Cummins C "mechanical" vs. ISC "electronic" engine choice

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Cummins C "mechanical" vs. ISC "electronic" engine choice

May 08, 2013, 01:53:13 pm

Hi Folks,

New member here, motorhome shopping (first Class A). Been reading and getting to know the forum and just soaking up the information and the overall good "vibe" of the membership. Everyone seems so satisfied overall, and so helpful and enthusiastic, which is pleasant to read.

Our various parameters are leading us to something in the 1996-2000 range, 34-36', U295 or U270. The newer end of that range has the Cummins ISC engine, whereas the earlier ones have the Cummins C/"mechanical" engine.

Since I can't possibly get all my various questions into one logical thread, this is one of those "all else being equal" questions so as to isolate one variable, which is the engine. It sounds like one couldn't really go wrong with either, but I'd still like to hear what people have to say about one vs. the other. On the one hand, there is the idea of the C engine being "old reliable," simple/sturdy, time proven (which does appeal to us, and was a tenet we stuck to in our previous boating and which served us well). On the other hand the ability to get computer/diagnostic information on the ISC is also very appealing, and as much as I like old/traditional/simple -- time does march on, and improvements are made. I like information, and the diagnostics available on the electronic engines give a person that in spades, it seems.

In reading, I figured out that the ISC is not common rail (that seems to have come in around 2003, and and thus will not be in our target coach range at all, so "not an option," I don't think). Common rail sounds really good. However the ISC has the "CAPS" system, which apparently was a bit of a stepping stone and built for four years or so prior to common rail. Does that make the ISC sort of a "worst of both worlds" such as you sometimes see in the early stages of a concept that ultimately proves to be wonderful it its later iterations? Would you feel, "I'd go mechanical or common rail but avoid ISC"... or is that a non-issue in reality? In stepping up to our first Class A, which already feels a bit scary/complicated in a "lots of things that could potentially go wrong" way, does the ISC just add yet one more thing along those lines? Or is it something you would seek out over the mechanical (and if you don't mind adding why, I'd be very interested to hear your thoughts).

(Not meaning to focus only on the possible negatives, because of course the wonderful positives are why we are looking for a Class A/Foretravel to begin with.)

Thanks, and hoping to join you all as a new owner (fingers crossed!)
Alex

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #1 – May 08, 2013, 03:56:19 pm

Our coach is 1997 U295 36'. It has the C8.3-325 with Banks Stinger. It works. We've had the coach three years and driven it 30K miles +-. The engine has around 90K miles total. I don't recall any problem with our C8.3 other than having to fix a throttle return spring.

Our experience has been that we get just over 7 mpg. We drive 65 mph when conditions allow and pull a 4,000# Jeep. Folk with the electronic controls report about 8 mpg and have the advantage of real time monitoring of a lot of sensors.

My "target FT" was a 1999 U320 36' or 40' coach. The 1997 U295 with Jeep attached came available at about half the price of the "target FT," so we bought it and have been pleased.

Pick your target price, allow about $6K to $12K for first year improvements/maintenance/surprises and watch for coaches that fit the parameters. We got the lead on ours via a post on this forum. The coach was listed on Craig's list, and that listing was mentioned on this forum. We called about two hours after the initial post. The coach was six miles from our home and we closed the deal within about a week.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #2 – May 08, 2013, 05:24:53 pm

We have an ISC (electronic) engine, and have had no problems with it in ~41,000 miles, other than an exhaust manifold crack which happens to both 8.3 and ISC. I really like the ability to monitor all the electronic controls and sensors on the engine (via Silverleaf VMSpc).

Our galactic MPG average (actual miles / actual fuel used) is 7.6 MPG, towing a 3500 lb toad, and running at 30,100 lbs at last weighing.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #3 – May 08, 2013, 06:24:01 pm

Forrest, our '97 34' U270 with C8.3 325 yields about 8.5 mpg with Trans MODE "on" and about 8 mpg without. Very peppy for a motorhome, and does hills just fine.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #4 – May 08, 2013, 06:31:32 pm

Alex, I think you summarized the differences better than most. No problems with either mechanical C or ISC, just the march of progress. We have mechanical C and like our friends with ISC, both work well and I assume both groups do not wish they had what others have. One is simpler and one has SilverLeaf capability.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #5 – May 08, 2013, 07:44:44 pm

Not cast in stone but I have heard that compared to the mechanical engines, the electronic engines get 5-7% better mileage and the super high pressure (25,000-40,000 psi) common rail injection is good for another 5-7%. Indirect chamber diesels with glow plugs lose about 10% to direct chamber injection and also lose efficiency as the pre-chamber loses heat to the cooling system.

