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Location:
Lost in the K hole
Registered:
May 2002
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 estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 12:41
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a bit of a topic to chew on...
how does one estimate fuel injector duty cylce, both at the peak of the rpm/power band, and elsewhere in the load/rpm range? and from this, estimate volume fuel consuption (or vice-versa) ??
is it as simple as estimating the HP production at any given point, and from this directly calculating the volume of fuel required to produce such hp? i imagine this would be an underestimate at best considering the richness of some fuel mixture under high load (for cooling rather than hp production etc).
http://injector.com/injectorselection.php
is there anything more accurate?
im wanting to determine approx what volume of fuel might be entering the system at 3500rpm and med/high load.
i was thinking of using a java prog like above for determining peak hp injector use (at say WOT 7000rpm peak power) and just proportionally reducing that figure to estimate fuel use at 3500rpm... reckon this is feasible?
i dont see why not, but just wanted to throw it out here...
cheers
ed
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:05
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Ed,
get Megatune from the megasquirt yahoo group.
you can put it engine size, injector size, AFR, and it tells you the "ideal" pulsewidth required if you have 100% volumetric efficiency.
or,send me some info, like rpm, injector flow, number of injection events per engine cycle, engine size, number of cylinders, and i willplug it into my MS, and use the Megastim  to show what the pulse widths and duty cycle will be.
i will also need you to estimate the VE of the engine at the rpm you want.... (or just say 100% for a max figure for duty)
will take me all of 5 seconds... (or so)
Cya, Stewart
the algorithm MS uses for PW calcualtion is around somewhere, ou could use that as a basis for plugging in..
or you could do the same by calculating amount of air per cylinder, working out amount of fuel for given AFR, then working out % of injector cycle required to provide this..
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Location:
Montrose, VIC
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:06
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Multimeters that can measure duty cycle aren't that expensive, and it's a reasonably accurate way of working it out. See if you can borrow one off someone, or even just go buy one 
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:17
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Ed... you want to know this so you can find the appropriate injector size for your engine right?
Not to measure the pulse-width like the guys above are sugesting?
You can only ever make a good guess, as you probably realise.
I made up a excel spreadsheet to calculate such values as you are after.
Im not really willing to make it avaliable publicly though, as its not proven.
But if you would still like a look, i could email it to you.
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Location:
Lost in the K hole
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:22
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hmmmm, ok....
3200 rpm
90rwkw
13.5:1 afr
i think the VE starts to go over 100% here  but lets assume 100 or 110 max for now.
6 injectors
2 injection events per cycle (3 batches of 2 firing)
injectors flow 285cc/min @ 39psi
would LOVE to know total volume of fuel per min entering the system in this configuration.
cheers
ed
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Location:
Brisbane
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:28
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If you know VE, swept volume per cylinder, and AFR, it should be simple arithmetic to determine the injector pulse width. From there you factor in fuel pressure and flow rate per injector and you have an approximate indication of fuel flow!
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Location:
Lost in the K hole
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 13:29
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| M.W.P. wrote on Mon, 26 January 2004 00:17 |
Ed... you want to know this so you can find the appropriate injector size for your engine right?.....But if you would still like a look, i could email it to you.
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not quite...
im trying to estimate fuel volume delivery at a certain rpm/load point so i can calculate relative ratios for supplementary methanol injection (apprx 4-5% total fuel volume). i need this so i can order jet sizes on tues morning.
it a bit of 'swing and miss' but id like to get in the ballpark as best as possible 
as for your excel spreadsheet, please do, id be interested to have a look non-the-less
not quite on topic, but i think youd be interested in thsi too:
http://offroadvw.net/exceldyno/
played with it today, and its very good
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Club Member
Location:
sydney
Registered:
May 2002
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Re: estimating injector duty cylce, and fuel delivery volume...
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Sun, 25 January 2004 19:32
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hey stu... wanna come and apply some of those theroies and your MS program to my ecu when i fire the car today
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