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Old 07-23-2021, 05:15 AM   #1
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6.7 just isn't enough engine

I'm not sure if any of the Jayco factory people read these threads or not (they should)

I am currently looking to buy a Showhauler or Renegade motorhome similarly configured as the Seneca 37FS I currently own for one simple reason - If you are towing anything, the 6.7 Cummins in the Seneca just isn't quite enough motor. It's great in my 3500 Ram, but it doesn't weigh 25k+ by itself.

If the Seneca's had the 8.3 Cummins rather than the 6.7 I feel this would be the perfect RV for a family. The way the 6.7 is built that's in the Seneca (industrial version) , it is hardly any difference in size physically than the 8.3. I own both in trucks for my business. The 8.3 has a HUGE amount of more power.

Don't get me wrong, if the Seneca is not towing I can stay in the hammer lane in most situations. But if you have a trailer behind it with a jeep or you have some side by sides (which in total do not weigh 5000 lbs) you better be ready to go into creep mode if you hit any hill what so ever. I have found the worst hills for the Seneca aren't big ones in the mountains (I expect these to slow me down), but the slight long hills in the Dakota's, Nebraska and Kansas. These little hills kill it.

I did a full delete on the Seneca prior to this trip out west to ride Sie by Sides. It helped a little. I did it so I wouldn't get stranded because of DEF issues like I did on the last trip, not for increased HP. I do see about 1.5 mpg difference now.

Just my 10 cents.

Alan
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Old 07-23-2021, 05:39 AM   #2
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Originally Posted by Clayduster71 View Post
I'm not sure if any of the Jayco factory people read these threads or not (they should)

I am currently looking to buy a Showhauler or Renegade motorhome similarly configured as the Seneca 37FS I currently own for one simple reason - If you are towing anything, the 6.7 Cummins in the Seneca just isn't quite enough motor. It's great in my 3500 Ram, but it doesn't weigh 25k+ by itself.

If the Seneca's had the 8.3 Cummins rather than the 6.7 I feel this would be the perfect RV for a family. The way the 6.7 is built that's in the Seneca (industrial version) , it is hardly any difference in size physically than the 8.3. I own both in trucks for my business. The 8.3 has a HUGE amount of more power.

Don't get me wrong, if the Seneca is not towing I can stay in the hammer lane in most situations. But if you have a trailer behind it with a jeep or you have some side by sides (which in total do not weigh 5000 lbs) you better be ready to go into creep mode if you hit any hill what so ever. I have found the worst hills for the Seneca aren't big ones in the mountains (I expect these to slow me down), but the slight long hills in the Dakota's, Nebraska and Kansas. These little hills kill it.

I did a full delete on the Seneca prior to this trip out west to ride Sie by Sides. It helped a little. I did it so I wouldn't get stranded because of DEF issues like I did on the last trip, not for increased HP. I do see about 1.5 mpg difference now.

Just my 10 cents.

Alan

My 2020 37K has all the power I need pulling my jeep. I can pass big rigs or keep up with on grades.

Just curious, are you selecting performance mode on the transmission when towing?
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Old 07-23-2021, 05:43 AM   #3
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Mine is a 2012, there aren't any adjustable transmission settings. It does fine on flat ground. Its the hills that it needs some help.
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Old 07-23-2021, 05:49 AM   #4
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I’ll jump in. We have a 2018.5 S2RV that I have towed a Chevy Colorado in the past. We have upgraded our toad to a Chevy Silverado 1500. I don’t drive that fast but have never complained about power. Should I consider “performance mode” pulling the new toad?
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Old 07-23-2021, 07:56 AM   #5
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Originally Posted by Clayduster71 View Post
... I did a full delete on the Seneca prior to this trip out west to ride Sie by Sides. It helped a little. I did it so I wouldn't get stranded because of DEF issues like I did on the last trip, not for increased HP. I do see about 1.5 mpg difference now.

Just my 10 cents.

Alan

What is a "full delete"?
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Old 07-23-2021, 08:04 AM   #6
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It also comes down to price point. Bigger engine requires M2 chassis. I've got the S2RV/6.7. Are there times climbing mountains I wish it had more power - yes. But overall I am very happy, especially in "Performance Mode" on the transmission.

I did the long uphill grade between Flagstaff and Phoenix with a buddy in a Verona. He was able to climb it 5 mph faster than me 43 vs 48.
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Old 07-23-2021, 08:35 AM   #7
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All the emission equipment has been taken off and the computer reprogrammed.
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Old 07-23-2021, 08:59 AM   #8
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Mine is a 2012,
They did go to the 360 HP vs your 340 HP as well as an updated trany. So improvements were made.
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Old 07-23-2021, 09:45 AM   #9
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Can us newbie's get a quick refresher on how to put it in "performance mode"? I have a 2021.
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Old 07-23-2021, 09:50 AM   #10
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All around Yellowstone climbing the hills and never below 45. Retired and in no hurry to get anywhere.
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Old 07-23-2021, 10:40 AM   #11
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I’ll jump in. We have a 2018.5 S2RV that I have towed a Chevy Colorado in the past. We have upgraded our toad to a Chevy Silverado 1500. I don’t drive that fast but have never complained about power. Should I consider “performance mode” pulling the new toad?

