If you "choke" the
> exhaust through a single exhaust, (sorry, couldn't help it.) then your
> exhaust pulse rate will be 4, 6, 8 times this rate.  Clearly 10us is too
> slow to detect an exhaust pulse if you only have one probe, and it's
barely
> quick enough if you have 4,6,8 probes.
>
> Am I missing something?
>
> Mike Diehl.
>
> -----Original Message-----
> From: Bernd Felsche
> To: diy_efi at diy-efi.org
> Sent: 9/12/2001 6:37 PM
> Subject: Re: EGT and O2 sensors time resolution
>
> Santi Udomkesmalee tapped away at the keyboard with:
>
> > 2 questions...
> >
> > 1)  What sort of time resolution do EGT sensors, and O2 sensors have?
>
> O2 sensors can be faster than the stream of exhaust gas from the
> valve. Depending on type, placement and temperature, you're looking
> at response times in the region of 10 to 100 milliseconds.
>
> EGT depends a great deal on the type of sensor and the exhaust gas
> temperature _gradients_. i.e. how quickly they rise and fall. The
> sensor has a finite response time dependent on its thermal mass.
> Response time to reach a "near enough" reading can be in the
> seconds.
>
> > 2)  Would a closed loop system be benificial to a high performance
> > application?  That is to say, ideally the engine should be at WOT
> > or idle most of the time.  Would there be any gains to
> > implementing some sort of closed loop system in this application?
>
> What sort of high-performance application? Aircraft?
>
> Just the usual benefits:
> Engine life, mainly. Also fuel consumption and engine power
> optimisation along with emission control.
>
> Other main benefit is that it allows more aggressive control
> strategies.
>
> BTW: An engine should never idle. That's 0% efficiency. :-)
>
>
> --
>  /"\  Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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