What Year Diesel Engine To Buy?

[bmcfaror]

I am looking at upgrading our diesel pusher (2004 Endeavor with 330 Cummins).

I am finding good prices on 2008/2009 coaches, but am concerned about the cost of emission equipment maintenance. Would one of you experts out there be able to give me advice about purchasing a 2008/2009 versus one of the newer DEF burning Cummins engines?

I don't want to make a big mistake....

[RVerOnTheMove]

You will save money by buying a coach that does not require DEF. Coaches built before this requirement will not have any ongoing issues that should prevent you from buying one.

[wolfe10]

This is a definite "Opinion" issue.

While engines requiring DEF are more complex, they have more HP, better MPG and less emissions than the older ones. Kind of like when gasoline engines went to catalytic converters.

If someone knows of a statistical evaluation or reliability rather than an opinion-based one, would like to see it.

[dickandlois]

The engine one chooses is more a personal issue as Brett mentioned.

The poster mentioned that he has a 04 or 05 model year at the time and should have first hand experience with the VGT Turbos.

Regarding the DEF system on Diesel engines. The only information I have reference to and no direct records.

They do not like long idle times, stop and go causes issues with the system. They have more problems with the system in cold weather keeping the system hot enough to not set check engine and loose of power.

The solution has been to keep them running at a high idle and running in a lower gear to keep the exhaust system temperatures up.

This temperature issue has also shown up with failed EGR valves failing due to soot build up in the valves.

Have not had any feedback regarding over the road issues where things can run hotter.

The engine builders get more real time and world information over the years and things should get resolved,but does one want to be one of there guinea pigs.

Hope this limited information helps.

Rich.

[rorr1821]

If you are purchasing a 2008/2009 unit it should have an engine that was built before Jan 1 2010. So if it is a Cummins engine it should only have a particular filter on the exhaust and not require DEF additive. I have a 2008 unit with the ISL HP Cummins engine with a particular filter and have 33,000 miles on it even though I am not fulltime. I have had no problems with performance. The exhaust tailpipe does not have the black soot on the inside as I have found on my previous units which I attribute to the particular filter. The MPG is the best I have ever had on a motorhome and the pulling power is outstanding. I was told by Cummins that my engine could be reprogrammed to HP for around $800, but based on its performance I decided not to exercise the option. I would also added that a major consideration in your decision process should be what I refer to as a weight to power ratio. If you you have a heavy coach and marginal engine HP you may not have an enjoyable driving experience. If you travel to high altitudes keep in mind that for every 1000 ft above sea level you loose about 3% in performance. Engines are rated at sea level.

[wolfe10]

If you travel to high altitudes keep in mind that for every 1000 ft above sea level you loose about 3% in performance. Engines are rated at sea level.

I think you will find that many diesels are rated at full HP up to 10,000' due to their turbo "making air". Yes, normally aspirated engines, both gasoline and diesel do loose HP with altitude due to thin/less air.

[five]

...If you travel to high altitudes keep in mind that for every 1000 ft above sea level you loose about 3% in performance. Engines are rated at sea level...

This is true for non turbo engines. Virtually all diesels are turbo, so they are not bothered by altitude...the turbo keeps packing in the air. The engine doesn't know if it in Key West or climbing the Rockies.

One other consideration with DEF, when we were looking for newer MHs in 2010, we were informed that a new MH with DEF vs one without DEF would cost about $11,000 more.

[tbutler]

Be aware that coach manufacturers purchase engines in quantity and then install them in coaches until they run out of that stock. Your 2008 coach may have an engine manufactured in 2007 or even 2006. Don't assume that the year of manufacture of the coach matches the year of manufacture for the engine.

[wolfe10]

Tom is correct-- chassis builders bought ahead each time there was an EPA tighter standard as engine price also went up. And EPA standards follow the engine. So ENGINES manufactured after 1/1/07 are different than earlier engines, as are ones built after 1/1/10 when DEF became commonplace.

[five]

If you have any questions as to it's engine build date, call the engine manufacturer with the engine serial number.

If you have a question about chassis build date, call your chassis manufacturer with your VIN.

[hermanmullins]

There was a story out several years ago about Cat Engines. It seem that they had on static display one of the first engines manufactured by Caterpillar. They took it into the shop put it on a test stand, cleaned it up, tuned it up and ran it on the dyno. It was said to have ran as good as any of the new engines and exceeded all EPA requirements.

Now this tells me that being old ain't so bad afterall.

Herman

[Friendship37]

Old can be better. Simplicity is a trait I look for in most things.