Personally I use the Mode program all the time, even when not towing, much better throttle response and acceleration and fuel economy is the same in either mode. If you choose not to use Mode when not towing I would definitely use Mode when towing anything.
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Old 07-23-2021, 10:44 AM   #12
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Mine is a 2012, there aren't any adjustable transmission settings. It does fine on flat ground. Its the hills that it needs some help.

We have a 2018.5 which has no problem towing, perfectly happy how it goes up the hills, even towing a 12k trailer. But I do have more base HP, Torque and bigger transmission with 2 programs. Did you know that you could have had your HP upped by Cummins for a small fee? Probably the biggest issue in some of the older units is the transmission programming, there are alternate programs available that really helps them a lot....many here have had their Allisons reprogrammed if you do a search here.
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Old 07-23-2021, 10:46 AM   #13
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Can us newbie's get a quick refresher on how to put it in "performance mode"? I have a 2021.

Once you start the engine, just press the "Mode" button on the trans shift panel then select your gear......you will notice a big difference. It will default to "slug" program when you turn the key off so you have to hit Mode every time you start up. I use it every time.
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Old 07-23-2021, 07:31 PM   #14
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Mine is a 2012, there aren't any adjustable transmission settings. It does fine on flat ground. Its the hills that it needs some help.
Clayduster - I read you have a 2012. If that is correct I wonder if your tire size/rear axle ratio matchup might be different enough from the 2013-up models and might be a factor in your dissatisfaction. You have 19.5" tires, and I have no idea what your rear axle ratio might be. While typically smaller diameter tires make an axle ratio seem "lower" (higher numerically). But if Freightliner/Jayco put a "higher" (lower numerically) ratio and overshot the mark? I wonder if that could lead to your perceived performance ills.

My 2014 has 22.5" tires and a 5.13 ratio per the visor tag. At 70 mph in 6th gear I am turning right around 2,000 rpm. Any idea how those items compare to yours?

Have you performed or considered the power uprate from Cummins to 360/800? But I think I also read you did a delete so they (Cummins) probably wouldn't touch it with a 10' pole. And you mentioned there aren't any transmission settings. Are you referring to a "Mode" button like the S2RV units have? That is correct, our 2500 Allisons don't have a mode button but many of us had a performance shift schedule programmed into the transmission module. And for me and others it made a world of difference in how it performs. Between my power uprate and trans tuning I only lack for power on the steepest/longest grades. Most interstates I can now maintain the speed limit passing the semis on the hills instead of following them!
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Old 07-24-2021, 05:23 AM   #15
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I don't have the mode button like the later year models, just a shifter. I will see my RPMS at 70 the next time I have it out. It has more get up and go since the delete. I am not sure where he set the HP but I'm going to ask. I may get him to turn it up more. Regardless, a 6.7 in something this big just isn't enough motor. It's FAR better than a gas burner though, lol.

Renegade has a new model now called a Verona 40VRB. It's 40.5 feet long, bunk over the cab, King Size in rear, bath and a half. It comes with a 8.9 liter Cummins on a real M2 chassis. This may be the new RV for me. I've not seen a thing about it so far I don't like.
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Old 07-24-2021, 10:31 AM   #16
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I just bought the 22 Renegade Verona 40VRB. My 2012 Seneca 37FS is officially for sale.



No doubt that you are aware that it is now a "hot potato". Dealers cannot take it in to resell,the new owner has to be told of the delete and it won't pass an emission test if the new owner is in a state that requires that. It becomes a "buyer beware" situation.
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Old 07-27-2021, 05:21 PM   #17
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I have a 2014 37FS bone stock. My last scale ticket a few weeks ago was 28,000 Flat-towing my Grand Cherokee. This past week, I had a U-Haul car hauler with that same Grand Cherokee on it so maybe 1,000 lb heavier. Neither made any difference In hill climbing power.

Based in the West, 5-6% grades are common. My worst is I-8 going into San Diego but I never get below 40-45 MPH. I’m often passing loaded semis at even that speed so I’m certainly not the slowest.

In the cruise, I usually drive 65 which is about 1,850 RPM. But, 70 is easy to maintain and not much worse on fuel economy.

This motor is for sure adequate for me. But I see why folks go for the class 8 chassis super Cs. Nothing beats having a D13 or DD13 with 455 HP and 1,800 Ft Lb torque with the right axle to climb effortlessly with low revs.
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Old 07-28-2021, 12:05 PM   #18
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I had my engine uprated to 360. made a big difference. just returned from our annual 2 month trip out west and had no issues towing a 20`6 pilot on dolly. long slight upgrades were no problem for me. we were traveling with two other units, a Tiffin and a Precept. niether kept up with me and i was the only one towing.
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Old 07-28-2021, 12:28 PM   #19
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What is a "full delete"?
It is the complete removal of a Diesel powered vehicles after treatment system.
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Old 07-28-2021, 12:32 PM   #20
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It is the complete removal of a Diesel powered vehicles after treatment system.
Which renders the vehicle illegal for street use in the US. As such it is not insures let for use on the streets.

It’s a risk some are willing to take.
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