EGT for mixture setting?

[Frank Parker]

> 
> A very conservative method would be to tune A/F for the same EGT at 
> WOT across the rpm range. A more aggressive approach would be to tune 
> A/F for a shallow but constant rising slope vs rpm. There are lots of 
> ideas as to a maximum EGT which you shouldn't exceed. Some like to
> use about 1800 F on dyno, but that's pretty short term. I love it when
> the exhaust glows red!
> 
> Ed Hernandez
> Ford Motor Company
> ehernan3 at ed8719.pto.ford.com
> 
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.
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)???