The time has come!

As a number of you know, I have long felt that if an FMC is to be converted to a diesel engine today, the best engine to use is the GM Duramax 6.6L turbo diesel along with the Allison 6spd double overdrive transmission.  Some indepth discussion of what engine to use has been discussed in other threads.  To my knowledge, only one coach has been so converted to this point in time.  Conversions done in the 1980's and 1990's did not have this engine as a choice as it wasn't manufactured until 2001. 

FMC's did not have a diesel originally as the smaller diesels that would fit into the coach at that point in time were "dogs" as the former FMC Motor Coach Division Sales Manager has stated.  They would not provide the performance characteristics the designers were looking for so the Chrysler 440-I was the engine chosen.  It was a good engine then and it continues to be a good engine to this day.

Converting a coach is not a small undertaking!!  It is inappropriate for the vast majority to even consider.  They should just drive their coaches and enjoy!  For a few though, the positive features of a good diesel conversion outweighs the cost and trouble of going through the conversion process.  Personally, I have been balancing on the edge for some time.  I have reached the point in my life where I needed to either do it or abandon all thoughts of doing it.  I tipped over to the "do it" side!

At present, the coach is still in my driveway and the donor vehicle (pictures in the album section) is in Gilroy at a fellow FMC owner's home.  He has a larger driveway!  As some of you suspect, the person who so generously is helping (leading?) the way in this project is Eric Whedon, #587, and he is also host of the Northern California Work Days (you need to seriously consider being at the next one!).  His expertise in electrical and computer control systems in addition to his mechanical abilities is what is going to make this project doable as this is a computer controlled engine and a computer controlled transmission.

I want to stay away from cost issues during the project, but will be maintaining a detailed cost and labor record so at some point cost figures will become available.  We also intend to keep a detailed photo and written record of the what and how of what we do.  This will also be available later to help guide someone else should they want to follow the same path.

For now, wish us luck and stay tuned!!!

Terry, the transmission adds a couple of hundred pounds fairly close to the centerline of the rear axels.  The engine adds 100-150 lbs further back.  The overall length is about 1-2 inches longer than the stock setup.  The replacement radiator should be lighter than the stock one and will counteract some of the weight increase.  This is particularly good since that is weight that is further back and has greater positive or negative effects.

This setup has a lot of aluminum in all of the components so it is the lightest diesel/transmission combination that is available.  For comparison, the DD 8.2TD with transmission adds about 800-1000 lbs. In my specific case, I already switched to the AT545 transmission from the 727 a number of years ago and gained that weight at that point in time. 

My new transmission and bell housing will actually be lighter than the one I am currently using.  So in my specific case, I may have an actual net reduction in weight after the radiator is also taken into consideration.

Close enough for me.

Since my last posting, work has continued with interuptions for family matters and weather as we are working outside.  We are ensuring that we properly identify everything that is removed or disconnected so that anything that is to be reused will be clearly identified.

I have posted more pictures in the album section with descriptions of what is being done.  The engine's actual removal from the donor will happen in a couple of weeks, weather permitting.  Then it will get even more interesting.

The work progresses.  The transmission lines, driveline, etc. have been removed.  We then moved up into the cab and finished removing the interior stuff such as seats, center console and floor mat all of which have been sold.

That opened it up for the disassembly of the dash to begin so that the guage cluster, throttle pedal assembly and body control module could be removed.  More pictures have been added to the photo album.

Yes.  

We are doing a "full swap" to the extent possible in this case.  You could do a "minimal swap" which would not involve the dash cluster, etc. and with that swap you would retain the original guages/dash.  We are doing it as the full swap so that the benefits of the full guage cluster and the Driver Infornation Center (DIC) would be retained.  This includes cruise control.  The exisiting systems on all non-computer controlled engines will not work as there is no linkage for the cruise control to attach to.

An example of the two levels of conversion are like what we are involved in right now when it comes to the engine fan.  The donor fan will not work as it is a puller and not a pusher fan.  It also has an ambient air (exiting the radiator) thermal viscous clutch to control fan speed which also will not work as the air is going the opposite direction and will never engage the fan.

The simple solution would be to just remove the clutch and bolt the fan, by using an adapter, to the idler and have the fan operate at engine rpm the same as our fans do on the 440, 8.2, 5.9 etc.  The drawback to that simple solution is that the fan is always drawing full horsepower for the given rpm and, therefore, energy and fuel.

