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Old 06-26-2021, 07:33 AM   #1
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Tiffin Allegro Red 340 38 LL - POWER?

I've got a deposit on a 2021 Tiffin Allegro Red 340 38 LL. It has 340 HP Cummins. A Tiffin service rep told me that if I tow my wife's Lincoln Nautilus Flat I may get down to 30 MPH going up long grades. We live in PGH and I want this to go back and forth to New Port Richey, FL so I will be in the mountains for 50% of trip.

Can anyone that may own this coach or one with similar power give me their opinion as to how it will perform? Thank you!
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Old 06-26-2021, 09:13 AM   #2
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I have a 2016 with the 360 hp and tow a 1500 Ram.

On some grades, you need to be patient. 2/3/4% is not that big of a problem. Beyond that, you need to get a cup of coffee, and settle in for the haul.

FYI, we did some of those grades in 109f. Not an issue. Everything was nice and stable temp-wise
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Old 06-26-2021, 09:17 AM   #3
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Thanks

Thank you. My biggest challenge coming back to PA from FL will be Fancy Gap
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Old 06-26-2021, 09:48 AM   #4
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Quote:
Originally Posted by BillW15237 View Post
I've got a deposit on a 2021 Tiffin Allegro Red 340 38 LL. It has 340 HP Cummins. A Tiffin service rep told me that if I tow my wife's Lincoln Nautilus Flat I may get down to 30 MPH going up long grades. We live in PGH and I want this to go back and forth to New Port Richey, FL so I will be in the mountains for 50% of trip.

Can anyone that may own this coach or one with similar power give me their opinion as to how it will perform? Thank you!
He was being honest with you. As with most diesels, you won't be the first one up the hill but you will get there. It will be far more important coming down the other side of the grade and controlling your speed.

You will need to learn to keep your speed down by using the exhaust brake and the trans to keep your speed under control. If you let it speed up too fast, the trans will up shift to protect itself, and then your only alternative is using the brakes. Ideally you want to go down a mountain grade with little or no use of the RV brakes. Downshift early, let the trans hold you back. Let the speed racer guys go around you, either RV's or trucks. Remember it all about the journey, not the destination. So slow down and enjoy the ride.
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Old 06-26-2021, 09:56 AM   #5
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Thank you brother. Many many years ago I trucked from coast to coast. So I hear ya loud and clear about heating up the brakes. I may just opt to have another car in FL and use this coach WITHOUT towing.
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Old 06-26-2021, 10:04 AM   #6
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BTW...I chose the 340 38 LL because of the floorplan. I want enough room for my wife to get to the bathroom and or kitchen with the slides in. My dog needs to be able to walk around too. Anything I found with more HP does not have enough room going down the road.
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Old 06-26-2021, 11:43 AM   #7
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Recently i hit a 7% grade on I26 in NC south of Asheville, I have a 360HP and tow an F150 (about 5400lbs). I slowed down to about 40mph on my way up. Just be patient, you will get there. It thought I had a problem but once I crested the grade I started to speed up. I was also surprised at how quiet it was with the engine 37 feet behind me.
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Old 06-26-2021, 12:13 PM   #8
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We have the Breeze with the same ISB and 2500 Allison transmission. We run a short, but steep hill to and from storage with a grade of 11%. Our rig drops down to 40mph to get over that hill and we are not towing. However, we had little problem making good speed on Interstate 6% grades.

The issue is that the ISB has the ability to deliver reasonable horsepower to keep the RV moving well, but the Allison 2500 torque management control software limits available power to protect the transmission.

There are a lot of real advantages to the RED 340, so it will deliver you good value. Just be aware that, while it has a reliable and able drivetrain, you will experience limited performance as torque requirements increase at higher speed.

Tactics - travel light, learn to keep the boost as close to max as possible when climbing (may need auxiliary boost gauge), and be ready to accept slower travel from time to time.

EDIT - a Google search turns up this info. .... I-77 makes a six-mile hill-climb of over 1,500 feet, with a grade of not over 4.5%, commencing one mile north of the North Carolina border, with a third northbound truck-climbing lane. The top of the climb on I-77 is a summit called Fancy Gap, and is over 3,100 feet elevation. The Mountain Directory says the area has a 5-6% grade for 7 miles.

If that's the worst of your travel, you should be OK.

