Thread:

Diesel Motorhome repower...

Originally Posted by Froggystyle

I'm not talking about going crazy... I am just looking to put a larger stock motor in it.

Like... dead stock. But bigger. In my mind, this shouldn't be any harder than taking a 5.3L truck and putting the 496 in it or something. Just a parts swap.

The thing goes 40 up the the hill, and gets real warm when it is cooking out. We came home from the river on Monday and at only 105 degrees out we were running the heater to keep the engine cool, and we weren't towing a boat.

Something's got to give, and the moho I want is about $300K, and I take a $30K bath on mine. (I only paid $100K for it new, list was $148K)

Frankly, I thought I was in mine right, and could sell what I got it for.

It seems to me it would be a whole lot easier and cheaper to do a few upgrades to the package you have. Just stick to bolt on stuff like exhaust, intake, programmer, things like that.

I know on my Duramax I had it was a total dog towing without the programmer and extras. I towed our race truck down to Mexico in 2005 for the Baja 1000 and loaded on the trailer it probably was about 10,000 lbs plus the bed full of spare parts, tires, tools, race fuel, etc. On the way home my Edge (an old model) malfunctioned so I disconnected it and drove the rest of the way without it. The truck was extremely disappointing without it hooked up. That truck had almost 70,000 miles on it when I sold it and never had any problems whatsoever with the exception of the Edge malfunction.

Originally Posted by STV_Keith

For the money you're going to spend, I'd look at the possibility of major cooling system upgrades and more power in that motor. I mean, you can get a programmer or box to turn the power up for $500-1000, and we know the motor will make 500rwhp without issue, then spend a few grand on a larger/better IC and radiator and or add another rad somewhere - get creative - it's what you do. WAY cheaper than doing a swap.

You know my static answer on this stuff...call Steve.

You and I are on the same page here....you just typed faster than I did.

Wes,

You know I have a similar rig and see a few of the same problems....when's it's really hot outside the motor will climb in temp but never high enough to require turning the heater on. I am running a 40HP tune on ours and it tows 55 to 60 mph un the grapevine towing 8,000lbs.

For the money I think your best bet is to upgrade the Allison for 3K, upgrade the radiator, intercooler, and tranny cooler, and then spend some another 5K to 10k getting the motor built solid. You'll get a ton more power and still keep the reliability. There are very reliable Dmax's out there making 1000 + ft/lbs of tq. The trick is finding the right motor builder.

That's my $.02,

Chris

Originally Posted by Sig Ep Mock

Wes,

You know I have a similar rig and see a few of the same problems....when's it's really hot outside the motor will climb in temp but never high enough to require turning the heater on. I am running a 40HP tune on ours and it tows 55 to 60 mph un the grapevine towing 8,000lbs.

For the money I think your best bet is to upgrade the Allison for 3K, upgrade the radiator, intercooler, and tranny cooler, and then spend some another 5K to 10k getting the motor built solid. You'll get a ton more power and still keep the reliability. There are very reliable Dmax's out there making 1000 + ft/lbs of tq. The trick is finding the right motor builder.

That's my $.02,

Chris

Easy to do for ballers like you guys!

Originally Posted by STV_Keith

For the money you're going to spend, I'd look at the possibility of major cooling system upgrades and more power in that motor. I mean, you can get a programmer or box to turn the power up for $500-1000, and we know the motor will make 500rwhp without issue, then spend a few grand on a larger/better IC and radiator and or add another rad somewhere - get creative - it's what you do. WAY cheaper than doing a swap.

You know my static answer on this stuff...call Steve.

Thing is, I am always worried about cylinder head temp. My truck runs at 1300 or so for EGT when towing up the grade, and I think this thing will be at 1300 the second I leave the garage. I don't think you can make 500 with this kind of a heat load... If you can, I am stoked, but I know that when I tow the hill with my 2500, the EGT sits on the cutoff, and I am not making anywhere near the power I make if it is running cool with a lower load. Probably actually close to stock is the way I figure it.

I have de-tuned the Edge while climbing to see what setting it goes to that ends up feeling like less power, and it is dropped all the way to "1" before it starts losing RPM's.

Figure it is at 3000 RPM, 35-40 mph for 20 minutes straight when climbing. On the back side, it is harder and slower, but only for 12 minutes.

I just don't think the D-max can pull that load.

Originally Posted by Lavey29

Will it be a business write off expense for the shop moho? Might make it more pallatable then...

It is certainly a write-off, and a lot more palatable than a new rig.

Figure if I got into a new rig, close to what I want at fire sale prices it will be $150K minimum. In order to get a toter this small, it will not be used, and will be a new, special order and construction. I will lose $30K on the coach I have, assuming I can get $70K for it which may be a pipe dream at best. Figure on $60K and losing $40K to be conservative. Tack the $40K on to the $150K and I have doubled my payment to $190K... something I probably can't even swing financially anyway.

The reality of finding a 33' motor garage with a big engine that is nicer than mine is a zero possibility. They aren't out there. I have the baddest one they make in 33', and it needs more power, and little else.