That said, it's sure nice to be able to push start an older diesel without a battery to worry about. OK, I know some diesels need 12V to open the fuel solenoid.

For you MBZ diesel owners, you can push start all of them with automatic transmissions. No battery needed. Same with gasoline models but you need minimum voltage.

Pierce

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #6 – May 08, 2013, 07:59:13 pm

alex
you can search the forum, but engine and tranny problems of any era
are far and few between. the rest of the coach would be more of a
concern to me.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #7 – May 08, 2013, 08:14:52 pm

Quote from: Dave M – May 08, 2013, 07:52:43 pm

Pierce,
Great info on the M-B, push start even with auto trany, think that would qualify for a toad, just put in neutral and go ? Like the old Chevy Power Glide etc ??
Thanks

No, they recommend only a few miles for a tow. Can't remember the number. They have a extra pump so you get the car to about 35 mph in neutral and pull it back into first and it lights off. I lost a glow plug in Santa Fe in winter in a 190D but had AAA give me a tow and away I went. My old 450SE had a battery failure with only dim engine lights on. A three speed automatic, it started at the bottom of the hill. Was up at an old mine with no one around. Would still be walking if it didn't start.

I have heard all GM hydramatics in the 1950's could be started the same way. As I remember, they had a real stump puller low gear.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #8 – May 08, 2013, 08:15:36 pm

Amen. Condition, floor plan, tires, batteries, options, use, more important than engine to me

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #9 – May 08, 2013, 08:29:44 pm

Thanks to everyone who has replied so far. I had searched and had not found much (which does probably indicate both engines are great, but is also why I figured I'd start a thread to ask), although on some other forums (when I searched the general web) there was some discussion of lift pump/CAPS pump on the ISC in SOB's. Apparently the CAPS pump is rather expensive; maybe somewhere around $5k (not that I researched it directly), but I didn't see too much about them going out.

I do hear you on the rest of the coach being more of a concern in terms of things that can go wrong and general condition/care - the engines don't seem to be too delicate. Our minds are working overtime , asking both "is this the right move," and "if so.... which particular coach?" So we're looking for objective "choosing points" between the various models, if there are any. Realistically, we know that anything we buy will probably check some boxes and miss others -- since we're not buying a new custom-built-for-us coach. Again, I've been really impressed with the tenor of the forum, and with what I have read and seen of Foretravels. That's certainly an item in the "plus" column.

For the same "buck," I've always been more attracted to an older, well-maintained example of something that was very high quality to begin with over a brand-new, "lesser" (and maybe flashier) version. In that area they all seem to measure up beautifully.

Alex

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #10 – May 08, 2013, 09:07:10 pm

Keep in mind you're only considering buying your first Foretravel... ;o)

We're on our 4th motor home and second Foretravel in 10 years of full-timing.

Someone told us "You're just buying your first motor home" and we laughed at them....

i'm sure glad they're not around to laugh at us!

best, paul

Quote

For the same "buck," I've always been more attracted to an older, well-maintained example of something that was very high quality to begin with over a brand-new, "lesser" (and maybe flashier) version. In that area they all seem to measure up beautifully.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #11 – May 08, 2013, 09:27:54 pm

In my book, the Cummins C8.3 mechanical engine is a much easier engine to diagnose. You don't need a computer. Computers have turned Cummins Techs into replacement parts ex-changers. They can't diagnose without the computer, and with the computer they throw parts at one of several problems until they get it right. And you end up paying for all those unneeded parts and extra labor. But the C8.3 limits one to Foretravels before 1998. I know of a one year old Class 8 rig that has been in the shop over 100 times in the past year. The check engine lights keeps coming on and they can't find the problem yet.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #12 – May 08, 2013, 10:26:39 pm

I drove a country coach intrigue where the 300 cummins had been turned to to 409 Dyno horsepower. Can't remember how he did it but a call to banks might be interesting.

