CAt vs Cummins for my next rig - diesel pusher

The smaller engines and lower end rigs generally have rear radiators rather than side.  Side rads cost more and use up some bay space, so they tend to appear only on larger and higher end rigs.

As for Cummins vs Cat, I would ignore that factor in choosing a rig.  They are both excellent and service is widely available for both.

I have lost confidence in Cummins.  I know the big problem I mentioned occured on ISL engines but based on the Cummins recall and fix of installing a warning light to let the driver know that failure will occur shortly rather than fixing the manufacturing defect I would wonder what they would do if a new engine had a manufacturing defect.  Things can and do happen during manufacture.  But the ONLY proper way to fix a manufacturing defect is to fix it not install a warning light.  For me we have had our last MH powered by Cummins.  JMHO

I wouldn't be so quick to criticize Cummins; At least they made customers aware of a potential issue. We have the other brand in our boat and had to limp home when both engines broke studs holding the turbos. The resulting mess wasn't pretty - air filters clogged, engines sucked the filters down, soot bypassed the squished filters, and every square inch of the engines, transmissions and engine room was covered in black, oily soot. Had to dismantle the salon to raise the decks so the techs could remove the blocked aftercoolers and replace the broken turbo studs.

There had been a "service bulletin" issued to dealers with a specific instruction "do not replace until failure occurs". I read it when a tech inadvertently left it on the boat. The engine manufacturer paid for almost all the cleanup, salon teardown, and repair work, for which I was grateful. Fortunately, we were relatively close to shore, nearing the end of a journey up the CA coast. But, had we been 20 miles offshore in bad weather, that could have been a lot more serious than it was. Had I been notified of a potential problem, I would have had the simple replacement of studs done before we left home.

IMHO Cummins should have been required to fix the manufacturing defect that could lead to the engine dumping its guts out all over the highway which could very well be a safety issue.  It sure would not give sombody any comfort to know they have a light that will illuminate letting them know their engine is about to sprew its insides all over the road.  What if this happend on a bridge or anywhere that there was not room to pull over.  Very good potentional for an accident IMHO.   Like I said when I heard of the Cummins fix I lost ALL confidence in them.  IMHO Cummins should have fixed the internal manufacturing defect insted of expecting their affected customers to worry if and when their warning light would illuminate.

Understood Ron, but at least they were warned the engine might fail and had the option to stay home. I'd much prefer to break down on a highway bridge than 20 miles offshore in bad weather.

On the first leg of the same trip, we had to head for the nearest port of refuge when the weather forecast was dead wrong. I found myself having to make a wide U-turn in 20'+ seas, heading to a strange harbor while dodging reefs and praying we wouldn't capsize. Had we lost power at that point, we would have been in a world of trouble.

Tom said:

Understood Ron, but at least they were warned the engine might fail and had the option to stay home. I'd much prefer to break down on a highway bridge than 20 miles offshore in bad weather.

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About that option do you know anybody that bought a motorhome to stay home.  I don't really consider that a good option.  IMHO The ONLY proper way to address that issue would have been for Cummins to fix their manufacturing defect.  I know that the defective part was supplied by to Cummins by one of their vendors but surely Cummins should be inspecting the components they are installing on a new engine.

On the first leg of the same trip, we had to head for the nearest port of refuge when the weather forecast was dead wrong. I found myself having to make a wide U-turn in 20'+ seas, heading to a strange harbor while dodging reefs and praying we wouldn't capsize. Had we lost power at that point, we would have been in a world of trouble.

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Glad you didn't have engine failure at that critical time. 

How comfortable would you feel taking the boat out if it had a pair of the affected Cummins ISL engines and Cummins had fixed the problem by installing an idiot light?

Based on the two stories, which engine would you have in your next coach? I'd much prefer to be told and be able to make the decision to leave or stay home than unwittingly put lives in jeopardy because I didn't know there was a potential issue. One of my worst fears is drowning.

Let me put it this way would you buy a brand new coach knowing that the engine has a manufacturing defect as some of the ISL?  Probably not.  Now would you buy a used coach if it had an idiot light installed to warn you that the engine is about to fail because the engine has a manufacturing defect?  Also probably not.

Maybe I wouldn't buy either next time around Ron, but that does limit the options. Personally, despite the two stories, I believe both brands of engine are OK and, given some of the alternatives, are good value. I might think twice about buying a coach having the 'known bad' engine, but wouldn't rule out other engines from the same manufacturer.

