Workhorse GM8.1L engine problems

[Gary RV_Wizard]

I've been told there is a V10 torque/hp graph in the Ford Commercial Truck literature, but have not found it online. Like the 8.1L V8, the Ford V10 does a nice job of torque at mid range but the horsepower does not appear until much higher RPMs.  

Ford claims that about 80% of peak torque is available at 2100 RPMs. Peak torque on the latest 3-valve V10 is something like 457 ft lbs, so 80% would be about 367 ft lbs. Using the torque-to-horsepower formula, that says the horsepower @2100 is about 147. 

No gas engine makes much horsepower at low RPMs.

 

[Photog]

No gas engine makes much horsepower at low RPMs.

Gary,

I agree with you.  But what is your point?  At 3900 to 4200 rpm the gas engines produce as much HP as is needed.  Gas engines have shorter lives due to this fact.  That's why long hall truckers use diesels.

As far as MH usage goes, gas at 3900 works as well as diesel at 2000.

Both types of engines work quite well.

Bill

 

[2KViggen]

sorry this has gone of subject a bit..... but it's still good info!!

I would say long haul trucks use it for longevity & possibly more importantly the tq.  Did I mention how fristrating (Ok amusing) it was on my trip to tetons/yellowstone/glacier having semis with a full load & sometimes 2 full 53ft trailers flying by me going on hills in my 38ft WH pulling my jeep unlimited.  I just kept thinking DAM that tq must be nice  :'(

Seems like the only time my RV would go close to 4K RPM's is when I hit the hill descent button & the RPM's raised up keeping the RV slow going down steep grades.  Otherwise my coach would rarely go much above 3K & after seeing the dyno plot I see why now. 

 

[Gary RV_Wizard]

As far as MH usage goes, gas at 3900 works as well as diesel at 2000.

Would make little performance difference if the gas engine could start out running at 4000+ rpms, but it has to build up through 1000 and 3000 and 3000 to get there. And to be as effective as the diesel, a gas engine should really have a 8 or 10 speed tranny to help keep it in its power band. Until Workhorse started using the 5 & 6 speed Allisons in their chassis, no large gas motorhome had better than sluggish performance. I'll take low RPM torque and horsepower over high any day.

I'm not anti-gas for motorhomes. Had a 2002 gas chassis that performed just fine, thank you, and cost far less to buy and less to own than my current diesel.  But I'm pushing around 37000 lbs now and need plenty of low end grunt to get it moving. A gas engine simply doesn't deliver that.

 

[miket]

Not sure if this applies here, but Workhorse had issued a notice to check the radiator fluid level on receiving a new coach, as some had air pockets and the radiator was not filled high enough to draw from the plastic jug. This probably has now been corrected, but was an issue in the past year.

 

[02 windsport]

I am extremely pleased with my 2002 GM 8.1 and Allison powertrain. I did have one engine failure that was a minor concern.  On my way back from Dover a rocker arm on one of the exhaust valves broke. It was covered by GM and has been fine ever since.

 

[max49]

  Unfortunately my 8.1 self destructed after 5 yrs and 28000 mi.  Something just let loose and sounded terrible. It kept running to get me off I-70 at the Georgetown exit. Had it towed to Burt Chevrolet in Denver.  Waiting to see what "Interstate Star" extended warranty says.
  I think the gas engines should be only used in no bigger than a 25' CL C  especially not in the mountains.  Even the big 496 Cu In 8.1 sounds like a screaming 2 cycle engine at 4 to 5000 RPM trying to get over the mountain. It's even kind of embarassing and scary sometimes.  Mine's  only an 18,000 lb rig with the 4 speed. The Allison 5 or 6 speed should help but then the MH weighs 22 to 26,000 LB  so they can't be any better.
  It's too bad we can't get the same MH with a diesel for a 5 to 10 K upgrade like we can in a PU truck.
  I had the 460 in a 28' Winnie Minnie that still ran good after 72,000 miles but it screamed at 4000 RPM + over the mtns @ 30 MPH too.