I used to manually turn in the fuel screw myself on 8.3 engines. Little plug and mark the adjusting wheel with finger nail paint so you could see it turn and add 1 1/2 turns. Ran better and mileage went up slightly. The trans senses power and short shifts more.

Long ago so my memory is good. Thought I was going to say bad didn't you?

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #13 – May 08, 2013, 11:10:12 pm

I would not worry too much about which engine to chose. Both are very reliable and long lived, especially in an RV application. You will wear out the coach before the engine. Pick the coach that fits your needs and has been well looked after. Good luck with your search and welcome to Future Foretraveler.

Keith

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #14 – May 08, 2013, 11:19:46 pm

Alex,

Engine should be way down the list of deciding factors Condition, floorplan, tires/batteries/refrigerator, upgrades, dual pane windows, smart wheel, ducted air, hose reels, and a host of other items will make the coach more or less desirable rather than mechanical vs. electronic engine.

Just my 2 cents....

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #15 – May 08, 2013, 11:34:17 pm

Prior to buying my '92 U-280 in april of '03, I called Customer Service at the Home Office of Cummins and asked the rep, "with 79,000 miles on my C8.3, how many miles before I can expect to have major engine service?" The fellow said, "If you maintain it (fluid and filters) according to Cummins' recommendation, plan on bringing it in betweein 450,000 to 500,000 miles for valves, etc." After 10 years of owning the coach, it now has 160,000 miles.

So, as others have said, the engine (mechanical vs ISC) should not be the issue, aside from benefiting for the electronic readouts..

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #16 – May 09, 2013, 12:33:03 am

My experience with the 8.3 mechanical engine is similar to my experience with the 12 valve 5.9 Cummins engine that was in the pre 2000 model Dodge pickups. Absolutely bulletproof, simple, with a basic injector pump that, in the unlikely event it goes out compared to the electronic pumps, is simple and cheap to rebuild. It fires instantly and runs reliably. No capacity for electronic monitoring, and really no need for it either. It's a basic workhorse that gets me 10+ mpg driven conservatively. Feed it clean fuel, keep the coolant in spec, kick the tires and light the fires. What more could you want?

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #17 – May 09, 2013, 01:13:34 am

My power comment applies to most of the boys and some of the girls. The companies charge more money for bigger engines and prettier interiors.

My buddy and I did well to put better interiors in cheaper coaches and turn up the motors like the more expensive models.

Changed window treatments, tile, audio and video stuff, furniture, paint jobs, slate floors, diagonal tiles.....

We custom built dozens of cc intrigues and Monaco dynasty's to look like affinities and signatures. Larceny made deals. Prettier and faster for less money helped us.

Realize modding these is easy. Just a small application of cash. Haha.

Countless conversations with rv'ers all stopped when I asked an answer to a simple scenario.

Diagrammed this many times on my desk across from prospective customers. I could do it upside down.

Imagine you are coming up to a four lane stop light in the slow lane. Car is in front of you and the inside lane is open....

Do you pull over to take the empty lane? Or sit behind the right lane guy and never notice the empty lane? 100% accurate on how much motor you need.

Midwest and east hill stuff was easier. Oh the Rockies? You need more power especially if you moved over to the inside empty lane.

No one ever bought a less powerful motorhome unless they were downsizing due to decreased driver skills.

Favorite story about downsizing was being in Minot for the FMCA rally for the "why not in Minot" rally, the one with the hailstorm, and in the parking lot in the front row was an extremely well dressed gussied up old gal with a cane and rally badges down her chest and a luxury class "b" van bubble top parked in a front space.

Wow Johnny and I said. Her FMCA plate was #16. 1995.

More fun to drive a more powerful Rv. Period.

Versus you look at a map and the scenic route is up a mountain and you are impatient and 40moh in the hills playing dodge in and out of the truck lanes irritates you.

I sold left lane motorhomes if not towing and the boys and girls loved me.

A 87 grand villa 300 cat ataac would pull 90 up a 6% grade given long enough at 8 mpg wide open.

20,000 pound motorhome on a 26,500 chassis.

Buy enough motor is what I am saying or be able to mod the one you have as normally this issue comes up.

Find a bigger than 6% interstate grade to test drive any motorhome versus be disappointed.

Unless you are the slow lane type driver? Most rver's are not if they rounded up the money to buy an Rv in general.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #18 – May 09, 2013, 01:30:54 am

Thanks for the continued input about the engines and the other factors to consider "instead." Very useful and appreciated.

