Gas vs Diesel (I've read the FAQs!!)

[ZagiFlyer]

Hello to All,

We *still* have the Thor Jazz in my sig, and it's still a going concern, but the wife is up for a change and "we" are wondering if a Class A would fit the bill. Many of our trips are long-range and we'd like to be comfortable driving cross-country -- my daughter has informed me that the back seat of an extended cab is not making her back happy on 6, 8, 12 hour drives.

Keeping in mind that we're coming from a 5th-wheel towed by a 6.0L gasser, my wife is under the impression that a DP will fly up the Grapevine (6% grade) at 50-60 mph. Is this true? I wouldn't expect it, since the HP/torque required to move 26,000 lb up a 6% grade at 50 mph would be enormous.

I've read the FAQs and searched the forums, but I didn't find anything specific enough so here is my question:

Thinking along lines of the Grapevine or other steep/long grades:

• At what speed are you 36-40 ft. DPs getting up steeper grades
• At what speeds are you 36 ft. gas Class A's getting up steeper grades?

For comparison, my rig gets us up the Grapevine at about 35 mph, but it's struggling mightily at 4400 RPM.

I need to set her expectations realistically if I am to acquire any semblance of domestic tranquility when we upgrade.

Thanks!

[mike_brez]

All the talk about going up I would be a little more concerned about going down.

[holstein13]

I haven't driven the Grapevine, but I've been on plenty of other mountain passes while driving through the rockies in our 2011 Storm with 352 HP and 457 pounds of torque (or 45.7 lbs per cylinder).

Had no troubles going up the mountains between 50 and 60 mph.

Soon I'll be upgrading to a King Aire with 1,950 pounds of torque (or 325 lbs of torque per cylinder). Of course the King Aire is 2.5 times as heavy; but given the comments on this thread, I think it will do just fine.

[JimM68]

rgatijnet1 wrote:
To make the decision easier for the OP.....I do not know of any Class A built in the last 10 years, that will NOT make it to the top of any Western highway pass, whether it has a gasoline or a diesel engine. They all will get you to your destination.

AMEN. The best travel is a class A motorhome. Best of the best is a DP. Get up and walk around when you want to, go potty, make a sandwich, heck in most states passengers can even enjoy an adult beverage.

And the view out that huge windshield while our knight glides quietly and effortlessly down the highway is just the best there is.

[rgatijnet1]

To make the decision easier for the OP.....I do not know of any Class A built in the last 10 years, that will NOT make it to the top of any Western highway pass, whether it has a gasoline or a diesel engine. They all will get you to your destination.

[Daveinet]

Bruce Brown wrote:
Not the Grape Vine, but Rt 26 out of Johnson City, Tn;
2000 V10 gasser MH - brought to it's knees, 30 MPH tops
2003 DP w/ Cat 3126, 330HP/860 TQ - 55 MPH
...
If you're ready for a DP skip the HP number and look at the torque.

I'd like to see you reconcile your statements with the post from Greyhost above. My guess is you have not considered the weight of either coach, or the altitude. An old V10 has serious breathing problems, which will be exacerbated by any kind of altitude. No doubt that is a big factor, so you argument of torque doesn't hold water. (never mind that it defies physics)

docj wrote:
I fully understand that it is the HP to weight ratio that governs how fast you can climb a hill, but the torque of a big block diesel is what makes the driving experience so enjoyable.

This statement probably more accurately describes how one should approach diesel vs gas, or high torque vs high HP. High torque means you don't downshift to achieve maximum engine HP. High HP/low TQ achieves maximum HP by downshifting. HP to weight ratio determines how fast you will go up a hill. The torque rating will tell you how often you downshift to achieve that power.

[Greyghost]

I can give 2 recent examples of a gasser and a DP climbing the Grapevine.

21,000 LB gasser 35.5' 8.1 ltr Vortec engine on a Worhorse chassis. 62 mph climbing the Grapevine (GV). Due to front engine a lot of fan noise from the cooling fans. Calculated 7.2 - 7.8 mpg.