[GaryS2]

The best engines are the older mechanical pumps, they are simple and made to run forever. The new electronic injections work good until some thing fails and could be considered an improvement when all is well. But engines were never intended to suck their own exhaust into the intake. It takes quite a spin master to convince me that they are an improvement.............so the exhaust is a trifle cleaner yea but the engine life is cut in half, for most motorhomes that still does not matter as they seldom ever get that many miles anyway. So look for a turbo engine, that has a mechanical pump and charge air cooler and you have the best.................most likely it is between 2005-2007 after the 2007 they all have the EGR and DPF and some have the DEF as well, none of that exhaust after-treatment is an improvement no matter who spins the tale.

[GaryS2]

My final $.02 worth is look for a pre 2002 DD60 the 2003-2006 had EGR issues. Or look for a Cummins N14 1980-2000 best was celect 1997-2000 the Cummins ISM pre 2002 was known for good fuel economy. Or look for Cat C14 it was a good engine but used a lot of fuel stay away from the Cat C12 it was known for bad fuel economy and the C13 was known as the big yellow lemon. Ask any old trucker at a truck stop they well tell you they hate the new trucks with all of the EPA garbage on them.

[MikeCanter]

Not sure I agree with that earlier statement that altitude does not reduce power on a turbo charged diesel engine. If somebody has driven up over 5000ft then you wouldn't say that. I have a Detroit Series 60 and when climbing up over 5000 ft there is a definite reduction of power and up over 7000 ft it is even more noticable. My turbo is showing 42 lbs of boost the whole time and I keep it at the peak horsepower RPM when climbing and the higher I get the less power I have. There is only so much that turbo can do to compensate for the thin air.

[five]

I'm certainly no engineer, but in theory, the turbocharger remedies the altitude problem by compressing the air back to sea-level pressures in order to produce rated power at higher altitudes. The altitude at which the engine is producing full power is known in aviation terms as the critical altitude. When the vehicle is above that altitude, engine power output will decrease as altitude increases just as it would in a naturally aspirated engine.

[MadHungarian]

Not sure I agree with that earlier statement that altitude does not reduce power on a turbo charged diesel engine. If somebody has driven up over 5000ft then you wouldn't say that. I have a Detroit Series 60 and when climbing up over 5000 ft there is a definite reduction of power and up over 7000 ft it is even more noticable. My turbo is showing 42 lbs of boost the whole time and I keep it at the peak horsepower RPM when climbing and the higher I get the less power I have. There is only so much that turbo can do to compensate for the thin air.

I'm certainly no engineer, but in theory, the turbocharger remedies the altitude problem by compressing the air back to sea-level pressures in order to produce rated power at higher altitudes. The altitude at which the engine is producing full power is known in aviation terms as the critical altitude. When the vehicle is above that altitude, engine power output will decrease as altitude increases just as it would in a naturally aspirated engine.

Actually, if I'm not mistaken, it's the quantity of air molecules at altitude that effect performance, not barometric or turbocharger pressure.

[jrwitt]

You are correct that the quantity of air molecules affects the performance. When the turbocharger compresses the air, it is adding molecules. Air at sea level has the same percentage of molecules as air from the higher altitude that is compressed to sea level.

[mpierce]

I think there is some confusion between DPF, diesel particulate filter, and DEF, diesel exhaust fluid.

DPF came out first. They are/were a pain. They burned fuel to clean them out. Caused problems.

DEF was then added. By adding DEF, the makers are able to tune the engines better, and greatly reduce the particulates going to the DPF. Thus, increasing mileage and reliability.

The restrictions of long idling, slow driving, definitely applied to the DPF only engines. Caused them LOTS of problems, as the amount of particulates at idle was overwhelming them.

When the DEF is added, it greatly reduces the particulates going to the DPF at idle, making idle and slow driving much less of an issue.

I have had both type engines, and I GREATLY prefer the newer ones with the DEF added. The fuel mileage is better, and the problems are lessened.

[manholt]

I bought new a 2011 Allegro Bus 36' with a 450 DEF Cummins. Yes, I had power but I only got an average, over 3 years, of 7.2 mpg. The DEF tank was located on right rear....could not use pump at any truck stop and filling tank is a pure pain in the back, when your 6'8"!!! Per Cummins, the reason for a 450 HP was due to the 12% HP loss, due to DEF.

I hate the DEF system. All it does is keep Al Gore, the green huggers and Government happy for extra taxes! I ask myself, why is it that the biggest polluters out there, are exempt from DEF?

As for Turbo and fuel MPG/Power at higher elevation...we covered that in another posting. Sorry Brett, but your theory in 12' counter your reply to me about lousy MPG in Oregon.

Carl C.

10' AMC Tradition 45' Cummins 425

[kebowers47]

Perhaps I can shed some much needed clarity on exhaust treatment of diesels. Stage 1) was using exhaust gas recirculation (EGR) to reduce oxides of nitrogen (NOx). The recirculated mostly nitrogen lowered the peak combustion temperature, dramatically decreasing NOX.