 

[34footer]

are you sure only 150hp at 2K ish?  That seems totally out of whack for a low revving large displacement v8!  I just made it home from a trip in my workhorse powered coach, I do not see how 150hp (2000-2500rpm's + ) could pull my coach along at highway speeds (60-75mph) in 6th gear - 38p from fleetwood

I would think these engines should have 150hp around idle.... from 1000 rpm's+ it should be well into it's powerband. 

Where did you get that info with it's power at that rpm? 

Once you get a vehicle up to speed it doesn't take a lot of HP to keep it at that speed on a fairly level highway. You need the bulk of power for towing capacity, passing, climbing, etc.
J

 

[Gary RV_Wizard]

When we had a 22,000 lb coach with the 8.1L and a 5 speed Allison, I was quite impressed with how well it performed, even in the 7000+ ft altitude in Yellowstone.  Long 6% grades took their toll, of course, but 35 mph still got us to the top. I usually kept it under 4000 rpms, even in the steepest climb.  Most lesser grades it just ate up.

The 5 or 6 speed Allison is a major improvement over the  4 speed

 

[FrontrangeRVer]

Max, let us know here what they tell you is the failed part, and also how Burt Chev. treats you.  We are at Fun Valley as we speak, and we have almost the exact same mileage as you.  About 95% of my mileage has been at altitudes above 7,500 feet, so we are in the same "travel" boat as you are.  We do run our 8.1 at 4K RPM going up and down the passes around here.

 

[max49]

  Burt has worked on the MH a few times before when it was under warranty, and I was always happy with what they did and never tried to charge me extra  for things like some RV places do.
  I'm not real happy with them right now.  When I called them they said they would'nt be able to work on it until Tu. It's now Fr and  it's sitting right where the tow truck left it and nothings been done.  They say they won't do any thing until they talk to the extended warranty co.  but just doing that, seems to be a problem for them.  I doubt the warranty co is just going to tell them to put a new engine in it until they take it apart to see what's wrong.
  I hope this works out. I'm in a pickle right now.  They said they would start on it Tu and Fr they still haven't.  Road Care towed it there at my request so if I have to have it towed some where else , it'll cost me $500 or $1000. Not to mention, it's hard to find places that will work on these and who knows if they will do what they say they will.    Do you guys think I'm being too impatient?  I think they should do what they said they would do, but I need to be careful or be prepared to have it towed some where else.
  K&C RV said it would be a couple of weeks before they could start on it.

 

[Ernie n Tara]

There has been a lot of discussion here that it doesn't take much power on the straight and level; I'd disagree with that statement because drag is a (the?) major issue in most cases. As a note, this is why gas rigs that shouldn't do well in the mountains often actually get better mileage on the flat sections at elevation (mine, a V-10, actually gets about 1.5 mpg better, all else being equal at 8,600 ft. - South Fork, CO).
The reason:

Drag = 1/2 * P * V^2 * CsubL * Area

Where
P = 0.0023  (for air = 1.0 for water) Note this is at sea level; higher=thinner air, = lower P
V = Velocity in feet per second
CsubL is coefficient of drag; about 0.8 for a flat surface (1.0 for a perfect flat plate)
Area = Frontal area (about 85 ft. sq. for MH)

At 35 mph, drag is about 206 lbf.
At 70 mph, drag is about 824 lbf.

To put the above in context, consider that my Ford V10 turns about 3,000 RPM at 70- and 1,500 at 35-mph, both in high gear. The only difference in HP  required (neglecting rolling friction) is drag. This is about 100 vs. 250 HP by Garry's chart; actually less since alternator drag, etc. are about the same or do not increase linearly.

Ernie

 

[Mark R.]

The gas Vs diesel questions will live for ever,  we all know most of the basic answers to the questions of cost, torque, HP,RPM ranges etc.. The question I would love to ask the major manufactures is why do you guys not build a big gas engine, built to handle the heavy rigs that the small V8's and V10's are being used in? To the best of my knowledge you can build a 400 HP gas engine with a max RPM of about 2500 easily , you just need to add some cubes like you do with a diesel engine. Not to say you can install this engine in your motor home but a eight cylinder light aircraft engine with 400 HP has a displacement of 720 cubes, and is built to develop that HP or close to it full time and last a long time. So why not build a big cube gas motor for RV's? Years ago large gas motors were built for boats (Palmer was one) slow turning high torque chuggers.  So if it cost too much to build a diesel then build me a 700 to 1200 cubic inch gas motor, I see no reason not to, opinions welcomed!
   

