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Old 10-11-2018, 08:52 AM   #1
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ISL 400 to ISL 450

I was at a Rally last week where a Cummins dealer had set up a booth. I asked about the possibility of upgrading my ISL 400 to a 450. They sent a tech to my coach he plugged his computer in and yes an upgrade was available. I choose to have the upgrade done and was able to maintain my warranty on the engine.
If your coach is out of warranty the upgrade is substantially cheaper.
Not everyone is going to be able to get their ISL upgraded, Radiator size and the transmission installed have a lot to do with it. The Cummins tech told me the engines and transmissions are assigned for lack of a better term batch numbers. If your in a batch and there is a more powerful option available in that batch an upgrade is possible. It is a case by case thing a few other folks at the Rally had their coaches checked and mine was the only one eligible for an upgrade. I did not ask about what was possible with an ISB engine.
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Old 10-11-2018, 05:01 PM   #2
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Did they also upgrade your torque rating, or just turn the RPM limit up??
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Old 10-12-2018, 06:41 AM   #3
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The ISL 400 and 450 both have the same max tq numbers 1250. The technician reflashed the ECU to a different specification. What appears to have happened is that the TQ curve was widened considerably. There does not appear to be any RPM differences. Looking at the Cummins literature the 400 and 450 have the same tq setting of 1250, and the 330 and 350 have the same max tq of 1000. It is speculation on my part but I suspect the only upgradable engines are the 400 and 330. ie: the batch thing I mentioned in my first post.
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Old 10-13-2018, 05:54 AM   #4
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Just curious what it cost if you don't mind sharing. Either way thanks.
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Old 10-13-2018, 08:44 AM   #5
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Under warranty just shy of 1K, out of warranty under 400.00.
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Old 10-13-2018, 10:17 AM   #6
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Sorry, I didn't explain it well.
Horsepower is a calculated number. In the early days it was used to compare steam engines with horses. Measured torque is multiplied by the RPM and then divided by a constant (5252 radians per second).
(RPM * T) / 5252=HP

The point is if they didn't increase the torque, then they increased the RPM to increase the horsepower number.
Another point of misunderstanding is an ISL 8.9L engine is an ISC 8.3L engine with a longer stroke crankshaft. They are great engines as long as you don't get one during the bad wrist pin years.
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Old 10-14-2018, 05:39 AM   #7
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Sorry, I didn't explain it well.
Horsepower is a calculated number. In the early days it was used to compare steam engines with horses. Measured torque is multiplied by the RPM and then divided by a constant (5252 radians per second).
(RPM * T) / 5252=HP

The point is if they didn't increase the torque, then they increased the RPM to increase the horsepower number.
Another point of misunderstanding is an ISL 8.9L engine is an ISC 8.3L engine with a longer stroke crankshaft. They are great engines as long as you don't get one during the bad wrist pin years.
So it's same block Vito? Same bore too?
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Old 10-14-2018, 05:41 AM   #8
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Under warranty just shy of 1K, out of warranty under 400.00.
Thanks. Been wanting to see how much they could add to my 350 ISC if it's even possible.
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Old 10-14-2018, 06:57 AM   #9
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vito
If you go to the Cummins web site you can see the tq/hp curves of the ISL 400 and 450 in a chart format. On a 400hp the tq goes to 1250 at 1400rpm and immediately drops from the peak. On the 450 the tq hits the max of 1250 at the same rpm but stays there until 1500. At any RPM above 1400 the 450 has a tq advantage of up to 175ftlbs which is where the additional HP comes from. Both engines have max HP at 2100rpm.
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Old 10-14-2018, 07:26 AM   #10
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Great report. I have called three Cummins dealers and they either don't return my calls or give me some off base information.

Did you notice a substantial improvement?

I had a digicrtv module on my 400 ISL and the performance was documented via dyno. It was felt in the seat of the pants too.

However, after a long story and several flash upgrades the module would make the coach go into the limp mode when trying to turn the module up much at all.

I gave the module to another rver.

I really miss the hill pulling power I had.
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Old 10-14-2018, 10:30 AM   #11
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I noticed an improvement. Have to find some bigger hills to really know how much of an improvement. I'll know more after takin it thru the TN mountains in Jan.
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Old 10-14-2018, 10:45 AM   #12
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We have been through the Rockies many times and multiple times up and down some of the passes. Our 450 has been able to keep pace easily with the truck traffic with no heating issues. On very hot days the temp climbs noticeable but drops right back down when you crest the peak. I think anyone that has a unit can be turned up will definitely benefit from the upgrade.
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Old 10-15-2018, 08:16 AM   #13
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I would love to be able to upgrade our ISC 350. Just yesterday we were in Highway 40 going west in NC and had to climb the continental divide. I had to go as low as 45 in 4th gear for quite awhile. As slow as it felt we passed several big trucks. I am not even sure if that rates as a big climb or not compared to others...lol. Would love to be able to hold 55. On a good note it never got past 188 temp wise. In fact since all the cleaning of the coolant system (double flush), new hoses, and new OAT coolant it has yet to get over 190.
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Old 10-15-2018, 08:31 AM   #14
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I installed the Banks kit on our '02 DSDP with ISC 350. Made quite a difference too. New turbo housing, new actuator, Ottomind control box and wiring harness.
Unfortunately the company that made the Ottomind box quit making them and Banks never found another company to make them.
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