It required engine and lube oil manufacturers to change things --a LOT for lube oil formulation scientists. Soot loading of the lube oil more than doubled, and the lube oil had to have MUCH better soot dispersion capability, and oil filters had to have much more soot holding capacity to prevent 'bore polishing' and resultant high lube oil consumption-- so much for Stage 1.

Remember, all along the engine folks were beating on refiners to make better diesel with much lower sulfur. They also improved fuel injector technology, piston crown shape and cooling, and other 'metal modifications' to improve fuel economy , durability at high soot loadings etc. There WAS a steep learning curve.

Stage 2 was to further control exhaust soot---particularly the very fine particles (less than 2.5 microns in diameter). Particulate filters were in addition to much improved very high pressure 'common rail' electronically activiated fuel injectors with better optimized spray patterns--which improved fuel economy and reduced particulates This is DPF.

The fundamental issue is how to filter well (to minimize small particles) without plugging up. A host of chemical and mechanical issues were/are at odds. The most common is now ceramic filters that a periodically 'burned clean' by injecting more fuel and air in the hot exhaust to burn off the soot. Now remember, the 'turbo' should extract a lot of energy (heat) from the exhaust to power the compressor side to improve engine power and efficiency. Then you have to add a lot of heat to burn off the particulate filter ever so often.

There are different methods used by different engines to determine when to do a burn-off.. Then the EPA mandated ultra-low sulfur diesel in all road trucks (and now off-road and railway, and ships too!). That caused lubricity related problems with certain injector pumps and fuel design scientists had to make and use 'lubricity additives. The ULSD is, by far, the lowest sulfur in any fuel gasoline, diesel, kerosene, lpg. Making it required refiners to spend $ Billions in research and new high pressure hydrotreaters, new catalysts, more hydrogen manufacture---all of which substantially increased the cost of making ULSD as compared to the old stuff.

At first, there was not enough ULSD to go around and prices soared (law of supply and demand) . While ULSD prices have lowered SOME, they are still way above the real COST of making it. Other things being kept equal, the true 'cost' to make ULSD should not be more than about $0.10 per gallon than regular unleaded gasoline. ULSD also substantially lowered particulate formation, so soot filters are not as problematic as they were.

Now comes Stage 3 where we are today. NOX levels were still too high according to the EPA. There are two (2) ways to lower NOx emissions---1 is to reduce the combustion temperatures--with the brief peak period making the lions share of the NOx. EGR does that , but also robs power from a given engine displacement (recirculated exhaust has much less oxygen than fresh air so it acts as a diluent--you are basically compressing Nitrogen and circulating it, taking horsepower to pump it around.

The other easy to reduce NOx is to convert it back to Nitrogen and water vapor, which is what Diesel ExhaustFluid (DEF) facilitates.

This requires a catalyst (reactor), injection , control, and monitoring systems, etc., but does not rob horsepower, and actually allows MORE power and better fuel efficiency---efficiency goes up and combustion temperature goes up, which makes more NOx , but you easily handle that with the DEF and catalyst. VIOLA for a measly $10,000 or more, you get better fuel economy, much lower NOx emissions, and much lower tiny particulates (and much lower sulfur oxides SOx emissions) all of which have dramatically improved air quality in about 2% of the US territory and 5% of the population.

Modern, up to date diesel engines running on ULSD ARE much cleaner running, give improved fuel economy, and-----only cost a 150 $Billion to invent and a whole lot of additional fuel costs (money transferred from 'the people' to refinery stockholders.), the majority of whom are the 1% folks. The additional capital investments this required have long been recovered and paid for.

[rpelatt]

WOW! Thanks for the info! That also explains why diesel has remained so much higher than gasoline. For the last several years it seemed to be a total waste of money to buy a diesel powered car as the supposed 30 -40 % better fuel economy was dwarfed by the 50% higher cost of diesel fuel.

[jplante4]

If your boost gauge says 42 psi then you're getting 42 psi. It matters not whether the coach is at sea level or 7000 MSL. The fuel/air mixture is set to available air. I don't see how altitude can effect a turbo-charged engine.

[wolfe10]

Is that 42 PSI or 42 column inches of boost? Roughly 2 column inches per PSI.

[dickandlois]

Jerry and Brett, when one tries to calculate boost, there are a number of variables.

I tend to use the readings as a reference(on system health) and not what might be the true pressure at any given time at the intake manifold. The true pressure is important regarding what the engine is specked for in regards to maximum boost.

This link is to information on what factors into boost and what one is reading on a gauge.

https://www.turbobygarrett.com/turbobygarrett/sites/default/files/PDF/Turbo%20Tech%20103.pdf

Rich.