Converting early gas MH to Duramax? Possible?

[JeepSJ]

Very nice! Are you monitoring your intake air temps? I was wondering how that water/air intercooler was working.

[BigRabbitMan]

Very nice! Are you monitoring your intake air temps? I was wondering how that water/air intercooler was working.

That question raises one of the little glitches with my system. I installed the Banks system with their IQ monitor/controller with lots of readouts. The problem I have is that it doesn't work with the long extension cord that I have to use to reach the front (30') so that I can monitor things while on the road. It works fine while only using the short cord that comes with the unit but since my engine is in the rear, I can't use it while driving. I will be contacting Banks to see how this can be resolved. In the meantime, I know the water is warm/hot when stopping so it is taking heat out of the air stream but I don't know the actual air temp while under load.

I do have a second issue as the turbo vane position sensor is not functioning with the new sensor. The result is that I am always at full boost so have driven very conservatively. I will be starting a new thread about that issue at some point.

[convert2diesel]

That question raises one of the little glitches with my system. I installed the Banks system with their IQ monitor/controller with lots of readouts. The problem I have is that it doesn't work with the long extension cord that I have to use to reach the front (30') so that I can monitor things while on the road. It works fine while only using the short cord that comes with the unit but since my engine is in the rear, I can't use it while driving. I will be contacting Banks to see how this can be resolved. In the meantime, I know the water is warm/hot when stopping so it is taking heat out of the air stream but I don't know the actual air temp while under load.

I do have a second issue as the turbo vane position sensor is not functioning with the new sensor. The result is that I am always at full boost so have driven very conservatively. I will be starting a new thread about that issue at some point.

Stephen:

I concur with your decision to contact Banks. Your sensors are either resistance or hall effect, both would be adversely effected by length of harness. Same goes for the EGT. There might be a way to calibrate the unit to compensate for the length of wire but only Banks could tell you how. I do know that EGT leads can be purchased with different length/resistance specs.

Good luck

Bill

[Hal StClair]

Not to hyjack a thread but I have a 1977 GMC that I've installed a 2000 H1 6.5TD with 4l80e trans. I used a B/W transfer case from a Revcon MH and went forward to a 2012 9.25" AAM front diff out of a one ton Chevy. We've put about 3000 miles on it since September and have very few nit's to pick so far.
Not a swap for the faint of heart for sure, but a nice match.
Hal

[BigRabbitMan]

The following is a report that I just posted on the FMC Owners Club website. It should bring you up to date as it includes a mileage check on flat ground and one in the mountains.

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Since I now have just under 5,000 miles on my conversion, I thought that I would do an update.

The first thing to note is that I am very happy with what I call the "drivability" of the coach. I like the ease of merging with traffic at speed, not slowing down for most hills, engine starting in a revolution or two, butter smooth shifting, a 700 mile fueling range, an even quieter interior and other smaller factors. Many people are interested in what my fuel mileage is as that is a significant factor with any motor home. Historically, with the 440 I got about 7.0 mpg most of the time. That is probably about average for an FMC.

As expected, I have seen a significant increase. Since fuel mileage varies with driving style, weather, terrain etc. I decided to do some close measurements under specific conditions to help define what was occurring rather than just post a series of numbers. So on a recent trip to CA I decided to do a flat land test and a mountain test.

The flat land test was from Redding, CA to Bakersfield then back north to Santa Nella, CA. That was a run of 674 miles over three days time. The first half of the trip was with a storm coming in and a lot of cross wind. The second half was with relatively calm winds. I also made five diversionary trips into towns for various reasons so it was not all straight down the freeway driving. I spent most of the time in the truck lane at 60-63 mph as it was a comfortable driving speed and I didn't want to be in and out of the 70+ mph left lane. The net result was that I got 14.7 mpg for that segment of the trip. I was not towing the Subaru Brat.

For the mountain segment, I went from Redding, CA home to Cottage Grove, OR. The beginning and end of the trip were at a similar altitude with an initial gradual climb from Redding to Weed at 3,900 ft. It then dropped down to the Shasta river and back up to 3,000 ft then back down to the Klamath river. Those were 4 or 5 mile 5 & 6% grades after some flat stretches. It then went from the Klamath river down in the canyon up to the top of the Siskiyou pass in Oregon at a little over 4,100 ft which is the highest point on I-5. After dropping down the 7 mile 6% grade into Ashland it became a series of ridge crossing with the first several at the 2,000 ft level then into the valleys in between. As I continued north, the ups and downs became less significant until I reached home in Cottage Grove. Again, I was primarily in the truck lane except when passing trucks on grades. When descending 6% grades, I slipped the Allison 6 speed tranny into third gear (which is the same gearing as second gear in the 727 tranny) and came down the grades at 50-55 mph without needing to use the brakes.

The mountain portion of the trip was 301 miles and the coach got 13.3 mpg which is a respectable number for mountain driving in my opinion.

With those two numbers in mind and the conditions that created them, I expect my long term number to be somewhere in between them. Towing the Brat will probably reduce those numbers by a mile per gallon. Even with this kind of fuel mileage, it will take a lot of miles to recover most of the cost of the conversion excluding the unpaid labor cost for myself and the others who invested significant hours as well.

But, yes, I am glad that I did it and hope to see all of you on the road or at a future rally. Schedule yourself for the June Mega Rally in Carthage, MO and you may have the opportunity to take my coach for a test drive.

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There is now a second FMC owner converting his coach to a Duramax with 6 speed Allison. Here is the link to his thread on the FMC Owners Club website. He, also, has received good information from this site and its members. http://fmcowners.com/mbbs22/forums/t...sts=54&start=1

[BigRabbitMan]

In the above post I mentioned that I was going to a rally in Carthage, MO from my home in Oregon. Well, I went to that rally and then continued on to the East coast including SC and Virginia, on up into Canada through Detroit, then back via MN and South Dakota. In all, from my door back to my door was 8,424.6 miles! It was a great trip and it gave me a chance to drive the coach extensively under different conditions and see how it performed.

It met all of my expectations and much more. At my Canada stop, we tweaked the adjustment of the front end elements and got the last of the play out of the system. It now tracks like it is on rails.

Up until the Canadian stop, I ran the Banks tuner on Normal or the stock tune. At that point I changed it to the Economy tune just to see what, if any, difference it would make. Up until that point, I had 11,289 miles on the conversion with an average of 14.02 mpg. From that point home via the northern route with a couple of diversions along the way, the coach averaged 15.08 mpg over that 2,907 miles.

Yes, I am very surprised and pleased to be getting mileage like that in a 15,000 lb. motor home. I will continue to monitor fuel mileage for the next year or so just for the record.

I thank the group for its support of this project,

[a5150nut]

Glad to hear of your success. That's a long ways from Morgan Hill where it all started.

[arveetek]

In the above post I mentioned that I was going to a rally in Carthage, MO from my home in Oregon. Well, I went to that rally and then continued on to the East coast including SC and Virginia, on up into Canada through Detroit, then back via MN and South Dakota. In all, from my door back to my door was 8,424.6 miles!

If you should ever find yourself coming through Carthage, MO, again, please let me know. I work for an RV dealer here in Carthage, and would love to see your rig.

Casey