[Archived]

OK, Tom, post a link to show what the upper pyro limit should be.

Over the years there have been a lot of “experts” who know the temps have to be no more than (insert whatever number you want here) but so far I have never seen any limit or even suggestion by Detroit to define what it should be.

[DON]

The pyro upper limit depends on where the probe is installed. This varies by engine type, installer. Ie, turbo, non turbo, in exhaust manifold, before turbo, after turbo, etc, etc. So one size does not fit all.

[Fred F.]

Kind of.

My 8V92 had a pyro for each bank and having been flying turboed planes I knew there were limits. But my plane (P210N) did not have a specified TIT (tubo inlet temperature which is akin to pyro temps) which was unusual because every other gauge had limits, marked on the gauge plus listed in the limits section of the book.

So I called Cessna and was fortunate enough to speak to the test engineer who did the flight testing of the plane. He said before he answered my question as to the limit he needed to go to the files and make sure he had the correct answer. When we spoke again he said on my model and serial number plane there was no specified limit because there was no power setting or mixture setting combination that would meet or exceed the turbo limits.

So when I got my 8V92 equipped coach with no limits marked on any gauges and none in the owner’s manual I started crawling all over the Detroit web site, engine manuals, service manuals, etc. and found two things. No limits were marked on the gauges because as a DDEC equipped coach the ECM handled those limits. If any limits were about to be exceeded the ECM would derate the engine or stop the engine and apparently Detroit and Prevost did not want drivers worrying about looking at gauges. The ECM on coaches I am familiar with does not use pyro information for any purpose. Later versions of Series 60 might for the emissions systems but I don’t know that for sure.

In all my investigation I could not find a single word about pyro limits.

[rafael]

Beets the hell out of me, 1100 was the magic stay under number at the time.

[glen]

With electronic engines of today the computer will derate the motor before harm.

In the old mechanical motor days your pyrometer was of the utmost importance if you were a mountain truck.

All I know is 1100, 1150 is fine. 1400 and your starting to burn up.

Later

bv