OTOH I'm not planning on buying another coach or another boat. We're quite happy with the ones we have  ;D

We are not planning on buying another coach for the same reason.  However, I have told American coach that I will not even consider a new coach with a Cummins engine.  Interesting I am not the only one that feels this way.

Back to the original question ... All other factors being equal, if choice of engine is the only thing left, the one factor that might weigh heavier in the equation would be torque. HP is a derived number (IIRC we have an explanation in the library).

Ron said:

IMHO Cummins should have been required to fix the manufacturing defect that could lead to the engine dumping its guts out all over the highway which could very well be a safety issue.  It sure would not give sombody any comfort to know they have a light that will illuminate letting them know their engine is about to sprew its insides all over the road.  What if this happend on a bridge or anywhere that there was not room to pull over.  Very good potentional for an accident IMHO.  Like I said when I heard of the Cummins fix I lost ALL confidence in them.  IMHO Cummins should have fixed the internal manufacturing defect insted of expecting their affected customers to worry if and when their warning light would illuminate.

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Rod failures are not uncommon and thus this particular manufacturing defect went undetected for some time as it was simply seen a a random occurrance . However, once investigation showed it was part of a pattern Cummins did a review to determine the best way to approach the problem taking into account any possible safety issues and the impact on customers as well as usual cost issues. The defect rate was forecast and likely failure scenario.  In addition, it was found during the review that an existing sensor planned for 2007 engines could be used to accurately predict this type of pending failure. 

This defect was forecast based upon statistical data to affect about 60 RV engines and most were expected to be early failures on way to dealers i.e. maybe 25+ would be delivered to customers. Cummins put in place a process to assure that the affected customers on longer mileage vehicles got quick service and from comments I have seen on many forums and reviewed with Cummins it was well executed and received.  The so-called idiot light is really just the end indication of a quite smart software program running in the ECM and one benefit of having it installed is that it will find out whether the engine is having the problem before it goes to a major failure thus turning a possible 2-3 week repair into a 2-3 day one. In fact, in one instance I am aware of, when after installation of the sensor the engine was started and it immediately showed a defect allowing the problem to be corrected right then. Historical actual data to date shows the defect rate is below the forecast  and the sensor did allow a number of customers to get to repair place before the major failure occurred.  I have an ISL400 not within the affected range but I did have the sensor installed. As I noted before, rod failures are not uncommon in any engine builder i.e. they do happen for a number of reasons and I therefore saw a benefit to having it for added information JIC.

The information I am reporting here is my understanding from talking to Cummins personnel but may be in error and certainly does not represent Cummins position per se. 

Ron said:

Let me put it this way would you buy a brand new coach knowing that the engine has a manufacturing defect as some of the ISL?  Probably not.  Now would you buy a used coach if it had an idiot light installed to warn you that the engine is about to fail because the engine has a manufacturing defect?  Also probably not.

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Ron

The coaches in question have neither of the issues involved with the installed engines. It is a non-factor.

so now my next question would be, how similar is the ISB 300 I'm considering to this ISL?
do they have the same problem?
I'm not too familiar with the differences between the different Cummins engines.

joester said:

so now my next question would be, how similar is the ISB 300 I'm considering to this ISL?
do they have the same problem?
I'm not too familiar with the differences between the different Cummins engines.

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No the problem mentioned was only on some ILS engines.  My concern is how Cummins addressed the factory defect. 

Completely different engine, even a different block.

I have no concern at  for the 8.9L ISL in my 2004 coach. As Leo explained, very, very few engines will ever experience the failure or even the idiot light warning of it.

I think I have come up with what I think is a fair assumption - as far as a shorter coach - 32-34' DP -
the difference between the CAT and Cummins ISB is not really enough in the 300-325 hp range where it alone should be a deciding factor, correct? It seems that in the 2005-2006 years we're looking at, CAT seems to have more torque than the Cummins ISB for comparable size engines, but most everyone who has either of these engiines is pretty satisfied.
thanks again for your input -
Joe

If you are interested in getting a good idea of how horsepower and torque relate I suggest you look at this

Wayne

Wayne

I understand everything you wrote, but there is one situation where torque is king and that is if you ask the question what is the steepest hill I can go up in my lowest gear? That is determined by the torque peak.

Bob

Bob

I did not write the article. I just referenced it to look at. My basic opinion is with proper gearing, there is no difference in getting 300HP from a gas engine, a diesel engine or an electric motor. The horsepower delivered to the drive wheels is what does the job. The gear ratio is just as important.

Wayne