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Old 05-29-2019, 12:48 PM   #29
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Vincee --


The 2007 Damon Astoria 3774 I had until three months ago had the 300 HP 5.9L ISB engine (pre-DEF engine) that performed well in the Texas Hill Country and climbing big bridges on I-10 in Louisiana. I asked my repair shop (RV Masters) in Houston if that engine could be "tuned" for higher horsepower and the answer was "yes" but they advised not to do so. Reason was the 300 HP ISB was coupled with an Allison 2500 MH transmission which is not rated for the higher torque from a higher horsepower engine.


What transmission do you have coupled with your 6.7 L engine? If you have an Allison 2500 MH transmission like I had, be sure the transmission would be damaged by higher torque coming from an engine tuned to provide more HP and torque.


My current Newmar Ventana LE has the 360 HP version of the 6.7L ISB engine coupled with an Allison 3000 MH transmission. The bigger engine is needed because the Newmar is 3 feet longer and 7,000 lbs. heavier than the Damon. The 6.7 L engine has performed very well thus far.
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Old 05-30-2019, 08:21 AM   #30
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fagnaml, thanks for the info. My rig has the ISB 6.7L coupled to an Allison 2100 tranny. The work is being done right at the WNY Cummins Service Center, tomorrow. Before they could tell if mine was upgradable I had to supply them with the engine serial number which opened up a vault of info on my rigs set up. I wonder if the different Allison models have anything to do with the weight of the rig it sits in besides power?
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Old 06-02-2019, 10:00 AM   #31
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Quote:
Originally Posted by vincee View Post
fagnaml, I wonder if the different Allison models have anything to do with the weight of the rig it sits in besides power?
Yes. The manufacturer will use the appropriate size Allison transmission based on the size of the vehicle as well as the GVWR and HP/TQ ratings of the power plant in the vehicle. The transmission and rear ends MUST be taken into consideration when spec'ing the engine in the vehicle or turning up the power in the current diesel engine.
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Old 06-28-2019, 07:24 AM   #32
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I have just recently purchased a 2002 Monaco 40' with a Cummins 350 diesel and while travelling in the hills of the Finger Lakes the other week, I found there was not enough hp/torque to keep me at 55mph. On more than a few occasions it slowed right down to about 40mph with my foot on the floor and dropping down gears.

But I think that was due to the weight it was hauling.

The coach it's self weighs in at about 30,000lbs and the towed car weighs in at just over 3,000, so that's a lot of weight to be hauling up hill.

And going down hill it wanted to get up to 70+, I was always on the exhaust brake and foot brake.

Quite an experience, but not a concern.
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Old 06-30-2019, 12:27 AM   #33
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Increasing the horsepower does not necessarily mean an increase in the maximum torque.

A power increase comes by reprogramming the ECM to make the engine produce the more torque at a higher RPM. For example, the 400 HP ISL produces its maximum torque of 1,250 lb/ft at 1,400 RPM. But because thatís a fairly low RPM, itís only 333 HP.
1250 X 1,400 / 5252 = 333 HP

As the RPM increases from there, the torque drops off slightly. The engine produces only 1,050 lb/ft of torque at its HORSEPOWER peak of 2,000 RPM.
1050 X 2000 / 5252 = 399.8.

If you can get the engine to produce 1,200 lb/ft of torque at 2,000 RPM, you now have a 450 HP engine.
1200 X 2000 / 5252 = 456 HP.

Thatís a simplified explanation of how the horsepower rating can increase while the torque rating remains the same.
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Old 06-30-2019, 03:29 AM   #34
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I've got the 400 ISL... what a beast! It will pull my 4500 lb toad at idle with the wheels locked.... yup... I did that...
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Old 07-01-2019, 09:06 AM   #35
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SC40, at least you know you have "more power than you need" LOL!
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Old 07-01-2019, 09:10 AM   #36
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Very satisfied with my upgrade to 360/800. Total cost was $357. Local Cummins shop had a free recalibrate with any service order, a $100 savings, plus they gave me 10% off for being a member of the Cummins Parts Club, I'm not. You really feel the difference on accelerating from a dead stop.
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Old 07-04-2019, 05:38 PM   #37
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Wouldn't 100% torque at 0 RPM mean the engine isn't yet turned on or yet in motion?

Also, isn't that the exact reason trains run on GE electric engines and most if not all cruise ships.

Just the way electric motors work, yes they are "on" and full power can be applied before they even turn, hence 100% power or torque at 0 RPM.


I believe most rail locomotives are diesel/electric. Diesel engines generate electricity to run electric motors.
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Old 07-04-2019, 08:38 PM   #38
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Just the way electric motors work, yes they are "on" and full power can be applied before they even turn, hence 100% power or torque at 0 RPM.

Not quite. No matter how much torque is on the shaft, if the RPM is zero, the horsepower is also zero.
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Old 07-05-2019, 02:25 AM   #39
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Not quite. No matter how much torque is on the shaft, if the RPM is zero, the horsepower is also zero.



Ok, but my point was 100% torque, I was just trying to simplify, you need movement for HP, not for torque, simple mechanics really. Mechanics I understand, physics not so much, or at all really.
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