Mike V. Florida
Well-known member
Where did the magic number of 160 degrees come from?
Engine temp
- Thread starter Mike V. Florida
- Start date
HoarseWhisperer
Well-known member
Not sure. 160 degrees for what? Thermostat, rad, water, inlet pipe, outlet pipe, engine, head, oil?
steve s
Well-known member
FWIW, I read somewhere years ago that cars with cast iron cylinder heads run better at 160 whereas aluminum heads run better at 180. Don't know what the nature of the "better running" was, and, sadly, I haven't been able to find the source again.
I also understand that 160 is a minimum to achieve vaporization of blow-by combustion byproducts that wind up in the oil pan. Higher temps put you closer than necessary to the boiling point of your coolant, which is especially important if you're using just water in an open system, and even more important in the old days if you were using methanol based (non-permanent) anti-freeze.
All other things being equal, the higher the combustion chamber temperature, the higher the thermodynamic efficiency of an engine. Unfortunately, another consequence is that the oxygen and nitrogen in the intake air react much more rapidly to form NOx pollutants at the higher temps. That's why, in the primitive air pollution control days of the 70's, mileage and power went all to heck when the federal mandates could only be met by lowering engine temps. When catalytic converters were developed, the NOx could be taken back apart before release and the engine temps and performance were cranked back up.
I'm not saying it's not true, but I don't understand the business about racers using 160 thermostats, and it's not just because of their misuse of the word "atomization".
Steve
I also understand that 160 is a minimum to achieve vaporization of blow-by combustion byproducts that wind up in the oil pan. Higher temps put you closer than necessary to the boiling point of your coolant, which is especially important if you're using just water in an open system, and even more important in the old days if you were using methanol based (non-permanent) anti-freeze.
All other things being equal, the higher the combustion chamber temperature, the higher the thermodynamic efficiency of an engine. Unfortunately, another consequence is that the oxygen and nitrogen in the intake air react much more rapidly to form NOx pollutants at the higher temps. That's why, in the primitive air pollution control days of the 70's, mileage and power went all to heck when the federal mandates could only be met by lowering engine temps. When catalytic converters were developed, the NOx could be taken back apart before release and the engine temps and performance were cranked back up.
I'm not saying it's not true, but I don't understand the business about racers using 160 thermostats, and it's not just because of their misuse of the word "atomization".
Steve
Mike V. Florida
Well-known member
OK, that's sounds good. I've heard for years about 160 degree thermostats but since the A's never had them I often wondered where that number came from.
Chris in CT
Senior Member
Hi Mike, Just a few things added to the above very good information. Steam "vapors" begin to form at 180 degrees, not a problem at all with a sealed (pressurized) cooling system, but could cause excessive evaporation in a open cooling system. More than a few marine engines have 140 deg. thermostats, and with regard to the atomization answers given above, it is clear that these engines are kept cooler to avoid the collection of explosive fumes in the engine compartment (with the flame arrestor, of course). I have found that my own A runs much smoother and quieter with the 160 deg thermostat I installed over two years ago.
Happy Motoring!
Happy Motoring!