Originally Posted by Sig Ep Mock

Wes,

You know I have a similar rig and see a few of the same problems....when's it's really hot outside the motor will climb in temp but never high enough to require turning the heater on. I am running a 40HP tune on ours and it tows 55 to 60 mph un the grapevine towing 8,000lbs.

Our boat on the trailer is 6K#, but we have the 1200# Rhino in the back of it too. Plus, I think mine might weigh a little more than yours stock with the lift gate and stuff.

Originally Posted by Sig Ep Mock

For the money I think your best bet is to upgrade the Allison for 3K, upgrade the radiator, intercooler, and tranny cooler, and then spend some another 5K to 10k getting the motor built solid. You'll get a ton more power and still keep the reliability. There are very reliable Dmax's out there making 1000 + ft/lbs of tq. The trick is finding the right motor builder.

That's my $.02,

Chris

Good advice, my worry is the inherent reliability of the aluminum head under heavy load. I don't think you get a heavier load than a motorhome towing a boat realistically.

Who knows... This is probably the right path, and Keith knows more about this stuff than anyone I know, so I will likely take his advice on this. Should have just called I guess...

I just absolutely can't have failures, and driving by your EGT is never particularly a good idea.

The exhaust is huge on this thing too... like, 4.5" pipe out of the turbo I think. When I changed the exhaust on my 2500 I didn't even notice a decrease in EGT at all.

What size/series and power rating of the Dura Max you have currently?

Originally Posted by Froggystyle

Thing is, I am always worried about cylinder head temp. My truck runs at 1300 or so for EGT when towing up the grade, and I think this thing will be at 1300 the second I leave the garage. I don't think you can make 500 with this kind of a heat load... If you can, I am stoked, but I know that when I tow the hill with my 2500, the EGT sits on the cutoff, and I am not making anywhere near the power I make if it is running cool with a lower load. Probably actually close to stock is the way I figure it.

Is that a LLY or LBZ? Again, call Steve for the specifics, but I'm pretty sure the Dmax will take more than 1300 continuous. I know the Cummins 04.5+ motors are rated for 1550* for 30 mins. Also, there may be more Steve knows about how to tune the WG/VGT actuator to make it work better. A bigger/better IC should be worth 100-200*F drop in EGT. I know my truck lost 100*F with my factory replacement (stock size, but 3" instead of 2" thick) IC, and at a lowly 15-18psi boost (all it takes to tow the STV up 7% grade).

The beauty of that big package you have is likely you have some room underneath the chassis. I'm thinking another almost full-size radiator, plumbed in with fans - that would double the water capacity and radiation capacity of the system. You could even go with a water/air IC and only turn the pump on for the long grades, using it only when you needed the extra help beyond the stock IC capabilities. Water/methanol injection is another option too...and you have plenty of space for a tank. All things you should ask the man.

Originally Posted by Sig Ep Mock

Wes,

You know I have a similar rig and see a few of the same problems....when's it's really hot outside the motor will climb in temp but never high enough to require turning the heater on. I am running a 40HP tune on ours and it tows 55 to 60 mph un the grapevine towing 8,000lbs.

For the money I think your best bet is to upgrade the Allison for 3K, upgrade the radiator, intercooler, and tranny cooler, and then spend some another 5K to 10k getting the motor built solid. You'll get a ton more power and still keep the reliability. There are very reliable Dmax's out there making 1000 + ft/lbs of tq. The trick is finding the right motor builder.

That's my $.02,

Chris

Banks does a bunch off stuff with the D-Max's including a marinizing package that is new.

Might be worth a call. Tell them who you are and you want to talk to Gale about a project. Maybe he can talk with you directly and spill the D-Max beans.

Stock Cat power in this chassis is C7 250 hp and less then 700 lb feet TQ. That is not an option I would think.

Originally Posted by jordy

OK, so talking with the guys in my shop, it seems as though there may be a legitimate problem with your engine, which is creating the overheat... We had one of our service trucks have issues with the fan clutch, and they run those trucks heavy, but never to the point of having to run the heater. Are you running a boost gauge on the MOHO??? Another possibilty would be a loss of boost somewhere in the charge air cooler, or the boots/plumbing from the compressor up and around to the intake. Just some stuff to check out as everyone was in agreement that it shouldn't be that much of a pig and have heat problems being stock.

They also agreed that if you were going to do anything, buying a 6500 chasis with an 8.3 Cummins would likely be the way to go and then just flip flop the bodies. The 5.9 will be a torque monster, but ultimately, it's still a smaller displacement and will end up working harder than something like the 8.3.

Now that I read your post Jordy I remember reading a bunch of stuff on the FullSizeChevy fourm about 05 LLY's running HOT on long pulls and then blocking off EGR's and a few other things.

Might be worth a search over there Wes.

http://www.fullsizechevy.com/forums/...n/diesel-tech/

I would search it but I can't pull the username and password out of memory.