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Topic: Regulating water temp on mountain uphills (Read 1955 times) previous topic - next topic

Re: Regulating water temp on mountain uphills

Reply #20 –
Many RVs find out that winter driving and summer driver are way different. High altitude and high temperatures make cooling management important to keep your engine healthy.

Parent bore engines like the 5.9 Cummins, 3208 CAT will tolerate a little higher temperatures, Wet liner engines like the 8.3, 10.8 Cummins, Detroit 6V-92TA, 3176 CAT have sealing rings at the top and bottom of the wet sleeve and need a little more care when it comes to high engine temperatures.

I don't let the temp go past 200 without slowing/gearing down, keeping the rpm up at about 2000. If that does not do it, I drop another gear. As an example, we can charge up and out of Death Valley in the winter without a thought about temperature but in summer, I've had to go down to first gear to keep the temp down.

Pierce

Re: Regulating water temp on mountain uphills

Reply #21 –
Quote from: Barry & Cindy –
Overheating is a common result from letting coach drive itself. 'The Secret' is for us to drive coach.

Yes, the magic words.  You do NOT put in in "D", set cruise control and go-- unless you have a very thick wallet that you want slimmed down.

Re: Regulating water temp on mountain uphills

Reply #22 –
On our coach pushing the MODE button on the Allison touch pad makes the transmission much more willing to automatically down shift on grades, and to hold the lower gears longer when moving from slow speeds up through the gears to cruising speed.  I use MODE a lot in the hills cuz I like the feel of the Allison smoothly shifting up and down, and it makes the coach seem more lively.  A plus is the fact that it tends to keep the engine RPMs higher and coolant temps lower.



Re: Regulating water temp on mountain uphills

Reply #23 –
Quote from: wolfe10 –
That would ASSUME (yes, a big assumption) that all who want more power also know how to use it properly.  Sadly, in many cases an erroneous assumption.
Ding, Ding. You win the prize Brett. Having power and being able to manage said power is sadly a gap not often bridged. It might even be worse with a lower power engine. As most just throw a heavy rock on the throttle of a low power engine.

Re: Regulating water temp on mountain uphills

Reply #24 –
Quote from: Chuck & Jeannie –
On our coach pushing the MODE button on the Allison touch pad makes the transmission much more willing to automatically down shift on grades, and to hold the lower gears longer when moving from slow speeds up through the gears to cruising speed.  I use MODE a lot in the hills cuz I like the feel of the Allison smoothly shifting up and down, and it makes the coach seem more lively.  A plus is the fact that it tends to keep the engine RPMs higher and coolant temps lower.

While either Power or Economy mode can be the "primary" mode (i.e. when you turn the key that is the mode is goes into until you press the mode button, 99% of motorhomes come with power mode as the default and you have to push the mode button to get economy mode. Amy Allison dealer can set either power or economy mode to be the default setting.

In power mode, the transmission acts as you suggest-- keeps RPM higher on both up and down shifts under high throttle.

My approach is different-- more "manual transmission" more "driver control": I am in economy mode 99% of the time and use the down and up arrows to change that.  The only time I am in power mode is if I say "I am willing to pay a lot more fuel for a little more performance"-- passing on two lane roads for example where I don't want to take my eye off the road to upshift.

There is NO "correct way" to do this.  One has to balance what is best for THEM.

Re: Regulating water temp on mountain uphills

Reply #25 –
To add to the power vs lack of power. My 1977 GMC General had a 855 cu. in Cummins making 350 H.P. and weighed 53,000 lbs. It would go over the 405 grade here in Los Angeles at 55 MPH in high gear at partial throttle and got 7.5 MPG. My '81 International with a 466 cu. in. engine weighing 31,000 lbs. came over the same grade at 40 MPH 11th gear full throttle and only got 5 MPG. No replacement for displacement.

Re: Regulating water temp on mountain uphills

Reply #26 –
14 liters! What Cummins is that? N14? Supposed to be an excellent engine. Huge torque.

Pierce

Re: Regulating water temp on mountain uphills

Reply #27 –
Yup, since diesel do NOT need to have a stoichiometric fuel ratio (i.e. they can happily run LEAN) a large displacement engine at lighter throttle (and therefore more air than fuel mixture) does not give up MPG to a smaller engine at higher throttle making the same HP.

Re: Regulating water temp on mountain uphills

Reply #28 –
Quote from: Pierce & Gaylie Stewart –
14 liters! What Cummins is that? N14? Supposed to be an excellent engine. Huge torque.

Pierce
Never needed any parts so not sure what model they called it. In the business we just called them Cummins 350's same cu. in eventually went to 650 HP. with 2 turbos

Re: Regulating water temp on mountain uphills

Reply #29 –
Some Allison tranny's like ours are programed to normally be in power mode and when we press mode button tranny shifts change to economy staying in higher gears longer.

And some Allison's like Chuck's are programed to normally be in economy mode and when they press mode button, tranny changes to power mode.

I am not sure but maybe the smaller Cummins engines like our C8.3 normally are in power mode and larger M11 normally in economy mode.

BTW, we never change to economy as it tends to stress/lug engine a little more.  Our hill climbing downshifts are usually manual and paying little more for fuel is less expensive than fixing engine & tranny.
 

Re: Regulating water temp on mountain uphills

Reply #30 –
Quote from: wolfe10 –
Yup, since diesel do NOT need to have a stoichiometric fuel ratio (i.e. they can happily run LEAN) a large displacement engine at lighter throttle (and therefore more air than fuel mixture) does not give up MPG to a smaller engine at higher throttle making the same HP.
Brett has it. At idle, a diesel engine may burn 140 parts air to 1 part diesel. At full load, the ratio is more like 15/1.

Pierce