TPI and thermostats

[George M. Dailey]

Gentlemen,

A while back I inquired about cold thermostat = more power for tuned port FI
engines. As a testiment of my typicly bad luck, the original thermostat in
the engine was stuck open. Temps were at record lows in MS, so I drove it as
is for several days. Fuel economy was 10-11 mpg (city). After changing the
thermostat to 180 (instead of 195 per GM) fuel economy did not improve much
and, I still had heater temp problems. I changed the thermostat to a high
quality 195 F unit and tossed the cheap 180F AUTOZONE unit. It looks like
the final MPG figure for the week will be around 14 - 16 mpg, and the heater
is putting out like Bessmer Furnace.  

Question: My TBI engine used a 180 F thermostat and got 12-13 mpg city. Is
the difference software or engine thermodynamics? Why did the cold TPI motor
fall on it's face?

BTW, I could detect a slight increase in power. I can imagine that the
electronics may have allowed the A/F ratio to thicken a bit and advanced the
timeing as part of the 'warm up code'.  The Chilton manual does list
incorrect or damaged thermostat as a possible cause of low fuel economy. 

Hate to ask this one but, since I lost my pride due to a bad love affair
years ago, here it goes :-[]   Up to a limit, could one expect better
economy at ...say...220F (secondary fan turn on point)? I am aware of the
lubrication problems and detonation at high temps, what are others?

thanks, 

GMD