Champion dual fuel generator, convert to nat gas?

MEXICOWANDERER wrote:
I have converted three generators to natural gas from liquid gasoline fuel. All three were subsequently fired with modified Impco carburetors and all three were operated at +5,000 ft altitude.

Subsequent loading of the pair of 12,000 watt Onans, caused them to run out of prime mover power at 8-9,000 watts depending on temperature. After much debate a switch to JAHNS cast pistons was made. The domed pistons were thought to raise the compression ratio to above 10 to one from 8 to one. The engines were overhauled and assembled in Reno, NV.

The second type of engine was a Wisconsin V4 valve in block 37.5 original horsepower prime mover. The cylinder heads were cut .125" to raise compression. The assembly work was done on site.

Starting the engines then fine-tuning the air fuel ratio was am experience in maintaining patience.

Out of the box, the IMPCO carburetors would not allow the engines to fire. The main mixer orifice was enlarged .010" at a time. This was done by a propane mechanic thank god.

Enriching the mixture had solid repercussions. Too rich and the air cooled engines would overheat. Definition of overheat: In the dark the exhaust manifolds would glow dully red.

What a time-waster! Avoiding overheating the engines was a challenge. Industrial 240 fans were used in the gen sheds to flood both engines with ambient air.

Over temp shutdown was used on both systems with 290 degree block sensors used as a thermal limit. At that temp, engine lube oil temps were found to be in excess of 300F. I taught the caretaker how to parallel the pair of Onan generators.

NOTE: I was not satisfied with the outcome of this work. Moreso on the OHV Onans than the Wisconsin. Trying to equal or surpass the gasoline output resulted in engine overheating. My recommendation of using diesel replacement units was dismissed. The objection was based on a slight possibility of wind shift and diesel smell. 2nd Objection was maintenance involving dirty diesel lube oil.

But the corporation "principals" smiled and cut the checks.

on portable generators the advantage of conversion to NG or propane is more one of not worrying about bad gas, or having an infinite fuel source (NG). Realizing that power output WILL go down some, probably on the order of 10-15%.

On my honda 2200 and honda 2000 the tri fuel conversion so far has worked fantastic. Starts and runs easily on all three fuels, but as mentioned lower power output on Propane or NG. Honda having a fuel pump makes an easy conversion, when on propane/NG, power to the fuel pump is cut, run it dry, switch. It will sputter for a minute or so as the last bits of gas are combined with the propane/NG, then it's all set.