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propane amount question

Posted: Wed Jan 31, 2007 4:44 pm
by isban
Hey all this is my first post here. I have a propane gun and I was wondering if there an optimum psi or ratio that the propane should be at in the chamber that gives the best performance.

Posted: Wed Jan 31, 2007 4:53 pm
by Recruit
Yes there is a formula I dont remeber it off the top of my head. But it has to do with camber volumn.

Posted: Wed Jan 31, 2007 4:55 pm
by MrCrowley
Propane=your meter should be 4.2% of your chamber volume
MAPP= " " " " 4.6% " " " "

I think thats it. :roll:

Posted: Wed Jan 31, 2007 5:27 pm
by StealthSpud
Yeah Mr.Crowley I think that sounds right...mabye..

Posted: Wed Jan 31, 2007 5:53 pm
by willarddaniels
Propane burns between 2.4% and 9.2% fuel to air mixture. Optimal is 4.02%
One way to figure it out is fill your combustion chamber (and lead tube up to where your projectilesits) with water, measure the volume of water and multiply by .04 This will give you the volume of propane you should use.

Posted: Wed Jan 31, 2007 5:56 pm
by Pete Zaria
You guys got the ratios right: 4.0-4.2% propane, or 4.6% MAPP gas.

If you're using a meter system, this spreadsheet (called ProMeterEs) will show you what pressure to use to get a 4.2 or 4.6% mixture: http://www.spudfiles.com/forums/download.php?id=3213& .

All the math is done in volume, not length of pipe or anything. If you need to calculate the volume of your combustion chamber or meter pipe: http://www.online-calculators.co.uk/vol ... volume.php

For example, I have a 250ci (4" x 20") combustion chamber and a 7" x 3/8" meter pipe. I use two "shots" of propane at 65 psig each.

Peace,
Pete Zaria.

Posted: Wed Jan 31, 2007 9:04 pm
by isban
wow thanks pete those links are really helpful