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!

[TucsonJim]

dubdub07 wrote:

Daveinet wrote:

Bruce Brown wrote:


Do you want a 300HP/600#/ft diesel or do you want a 300/950#/ft diesel?

Me? Ignorant as I may be I'm skipping the HP number and going for more torque.

Your conclusion is a little misleading, as both HP numbers are the same. Of course if the HP is the same, the higher torque is more desirable. But the OP's question was about the speed an RV will go up a given hill. The torque rating has ZERO to do with the answer to that question. This is absolute indisputable fact.

Know what else is indisputable? My co-worker bought a new version of my DP with the new ISL. I have the ISC. His is 380/1150 and mine is 380/1050. His goes up the passes faster than mine. This would indicate that torque indeed is a factor and that ZERO to do with the OP is actually....disputable.

dub

It would be interesting to note the weight difference between the two units.

[dubdub07]

Daveinet wrote:

Bruce Brown wrote:


Do you want a 300HP/600#/ft diesel or do you want a 300/950#/ft diesel?

Me? Ignorant as I may be I'm skipping the HP number and going for more torque.

Your conclusion is a little misleading, as both HP numbers are the same. Of course if the HP is the same, the higher torque is more desirable. But the OP's question was about the speed an RV will go up a given hill. The torque rating has ZERO to do with the answer to that question. This is absolute indisputable fact.

Know what else is indisputable? My co-worker bought a new version of my DP with the new ISL. I have the ISC. His is 380/1150 and mine is 380/1050. His goes up the passes faster than mine. This would indicate that torque indeed is a factor and that ZERO to do with the OP is actually....disputable.

dub

[docj]

Daveinet wrote:

Bruce Brown wrote:


Do you want a 300HP/600#/ft diesel or do you want a 300/950#/ft diesel?

Me? Ignorant as I may be I'm skipping the HP number and going for more torque.

Your conclusion is a little misleading, as both HP numbers are the same. Of course if the HP is the same, the higher torque is more desirable. But the OP's question was about the speed an RV will go up a given hill. The torque rating has ZERO to do with the answer to that question. This is absolute indisputable fact.

I totally agree and, for once, we should all be on the same page.

More torque can make for a more pleasurable driving experience, but even that is subjective and is most noticed by people for whom driving is "fun" and not just a way to get from place to place.

I will admit that I love to drive and when I was a teenager my folks had a Ford powered by the old 352 V8 (not to be confused with the 351 Windsor and Cleveland V8's of the 70's). The 352 was basically a truck engine put into Ford's cars to fill a marketing hole at the low end of the V8 range. It was a horrible gas guzzler and my parents brought it back to the dealer several times to see if they could do something to improve the mpg. But to make up for these shortcomings it had a huge amount of low-end torque (just what you want in a truck engine). Looking back at it, I realize that my mother could have gotten somewhat better gas mileage if she hadn't enjoyed punching the accelerator so much! By comparison a few years later we bought my Mustang with a 289 V8 and it seemed anemic by comparison, even though the HP numbers weren't all that different. Plain and simple, torque makes driving fun!:)

[Daveinet]

Bruce Brown wrote:


Do you want a 300HP/600#/ft diesel or do you want a 300/950#/ft diesel?

Me? Ignorant as I may be I'm skipping the HP number and going for more torque.

Your conclusion is a little misleading, as both HP numbers are the same. Of course if the HP is the same, the higher torque is more desirable. But the OP's question was about the speed an RV will go up a given hill. The torque rating has ZERO to do with the answer to that question. This is absolute indisputable fact.

[Bruce_Brown]

OhhWell wrote:

Bruce Brown wrote:

Daveinet wrote:

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)

I have no idea why he was limited to 50 MPH in his diesel - ours does not.

As to the rest, I'm offering real world expirence, not a physiscs class. If it makes you feel better to say I'm wrong then OK, make yourself happy.

If you want to buy a low torque engine go ahead, I won't.

We've owned gassers and diesels in both our MH's and pickups. Gas has it's place, but when it comes to hard work I'll take a diesel every time, and the bigger the better.

Nothing wrong with loving a high torque engine as they make for a very pleasant driving experience. When you say ignorant things like ignore the HP number, it's all about torque; unfortunately, you are doing a disservice in addition to being just plain wrong.