Note - you will need your service brakes on down hill runs. Not too much, but the ISB can spin up fast as the RV is a lot of rolling weight for that displacement. Your toad braking should help and there is a different red line for loaded and unloaded conditions.
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Old 06-26-2021, 12:25 PM   #9
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Recently i hit a 7% grade on I26 in NC south of Asheville, I have a 360HP and tow an F150 (about 5400lbs). I slowed down to about 40mph on my way up. Just be patient, you will get there. It thought I had a problem but once I crested the grade I started to speed up. I was also surprised at how quiet it was with the engine 37 feet behind me.
Thank you for the response. Bob and Brenda, thank you for your service to our country!!! FREEDOM IS NOT FREE!
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Old 06-26-2021, 12:26 PM   #10
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Originally Posted by PKI View Post
We have the Breeze with the same ISB and 2500 Allison transmission. We run a short, but steep hill to and from storage with a grade of 11%. Our rig drops down to 40mph to get over that hill and we are not towing. However, we had little problem making good speed on Interstate 6% grades.

The issue is that the ISB has the ability to deliver reasonable horsepower to keep the RV moving well, but the Allison 2500 torque management control software limits available power to protect the transmission.

There are a lot of real advantages to the RED 340, so it will deliver you good value. Just be aware that, while it has a reliable and able drivetrain, you will experience limited performance as torque requirements increase at higher speed.

Tactics - travel light, learn to keep the boost as close to max as possible when climbing (may need auxiliary boost gauge), and be ready to accept slower travel from time to time.

Thank you Pat...safe travels to you as well!
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Old 06-26-2021, 01:34 PM   #11
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Quote:
Originally Posted by PKI View Post
We have the Breeze with the same ISB and 2500 Allison transmission. We run a short, but steep hill to and from storage with a grade of 11%. Our rig drops down to 40mph to get over that hill and we are not towing. However, we had little problem making good speed on Interstate 6% grades.

The issue is that the ISB has the ability to deliver reasonable horsepower to keep the RV moving well, but the Allison 2500 torque management control software limits available power to protect the transmission.

There are a lot of real advantages to the RED 340, so it will deliver you good value. Just be aware that, while it has a reliable and able drivetrain, you will experience limited performance as torque requirements increase at higher speed.

Tactics - travel light, learn to keep the boost as close to max as possible when climbing (may need auxiliary boost gauge), and be ready to accept slower travel from time to time.

EDIT - a Google search turns up this info. .... I-77 makes a six-mile hill-climb of over 1,500 feet, with a grade of not over 4.5%, commencing one mile north of the North Carolina border, with a third northbound truck-climbing lane. The top of the climb on I-77 is a summit called Fancy Gap, and is over 3,100 feet elevation. The Mountain Directory says the area has a 5-6% grade for 7 miles.

If that's the worst of your travel, you should be OK.

Note - you will need your service brakes on down hill runs. Not too much, but the ISB can spin up fast as the RV is a lot of rolling weight for that displacement. Your toad braking should help and there is a different red line for loaded and unloaded conditions.
Thanks for the update Pat!!! I may try to flat tow her car after all
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Old 06-26-2021, 02:21 PM   #12
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Thank you for the response. Bob and Brenda, thank you for your service to our country!!! FREEDOM IS NOT FREE!
Thank you.
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Old 06-26-2021, 09:54 PM   #13
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Tactics - travel light, learn to keep the boost as close to max as possible when climbing (may need auxiliary boost gauge), and be ready to accept slower travel from time to time.
PKI - can you please explain what you are referring to by "boost"?
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Old 06-26-2021, 11:31 PM   #14
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Boost is the amount of air pressure that the turbo is forcing into the cylinders to allow more fuel to be burned, which makes more power. Keeping the boost up is done by keeping the engine rpm's up when the demand for power increases, like pulling a hill. The bigger the grade, the bigger the demand.

Boost is measured in foot pounds. Turbo's are generally set by software designed by the engine manufacture, like Cummins. They generally try to limit the maximum boost allowed by how much pressure and stress a particular engine can safely withstand. The bigger the engine, the higher the boost pressures.

You can keep boost pressures up by keeping the rpm's up when approaching a significant grade. You can wait for the engine to downshift to a lower gear on it's own, but on a significant grade the vehicle will be slowing and rpm's dropping by the time the downshift automatically occurs.

I will usually manually downshift from 6th to 5th gear if a substantial grade is coming. That will increase my engine speed about 200 rpm and keep the motor operating within the "power band" as described by Cummins. For hill climbing Cummins and Allison recommends that your rpm be within 400-500 of the max governed RPM. On my rig, that max rpm is 2200.

And don't worry, you can't "over boost" your turbo, there is a built in "waste gate" that will open and release excess boost pressure if it exceeds design limits.
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