Musings on Dual Fuel Implementation

Propane, Butane, LPG, GPL, C3H8, C4H10
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FrankGRUN
Posts: 10
Joined: Tue Jul 22, 2014 8:31 pm

Musings on Dual Fuel Implementation

Post by FrankGRUN » Fri Mar 22, 2019 4:45 pm

For some time I have been going back and forth about finishing implementing dual fuel (LPG and Gasoline) operation on my Ford 460 powered motorhome. The 1982 E350-based 24ft unit was built at the factory with dual fuel including dual full size propane tanks (right and left) integrated with the fiberglas body structure and was delivered from the factory with an Accucarb mixer atop the Motorcraft 4BBL smog carburetor. I purchased the motorcoach in 2010 with less than 40,000 miles from the second owner, but the LPG mixer and associated components were long gone. Over the years, I have accumulated several IMPCO 425 and 300 mixers, Model E converters, DualCurve Dual Ignition Systems, Closed loop controllers, and various air horn adapters. But recently, I acquired an OHG X450 mixer, X-1 regulator/converter and air horn adapter. I have then been focussed on doing a clean and complete dual fuel installation.

In the interim, I added a Melling towing cam with straight-up timing to the 460 along with an Edelbrock 2166 Performer Dual Plane manifold, Hedman long tube ceramic coated headers, 3" single Magnaflow exhaust, Duraspark II ignition with Crane Hi-6S CDI module and a custom tuned (by a renowned carburetor expert) Edelbrock 1406 600 cfm carburetor. I also deleted the EGR and all other smog equipment while plumbing in a very effective cold air intake (measured air temperature at carburetor air inlet is just 5F hotter than the ambient at the entry to the E350 grill). The motorhome has the C6 3-speed automatic with Gear Vendors Overdrive, Hughes Towing torque converter, 4.56:1 rear gears and runs on 8.75R16.5LT tires for a measured 2342 rpm at 55 mph cruise. Last fall, before sealing it up for the winter, I completely changed over the engine accessory drive system from the stock v-belt to the late Ford "serpentine" belt system (Poly-Vee). This last operation opened up considerably more engine bay room for mounting the OHG X450 package.

As the snows cleared, I again started to review parts and prepare to rebuild the X450 and the X-1. But then a major event triggered this post. I acquired a Fitech 30003 Street GO EFI 400HP electronic fuel injection system. Suddenly, the many issues about rejetting the Edelbrock carb to take into account the air restriction and pressure drop introduced by the OHG mixer simply disappeared. Gasoline shutoff and turn on issues evaporated. Now with the O2 wideband sensor and Fitech ECU controlled AFR ratios, any impact of the mixer during gasoline operation has passed to the next dimension. With the addition of a CB Performance Black Box, I will add two programmable ignition control maps - one for gasoline and one for LPG. Further, with the Fitech throttle body, I can eliminate the 1" thermal phenolic spacer previously needed for minimizing fuel boiling with extreme underhood temperatures. This leaves me with a very critical 1.625 " clearance between the top of the OHG air horn and the bottom of the body bulkhead confining everything in the E350 engine compartment. The only price I seem to have to pay is the loss of a fuel flow signal from the LPG system to operate my mileage display on my Zemco ZT-3 Driving Computer!

Would appreciate any real world comments and observations that would temper the current euphoria! Sorry for the length.

C3H8
Posts: 1036
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Musings on Dual Fuel Implementation

Post by C3H8 » Fri Mar 22, 2019 5:12 pm

That's quite a project with many upsides. The only comment I can add would be its too bad you eliminated the EGR. EGR's are one of the true better emission devices manufacturers installed that did everything intended. A properly functioning EGR improves economy during cruise and lowers combustion temperatures. It works the same for propane or gasoline. In addition it reduces the oxides of nitrogen (Nox) coming out of the tail pipe. Other than that I don't see any downside to the changes you are considering. It will give you the best of both worlds allowing you to take advantage of the cheapest fuel price wherever you are.

C3H8
Posts: 1036
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Musings on Dual Fuel Implementation

Post by C3H8 » Fri Mar 22, 2019 5:14 pm

Forgot. Another EGR benefit. It allowed an increase in timing at cruise because of the lower combustion chamber pressures.

FrankGRUN
Posts: 10
Joined: Tue Jul 22, 2014 8:31 pm

Re: Musings on Dual Fuel Implementation

Post by FrankGRUN » Fri Mar 22, 2019 6:36 pm

Yes, only recently have I become aware of the EGR positives. Unfortunately, soon after moving to Reno, a Roadside Assistant helped me (I had run out of gas on a busy freeway) by taking off the air cleaner, squirting some ether in the carb while dropping the air cleaner retaining nut down the throat (all unknown to me - I was blocked by traffic in the driver's seat trying to find out what the H*** he was doing). End of story, within 3 miles, the engine seized! When I tore it down, I found the nut in cylinder #3 with the cracpiston and bent rod! I elected to replace the engine with a crate stock motor from Promar, and no EGR units were available. After that, I went to the non-EGR intake and block off plate, etc, etc.

But I certainly wish now that I wouldn't jumped to the EGR-delete advice I was getting. I'm about to experiment with max vacuum advance at lean cruise.

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