EGT for mixture setting?

[orlin steven jared]

> I have had a hard time getting a good relationship between absolute exhaust
> temp and a/f ratio and temp limits. I have taken data on my datalogger @
> 100 times/sec monitoring fuel pressure, turbo boost, o2 sensor voltage
> and egt. The type k t/c was located about 3" from head exhaust outlet
> flange. I saw about 1650 deg F max at wot, with about 10sec @ max 8psi 
> boost. I could adjust nonlinear fuel press regulator to add more fuel and
> see 50 deg temp drop. O2 sensor voltage went from about .82 to about .84,
> but std o2 sensors are very nonlinear here.
> Does anyone have comments on how egt temps change with thermocouple 
> placement and what max limits may be????. The turbo mfr suggests 1750 max
> inlet temp.

In my opinion, EGT's aren't really very useful in tuning AFR.  You will
spend more time and money doing this, and have more failures (most likely)
than if you just plunked down the initial investment in the Horiba UEGO unit.

The main advantage of EGT's is checking fuel distribution.

> As a secondary question, are there any sources from the wide range o2
> sensors other than the overpriced unit from Horriba ($2500-actually made 
> by NGK)???

You may want to look into Bosch.  Last I heard they were coming out with
some type of a comparable unit, with UEGO sensors for $250 ea., instead
of the $900 Horiba sensors.



STeve