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Old 07-30-2016, 09:11 AM   #1
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Does the Seneca have enough power

We just got back from a four wheeling trip to Colorado. I haven't put the Seneca on the scales yet, but I don't think we were packed real heavy. I had 1/3 fresh water and empty black and grey tanks. I was towing a Can Am Maverick side by side on a 12' aluminum trailer. About 2500lbs. We were traveling on I-40 from little rock to Colorado. It just seemed like we were struggling a bit to maintain speed on any kind of grade. Temp shot up and fan came on every time we hit a hill. If it was a long grade the fan may come on two to three times before we got over the hill. I had the cruise set at 68mph. The outside temps were 100 plus across western Oklahoma and Texas panhandle. I'm sure that had an effect on the temp and fan, but I wouldn't think that would effect power. Makes me wonder if I will be able to tow my jeep unlimited when we get ready to take it. We had a V10 class A prior to getting the Seneca. I was hoping for a power upgrade moving to the Seneca, but not sure we got much of an upgrade. However we never took the class A out west so it's hard to compare. Just curious what others think.

What does everyone else tow, and how does the Seneca handle the weight?
Is there anyway to get more power out of the 6.7Cummins? Is the tranny the limiting issue? I notice there is a 6.7 Cummins listed at 360hp and 800 torque. Anyway to get to that number with a flash?
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Old 07-30-2016, 09:54 AM   #2
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"...cruise set at 68 MPH" ??? Are you also inclined to take a 3 week holiday in 1 week?
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Old 07-30-2016, 10:52 AM   #3
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The Seneca has a pretty good power to weight ratio but if you're expecting the rig to hold 68 going up long and/or steep grades, prepare to be disappointed. A V10 would be screaming going up the same grades. Going up long grades in overdrive you should expect speed to drop off plus you will risk overheating the trans. On steep or long grades take the trans out of overdrive. Keep the revs up. And take it out of cruise. Expect to be about in the same speed class as semi's. I find that I am faster than some uphill and slower than others.

For a price you can get more power in a Dynamax Force HD or DX3.

Yeah that fan is noisy but you'll find that in 100 degree temps it will kick in every now and then.
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Old 07-30-2016, 11:06 AM   #4
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Our Memorial Weekend trip consisted of a fully loaded Seneca FK towing our 28' flatbed of ATV's and equipment. We scaled at 8640 Front Axle, 16,020 Rear Axle and 3700 on the Trailer Dual Axles. Total = 28,360 combined.

Take what Walt said in the post above - it will climb the grades just fine if you take the Overdrive OFF and take the Cruise OFF. We rolled 70-75 most of the trip, but you should expect to drop out of OD and slow down a little bit on the grades. The cooling system is going to kick in at 200 degrees, and it is like any other Medium Duty Truck/Tractor with the extra cooling noise - especially with outside temps 100.
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Old 07-30-2016, 12:37 PM   #5
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Also keep in mind you are at altitude, where the air is thinner. On hot days, thinner still and lower on oxygen. Even with a turbocharger, it's starting at a very low point in terms of cooling air and combustion air. Expect to drop HP, and when you simply keep the hammer down expecting everything the engine has, and it cannot produce the power you are demanding due to a lack of oxygen, you will produce more heat as well. It will get rid of less heat because of the ambient temperature and because of the thinner air. From a purely technical perspective, this is how engines are overheated and destroyed. Consider this a cheap lesson in not expecting the impossible from your powertrain, assuming you got it back home in one piece.
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Old 07-30-2016, 12:39 PM   #6
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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.
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Old 07-30-2016, 12:41 PM   #7
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"...cruise set at 68 MPH" ??? Are you also inclined to take a 3 week holiday in 1 week?
Too fast? Since we are still employed we can't waste much time.lol. We typically drive 10 to 12 hour days.
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Old 07-30-2016, 12:48 PM   #8
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Originally Posted by SloPoke View Post
Our Memorial Weekend trip consisted of a fully loaded Seneca FK towing our 28' flatbed of ATV's and equipment. We scaled at 8640 Front Axle, 16,020 Rear Axle and 3700 on the Trailer Dual Axles. Total = 28,360 combined.

Take what Walt said in the post above - it will climb the grades just fine if you take the Overdrive OFF and take the Cruise OFF. We rolled 70-75 most of the trip, but you should expect to drop out of OD and slow down a little bit on the grades. The cooling system is going to kick in at 200 degrees, and it is like any other Medium Duty Truck/Tractor with the extra cooling noise - especially with outside temps 100.


I'm sorry if this is a dumb question....is there a way to manually switch out of OD on e450?


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Old 07-30-2016, 01:50 PM   #9
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Switch for E450 OD

On our 2004 E450 there is a button at the end of the "PND21" lever to deselect/select OD.
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Old 07-30-2016, 01:51 PM   #10
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Mine is tow/haul.


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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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