Community Forums

lms1943 · 03-01-2012, 10:53 AM

We are new to class A motorhomes (2001 XC360 Airstream with a 300Cat/Allison. Peviously we had a 30' Airstream TT and a 2011 Dodge deisel, and had no problems with a 10-12 % grades. We are flat towing a Mini Cooper (weight 2400#). My question is what can I expect with the motorhome in the mountains

Thank You

jlfbatonrg · 03-01-2012, 12:22 PM

The key is horsepower to weight ratio. Your Cat has good torque, but I suspect you are pulling much more weight in your class A than in your TT. Most importantly, watch your exhaust gas temperature and your engine temperature. You don't want these temps to go high. If you're seeing the temperatures increase, shift the transmission to a lower gear, and try to keep your engine rpms around 2000. This should keep your temps in an safe range.

Jim

GaryKD · 03-01-2012, 01:36 PM

Hi lams,
What you'll need is patience. The longer the climb the more patience you'll need. Momentum is everything. Keep the momentum up as you begin the climb. If that is not possible, move to the right lane and the coach will tell you how fast it will go. Watch the engine temp and if it rises to an uncomfortable level, down shift the tranny. Like posted earlier, around 2K RPM should keep the engine cool. This is the most important thing.

Mike Canter · 03-01-2012, 02:00 PM

According to the specs what I believe you have is a 3126 CAT engine produces a peak of 300 HP at 2200 RPM and max torque at 1440 rpm. Torque only helps you in accelaration especially from a standstill. What gets you up those steep grades is pure horsepower. Try once to go up a steep 10% grade at your peak torque rpm of 1440 and see where that gets you. For those 10-12% grades you are going to have to be as has already been said at 2200 rpm. It is governed at 2400 rpm so you need to stay off of that. Select the gear you want for the speed you want. My guess is for that 10-12% grade you are going to need to be in 3rd gear at about 35 mph at 2200 rpm and you should climb all day.

They also say your best economy (sweet spot) for MPG is 2000 rpm at 60-62 mph.

Jim_HiTek · 03-01-2012, 08:13 PM

Rule of thumb is 1 HP for each 100lbs of weight, minimum (includes your toad). But, many people are happy with going up a hill at 35-45MPH. I don't have a problem with it, usually, since I'm retired and not in that big of a hurry. Mine is 115lbs/HP. A little underpowered. (Which I've since improved with propane fumigation since topping a hill at just 25MPH is a little too slow, even for me).

I do try to be a good road neighbor and pull over for following traffic when convenient.

jauguston · 03-02-2012, 09:24 AM

If your coach has a rear radiator check it or have someone check the CAC and radiator for dirt accumulation. It should be cleaned at least once a year. Find the slobber tube that vents the crankcase fumes and be sure it has a extension that exits behind and below the CAC and radiator. Those fumes mix with road dirt and form a sticky substance that plugs your CAC and radiator. Unless someone has added one you will not have a exhaust gas temperature gauge. When pulling a hill keep the RPM UP-2200-2300 at least. That is where you make the most horsepower and the cooling fan moves the most air through your radiator. Using Econo mode in the transmission forces it to keep rpm low. I don't recommend using it. I have tried both ways and see no advantage fuel mileage wise.

Jim

distaff · 03-02-2012, 02:51 PM

I can't say what you will experience - I drive in the Rockies frequently. I am usually able to keep 50mph but I have more engine, but also more coach (and I pull a Suburban). Cooling is important, so pay attention to the condition of your rad and pump as noted elsewhere.

I note that I have never seen either a 10 or 12% grade. The steepest I have ever seen is 8%.

Also note that up can cause you to slow, and possibly over heat, but DOWN can scare the wits out of you.