EGT and O2 sensors time resolution

[Bruce]

From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
Subject: Re: EGT and O2 sensors time resolution
> Bruce tapped away at the keyboard with:
> > From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
> > > 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.
> > Let's try the math on a v8 at 7,000 rpm single exhaust and sensor.
> Let's.
> You deserve all you get choking a V8 through only one exhaust! :-)

Swing by sometime, I'll take ya for a ride in a choked v8.
10 msec is wayyyy to slow to identify individual cylinder firings, on the
above example.  At over hig cruise speed your game is over.

> > > 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.

> > How so?.
> By eliminating the operational "safety" margins that are necessary
> because you're not measuring those quantities under actual, ambient
> conditions. i.e. fuelling and timing doesn't have to be as
> conservative to avoid excessive temperatures and emissions which
> might occur under worst-cse (or tuning session) conditions.
> The engine is operated under best-case conditions as far as is
> possible under ambient conditions given the physical engineering
> constraints.

So your comparison is for a none tuned to conditions engine to a closed loop
system.  the limits are with the engine not the tuning.
Bruce


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