pyrometer gauge

[gmcbuffalo]

When I am pulling a hill my pyrometers will read 1000 on the right and 900 on the left, is this a problem or normal? 8v92 and 5sp tranny.
GregM

[Jon Wehrenberg]

Likely normal.

The key is to determine what your readings have been over your time of ownership and to notice variation from those values.

I cannot remember what the spread was between the two pyros on my other bus but I think there was about the same spread as yours, but my higher pyro read a little higher, around 1100.

When my manifold gaskets started to fail my pyros went down and so did my turbo boost so the gauges did tell something was different.

[truk4u]

Greg,

I keep mine between 900 and 1000 and the needles are real close. I doubt that 100 degree difference is a concern and is probably normal.

[dalej]

Greg,

Check around the manifold on the right side (muffler side) for black exhaust residue, I had a gasket leaking and that made the temp run higher. Replaced it and it came back in line with the other.

Gaskets are easy to replace if thats the problem.

[Joe Cannarozzi]

I am with Peter on this one. Pyro is the most useless gauge on the dash. He unlike us in the flat lands is out West in the mountains where it supposedly becomes critical. I know from previous discussions Peter pulls hills with the throttle on the floor and if that driving technique does not produce too much exhaust temp nothing will.

Our 85 is not equipped with the gauge, no big loss. They are expensive to replace and very temperamental

[BrianE]

Don't agree with you on this one Joe. Running an 8V in the mountains one needs to pay attention to both pyrometer and boost. Sustained pyrometer temps above 1100 and/or boost above 20" IS going to result in an overheated engine. As I learned the hard way, this situation can easily be avoided by slowing down and shifting down to keep RPM's above 1700. The 8V is a great engine but it needs to be closely watched when working hard. Additionally, the cooling system on the 8V needs more attention due both to its' design and its' age.


Peter's experience is with the rare installation of a pyrometer gauge on his very early Series 60 Prevost. The 60 isn't nearly so temp critical. The engine cools better due to a better cooling system and it's basic ability to dissipate heat due to less mass. Also the 60 lugs down better and the 6 speed tranny doesn't hurt either.

[tdelorme]

My pyro needles had always stayed exactly the same. Both sides went up or down in sync. When the right side started moving up faster and coming down slower, I called the Detroit guy I trust. He said it was no big deal, more that likely some buildup on the sensor and to pay more attention to my oil and water temperatures. Several trips later they came back into sync and and are once agin the "pyro twins." It did get me in the habit of keeping a closer watch on the important gages.

[gmcbuffalo]

Thanks
DaleJ I did have a leaking right side exhaust awhile back and did replace the gasket. Maybe I should looking for a smaller leak?

Ii dirve the hills in Cruise control watching the tach, when it drops to 1700 I manually drop to a lower gear and go up when I am running 2100 again.

GregM

[dalej]

I drive pretty close to that, I shift just when the tach get to 1500 or just above.

[Loc]

The Prevost manual says not to exceed 1200 degrees on the pyros for an 8V92. I personally always tried to keep them to around 900 climbing hills which required gearing down and keeping the RPM's up. The 8V is a strong engine, but it does not like to get hot (I learned this the hard way). Keeping the temps a little lower will still get you up the hill and will keep the engine a lot happier. My pyro guages on the 8V92 were about 75 degrees (what appeared to be about 3/4 of the difference between the marks) different.