32,500 LB DP 40' 400HP Cummins on a Spartan chassis. The 6 speed Allison restricted me to 50 mph all the way to the top of the GV. No fan noise. Calculated 7.2 mpg. Eisenhower pass going west towards Grand Junction 50 mph on all grades.

The big difference is the air ride of the DP vs the sprung suspension of the gasser. There's also at lot less noise when climbing, on straight roads both were equal with regards to the noise factor.

Last but not least is the Engine Brake on the DP. Going down the GV in the gasser it was a constant management of transmission and brakes. Going down in the DP I only had to apply the brakes once on that last straight stretch to the bottom.

Seating in either one is usually limited to the driver and navigator. Other passengers will have to sit or law down on a couch. In some coaches the dinette will have seat belts which would allow the passenger to sit in the dinette.

We've had a 19' fifth wheel a 32' and 35.5' gasser and now the DP. This will be our last coach as we haven't seen anything that we like better.

[OhhWell]

LVJ58 wrote:
When we bought our current class A coach our prime concern was a comfortable livable floor plan that would suit our needs as it would be our home away from home.

We really weren't overly concerned with whether it was diesel or gas powered as we would be spending more time living in it than driving it.

Over the 14 years we've had it, haven't been disappointed as it has served our needs well.

Granted, we don't go blazing up those 7+% mountain grades, but it always gets us where we're going.

I do most of my own routine maintenance, i.e., oil/filter change, lube etc. at a cost under $50.00

Bottom line, get whatever type coach that you'll be comfortable with and enjoy it.

Best of luck and safe travels....:)

Out of curiosity, what speed does your coach take a 6-7% grade at? Ours should be pretty similar power to weight.

[LVJ58]

When we bought our current class A coach our prime concern was a comfortable livable floor plan that would suit our needs as it would be our home away from home.

We really weren't overly concerned with whether it was diesel or gas powered as we would be spending more time living in it than driving it.

Over the 14 years we've had it, haven't been disappointed as it has served our needs well.

Granted, we don't go blazing up those 7+% mountain grades, but it always gets us where we're going.

I do most of my own routine maintenance, i.e., oil/filter change, lube etc. at a cost under $50.00

Bottom line, get whatever type coach that you'll be comfortable with and enjoy it.

Best of luck and safe travels....:)

[KO]

I have nothing to add to the diesel climbing except my experience. I have driven my 38 ft 34,000 LB RV (powered by a CAT 330) on I-70 over Vail Pass towing my car. I think this is one of the hardest long climbs you will encounter on the intersate system. I had plenty of power going up and was passing many other vehicles.
The other part I enjoy is the braking capability the Allison 6 speed transmission provides (not to mention the engine retard). I have learned to pay more attention to coming down then going up.

[msmith1199]

ZagiFlyer wrote:
Hello to All,

We *still* have the Thor Jazz in my sig, and it's still a going concern, but the wife is up for a change and "we" are wondering if a Class A would fit the bill. Many of our trips are long-range and we'd like to be comfortable driving cross-country -- my daughter has informed me that the back seat of an extended cab is not making her back happy on 6, 8, 12 hour drives.

Keeping in mind that we're coming from a 5th-wheel towed by a 6.0L gasser, my wife is under the impression that a DP will fly up the Grapevine (6% grade) at 50-60 mph. Is this true? I wouldn't expect it, since the HP/torque required to move 26,000 lb up a 6% grade at 50 mph would be enormous.

I've read the FAQs and searched the forums, but I didn't find anything specific enough so here is my question:

Thinking along lines of the Grapevine or other steep/long grades:

• At what speed are you 36-40 ft. DPs getting up steeper grades
• At what speeds are you 36 ft. gas Class A's getting up steeper grades?

For comparison, my rig gets us up the Grapevine at about 35 mph, but it's struggling mightily at 4400 RPM.

I need to set her expectations realistically if I am to acquire any semblance of domestic tranquility when we upgrade.

Thanks!

See my rig in my sig. I don't drop below 45 on the Grapevine and I have a fairly heavy toad in the Dodge Dakota. I haven't tried it without the toad.

