Cummins 8.3 vs 8.9

[contrarymary]

Does anyone have any comments on which one is better or not?

[Skip426]

I can't speak to these two engines, but the 5.9-to 6.7 Cummins change was for power/emissions reasons. Basics of these two engines are the same just a displacement change.
Research at a Cummins web site may reveal the answers, if 8.3 production stopped when 8.9 started, then I would assume there would be not much difference between the two engines.

[rotts4u]

They are both great engines but they are different models. not jsut different year models etc.

Here is a thread with info.

Diff. between ISC and ISL?

The 8.9 is of course more powerful but the 8.3 is also a great and powerful engine that many find works well for them depending on the size of the coach toad etc

[Gary RVRoamer]

If bigger and more powerful makes it "better", than the ISL is better. I don't think there is any qualitative difference - just torque and horsepower.

The ISL is often installed with a side radiator rather than rear and that is somewhat "better" because it provide better access to the engine for maintenance and repairs.

[Doc C]

I am not sure you can say one is better than the other, it is matter of personal preference.

Having had two motor homes: one with the 8.3L ISC engine, GVWR 32,0000 lbs and my current one with a 8.9 L ISL, GVWR 34,000 lbs, I can tell you my personal comparison.

1. The coach with the 8.3L ISC fully loaded was approximately 1500 lbs less than my current coach. In comparison the 8.3L had better MPG. I could reach 9.0 to 9.5 MPG going from PA to Florida on I-95. The 8.9 L - at 8.0 is the best. In the hills of PA and NY I accually fine little different between the two in terms of MPG.

2. Cost of maintance on the two engines about the same.

3. Pick up and go - major differences. In the mountains and hills, the 8.3 L would dog down slowing down on major interstates from 65 to 50-55 mph. My brother had a Ford F-250 with the old 7.0L ford diesel engine towing a rather large 5th wheel and he would just wave to me as he went by. With the 8.9L - I never loss speed in these situations. Likewise, it has quicker pick up when swing out into the passing lane. I never worry if I get out in the 2nd lane and the guy that I am passing speeds up if I am going to get around.

To me the extra performace of the 8.9L is worth the drop in MPG.

There is a big difference between the two engines Torq, with the 8.9 L having about 25% more Torq. In fact the 8.9 L engine is capable of putting out more than 1200 foot lbs of torq, but the Allison 3000 transmisson is not capable of exceeding the 1200 foot lbs. To me it seem like cummings have the 8.3 L max out, while there is still some room in the 8.9L

Just my personal observations and preferences, some one else my other preferences. My neighobor loves his older Holiday Rambler Endeavor with the ISB engine, and GVWR of 26,700 lbs. A little slower doesn't bother him, but he loves the 10-11 mpg mileage.

Doc C
2009 DSDP

[Bobschle]

Doc,

The Allison spec sheet says the 3000MH can handle torque of 1250. I hope this is true as the Ellipse I am buying has the Cummins 8.9 ISL with 450 HP and 1250 lb ft of torque and an Allison 3000MH

Over 1250, you need to go to an Allison 4000 which can handle up to 1950 ft lb of torque

Bob