Cummings Diesel

[SGKane]

We are looking at a "new to us" Itasca Horizon 40'. we have two to look at. Both have the same floor plan however one has the 400 hp the other has a 350. This would be our first diesel motorhome, is the extra 50 hp worth paying a few extra dollars?
besides the added HP, is there any other differences I should consider?
Thanks in advance,

[Smitty77]

I've read many various opinions on CAPS era engines. My conclusion was that many were damaged in the early years after the **** to ULSD from Diesel 2, due to lower lubrication. And while todays ULSD is advertised to meet all lubrication needs, and does for sure for engines designed to run on ULSD. My own opinion is that adding a lubricant additive, I use XPD, to each tank - is cheap insurance.

My second concussion, after talking to real nice veteran mechanic of diesels, is that CAPS do not handle fuel starvation well. The fuel both lubricates and cools the CAPS. A filter system that is partially clogged, can restrict adequate flow to the CAPS. Also at engine first start up, a failing or leaking lift pump, can also send a smaller supply of fuel then is needed by the CAPS.

Keeping filters clean (Sure right to do so on all engines!), either keeping the Lift Pump healthy/or/bypassing it and adding an aftermarket fuel pump (We have the FASS pump only, not the additive fuel filters, as I felt CC had good quality filters to start with.), and also adding a Lubrication additive to each tank - provides your best chance of keeping a CAPS up and running for a longer life.

And note my first post, suggesting that the non CAPS era ISL Common Rail with VGT was I felt a positive for a coach:)! So sure not arguing that CAPS era engines are not as easy to maintain as the CMR's.

Opinions vary, best to all,
Smitty

[Sully2]

Go with the 400 hp version

[hershey]

I have never met a DP owner who said he has too much HP. Get the extra HP and relax.

[11178adm]

CAPS pumps are a pain in a truck chassis and a REAL pain in a DP

[mikebte]

CAPS can be a pain in the tail. Pain. I can not tell you how many caps pumps I replaced while working for Cummins. But I had nightmares about them.

[Smitty77]

All things being equal on he condition of the coach, go with the ISL400.

If still looking, and wanting to compare this coach with the ISL400 to another one. Try to determine which ISL400 is in the 04 model. It could be the older, and very mature, CAPS era ISL. Or, it could be then newer Common Rail with VGT ISL. The newer Common Rail would be a nicer engine to have, especially if it coms with an Exhaust Brake vs Jake Compression (The ISL vs the ISC, can be found with Jake Compression 2 Stage brake assist. While most of them come with a Exhaust Brake assist.)
The Common Rail and Variable Compression Turbo (VGT) has a more usable HP/Torque curve, and in many applications, you get added Braking HP via the Vanes closing up in the VGT providing more back pressure to help the Exhaust Brake. (I may not have described that accurately, but the VGT does provide a bit more Braking HP, as I understand it.)

And as always, coach layout and overall condition, usually trumps the specifics of the engine:)!

Best of luck to you,
Smitty

[mikebte]

Is it a Itasca Horizon 40KD?

May have disc breaks, dual pane Windows, power cord real if it is.

[mikebte]

Imho, Winnebago makes a great motorhome. I worked for Cummins for years. I have attached a link below for you to use. Put in the VIN and it will give you the factory equipped engine size and specs.

I now am an RV consoltant and use this link to ID engines. Hard to see past the radiator some times.
ISL OR ISC are both great and can be programmed for hp ratings.


http://www.gates.com/catalogs-and-resources/resources/repository/engineering-business-applications/v...

Just made link clickable.
Dick

[SGKane]

Thanks everyone for your thoughts. The one we are looking at is a 2004. Having a 1996 34' with the V8 I think this will be a huge upgrade.

[Ivylog]

"I believe the current version of the ISL is rated at 1250 torque so the Allison tranny must be able to handle 1250 not 1200."

I agree the current (2010+) ISL 450 is 1250 which means the current 3000 is good for 1250 (doubt they went to a 4000 tranny). In the years the OP is looking at the (400 HP) the 3000 is only rated for 1200... the same as my 04 ISL 400/Allison 3000 tranny.

[rr2254545]

I have a 360 in a 36ft motor home - I am truly surprised a 40ft would have a 350

Go with the 400

[Two_Jayhawks]

Ivylog wrote:
The ISC 8.3L 350 HP/1050 torque is a good engine and the ISL 8.8L 400 HP/1200 torque engine is nothing but a stroked ISC and it's an even better engine. It would help if you posted what year as it's possible to have a ISB 6.7L 350 HP/860 torque engine but doubt they would go two steps down from the ISL 400. The 1 HP/100 lbs is a pretty good rule of thumb so if loaded weight plus toad is 35,000 lbs... 350 is enough, but 400 would be better and if you can control your right foot, get as good or better MPG.

Because the Allison 3000 tranny is only rated for 1200 ft lbs torque, the ISL 400 has a flat torque curve from around 900 to 1400 RPMs giving it good pulling power over a broad band. The ISL 400 should have a torque rating of 1300 but because of the 3000 tranny it's only rated 1200. At 400 HP it's at the upper limits of it's rating... like in a ambulance.

Hi Ivylog
I believe the current version of the ISL is rated at 1250 torque so the Allison tranny must be able to handle 1250 not 1200.

[Ivylog]

Only took 14 minutes to correct the spelling... not a record and 2old you are at 30 minutes.
The reason one cannot tell any difference in a ISL 400/425/and now 450 is because there is not any when it comes to the torque... 1200.

[Ivylog]

The ISC 8.3L 350 HP/1050 torque is a good engine and the ISL 8.8L 400 HP/1200 torque engine is nothing but a stroked ISC and it's an even better engine. It would help if you posted what year as it's possible to have a ISB 6.7L 350 HP/860 torque engine but doubt they would go two steps down from the ISL 400. The 1 HP/100 lbs is a pretty good rule of thumb so if loaded weight plus toad is 35,000 lbs... 350 is enough, but 400 would be better and if you can control your right foot, get as good or better MPG.

Because the Allison 3000 tranny is only rated for 1200 ft lbs torque, the ISL 400 has a flat torque curve from around 900 to 1400 RPMs giving it good pulling power over a broad band. The ISL 400 should have a torque rating of 1300 but because of the 3000 tranny it's only rated 1200. At 400 HP it's at the upper limits of it's rating... like in a ambulance.

[Kayteg1]

Comparing diesel engine can be long story, so I would advise you to go to specific engine forum and read a lot.
General rule is that higher HP engine, but with step torque curve will make impression of lower acceleration than slightly lower HP, but with flat curve.
Other story as mentioned is engine chipping.
US manufacturers typically down-rate the engine for reliability.
Typical sample is that the same engine can be chipped for 300HP on tow truck, but 450 HP in fire truck.
Each program has its good and bad sides and it takes lot of homework to figure out what will be best for you.