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Old 08-17-2012, 01:57 PM   #1
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RPM sweet spot

What would be the RPM "sweet spot" with an ISC on flat ground? We're on 11R22.5 tires and an Allison 6 speed and weigh 31k. I try to keep the speed about 60 and have no issues with the power, Just want to hear from others what RPM's you cruise at
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Old 08-17-2012, 02:25 PM   #2
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Generally the best economy is about 200 rpm above the torque peak. The other issue is you have to get the transmission to shift into 6th gear. I would guess these two things would occur with an ISC at 1600-1700 rpm.
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Old 08-17-2012, 04:25 PM   #3
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if i run at 60 i find the tranny down shifts often.
if i run 63-67 it feels good and no down shifts except on long climbs.
the rpm is 1750-1850 according to the digital read out
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Old 08-17-2012, 10:54 PM   #4
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Mine seems to like 1650-1700.

If your trans is up/down shifting a lot, then run the trans with "mode" selected. Problem solved.
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Old 08-19-2012, 10:27 AM   #5
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I think you mean econ. mode
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Old 08-20-2012, 10:13 PM   #6
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What is the torque peak on the ISC330? 1500??
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Old 08-20-2012, 10:32 PM   #7
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Originally Posted by jlturner View Post
What is the torque peak on the ISC330? 1500??
Here's the Banks chart on the ISC 330:

You have 330 HP at 2000 to 2025 rpm and 950 ft lbs torque at 1400 to 1600 rpm. So 1500 rpm is right in the middle of it.

Here is the actual Cummins brochure.
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