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Old 02-26-2021, 09:46 AM   #1
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Performance comparison 350 Cummins to 425 Cummins

Am considering a trade from a 425 horse power 8.9 Cummins to a 6.7 350 horse power Cummins. in a 40' coach both of which are 2008 model Winnebago rigs. I am wondering how much difference I can expect between the two relative to fuel mileage and performance? Anyone have some input?
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Old 02-26-2021, 11:02 AM   #2
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The bigger (in liters) 8.9 is always better for a heavy motorhome than the smaller 6.7 liter engine. Less wear, more torque. As the hot rodders used to say, nothing beats cubic inches.

David
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Old 02-26-2021, 11:30 AM   #3
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Quote:
Originally Posted by DavidM View Post
The bigger (in liters) 8.9 is always better for a heavy motorhome than the smaller 6.7 liter engine. Less wear, more torque. As the hot rodders used to say, nothing beats cubic inches.

David

Hehehe ....Yes the saying was "There is no replacement for displacement :-)
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Old 03-13-2021, 09:50 PM   #4
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The bigger engine will have a little more parasitic loss, so with the same driving techniques, the consumption will be similar. With the smaller engine, you will have to watch that you don't overload it.
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Old 03-22-2021, 09:56 AM   #5
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Last year I traded a 2000 40' Newmar with an 8.9 350hp cummins for a 2014 42' Winnebago with an 8.9 450hp cummins. The performance of the 450 is incredible and the fuel consumption is equal or better in my opinion.
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Old 03-22-2021, 10:37 AM   #6
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No replacement for displacement was the qoute and it is very true . I have the 350 HP in a Journey 39Z and with a aluminum open car trailer and 2000 UTV its a dog in the mountains. I have to watch the RPM and even still run the risk triggers a check engine light. Usually exhaust temp issue do to the DPF
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