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Old 06-10-2019, 10:54 AM   #1
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Increase Horsepower

I have 370 HP 8.9L ISL engine that I understand can be reprogramed to increase the HP to 400 at a Cummins Service Center.

Question; Has anyone performed this upgrade and have comments to offer on PROS/CONS on making this change? Also, what was the cost?
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Old 06-10-2019, 12:24 PM   #2
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As far as the cost Cummins charges more if you are still under warranty. One person paid 1700$ for a 450 ISM up graded to 500 while still under warranty. Owner said a noticeable difference in performance and no change in fuel usage.
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Old 06-10-2019, 03:09 PM   #3
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I did the Cummins authorized "360hp tune" on my 6.7. Took if from 300hp/640tq to 360hp/800tq which made it just right (able to maintain 55-60 up 6% grade) and no reduction in mpg or any other issues.
RV was only 3 mo. old, still under warranty and cost ~$450 parts (the program) & labor
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Old 06-11-2019, 06:19 AM   #4
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Take the coach to a Cummins dealer. They will connect their computer to your ECU and tell you if an upgrade is possible. I had my 400 upgraded to a 450 last year by a Cunnins dealer at a rally I was attending. With the warranty the cost was right at 1K. If the unit is out of warranty it's about 400.00 for a reflash. Make sure you join the Cummins owners club as that will get you a 10% discount.
To be upgraded the transmission and radiator system will have to be compatible with the proposed upgrade. Last year at the rally I attended the 380 ISL's were not able to be upgraded to the 400 spec. Only way to know for sure is to take the coach to a Cummins dealer and have them connect the computer to your coach.
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Old 06-11-2019, 03:43 PM   #5
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Just be sure your Transmission is rated for the increase in torque
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Old 06-12-2019, 05:20 PM   #6
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What year is your engine?
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Old 06-13-2019, 04:25 AM   #7
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Old 06-23-2019, 10:30 PM   #8
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Quote:
Originally Posted by RVNewbie55 View Post
Just be sure your Transmission is rated for the increase in torque
That is the usual limiting factor. https://www.rvtechlibrary.com/transmissions/specs.pdf
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Old Yesterday, 12:35 PM   #9
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I assume you have an Allison MH3000 transmission. The Allison 3000 is limited to 1250 ft lbs, so you should be okay.

The 370 to 400hp upgrade does not raise the torque output, only the peak HP.
I'm not sure how much difference you'll notice as the primary difference will be the upper rpm limit.
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Old Yesterday, 07:06 PM   #10
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I assume you have an Allison MH3000 transmission. The Allison 3000 is limited to 1250 ft lbs, so you should be okay.

The 370 to 400hp upgrade does not raise the torque output, only the peak HP.
I'm not sure how much difference you'll notice as the primary difference will be the upper rpm limit.
Per Allison specs in that link, the MH3000 is limited to 1,200 lb/ft.
How could it not increase torque? https://www.bryantmotors.com/car-buy...er-torque.html
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Old Yesterday, 09:57 PM   #11
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Per Allison specs in that link, the MH3000 is limited to 1,200 lb/ft.
How could it not increase torque? https://www.bryantmotors.com/car-buy...er-torque.html
I am confused also, if you do not increase torque or engine rpm, how do you increase hp?
https://www.wikihow.com/Calculate-Horsepower
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Old Today, 09:56 AM   #12
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I am confused also, if you do not increase torque or engine rpm, how do you increase hp?
https://www.wikihow.com/Calculate-Horsepower
All three of the Cummins 2007 EPA ISL engines (370hp, 400hp, and 425hp) engines are rated at 1200 ft lbs. The difference is in rpm.

The other difference is the 370hp ISL engines usually have an exhaust brake and the 400hp engines have a Jake compression brake.

Also, the ISL is virtually identical to the ISC except for the longer stroke crankshaft. Cummins has done a great job of expanding the ISC into the ISL and improving power output. However, if you require more than 1200 ft lbs of torque you probably should shop for a coach with an ISM 500.
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Old Today, 10:31 AM   #13
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Quote:
Originally Posted by vito.a View Post
All three of the Cummins 2007 EPA ISL engines (370hp, 400hp, and 425hp) engines are rated at 1200 ft lbs. The difference is in rpm.

The other difference is the 370hp ISL engines usually have an exhaust brake and the 400hp engines have a Jake compression brake.

Also, the ISL is virtually identical to the ISC except for the longer stroke crankshaft. Cummins has done a great job of expanding the ISC into the ISL and improving power output. However, if you require more than 1200 ft lbs of torque you probably should shop for a coach with an ISM 500.
I think I get it. If you take an engine that produces 1200 ft/lbs at say, 1300 rpm and reprogram ecu to change that to say, 1800 rpm, you will realize higher hp because torque is produced at higher rpm, and torque X rpm is part of the hp calculation?
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Old Today, 06:56 PM   #14
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Torque X RPM / 5252 = Horsepower.

1200 lb/ft torque at 1800 RPM = 411 HP.
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