EGT and O2 sensors time resolution

[Bernd Felsche]

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! :-)

> > 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.
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