>
>
>>
>>The average temperature to form NOx is 2500 degrees. There are some in the
>>science community that say it's closer to 2700 degrees. The average temperature
>>of the exhaust leaving the engine is 1500 degrees. Just leaving the head and
>>entering the exhaust manifold the exhaust temperature lost 1000 degrees. Explain
>>how a cylinder and related cylinder parts like the valves and pistons designed
>>to handle temperatures of at least 2500 degrees ( and I'll bet they can handle
>>much higher ) will be damaged buy some lower temperature gas that can not escape
>>in it's normal manner? Years ago before catalytic converters and EGR valves
>>cylinder temperatures went very much unchecked. Engine pinged? Retard the timing
>>or buy premium fuel. The materials used today in the parts that make up the
>>engine are far better than what was used even 20 years ago. As much as you want
>>to keep this dead horse alive, you can not do it. A plugged exhaust will cause
>>loss of power and eventually keep the engine from running, nothing more. You do
>>not agree with that statement? Instead of three word grunting sentences, in a
>>logical well thought out paragraph. Explain how a cooling gas is going to raise
>>in temperature high enough to cause damage to parts that are thousands times a
>>second subjected to at least 1000 degrees higher temperatures? Parts that are
>>subjected to not only very high temperatures but very high pressures. >>
>
>
>Not coming to Hurc's defence, BUT a partially plugged exhaust CAN
>cause engine temp to go up. The reason the exhaust has lost 1000
>degrees is because the water jackets and other engine parts have
>absorbed all the heat.
>However, once it gets plugged a bit worse, the engine does not get
>enough air-fuel mixture to produce enough heat (or power) to do much >harm.
>
>A previous responder mentioned something about 1996 and newer vehicles
>having temp sensors at both ends of the cat.
>This is not correct. The have O2 sensors at inlet and outlet - and if
>both sensors read the same the computer knows the cat is not
>functioning.
>
>Also, someone mentioned the switching from rich to lean - and
>intimated that was required to allow the cat to work, because one part
>of the cat (oxidizing bed) required a rich mixture, and the other
>(reducing) required a lean mixture. This is also wrong.
>
>The catalyst DOES require a relatively rich mixture to function - but
>the switching back and forth from rich to lean is due to the
>non-linear nature of the O2 sensor. It can NOT determine the actual
>oxygen content, but knows if it is too rich or too lean. It switches
>between rich and lean to get the proper average mixture.
>There are a few vehicles that use a linear O2 sensor, and the mixture
>on these vehicles does not fluctuate. The Civic VX was one good
>example.