Can I run CNG with an additional regulator

Propane, Butane, LPG, GPL, C3H8, C4H10
C3H8
Posts: 1129
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Can I run CNG with an additional regulator

Post by C3H8 »

60 HP. WOW! Is anything made with 60 HP anymore. Smartcar maybe, but their so light they blow over in the wind. :D

Regarding the auto switchover from NG to LPG. A J reg requires neg pressure to release fuel. Anytime the NG system is supplying fuel it is has adequate Pos pressure and keeps the J closed due to the positive pressure. Once the NG pressure drops to near empty the pressure in the vapour line begins to drop. As soon as the pressure drops to a negative value the J begins to open and supplement and then take over until the pressure rises on the NG side forcing the J secondary diaphragm closed. The engine stays on LPG until the NG bottle is closed. To do this both lock offs must be open anytime the vehicle is running.

In theory this should work well. In reality it requires some compromise. As the pressure drops on the NG side the mixtures are going to begin to lean out prior to the LPG kicking in. This could create a condition of a lean backfire. The reason or market ideally suited to this is the large industrial engine market. The huge fuel draw they have usually results in a very fast switch over. These engines frequently run off NG wells with several hundred PSI, however the engines run the wells dry and switch to LPG. Over the next few days the wells regenerate and the engine switches back to NG. Typically we have had lean condition conditions on smaller engines. On a smaller engine, like your jeep a better method would be to monitor tank pressure with a sensor that could close the lock off. Once it gets down to about 200 or 300 PSI the sensor would shut the Ng lock off which would result in a quick loss of pressure and a quick switchover minimizing any lean condition.

Send me a PM and I can send you the IMPCO page as a PDF you can enlarge and read easily.

Steptoe
Posts: 1504
Joined: Fri Feb 02, 2007 8:32 pm
Location: JAFA , New Zealand

Re: Can I run CNG with an additional regulator

Post by Steptoe »

Thanks for all the input. I will plan on adding an external power valve for propane and just accept that cng is never going to run optimally in this engine design.........FWIW, I am overall quite happy running on lpg or ng even though the power output is so low. This jeep was never intended to be a powerhouse
Not having to worry about stale fuel, gummed up carburetors, fuel sloshing out of the tank on side slopes are enough to sell me. The easy starting and cheap fuel costs are just added bonuses.
Stale fuel.. I would have that issue with my boat, and vintage cars, to get around that I fill up on the way out on a fishing trip or car club event....
Fuel sloshing.....dump the stoch vents and cap and put in some that are designed to prevent doing so
with such low cylinder pressures , the fuel will be working so inefficiently there is a good change even economy would not justify the conversion, or even the capital expense and time....
Varnished up carb....never had the issue since using the moded fuels and total rebuild of the carbs.. I strongly suggest that varnishing is not a fuel issue.

I then dont see the purpose.....

Your better alternative would be as I suggest above, as I Have done with the Bradfords....around 8 or 9 years ago.. If i where to undertake again in retrosect, I would do what I have done again
And dont think I did not seriously consider alternative fuels on the Bradford....considering I do have hear the spare4 parts to do so....
End of the day I decked the cylinder pots, planed the heads, and still adjusted the Petrol fuel octane down.
My Spelling is Not Incorrect...It's 'Creative'

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