Re: thermostat

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: ortfamily@xxxxxxx
" 
" I like to keep the operating temperature of the engine at 175 to 190.
" Higher temperatures can cause knock, and the under-hood temperatures
" rise. Cooler air and fuel are more dense, so keeping the under-hood
" temperatures down is a plus. Higher under-hood temperatures also take
" a toll on the battery, hoses, belts, oil, and the paint on the hood,
" and will also affect your interior temperatures. The factory probably
" used a 195 as a compromise to sell in all climates, and likely used
" higher temperatures when they were first thinking about pollution. My
" cars seem to run better slightly cooler. With a 170 degree running
" temperature, I get adequate heat from the heater if the temp drops to
" freezing and I chose to drive it. If I get stuck in traffic on a hot
" day, no problems with overheating. Works for me, maybe something else
" will work for you. 

amc -always- used 195 degree thermostats.  they briefly flirted with
205 in the early '70s.  in general, the hotter the cooling system
runs, the less power is wasted to it, and the more efficient the
radiator is.

you can adjust a carb choke to work with a lower stat, but it's a real
no-no with efi systems.  to the ecm the engine never warms up, so it
never gets out of cold-start enrichment mode.

an aluminum-head engine can run more compression and might make more
power, but an iron-head engine will always be more efficient, all
things being equal, because less heat is drawn from the cylinder
where it can do work to the cooling system where it's a loss.  otoh,
higher cylinder temps means more octane sensitivity.

" On October 4, 2004 Ian Cudmore wrote:
" 
" > well we dont have winter in victoria usualy... we have maybe 2 months where
" > it drops below zero durring the night... never realy goes more then 5
" > below... and thats all celsius so its not bad. a very mild winter for the
" > great white north eh? but ok, you have changed your thermostats down to 160?
" > how come? overheating in the summer? i dont need to worry about that realy.
" > hardly ever breaks 30 on the island.

oddly since the rad is more efficient at higher temps the engine is
usually just fine even in the extreme southwestern summers.  and i can
tell you, around here where jan/feb average -1c, the difference in
heat between 180 and 195 is tremendous!  that radiator [heater core]
efficiency thing again...

" > At what temperatures will the engine be most efficient? thats realy what i
" > want to center on i guess. was there an enegeering reason behind 195? or was
" > it just practical for most of NA or what?

the hotter the better, for efficiency.  if you don't have to retard
the ign to avoid ping, run a 205 thermostat.

" > i guess a 15 pound cap is pretty standard? i think i've seen higher pressure
" > ones, they have like a pressure release valve on the cap right?  i would
" > assume that wouldn't be a nessicary change since again i'm not overheating?

7 for 180* and 15 for 195* are very common; most all have some kind of
pressure relief.  jeeps often have 18 lb and bmw has a 22 that fits
the common [our] rad neck.  there's a 26 and maybe higher for racers.

you need pressure relief to ensure the cooling system doesn't explode
in any extreme situation.

" > any suggestions? now i'm thinking 210 and maybe 225 are probably the way to
" > go?

that's the right area.  the 'normal' zone on your temp gauge goes
from 165 to 235; that makes 200 the middle.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen

adh@xxxxxxxxxxxxxxxxx                       and think what none thought