Ask yourself;

Do you want a 300HP/600#/ft diesel or do you want a 300/950#/ft diesel?

Me? Ignorant as I may be I'm skipping the HP number and going for more torque.

Take a look at the torque curves and you'll know why. :W Where an engine makes power is just as important as how much it makes. A low torque diesel just can't offer what a high torque one can. And until you've owned both (we have) you just won't understand.

[mena661]

The OP already got his answer and checked out back on page 3.

[Medico]

The DP will give a much better ride IMO. My heavy 45 foot DP will pull the big grades at about 45 to 50 depending on other conditions while towing my Jeep. It's a comfortable, quiet ride!

[Greyghost]

Bruce Brown wrote:
I have no idea why he was limited to 50 MPH in his diesel - ours does not.

I have no idea as well. My first trip south on I5 I put the pedal to the metal and once I hit 50 on the climb up the Grape Vine there was no further acceleration. I believe that it's an RPM issue that controls the speed. I can have the cruise set to 65 and it drops down to 50 on the hills. I just figured that the Allison was programmed that way to protect the engine and transmission. Now I just let it do it's thing. I'm in no hurry, I'm finally retired. :B

[OhhWell]

Bruce Brown wrote:

Daveinet wrote:

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)

I have no idea why he was limited to 50 MPH in his diesel - ours does not.

As to the rest, I'm offering real world expirence, not a physiscs class. If it makes you feel better to say I'm wrong then OK, make yourself happy.

If you want to buy a low torque engine go ahead, I won't.

We've owned gassers and diesels in both our MH's and pickups. Gas has it's place, but when it comes to hard work I'll take a diesel every time, and the bigger the better.

Nothing wrong with loving a high torque engine as they make for a very pleasant driving experience. When you say ignorant things like ignore the HP number, it's all about torque; unfortunately, you are doing a disservice in addition to being just plain wrong.

[OhhWell]

bluwtr49 wrote:
In an earlier comment someone brought up the going doing the hill once you've gotten to the top.....and that is a valid point since eventually you will go down.

Now, I don't know what a gasser does for engine braking but if you have never had the experience of a 2 or 3 speed Jake brake...that is something you need to try. Besides the cool sound you may never need to touch the service brakes on even the steepest grade.

On my Cat, I can't even keep in high all the time as it slows down to much. Need to toggle between low and high as needed.

Just something to think about.

A gas engine powered coach can descend just fine but it certainly isn't the same as having an exhaust brake. You just have to downshift properly and sometimes be ok with going a bit slower than you would like, just like on the way up the hill! You have to use the real brakes here and there as well but if you have a head on your shoulders, it's not bad.

[Bruce_Brown]

Daveinet wrote:

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)

I have no idea why he was limited to 50 MPH in his diesel - ours does not.

As to the rest, I'm offering real world expirence, not a physiscs class. If it makes you feel better to say I'm wrong then OK, make yourself happy.

If you want to buy a low torque engine go ahead, I won't.

We've owned gassers and diesels in both our MH's and pickups. Gas has it's place, but when it comes to hard work I'll take a diesel every time, and the bigger the better.

[bluwtr49]

In an earlier comment someone brought up the going doing the hill once you've gotten to the top.....and that is a valid point since eventually you will go down.

Now, I don't know what a gasser does for engine braking but if you have never had the experience of a 2 or 3 speed Jake brake...that is something you need to try. Besides the cool sound you may never need to touch the service brakes on even the steepest grade.

On my Cat, I can't even keep in high all the time as it slows down to much. Need to toggle between low and high as needed.

Just something to think about.

[rgatijnet1]

MRUSA wrote:

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.

So will a motorcycle, but that completely misses the point of this thread. The OP didn't ask if he could make it to the top, he was asking what the experience would be like while he does it.

Here is his first sentence, that you must have missed......
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.

[MRUSA]

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.

So will a motorcycle, but that completely misses the point of this thread. The OP didn't ask if he could make it to the top, he was asking what the experience would be like while he does it.

[ZagiFlyer]

Hello to All,

WOW! As always, the RV forum delivers! I want you to know that I sincerely appreciate all the answers you posted - you completely answered the question.

We can close this thread now, I have my answer.

Thanks again!