DD engine temps

[ChuckMC8]

On my 750 mile vacation thru the Tennessee mountains, I noticed that my 8V71TA ran noticibaly better at 190 degrees than at 180 (my target temp) I did not get over 190 degrees.
   So, what is too hot? if its 200, theres a very small window there from were it runs best and whats too hot. The book says 170to 195 normal temp range.
At what temp is it necessary to pull over and cool down?

[JackConrad]

Chuck,
   My understanding, which is not always correct, is that damage oocurs when the water turns to steam because the steam cannot absorb and carry away the heat from the engine. Since these buses only have about a 3 PSI pressure cap, steam probably starts forming at about 215,  so I would think 210 would be the absolute high temp and probably better to limit the temp to 205. Maybe someone with some BTDT experience can add more information.  Jack

[niles500]

These are max temps according to DD


CI & Gen.- 210

Mil. & Emer. - 230

Doesn't specify buses but I'd say 210 is max

HTH

[edvanland]

My MCI 7 with a 8V92 and 740 Allison will shut down at 210.  When mine gets to 200 I am looking for a spot to pull of the road.  I have new radiators, a extra radiator and misting system. At 200 I slow down even more and just hope there is a wide stop or off ramp.
ED
MCI 7

[RJ]

If the alarmastats are working properly, and haven't been by-passed, the two-strokes should shut down at 205 - 210^o.

Dropping a gear or two to keep the engine in the sweet spot of 1700 - 1900 rpm and still be able to accelerate w/o black smoke, even if it's 100^o outside, will keep the engine in the 190 range.

BTDT80K/YR

FWIW & HTH. . .

[HighTechRedneck]

Not an MCI and I'm not sure if 8V71TA's run at a different temp than 6V92T's but from the maintenance manual for my 6V92T powered RTS:

[pvcces]

Chuck, what you're talking about is what they did deliberately when they were building the Ketchikan airport in the 70s. When the heavies were pulling a grade, the temps would start to climb, and it made people servous, but they didn't seem to have any trouble from it.

They said they were doing it because the engines ran better.

There's something else going on in this field, too. Some people are claiming that they are getting better mileage and no boiling by using straight polypylene glycol. They claim that engine temps run a little higher, but with a boiling point of 370 F or so, there's no risk of losing cooling because of steam pockets.

While it's expensive to fill the system, it's not supposed to deteriorate from use or age.

For what it's worth.

Tom Caffrey

[HighTechRedneck]

There's something else going on in this field, too. Some people are claiming that they are getting better mileage and no boiling by using straight polypylene glycol. They claim that engine temps run a little higher, but with a boiling point of 370 F or so, there's no risk of losing cooling because of steam pockets.

While it's expensive to fill the system, it's not supposed to deteriorate from use or age.

While that makes it virtually boil proof, it doesn't transfer heat as well.  New engines are running at higher coolant pressures allowing higher operating temps while still running a water/antifreeze mix.