cummins or cat

[ron55]

I looking a DPs, what is the best engine to go with.
From the cat and cummins forums they both seem to overheat and low on power in the Rocky Mountains. I notice no DPs ever passed me in the mountains.

[MaverickBBD]

Both are good engines. If you notice no DPs ever passed you in the mountains then why you looking a DPs? If that is what concerns you.

[viper]

We've owned both a Cat and Cummins DP, as well as 3 other gassers. We had far fewer problems with the Cat than the Cummins. Probably there are others here that would say just the opposite based on their experience.
We entered the DP market with a 97 Beaver Patriot with a 330 HP Cat. Great engine-absolutely zero problems. Traded it in 99 for a Country Coach with a 350 Cummins-lots of problems from day 1-Blowby problems with diesel fuel all over tow car, sensor problems, replaced fuel injection pump twice. Fortunately, most of these problems were covered under warranty which Cummins took care of very well, but lots of downtime in service bays and when you're fulltiming that's a real pain.
In fairness to Cummins, in that year that 350 was a pumped up 325 and in the first model year they had lots of redesign and fix it problems to correct. Later models seemed to be better.
After owning those two, we decided to stick with gas- far fewer problems, lots less maintenance $$ to service and keep running.
Just our personal opinion

[Tha_Rooster]

I have a 400 Hp cat. runs great never been to the rocky mountains but I have cross the smokey mountains several times no over heating. I also have never been passed by a DP or a gasser. The big difference a DP maybe in 4th or 5th gear when a gasser might be in 1st or 2nd gear.

[smlranger]

Cat vs. Cummins is like arguing Ford vs. Chevrolet. Either are good engines that will likely outlast the coach if properly maintained. CAT stopped making OTR engines a few years ago so you will see only Cummins in most DP's nowadays (except for the really high $$ coaches that might use Detroit Diesels).

Our 2002 330 CAT has been fine. Over heating issues you may have heard of are often related to rear radiator DP's with dirty radiators/charge air coolers. Rear rad DP's need the cooling pack thoroughly cleaned at least annually.

I pulled the Beartooth highway from Red Lodge, MT to Cooke City towing a 2008 4,700 lb Ford Explorer. The CAT ran fine and never over heated.

[ron55]

Why am I looking at DPs? I blew up my workhorse 8.1 on Monark Mt and now a rebuilt. I have read on here how great DPs so I was hell bent to get me one untill I read the cummins and cat forums, all I see is overheating and 20mph up the big mountains in the Rockys.
I spend July and August in Colorado and all I ever see that climbing ok is the diesel PU and 5th wheel

[JimM68]

We've done the rockies twice in a gasser. Both times it got done. This year we upgraded to a DP. Haven't been out west yet, but it's still better, I'd keep it even if I had to push it.

Most of those problems seen in the 90's have been fixed permanently in newer engines.

Also, I like how our rear engine monaco puts the radiator and charge air cooler on top of each other rather than back to back.

[Keith K]

We've been all over the West and it's mountains for the past six years, first with a W24 gasser and now a C7 diesel. Both performed fine, and with proper driving technique, neither ever overheated. In your case, you don't sound convinced that a diesel will solve your personal needs, so I'd advise not to spend the money.

[BCooke]

Most of the people who switch to DP have not driven diesels before. They are different than gas engines! That is not just a no fooling.
You have to keep it in the power band of the engine when you are not just toodling along.
Remember the EPA wants the best mpg out of everything if they can not ban it.
My father did the Black hills and then got a recall for overheating. While not the Rockies he also never saw any overheating, but had the modifications made any ways. Last year he went to Rocky Nat Park and did not have issues while in that area. (I do not know his path to or ftom) He probably was doing 55 and I think once he said he did 45. When in hills like that he controls the trans.
This year I was able to switch from a v-10 to a diesel to pull my toyhauler. Pulls great.

[RJay]

The best characterization I've heard between a Cat and a Cummins is the Cat is faster off the line and the Cummins is better at top end. I have no basis for comparison or even know if it's true, but if it is I know I spend more time at top end.

[Batman_777]

CAT has more torque (initial power) and Cummins has better mpg for similar sized blocks. Cummins generally outlast CAT.

It is easier to find a Cummins repair shop if needed. CAT no longer makes RV motors.

I've been up and down CO I-70 many times. I do wish the MH engine was a size or two larger, but then I would also pay for it in less mpg. Keeping the rpm's in the power band is important. You'll need to know what the power band is for your motor. It differs from motor to motor.


Truckers say, drive the tach and not the speedometer when climbing. If you're in the power band with the correct gear, then that's all she'll do.

Go down the hill in the same gear you went up. Know what is right for your vehicle.

Downhill Braking:
- Keep the vehicle speed down. Use exhaust brakes if you have them and the area permits. Shift to lower gears.
- Brake some, then let off to cool. Brake some, then let off to cool. repeat allowing time for the brakes to cool. If you cannot maintain, pull over. I've seen truck tires on fire from the brake drums getting white hot. Plus, you can warp the drums and possibly crack them. Once the brakes get hot, the brakes will feel spongy. Too hot!! and they stop working.
- Don't let the vehicle go too fast since it takes way too much to bring it back under control again.
- I brake to bring the vehicle down say 10 mph, let it build back up and then brake again.
- I use a soft pumping action on the brakes.
- I do not hold the brakes down.
- I carry an infra red temp guage to check my brake temp when stopped.

[Chuck 1935]

Quote:

Originally Posted by ron55 Why am I looking at DPs? I blew up my workhorse 8.1 on Monark Mt and now a rebuilt. I have read on here how great DPs so I was hell bent to get me one untill I read the cummins and cat forums, all I see is overheating and 20mph up the big mountains in the Rockys. I spend July and August in Colorado and all I ever see that climbing ok is the diesel PU and 5th wheel

Guess it wasn,t all that fast !!!!
It all depends on what you want. I have a 34ft with a 330 Cat that passes everything and runs cool. They put the same engine in the 40fters. I doubt that it's all that fast in them.
Torque to weight my friend. Big show... No go !!
Buy a Motorhome for the floor plan without a consideration for whats underneath and it's a crapshoot.

[MONGO MAN]

Quote:

Originally Posted by ron55 I looking a DPs, what is the best engine to go with. From the cat and cummins forums they both seem to overheat and low on power in the Rocky Mountains. I notice no DPs ever passed me in the mountains.

Cat no longer makes NEW diesels for RV's.However, they are trying to sell Cat branded trucks & engines (trash - dump)which are manufactured by Navastar- International & serviced by cat dealers.
If you are looking for a used coach & have a choice I would go with Cat. My 08 Cat-C7- 35 ft.goes up the Fancy Gap 7% grade (between Va. & WV.) in 6th gear (2nd overdrive) without downshifting at about 1850 Rpm. and never overheats .(not towing)----OVERHEATING & LACK OF POWER SHOWS A LACK OF PROPER MAINTAINANCE.

[RJay]

Regarding the overheating problem, I think it's the result of improper or lack of maintenance and not the fault of the engine manufacturers. An initial proper and thorough cleaning of the radiator and every six months after, or immediately after driving on salted roads, will prevent any overheating problems as a result of insufficient cooling.