Hi! There's no definite answer here but... can anyone here please tell me the AVERAGE temperatures of the headers or exhaust manifold of gasoline or diesel engines?
What's the highest temperatures that they can reach?
Depends on operating conditions such as power. Exhausts on an aircraft or race car engine under high power conditions can literally reach red hot- I think that is about 1400 degrees. In average driving on a street machine it would be much less. Diesels, because of their higher efficiency are much lower in temperature.
Some of the paints I have seen for exhaust headers claim to be good for 1200 degrees, and seem okay for street machines but do not last that long on racing cars.
Years ago my brother in law had a Snap-On franchise.. one night we finished doing some truck maintenance and went on a quick freeway test drive with the 'dog house' (inside engine cover) removed.
The manifolds and first foot or so of pipe glowed pretty good in the dark. The glowing probably wouldn't have been all that noticeable in better light though. I'm sure had the engine been working harder, like climbing a hill, they'd have been brighter.
As far as actual temps, your guess is as good as mine. I wish I'd had an IR thermometer that night, it would have been interesting. (IR thermometers didn't even exist back then.)
Erik
I'm not usually concerned with the manifolds themselves, but rather the gases inside. Spark-ignited engines tend to run exhaust temperatures approaching 1200 deg. F, under most conditions. Sustained high speeds in racing can push that up considerably, but 1100-1200 is a reasonable assumption for "everyday" driving, or powering a generator, etc. Diesel exhaust temperatures vary a lot more, depending on the load. At idle, exhaust may be around 700 F. Moderate loads push that to more like 850-900 or so. "Full" load (rated maximum continuous output) on industrial engines I work with can reach 1100 or so. To sustain exhaust temperatures higher than about 1200 F, serious consideration has to be given to valve and seat materials and cooling, valve guide lubrication, and piston crown cooling.
I have seen cherry red exhaust manifolds and headers. Never checked the temperature... still below the melting point of steel and/or cast iron, but definitely above the melting point of spark plug wire.
Ray
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