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Alternative fuel for hack - LPG in gasoline motor

c64club · 2015-07-07T06:33:33Z

Topic for everybody but I start it as an answer to Sven's question.LPG conversion is very simple. For most carburetor fueled bikes there only "first generation lpg system" conversion is suitable. It contains a tank, pressure reductor(commonly blocked with evaporator) and mixer. And some filters, valves etc. In series you mount tank with valve (or with multivalve and filling valve-connector), liquid phase filter, evaporator-reductor unit, "register" screw valve and a mixer. English materials are available on the net. Mixer I could try to make so called "drill-in" into airbox or into carburetor (that acts as throttle only). Also I could try to make a flow-through miver. But there are ready made "plug and play" flow-through mixers on ebay: These are for 50-110cc bikes and for 125-150cc bikes with "generic" Keihin-copy PZ 22 and PZ 26 carburetors. There are also bigger mixers available but with very small flow: I have 200cc with PZ30 carburetor, so I decided to play with the mixer on lathe. Just turned some dimensions to fit them with bigger mounting circumference and bigger flow. Also drilled gas channels for bigger section and made some more holes on mixing section. Then polished everything to give a good flow, now it's better than original. Pressure reductor. I used standard car reductor-evaporator for 90bhp engines. As it's too big, I reduced a flow between evaporator and reductor sections by placing brass bush in channel and drilling it to get 20% section of original channel. Regulation is still something problematic. Iidle revs on heated engine are unstable or sometimes impossible, but it's a problem only in traffic jams or in town, where I appear very rare. On 300+ cc engines it should be OK. Car reductors just cant give such small flows stable. Small bike (or lawn mower) reductors don't have evaporators and are suitable for slightly smaller engines than mine. So I had to use a car one. Evaporator. The only problem in aircooled bikes is heating a reductor-evaporator. It's illegal (and not smart) to heat the evaporator directly by exhaust. Evaporation needs some heat, about 2-3% of energy that is radiated to atmosphere. In watercooled machines, you just connect evaporator's heating circiut into car's bypass flow. In AC there are few "patents", now mainly historic. You have to make some water circuit. Heating is most commmonly some thin pipe (6-8mm) wound over exhaust or over cyllinder, few winds. Then connected to electrical or mechanical pump, in some cases it's enough to have natural thermo-syphon flow. Also there exist some "patents" with oil to water heat exchanger instead.My patent is simple and effective. I bypassed an oilway in head's cap and connected it to evaporator's heating section. Such circuit does double job. Heats an evaporator and lubricates head valves with oil cooled about 10-15 Kelvin degrees compared to non-bypassed head. Also now I have 1.2 liters of oil in circuit instead of 1l standard (evaporator and hoses get 200cc). LPG is generally "drier" and "warmer" fuel than gasoline, so valves are happy with such cooler bath. In first version I modifier heating section in evaporator to be sealed with thin aluminium sheet instead of rubber membrane: But I also gave an old membrane "oil cooking test" and it emerged warm-oil-resistant, so the sheetmetal seal is unnecessary. Evaporator isn't needed in engines up to 50bhp with big tanks, that work in summer. You just get evaporated gas from tank. Dismantle syphon from multi-valve or install a stove bottle with valve up. Common practice in Urals/Dneprs etc, many taxi and grocery hacks in Asia work fueled that way, also scooters in Italy. But my rig will also work in winter and it needs more evaporated gas than scooter, so it needs a heated evaporator. In non-summer temperatures, propane in tank evaporates way faster than butane, so the mixture proportion changes and that makes another problems. Tank You need tank with specific multi-valve allowing it to tank without overloading. It automatically disconnects fillng-valve when liquid gas level in tank reaches 80%. This allows tanking non-empty tank, like a normal liquid fuel, without risk of disrupting a tank. I placed small, 20.5 liters tank in car's trunk. Of course 562's floor isn't suitable for installing a 30 kg tank. Also there is required for tank's mountings to withstand 20G deceleration in drive direction and 8G in side direction, to ensure that someone will not be hit by tank in case of serious . So I added a frame on tub's floor, mounted to tub's mounting bolts. Technically, any gas tank ("bottle") is suitable, even the stove ones, only they must be filled outside the vechicle and changed when whole gas is used, so you must have some small reserve bottle or you go more often on gasoline.Gas pipes - liquid and gas phase Liquid phase pipes in cars are made from Cu 6mm and 8mm pipe...

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Last Post by c64club 10 years ago

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c64club

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What with legal side of LPG conversion in USA? Can you just install and go? In Europe, years ago it was your problem, what you tanked. Now LPG conversions are highly restricted and of course you cannot do it by yourself

Posted : July 17, 2015 12:55 pm

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