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Engine temps
I was on I-77 today coming home from the gun show, started the climb up fancy gap, a long 7 mile climb and as always just left my tranny in cruise control as always on this climb. Today I noticed a couple things I had not seen the engine temp went to 210 and of course would go back to 180 and then back to 210, it was 95 outside! Also the speed usually stays about 55 today it went to 50mph on the climb, after reaching the crest temps still went from 210 to 180, just had it serviced is this something I need to be concerned about Gary
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14 Replies
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Gary,
I will defer to others smarter than I… but were your fuel, and waters consistent with what they have been in the past… Could the differences be attributed to additional weight?
Bill
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Sounds normal to me Gary.
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Sounds normal Gary. In fact what you are seeing is actually verification that your DDEC is controlling the fan clutch which is cycling properly to keep temps within the proper range.
As to the speed, the higher the temps, the lower the available HP because the air is less dense. When it is cold your hill climbing speed will increase.
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Thank you for the info, yes I was carrying probably 1000 lbs more than usual, and Jon the check engine light I called you about a couple weeks ago , after shuting the engine down and restarting I have not seen the telltale again, Gary
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Channeling my inner nerd… :), humid air is less dense and offers less cooling. As Jon said, hot air is less dense and offers less cooling, and so, hot humid air is even more less dense and offers even less cooling than hot air. We have no choice but to back off the power on ascents lest we overwhelm our cooling systems.
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Air Density makes a big difference.
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Actually Gary’s temps were doing what was expected and there was no danger of overheating based on the fac the temps were cycling up and down. It is when the temps slowly climb as the hill continues that signals a need to first back out of it a little, and second to have the cooling system checked as the radiator may be getting build up.
But the loss of speed compared to normal is because the engine just cannot make enough power because it isn’t getting enough air. I should say enough pounds of air as it does when the outside temps are lower.
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Old trucking habits are hard to break. I select the gears manually and pick the gear that allows me to keep about 3/4 throttle and climb the hill at whatever speed that makes. Yes I know you can stand on it both feet flat on the floor, but I would rather control the rpm’s.
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That’s where Tom and I have different driving styles. I drive slower than he does, but when I know I have a long steep hill I approach the bottom carrying a little more speed, I drop down a gear, put the transmission in performance mode and let the cruise control do its thing. Then I just sit and watch the temp gauge. As long as it is cycling up and down everything is OK.
For those unaware the cruise control will give a little more HP for hill climbing than your foot on the pedal.
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RE: For those unaware the cruise will give a little more HP for hill climbing than your foot on the pedal
Jon,
That’s interesting, can you explain how the cruise control can give more HP than your foot on the pedal as you described when climbing hills, please?
Thanks, Diane
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Diane, Probably because the computer knows what’s best for the engine and load. One of the smart guys will answer shortly. I use the cruise control all the time on my 2 stroke and seems like it runs and stays cooler better in this Texas heat.
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Certain DDEC set ups will allow the engine to produce more horse power when cruise is engaged. Using cruise on steep grades IMO is not wise, the cruise is not intelligent, it just tries to maintain a speed and will throw whatever it can at the engine to do that.
If nothing else it will be the least fuel efficient way up a hill…
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In commercial service, use of cruise control is encouraged because it is generally more fuel efficient, safer (prevents accidental speeding), and provides a better ride experience for the passengers. I’ve been told the extra HP is a “reward” to the driver to encourage use of cruise control.
The DDEC ecu allows your engine to use its full horsepower only when cruise is engaged. Without the cruise on, you can’t get the max HP from your engine, you get about 15 HP less. It’s the same process used by DDEC to de-rate or de-power your engine in certain “check engine” situations such as overheat.
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Bryan is correct. But fear not because while cruise control is a brainless function, DDEC is always working behind the scenes to protect your engine.
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