[dubdub07]

You can sure see who climbs on a regular basis and who does not. Living in CA you probably want to know what mountain climbing is all about in a class A DP. We camp with two of our three and sometimes all three and my grown son (22). They all have the same issue with the truck....it sucks to be in the truck for 12 hours. I drive and drive and drive and like night driving....so in a truck we were never in the FW, always in the truck.

Enter the DP. 40 feet of smooth luxury. TVs, videos, fridge, couch, table, beds, potty......now everyone wants to go. We are always in the coach when travelling and I can drive until I want to stop. First question asked in the morning.....where are we? No one but me knows how long I travelled.....

7-8% grades the norm here, with Jeep; 38K combined, 7.5 MPG, 45 MPH. W/O Jeep, 33K, 8 MPG, 55 MPH. Most times speed is limited by cornering, not grade. Never had a gasser pass me or another DP for that matter. FW can get up the hills pretty quick and may pass me. Trucker are 25MPH in slow lane....so I am thinking I am right on track with most. As far as 10MPG, that is a fantasy unless your whole trip is downhill.

dub

[WayneLee]

As others have said, there are a lot of factors that come into play on our Western mountains that our Eastern brothers don't encounter. To answer your specific question, it's been years since I went up the grapevine (Tejon Pass) in my current coach. If I remember correctly, I was able to easily make it at 55 mph towing my 4,700 lb Hummer H3. Tejon pass is around 4,100 ft elevation.

More recently, I have gone to Colorado on I70, going over Vail Pass a couple of times. At 11,000 ft elevation, the pass will take a toll on any RV. I was able to keep my coach at 50-55 mph and passing 18 wheelers and other RV's without any problem. And no problem with Donner Pass on I80 in California at 7,100 ft elevation.

In Southern California, I have gone over the Cajon summit (3,800 ft elevation) on I15 in San Bernardino at 50-55 without any problem. I don't try to break speed records on these passes, but keep my speed at the 50-55 mph range which is faster than most RV's and 18 wheelers, but slower than most of the cars.

A DP with our higher HP and higher torque engines can make it over these mountain passes without many problems. And, yes, I have been passed by Country Coaches and Prevost's with their 500 to 600 hp engines and double my torque.

[valhalla360]

The two questions (diesel vs gas and 5th wheel vs MH) are almost completely unrelated.

5W vs MH has almost no bearing on how fast you can go up a hill.

HP and torque determine how fast you can go up a hill (assuming a similarly sized overall rig).

Assuming you like your current 5er, here's a relatively cheap suggestion: Find a 2005'ish, PU with a diesel. In decent shape, you are probably looking at $12-16k for the truck. See how that pulls the same trailer up the grapevine. I'm betting, your whole opinion changes.
- If it works, you've solved your problem for a whole lot less than a new diesel pusher.
- If it doesn't, you should be able to get better than 90% back by selling the truck when you go to buy the MH.

[krivanj]

One thing that no one has mentionsd is the downhill grade. We had an old class A with a Ford 460 and it scared us in the Smokies and out toward Glacier NP. we bought a DP and everything changed with the exhaust brake. It also went right up the hills (isc Cummins 330hp, 27000 lb).
We traded on a new class c with the Ford V10 with the tow haul switch and did the same routes including all of Alaska and had no problems climbing hills (17500 lbs plus a 3000 tow car). It went from cozy to cramped so now we have another DP that we are just trying out, but it seems to be even better at hills than our last one.

[docj]

We run the kind of setup the OP is inquiring about. We have a 32,000 lb MH with a CAT C-12 with 425HP and 1550 ft-lbs of torque. With our toad we are less than 37,000 lbs. I'll be the first to admit that this much power to weight isn't necessary, but it sure is nice. We've not driven the Grapevine, but we did climb Cabbage Hill in OR and never went below ~53 mph.

I fully understand that it is the HP to weight ratio that governs how fast you can climb a hill, but the torque of a big block diesel is what makes the driving experience so enjoyable. With that much torque the MH drives not all that much different than a car in terms of how it accelerates from a stop.