 

[Ernie n Tara]

Mark,
Cost is the single issue (neglecting the safety issue). A gas engine with peak HP at lower RPM is (as you noted) of higher displacement. That means physically much larger and heavier. Note that a diesel engine must be heavier in any event since the combustion pressures are much higher (compression ratio is about double that of a gas engine) as well as the fact that diesel fuel contains more energy potential.
The difference due to ignition timing is another reason diesels are heavier; gas engines fire at the optimum time (spark ignition accurately controlled) for efficient combustion and permit much higher RPM for a given stress level. Diesel engines use compression ignition, a more random thing since its affected by temperature, fuel distribution and other random factors. High RPM horsepower is simply much cheaper to achieve, particularly when you consider the ancillary costs of a heavier/larger engine in a relatively small vehicle.
Ernie

 

[max49]

This is interesting but does any one really feel that the 8.1 Ltr is much more powerful than the 6.8 V 10?
How much gas would a 700 to 1200 cu in gas engine burn.  Could it pass the EPA requirements?  If Ford, Chevy or Dodge can sell you a pick up trk and  give you a turbo charged diesel  upgrade for  6 or $8000 extra, why can't the RV industry do this?  I've been climbing moutain grades about 30 MPH and had diesel pickups with 35' fivers with a boat behind that and blow by me going around 60 MPH.
Is this the RV industries fault, or is Ford, Chevy and Dodge just stingy with their diesel engines and won't sell them to RV chassis mfgrs?
  Of course this would cost us a little more because we'd need a diesel generator too,  but it just seems that motorhomes are the only heavy vehicle still trying to use the old gas engine.
  Anybody know how that little 140 or so HP,  Mercedes diesel in a CL A  climbs mountains.  But that little MH lists for about $140,000

 

[34footer]

  Anybody know how that little 140 or so HP,  Mercedes diesel in a CL A  climbs mountains.  But that little MH lists for about $140,000

Power to weight ratio.
J

 

[DonTom]

This is interesting but does any one really feel that the 8.1 Ltr is much more powerful than the 6.8 V 10?

Yes. The 8.1L V8 is 100 CID larger than the V10, so that extra size has to be doing something. It least the 8.1L  will have more torque and run at lower RPMs, regardless of HP.

I think of HP as for racing, not many RVers race them. More torque is considered better otherwise, for such as touring.

-Don- SSF, CA ​

 

[max49]

Has anyone experienced engine failures with the 8.1 vortec? I have a 2004 Winnebago and have had two engine failures, the first on with 17, 000 miles on it for a ring issue. And now a blown head gasket on the replaced engine with 7, 000 miles on it and they are telling the motor needs replaced again, this time out of warranty. Any feedback is greatly appreciated. Yes the unit has been maintained, and was in for service two weeks prior to the trip it broke down on.

  Here's part of my crankshaft from an '04 8.1 Ltr with 28,000 miles.  Shop says there are signs that it was partly broke for awhile before it went into 3 pieces.

http://i233.photobucket.com/albums/ee6/firstmrmax/IMG_3975.jpg

http://i233.photobucket.com/albums/ee6/firstmrmax/IMG_3973.jpg


He said it was not an oil related failure and was a manufacturing defect. Extended Warrant Co is supposed to inspect today hopefully, but maybe tomorrow.  We are trying for a complete NEW engine.

Edit: fix links

 

[FrontrangeRVer]

Wow Max!  This is the first time I have heard of a crank breaking in the 8.1.....and I agree it must have been a manufacturing problem from the get go.  Thanks for the pics....it breaks my heart actually.....

And good thing you didn't have that ultrapower ECM tune.....you would have been paying for this out of your pocket then!  I certainly don't miss mine! 

 

[max49]

Yea it seems pretty strange to me too.  I was expecting a piston, rod or maybe a main bearing.
  I thought the engine would outlast the rest of the box.  I'm glad I didn't modify the ECM either. That seems like it could possibly cause some problems for a warranty, even if it had nothing to do with the failure.