In an attempt to improve on that situation and have the fan only operate at the speed needed for conditions, we are currently looking for a fan clutch/controller combination that will electrically control the fan speed via a viscous coupling based on engine coolant temperature.  When cruising on flat land in cold weather the fan could operate at significanlty less speed than what is needed on a hot summer day if we find the right combination.  Given the amount of air that the fan will be capable of moving, the difference can be significant over a number of miles.

Stay in touch as we work our way through this project.  Your questions/sugggestions are always welcome.

We we haven't made much progress lately as we are working outside and it has been raining every weekend here in Northern California.  The mountains have 165% of normal snow load!  That has given us time to debate another conversion issue/question.

The question is: Should we move the donor steering wheel and upper steering column as well as the dash instruments to the FMC from the GMC Sierra? 

Changing the column would add the complications of doing that transfer, but would simplify the wiring as the four radio control switches, two DIC switches, shifting switch, tow/haul switch and cruise control switchs would no longer be needed to be rewired or moved to dashboad switches.  The steering wheels themselves are within 1/4 inch diameter of each other.  It would also be nice to have all of those controls on the "smart" steering wheel with the factory lighted rocker switches and their symbols.

Eric and I were fortunate to have Harry Day (and his wife, Sandy) stop by on their way south so that we could visit and debate the steering column question.  After that discussion, I believe we will be adding that change to the list of changes.

My coach will move to Eric's next weekend.  In the following weeks the engine and transmission will come out of both the donor unit and the FMC.  At that point, more pictures will be posted and we may have some more issues to solve. 

See the "For Sale" section of this site for things I no longer need and you may want.  I will be adding things over time.

The project continues.  Pictures and commentary continue into page 6 of the album.

http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=77&Page=5&sortdir=asc 

That link will take you to page 5 where we finish the preparation and start the actual extraction of the engine and tranny combination.

Thanks Terry!

Work has progressed and now the engine is out and the firewall has been cleaned up.

Pictures of the clean engine firewall are on page 7 of the photo album: http://tinyurl.com/7xt6pro

I also removed the unused Thermosan waste disposal unit and it is pictured there as well.  There is now a lot of nothing in the engine compartment.  The next step will be the lining of the existing firewall with sound suppressing material and then relining the firewall with a new layer of aluminum.

Donor engine extraction has happened!  The following link goes the first of the new pictures:

http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=77&photoid=2068

There are a couple of pages of pictures with comment.  You end up in the driver's seat.

Enjoy,

It will be quiet up front where I will be sitting!  The Duramax is a relatively quiet diesel.  I will be running a Banks tuner and will keep it in the Economy setting most of the time.  But if I select the extra 75 hp setting, it might not be so quiet for those that I pass.

The project moves forward. The fuel tank is out of the donor so that the fuel pickup assembly is assessable and the fan pulley is back from the machine shop.

http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=77&photoid=2301 

A little more progress has been made.  With the very capable and appreciated assistance of Larry Enoksen, #968, the fuel pickup assembly and the fuel tank have been removed.  Those photos start here: http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=77&Page=12&sortdir=asc 

Additionally, the master brake cylinder was also removed and taken to Randy Bradshaw, #299, for analysis and rebuilding.

And some more progress is being made.  Here is a link to page 15 of the photo album on this site.  The fuel tank is ready to go in and the generator has been removed and the dash gauge cluster has been removed.  See the comparison pictures of the 1976 gauge cluster and the 2006 gauge cluster.  What will take time with the gauges is the trimming of the new cluster and the design and fabriction of what will suround it and hold it in place.  Hopefully, it will also be pleasing to look at!  One step at a time.

http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=77&Page=15&sortdir=asc 

There just is a LOT of steps!

Well, the engine has been in and out a few times since my last post.

Here is a link to where the photo album has continued the installation process.

http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=77&photoid=2882 

At this point the engine is permanently in the coach, the parking brake mechaism designed and installed and the stuff is being put onto the engine such as the dual 145 amp alternators.  Click on the link and follow the pictures for the expalaination in the picture captions.

Come and see the coach in Carthage in July.

I would like make one correction to the above post in that it was Larry and Mark that did the real heavy lifting in getting the new fuel tank into the coach.  I could not have done it without their help.  Here is a link http://www.fmcowners.com/mbbs22/photos/show-album.asp?albumid=77&photoid=2951  to a photo of the tank being put into position.  You can see that some serious lifting was done by the two of them.  Mark is on the left and Larry is on the right.

