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Old 07-30-2016, 04:12 PM   #11
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There is never enough power, so yes there are times I wish the Seneca had a bit more. When I hit those grades towing my 1 ton dually I only pass when there is no traffic behind me or the passing traffic is slower than I know I can keep up with.
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Old 07-30-2016, 08:48 PM   #12
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Pretty much what everyone said. I tow a 7500 trailer and it does pretty well. I would like to have another 50 hp and 100-200 lbs -ft of T but it still does OK.
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Old 07-31-2016, 07:55 AM   #13
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Ok, so how do you safely get that extra power without destroying the engine and tranny. I have seen other motor homes with a 6.7 Cummins rated at 360hp and 800ftlbs torque. And additional 100ftlbs of torque could make a difference.
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Old 07-31-2016, 08:47 AM   #14
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Too fast? Since we are still employed we can't waste much time.lol. We typically drive 10 to 12 hour days.
Driving at 68 vs 58 [to make the math easy] will cost you about 100 miles on a 10 hour day. Probably more like 50 when you factor in a more consistent speed, at least 1 fewer fuel stop, and same time at rest stops. That extra speed really doesn't get you there that much quicker it just causes you more grief when you can't hold speed on a hill or the tank goes empty faster. Towing a trailer w/ATV is going to add load to the MH, especially when you are climbing a grade.

Slow down, forget cruise unless you're on flat ground, and use the tow feature on your tranny. You'll arrive at your destination pretty much the same time and for sure a whole lot more relaxed.
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Old 07-31-2016, 09:00 AM   #15
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Driving at 68 vs 58 [to make the math easy] will cost you about 100 miles on a 10 hour day. Probably more like 50 when you factor in a more consistent speed, at least 1 fewer fuel stop, and same time at rest stops. That extra speed really doesn't get you there that much quicker it just causes you more grief when you can't hold speed on a hill or the tank goes empty faster. Towing a trailer w/ATV is going to add load to the MH, especially when you are climbing a grade.

Slow down, forget cruise unless you're on flat ground, and use the tow feature on your tranny. You'll arrive at your destination pretty much the same time and for sure a whole lot more relaxed.
I agree, I'm not getting much further down the road, but when the speed limit is 75 running 58 is almost unsafe. I only run the cruise when we are on reasonably flat ground. It's easier to maintain a consistent speed. When I hit a grade I take the cruise off and kick it out of overdrive. The Allison tranny in the Seneca does not have a tow/haul mode that I am aware of.
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Old 07-31-2016, 09:25 AM   #16
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Ok, so how do you safely get that extra power without destroying the engine and tranny. I have seen other motor homes with a 6.7 Cummins rated at 360hp and 800ftlbs torque. And additional 100ftlbs of torque could make a difference.
The transmission is going to be the limiting factor. It is only rated for 340hp. The engine can safely make a lot more power. The other motorhomes have the 3000 series Allison transmission which has a higher HP and torque rating.
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Old 07-31-2016, 10:11 AM   #17
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pretty much did what everyone said. The cruise sets on 68 to 70. Just seemed like on very slight grades I was to the floor trying to keep it at 55. I always dropped it out of overdrive when my speed got below 55. Altitude shouldn't affect the diesel like it does a gas. Just curious if my experience was the same as others.
While the turbocharger creates its own atmosphere, it is limited in what it can do at altitude. Certainly a turbodiesel will retain more of its Hp rating at altitude than a normally aspirated gasser will, but you will still lose Hp and torque. Think about it for a moment. You are powering likely around 25,000 lbs up and down hills in less dense air at both high altitudes and high temperature, both of which are working against you. Your Hp is declining while your load (climbing hills) is increasing. The steeper the hill and the higher the altitude and temperature, the more horsepower you need to maintain a given speed. Is it insufficient if you have to drop below 68 on the way up? Depends on what you want. Unless you are interested in a system that will create much more Hp everywhere in order to maintain those speeds on hills in Colorado. Be prepared for lower fuel efficiency numbers pushing 380-400 Hp on the flats.

If you feel you need to maintain that speed, the only way to do it is boost the output of the powerplant. Once you do that, however, you may likely expose another weak link in the chain. The Allison is an awesome transmission, but it also has its design limitations. You could install a larger model of the Allison, or send yours to ATS in Colorado for a triple clutch rebuild to handle more power. Just be prepared to add cooling capacity at the same time.
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Old 07-31-2016, 01:13 PM   #18
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While the turbocharger creates its own atmosphere, it is limited in what it can do at altitude. Certainly a turbodiesel will retain more of its Hp rating at altitude than a normally aspirated gasser will, but you will still lose Hp and torque. Think about it for a moment. You are powering likely around 25,000 lbs up and down hills in less dense air at both high altitudes and high temperature, both of which are working against you. Your Hp is declining while your load (climbing hills) is increasing. The steeper the hill and the higher the altitude and temperature, the more horsepower you need to maintain a given speed. Is it insufficient if you have to drop below 68 on the way up? Depends on what you want. Unless you are interested in a system that will create much more Hp everywhere in order to maintain those speeds on hills in Colorado. Be prepared for lower fuel efficiency numbers pushing 380-400 Hp on the flats.

If you feel you need to maintain that speed, the only way to do it is boost the output of the powerplant. Once you do that, however, you may likely expose another weak link in the chain. The Allison is an awesome transmission, but it also has its design limitations. You could install a larger model of the Allison, or send yours to ATS in Colorado for a triple clutch rebuild to handle more power. Just be prepared to add cooling capacity at the same time.
I'm ok dropping below 68 on a grade. We went up Raton Pass in New Mexico at about 50mph. Slower than some faster than some. Down shifted to third and went right on up. That is to be expected on a long grade like that. I guess it's the slight inclines that I was a little disappointed with. I'm sure the outside temp had a huge effect on our performance. Headed back to Colorado in September, however this time I will be towing the jeep. Little more weight than the ATV. We will see how it does then.
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Old 07-31-2016, 02:01 PM   #19
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I'm ok dropping below 68 on a grade. We went up Raton Pass in New Mexico at about 50mph. Slower than some faster than some. Down shifted to third and went right on up. That is to be expected on a long grade like that. I guess it's the slight inclines that I was a little disappointed with. I'm sure the outside temp had a huge effect on our performance. Headed back to Colorado in September, however this time I will be towing the jeep. Little more weight than the ATV. We will see how it does then.
I tow my LJ behind the older Seneca (2006 Kodiak chassis with the 300Hp Duramax/Allison combination). Although I have yet to tow at high altitudes above 5000 ft, it seems to work reasonably well on grades in the 2000-3000 ft range. Soon, we will also be heading to Colorado with the Jeep in tow, and I'll have some experience to gauge with. Our friends have a 40 ft diesel pusher with about 400Hp. But that is 30000 lbs vs our Seneca, which is about 20000 lbs loaded. Should be interesting to see how it works out.
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Old 08-01-2016, 06:36 AM   #20
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For the readers with E450 based rigs, the tow/haul button is your friend in the hills. Also keep an eye on your throttle position and find a comfortable RPM where the motor doesn't sound like it wants to devour your gas tank. Cruise control in the hills will cause a lot of keeping it in gears for far too long, like when you crest a hill and it won't bump up a gear...

Tow/haul will also favor engine braking on the down hill side of things too.
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