Alex

PS: I would notice the empty left lane, but probably stay in the right in that situation in an RV or large truck. With cars I like good handling and a manual transmission, but am not that "into" horsepower. Not sure what that says in terms of which engine/Foretravel though.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #19 – May 09, 2013, 01:51:52 am

Quote from: Alex P. – May 09, 2013, 01:30:54 am

Thanks for the continued input about the engines and the other factors to consider "instead." Very useful and appreciated.

Alex

PS: I would notice the empty left lane, but probably stay in the right in that situation in an RV or large truck. With cars I like good handling and a manual transmission, but am not that "into" horsepower. Not sure what that says in terms of which engine/Foretravel though.

Glad you appreciate my thoughts. Then a good but not great power to weight ratio coach will work for you...

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #20 – May 09, 2013, 10:25:02 am

Quote from: Dave M – May 09, 2013, 07:02:09 am

Indeed the 60 lb to 1 hp & 19.5 lb to 1 ft lb does the trix for me
Sure not a sporty car, but it gets along just fine passing all trucks & RV's any many cars on the long mountains.

I used to time coaches from zero to 60mph. That way I had a comparison to other coaches and between the same models. Hard to know if a particular coach is running as well as its sister coach.

Hard to tell. Big coaches long ago took 40 seconds. A 87 ored 300 cat took less than 30 seconds. The prototype unicoach with the series sixty did it in 18 seconds. Wonder where that coach is today? Had long radiators along the floor for a natural convection hot water heating. Worked well. No fans needed. I drove every coach personally so I could tell if something needed addressing. I have not driven another u320 redtop so who knows.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #21 – May 09, 2013, 08:08:07 pm

We have Cummins C8.3-325 in a coach/towed combination that runs about 32,000# gross combination weight.

0 to 60mph - Yes
60mph to 0 - Yes

Not the slowest vehicle going up a significant hill - Yes
Inspires confidence and comfort going down a significant hill - Yes

Works for me! Find what's important to you, Alex. Get a coach that appears to meet your criteria. Refine your criteria with experience, then adjust the coach and your expectations. We were delighted with our first coach. We are stilled pleased that we bought it. However, we found that it would not fulfill our requirements. We only had it for eight months and then bought our current coach. The two coaches are the same model year, same length, and both diesel pushers with Cummins engines. The experience with the first coach inspires more appreciation for the current rig.

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #22 – May 09, 2013, 08:41:56 pm

Thanks, J.D. I like the part about inspiring confidence both up and down hills when towing. I'm sure a person could get used to that retarder! In fact, that's what pretty much finally put me off some lighter weight gas Class A's we were considering: Just test driving them without towing anything, I couldn't imagine myself feeling comfortable towing in challenging situations. Not fun to drive for days with a mental clench.

If it's not too nosey (and knowing it's different/subjective for everyone), I'd be interested to hear how you evolved into a different coach that was also very similar to your first one (but if you'd rather keep that private, totally understood, and your main point was still taken).

Alex

Re: Cummins C "mechanical" vs. ISC "electronic" engine choice

Reply #23 – May 09, 2013, 10:12:08 pm

Quote from: Alex P. – May 09, 2013, 08:41:56 pm

If it's not too nosey (and knowing it's different/subjective for everyone), I'd be interested to hear how you evolved into a different coach that was also very similar to your first one (but if you'd rather keep that private, totally understood, and your main point was still taken).

Alex,

See What led you to buy your first Foretravel for some information about changing coaches. Since that post, we have visited Missouri for Christmas, and Montana for New Years three times in the 1997 U295. The FT has provided safe and comfortable refuge for us in some harsh conditions. More clues about our experiences and reasons for having a Foretravel can by found by searching the forum for "blizzards" and member "J. D. Stevens."

Our first coach sold quickly to some people in Oklahoma. We recovered our purchase price. We had spent a few "coach bucks" fixing it up in the eight months we owned it. That coach again sold to some people in Missouri a couple of months ago. Again, it sold for what we paid for it in 2009. We visited the current owners on a recent trip. I gave them some flooring that had been lying in my garage for three years. I shared with them what I knew about their coach and showed them our FT. Their needs and budget are different from mine. They are pleased with the coach that wouldn't work for us.

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