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Propane Injection-Math

Come find a how-to on how to do something, or come write your own for other people.
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Unread postAuthor: FeLeX » Tue Jul 17, 2007 10:57 pm

1. It has everything correct. Its just that you are lacking common sense.
2. I rounded thing off because I didn't feel like typing 20 digit numbers in. It doesn't matter at all.
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Unread postAuthor: jimmy101 » Wed Jul 18, 2007 12:38 pm

You should write things for idiots like me. If you can't, then don't post "Propane Injection Math", call it "Wild Ass Guess at Propane Injection Math".

There is a crap load of difference between "typing 20 digit numbers" and typing in two or three significant figures. Learn the difference. It ain't rocket science, it is basic mathematics.

Why post at all if the answer you end up is only good to +/- 20% or so? Hell, people can WAG the numbers better than that.

There are several sites with the mathematics for designing a fuel meter, why post another that is inaccurate and hard to read?
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Unread postAuthor: FeLeX » Wed Jul 18, 2007 11:38 pm

Alright dumb crap. This is my last post to you. Its not inaccurate. Its just not worth typing in the whole 20 digit number because of the .01% error. It will work just as good and you would see no difference in performance. Plus this post is just to explain how to calculate it. Some how I don't see any one else complaining, they all said it was a very good post and even that it helped them. But then again, theres always some smart kid like you out there.
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Unread postAuthor: jimmy101 » Thu Jul 19, 2007 12:09 pm

Yes, there always is a smart kid out there that knows their ass from a hole in the ground.

And there is always a twit that doesn't understand basic math or how to write a lucid post.

The whole 20 digit number eh, how about a three digit number?
This is my last post to you.
Promise?
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Unread postAuthor: drumher » Tue Sep 18, 2007 8:59 pm

Damn !
Smart kid,..ass,..twit,..lucid,..eh ! How about anger management ?
Lead by example !
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Unread postAuthor: brother361 » Wed Oct 24, 2007 6:42 pm

call me a noob but how do u make a propane injection thing i rele need help with this
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Unread postAuthor: HaiThar » Wed Oct 24, 2007 6:51 pm

brother361 wrote:call me a noob but how do u make a propane injection thing i rele need help with this


Randomness. Spell check PLEASE. Anyway, for propane injection, people sometimes use a modified shrader and a shot thingy( I can't remember the name right now). Many people, however, will set up a system, that has two ball valves...So it will look like this:

(====) -----------|||| ============||||---------

There is also a pressure gauge on your chamber
(===) is a propane tank
----- is a hose
|||| is a ball valve
===== is a chamber proportional in volume to your chamber


sorry if its a bit unclear...
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Unread postAuthor: mark.f » Thu Oct 25, 2007 5:51 am

Simply put:

<table><tr><td><pre>
IF chamber does not displace air as propane is injected
THEN
P<sub>m</sub> = 0.6174V<sub>c</sub>
-----
V<sub>m</sub>

IF chamber does displace air as propane is injected
THEN
P<sub>m</sub> = 0.59241V<sub>c</sub>
-----
V<sub>m</sub>
</pre></td></tr></table>

Where:
P<sub>m</sub> = pressure of propane meter in gauge PSI
V<sub>c</sub> = volume of combustion chamber
V<sub>m</sub> = volume of propane meter, (in same units as volume of combustion chamber).

EDIT: that's the second time I've done that. For some reason, if you put P<sub>m</sub> as being in absolute terms... it doesn't work. It really annoys me too because one side of the equation is in PSIA and one side is in PSIG. I think it has something to do with propane staying inside of the meter after injection, so here's my hypothesis.

You have a combustion chamber and a meter pipe. The combustion chamber is 100 cubic inches and the meter pipe is one cubic inch in volume. Atmospheric pressure is in terms of PSIA, and final pressure of the meter is in terms of PSIA.

If you inject using the above formulas and use the output in terms of PSIA and not PSIG, then when injecting, one atmosphere at one cubic inch will remain inside of the meter pipe, unless you allow enough time for the meter to completely diffuse it's propane into the chamber.

Since most spudders just open and then close their ball valve, (which is more efficient because you don't have to bleed the meter before injecting every time), the absolute output of the equation won't cut it. You will be one cubic inch short because that volume of propane stays inside of the meter.

Adding another 14.7 PSIA to your meter pressure will bring that cubic inch back into the chamber, and leave another inside the meter. So, the output would more correctly be written in terms of absolute PSI as:

<div align="center">Image</div>
<div align="center">Where P<sub>m</sub> is in PSIA</div>

Of course, since the average spudder rarely wants an answer in PSIA, we can simple use one of the above equations, and say that P<sub>m</sub> is in PSIG.
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