It is exciting to see a light at the end of the tunnel and know it is NOT a train!!

Still not a train at the end of the tunnel! The work continues on getting the coach on the road and to Carthage.

This link takes you to page 23 of the photo album.  http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=77&Page=25&sortdir=asc   It shows the location of the water to air intercooler (technically an "aftercooler".

Still plugging away on the project.  Here is a link to page 27 of the photo album.

http://www.fmcowners.com/mbbs22/photos/photo-thumbnails.asp?albumid=77&Page=27&sortdir=asc

Don't know where you left off in your picture viewing, but the last two pages at the moment are #27 and #28.

The time to turn the key is getting close.

The trip went well and it was very rewarding to be back at the wheel of my coach after a five year hiatus.  Of course not all of that time was due to the work on the coach as we moved to Oregon from California and then bought another place that required a lot of rebuilding and then moved again! 

For this trip, I was pulling my '87 Subaru Brat loaded with my tools and a few extra things as a tow vehicle.  The Brat weighs 2600 lbs. plus stuff in the back.  The main effect of having a tow vehicle is on the grades, both up and down: more power needed to go up and more braking needed coming down. 

The engine performed as expected running smooth as silk and starts immediately.  The first thing I noticed is that the six speed transmission keeps the engine in its efficient power band (1600-2000 rpm) so smoothly the shifts are not noticed unless one is looking for them.  At 65 mph the engine is turning 1800 rpm which is just right as a small hill that would cause the engine to slow actually pulls the engine into a slightly higher torque point.  At 55 mph the engine is turning 1500 rpm which is the bottom of the usable torque band (1500-3200 rpm).  The wide torque band would come in useful with the current configuration.  Our earlier test runs over Pacheco Pass (1300 ft.) had shown us that pulling a grade at speed would overheat the engine as it will make more power and thus more heat than the cooling system could reject.  

Cruising on the flats at 65 mph the temp gauge reads 210 degrees which is what it also reads going down grades so I don't know what the actual temperature is in degrees.  Ostensibly it has a 180 degree thermostat.  I have a second sensor installed so at some point I will rig up a digital temperature gauge and see what it says at the various places on the OEM dash gauge.  As previously reported, the dash speedometer and my GPS agreed on the MPH so that makes the mileage traveled figures as correct as they will ever be and as correct as they were in the original vehicle. 

The trip was made in three segments.  The first was from Gilroy to Dixon where I made a stop at our favorite produce stand.  At that point I checked the mileage and mpg.  I had traveled 125.6 miles and it had gotten 14.5 mpg to that point.  There were only a few hills and one low pass for that segment.  From there I turned North and into a strong headwind.  I took it out of 6 and put in into 5 which is 10% lower gear than 6th.  Rpms went up by a couple hundred to 1800 and the temp held steady just to the right of the magic 210 mark on the gauge.  For some periods I was able to slip stream a truck or two for awhile.  I then stopped in Redding, CA to stretch my legs and check over everything prior to the mountains.  At that point I had traveled 288.8 miles and had gotten a cumulative 14.1 mpg.  Not surprising with the head wind and some hills.  The third segment was from there to my house in Cottage Grove, OR.  When I arrived there I had traveled 583.0 miles and had gotten a cumulative 13.1 mpg with that stretch being mostly mountains with some flat sections thrown in.  That section has two passes at 3000 ft+/-, one 4300 ft pass and several more at 2000 ft.

Yes, I will be at Red Oak next June.  See you then!

The fan is a viscous clutch and not an electric motor.  The fan and clutch were OEM for the UFO chassis built by Workhorse which had a pusher setup like the FMC but with a GM 8.1L engine.  The computer for the 8.1 had the ability to control the fan speed.  I have a nephew that is building a stand alone controller for me, but it is not complete at this point in time so I traveled without the controller.  The default for the clutch is full on so not having the controller just meant that the fan clutch was fully engaged at all time.  The controller is going to have to be re-configured as the normal temps for the engine are higher than previously thought.  Heat rejection was one of my early concerns as the Workhorse fan has fewer blades and is slightly smaller than the Duramax fan.  That aspect will be getting some review over the winter.  For now, the coach is very usable and it will get used!

Sag on

Kjetil, #477

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, 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 vallleys 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 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.