400hp 9.2ISL Cummins or 400hp C9 Cat

I have the 3126 in my 2002 Itasca Horizon - and it's the early version of the Cat C7. The C7 change was partly due to the emissions stuff and I'm glad I don't have that - as the MPG suffers.

My 3126 now has 92K miles on it, and if I'm not towing anything and keep the speed to around 62mph I do get 9.5-10.5 MPG (also with no headwind)

Towing I usually get around 8-8.5MPG if I have my 33' long enclosed trailer.

I really wanted to get the ISB engine, as they were known for good MPG, but the coach I found had the floorplan and price that was nice, so I got the engine I got, and it has performed well for me as I bought it with 24K miles.

I think some confusion has entered this thread.

OP is comparing the Cat C9 and Cummins ISL.

Same size/displacement and HP.

The C7 is a smaller engine (7.2 liter vs 8.9/9 liter), but a very widely used one.

No matter how you look at these two engines, they were/are both popular in certain brands over certain time periods. The Cat C7 was the engine to have when it started showing up in DP's. Then the manufacturers started gravitating toward the Cummins ISL when it came available. The Cat C9 started showing up in certain brands like Beaver and a few others. At some point Cummins started to dominate the market.

Soooooo.....either will be a good engine, it just depends on your budget, which will dictate the year of coach you can afford, which will dictate which engine was the most popular then.

****Wolfe....I had C7 on my mind when I posted, but still the same outcome with engine availability. I corrected my statement.

bluwtr49 wrote:
Since a Cummins or a Cat are the most prevalent engines for MH's it's not something to fret about. Both are great engines. Noise??, I'm not sure you can tell the difference while driving. I hear a lot of both and they all sound the same to me unless the muffler has been changed than either is load outside.

I have a friend with a Cat 350 that I have been traveling with for four years. We have a ISL400 Cummins. I'm sure you can't tell the difference driving down the road. But, when we pull into a rest stop and leave our engines running you certainly can tell the difference. His is much louder than mine. That being said. He gets nearly a mile per gallon better than I do. Not sure if there'd be that difference if he had a 400. My coach is much quicker when pulling out on to the super slab. Probably the difference in torque.

DSDP Don wrote:
It's hard to quantify, but I agree with "sprintmod1" on the two engines. My sister had a 34' DP with the 350 Cat. I had a 36' DP with the 400 ISL. Their coach was quicker, but I soon pulled away from them. When we would fuel up, I always look a less, (about 1/2+ mpg better) even though I had a larger coach and engine.

I know many of the older 525HP Cats, drank a lot of fuel. I don't think you can go wrong with either engine, but my vote would lean toward the Cummins.

That 350 Cat was based on the old 3126 - but at 7.2L it's not a small block but certainly not a big block either. It was also only rated at 860 # TQ.

The 400 ISL is rated at 400/1200, and is 8.9L large.

I'm guessing - only guessing, theirs was geared a bit lower.

Our last MH had the 7.2 Cat, or current MH has the ISL. The difference is night & day. There is no replacement for displacement. :B

I don't know why everyone calls the 05 engines pre emissions. They are pre DPF but still have emission programed ECM's . The Acert Cat's have EGR. The big Cats of that era have big problems with the twin turbos and the EGR set up. In the trucking world pre emission refers to pre 02 or 03.

Moisheh

We ordered and took delivery oct 2005 of our o6 Rev LE40E. Bath and a half. C9 cat, pre-emissions. 90,000 miles no regrets. 8mpg. Just follow a maintenance schedule.

It's hard to quantify, but I agree with "sprintmod1" on the two engines. My sister had a 34' DP with the 350 Cat. I had a 36' DP with the 400 ISL. Their coach was quicker, but I soon pulled away from them. When we would fuel up, I always look a less, (about 1/2+ mpg better) even though I had a larger coach and engine.

I know many of the older 525HP Cats, drank a lot of fuel. I don't think you can go wrong with either engine, but my vote would lean toward the Cummins.

Blackdiamond wrote:

tropical36 wrote:
I appreciate the feedback so far, and we've been sort of, sort of, looking at the earlier Fleetwood Revolutions which were built on the American Platform and the Spartan chassis, but weren't called American and not until about 2012 or so.
Looks like the 06 and 07 are Cat engines and the 08 being a Cummings.
Really like the 1 1/2 bath model and the quality look of these coaches in general.
So what about parts and labor costs between the two, if and when that's needed and something the average gear-head doesn't want to do for themselves?

My vote would be the 07 and earlier, not because of the cat, just due to the fewer smog controls on the pre-08' engines, the new laws made cat leave the market.

Good to know and always wondered why the Cat pretty much disappeared from the RV market.

Blackdiamond wrote:
My vote would be the 07 and earlier, not because of the cat, just due to the fewer smog controls on the pre-08' engines, the new laws made cat leave the market.

Thats one of the reasons we bought when we did. Our MH is an '08 with a '06 spec engine in it. No smog, no DEF, no ultra-low sulfur required. The best part was seeing as they needed to go, the normal $6800 adder for the ISL was waived. Win! :B