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Old 07-19-2021, 04:10 PM   #1
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Up-rating a Cummins ISL 400hp to 450hp

Is there anyway to tell by serial number which 400s can be up-rated to 450hp?Maybe a range of serial # or build date, color of the dipstick, anything? John
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Old 07-19-2021, 05:16 PM   #2
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Is there anyway to tell by serial number which 400s can be up-rated to 450hp?Maybe a range of serial # or build date, color of the dipstick, anything? John

Check out this link:



https://www.cummins.com/care-search-...werid=16777217
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Old 07-19-2021, 07:40 PM   #3
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I called Cummins and gave them my engine S/N and CPL number, they told me mine could only be uprated to 425 HP.
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Old 07-19-2021, 07:43 PM   #4
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I called Cummins and gave them my engine S/N and CPL number, they told me mine could only be uprated to 425 HP.
What is CPL #?
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Old 07-19-2021, 08:13 PM   #5
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What is CPL #?
CPL is the Critical Parts List. The number may be stamped on the same plate as the engine serial number. The CPL number identifies what list of critical items are part of your engine build. Not all engines will have the CPL number, but if it's there it helps to include it. The CPL is for a series of engines, not for a particular engine. In other words, many engines in the same line can have the same CPL number, but they will each have a unique Engine Serial Number. The ESN is the most critical piece of information to give Cummins and from that they can tell the limit of a horsepower upgrade.
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Old 07-27-2021, 12:11 PM   #6
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how is it uprated...ECM flash/update?
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Old 07-30-2021, 10:10 PM   #7
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I have the ISL 400. Manufactured December 2006. I sent my engine serial number to Cummins to see if it could be uprated. Received my answer today and my engine is maxed out at 400.
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Old 07-31-2021, 06:28 AM   #8
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That is what i am afraid of and why I don't want to buy a 400 without knowing if it can be uprated. John
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Old 08-03-2021, 05:20 PM   #9
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My 2015 380hp was uprated by Cummins to 450hp and I now do the happy dance!
Without the toad hooked up itís actually a bit much! 😳
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Old 08-03-2021, 06:15 PM   #10
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Mongo159 'If you find a RV you like, find out the engine serial number then send Cummin the number and they will be able to let you know if it can be uprated.
Mine is the last of the engines before they went to when to DPF in January of 2007.
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Old 08-08-2021, 03:47 PM   #11
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I have a 2007 motorhome with a 2006 400 ISL build. Checked twice with Cummins and they said it was not upgradable for more power that it was maxed at 400hp. I purchased a Ag Diesel Solutions model 12100 for my engine which is the high pressure fuel rail system not CAPS. My Aladdin said over the last 45,000 miles an average of 6.4 MPG. I have driven about 2000 miles now with it installed. It has a 10, 20 & 30 % power increase settings. 10 & 20 showed little to no improvement. Finally left it on 30% and over the last 800 miles have averaged 9.3 MPG. I weigh about 33,000 pulling toad weighing 4,700 pounds. 62 MPH at 1500 RPMís seems to be the set spot for me. I ran a code scan after install and had one code which was turbo boost. Erased it and no more codes since. It is very simple install anyone can do. Ag Diesel Solutions has great tech support and a warranty second to none.

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Old 08-11-2021, 06:03 PM   #12
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That is what i am afraid of and why I don't want to buy a 400 without knowing if it can be uprated. John
The uprate only changes HP, the torque will still be 1200 pounds. I don't think I would not buy a coach over 25 -50 HP, especially a 400 ISL, the best RV engine ever made.

With that said, you can chip the older ISL's. I had a 2005 Monaco Diplomat with the 400 ISL. I changed the rear engine fan to a more efficient unit, sold by Source Manufacturing, a vendor on here. It "returns" 25 HP on a ISL engine. You could feel it out of the hole. I also added the Digi Cr chip to my ISL, it was dyno'd at 52 additional HP. My Diplomat weighed in at 32K and was a fricking rocket with the above additions. I could pull any grade, out west, at 55+ towing a 5K truck.

Fast forward to my 450 ISL (L9) and 42K weight and I'm at 40mph on the grades. The extra HP isn't always the trick....eight has a lot to do with it.
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Old 08-15-2021, 09:25 AM   #13
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Horse power is just torque x rpm. Getting more horsepower with the same torque means they are upping the rpm at which the motor puts out its max torque. So if the peak torque was at 1400 rpm and you up that to 1650 you are going to have a better driving coach. Especially if they can map the torque band maxed throughout the rpm range.
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Old 08-15-2021, 06:28 PM   #14
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shootist, is that bad or better for your engine. Also, what do you mean by "a better driving coach"? Tks John
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