rad and coolant,

Robert Harris bob at bobthecomputerguy.com
Thu Oct 23 17:18:45 GMT 1997


Coolant temp is almost irrelevant. It's the result of heat transfer from the 
block and head.  Its secondary.  What is relevant is the metal temp on the 
combustion side. This is what the fuel/air and piston actually live with. 
 Regulating water temp is sort of like trying to air condition a room by 
regulating the condenser temp.

Remember, on the fire side, temps peak at 2000+ degrees depending on load etc. 
 The piston crown lives at about 500 to 600 average, the walls about 400, yadda 
yadda etc.  The coolant is at the low end of this thermal gradient and is 
subject to immense delays because of thermal mass etc.  The ideal would be to 
sense the metal as close to the fire side as possible - without sensing the 
fire - preferably in the chamber area. Regulating this directly controls the 
critical temp and eliminates much thermal lag, changes in heat transfer 
efficiency brought by outside temp, speed, corrosion etc. Probably the best way 
is a thermocouple tapped into the head at each chamber drilled to just below 
the surface, or perhaps a spark plug cylinder head thermocouple used on air 
cooled aircraft/ultra light engines might work.

Then feeding this data, along with load data and anticipated load from your 
EFI/engine management system into a simple controller would keep the metal temp 
where it should be.  Remember with the right thing being sensed and a decent 
control system, the mechanicals can be downright crude.  Witness the extremely 
deadly Sidewinder Air to Air missile - its control surfaces can only be full 
left, full right or center - nothing in-between - yet this simple ass system 
drops em dead like Raid at a Roach Festival.

Just my obnoxious $.02 worth.
If the first ingredient ain't Habanero, then the rest don't matter.
Other Obsessions: Ferro-Equinary , 1972 "Killer Whale" Mustang
Currently Interred in the Peoples Democratic Republic of California - Stalag 
Montclair
Puck da guns - ban Politicians!!!!!
Robert Harris <bob at bobthecomputerguy.com>
Subject:	Re:electronic engine temp control
>
> The best off the shelf solution mechanical is to use a headder and connect
> several heater control valves in series. Use solenoids valves to open them
> in stages via a simple electronic control system. In theory, one could
> probably hold the temp at 218F or so reguardless if the engine is idling or
> crusing 75mph. I noticed that my engine temp drops at highway speeds. Don't
> know how much... just that it does. I also know that the coolant system is
> quite capable of operating at 230+F without any problems or modifications.
> Does anybody have some fuel consumption vs engine temp data for an 89' GM
> 350 TPEFI?
>
> GMD
>
> At 05:51 AM 10/20/97 -0700, you wrote:
> >Well it would seem to me that with all the computer experts around here
> >somebody would come up with a control valve that could could be
> >programmed for whatever usual running temp, with a switch of some sort
> >for a performance mode that would run temp down to 160??
> >
> >
> >
> >-----




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