Omega Owners Forum
Chat Area => General Car Chat => Topic started by: TheBoy on 29 November 2011, 19:56:19
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Sure somewhere along the line, I've got it all arse about face....
Our 3.0l cars have, obviously, a displacement of 3.0l. Any one piston will fire every other revolution. So 1.5l of 'firing' displacement per revolution?
Petrol to air ratio is approx 1:14.5?
So by my maths, uses 1500/14.5 = approx 100ml petrol per revolution. Or 1l per 10 revs, or 10l per 100 revs.
So at 600 rpm idle, uses 60l a minute.
My maths is rubbish somewhere, but where?
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Everyratherwhere by thelook of that. :D ;D ;D
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
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Maybe 14.5/1500??
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Going by the info screen my 2.5 uses 0.2l per hour on tickover, so I fink you got something wrong ;D
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or may be 60 millilitres?? :y
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as far as I know 14.7 grs of air and 1 gr of fuel.. 14.7 gr of air must be converted to volume in related temperature but cant remember the related formula .. something like pv=nrt etc :-\
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::) "Men and Maths.....
......know your place!" :P
;D
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probably this one
http://www.stealth316.com/2-air-fuel-flow.htm (http://www.stealth316.com/2-air-fuel-flow.htm)
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::) "Men and Maths.....
......know your place!" :P
;D
dont tar ..... ;D :P
I'm a bit rusted as its more trhan 20 years but I was good at chemistry.. but these rpm maf readings mess up my mind :-\
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Its 42 TB - that's the meaning of life :) ;)
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2 things missing:
Your calculation of air volume assumes 100% volumetric efficiency. That won't be achieved because the engine won't suck its' complete swept volume in each induction stroke, especially at idle, because the cam timing, intake design, etc. isn't optimised for running at 600 RPM. The throttle is also almost closed, which doesn't help. ;)
You are comparing volumes of air/fuel when the stoichiometric mixture you have quoted by mass, as said.
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yep..here are the calculations
http://www.google.com.tr/url?sa=t&rct=j&q=air%20to%20fuel%20ratio%20volumetric%20calculation&source=web&cd=10&ved=0CHAQFjAJ&url=http%3A%2F%2Fwww.chem.mtu.edu%2F~jmkeith%2Ffuel_cell_curriculum%2Fdesign%2Fmodule1%2FALL.doc&ei=8D3VTp2bK9GE-watwPiODw&usg=AFQjCNFvc7GE_CygNSROG_9Dl_N8VQoxEg&cad=rja (http://www.google.com.tr/url?sa=t&rct=j&q=air%20to%20fuel%20ratio%20volumetric%20calculation&source=web&cd=10&ved=0CHAQFjAJ&url=http%3A%2F%2Fwww.chem.mtu.edu%2F~jmkeith%2Ffuel_cell_curriculum%2Fdesign%2Fmodule1%2FALL.doc&ei=8D3VTp2bK9GE-watwPiODw&usg=AFQjCNFvc7GE_CygNSROG_9Dl_N8VQoxEg&cad=rja)
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and of course this 14.7 changes , so not easy to calculate
http://www.fuelairspark.com/Products/Documentation/C-Com/Help/targetaf.htm (http://www.fuelairspark.com/Products/Documentation/C-Com/Help/targetaf.htm)
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Okies .. to "redo" TB's calculations ... as best I can and hopefully I've got it right .....
1500 cc of air per revolution @ 600 rpm (idle) = 900000 = 900 ltrs air /minute
Relative density of air is 0.0013 kg/ltr
so 900 X .0013 =1.17 kg of air /minute
"perfect" ratio of 14.7:1
so 1.17 / 14.7 = .07959 kg fuel/minute
Relative density of petrol is 0.72 kg/ltr
.07959 / 0.72 = .11054 l/min
.11054 l /min = 6.6326 l/hr = 1.46 galls/hr
HTH :)
This is the "theoretical case" as it assumes a full swept volume and a 14.7 ratio ... as Kevin says .. this just won't happen ....
In reality less volume will pass the MAF so less fuel needed, but ratio will be lower so more fuel needed .... :(
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Sounds more like it. ;) ::)...........me being an expert an,all. ;D
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My head hurts ;D
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To put it another way, injector duration is about 3ms at idle.
600 squirts x 6 cylinders per minute.
600x6 * 0.003 = 10.8s of injector open time per minute
injector flow is about 250cc/min
10.8/60 * 250 = 45cc/min
I suspect this is still an over-estimate because it neglects the non-trivial open/close time of the injectors, but it shows we are in the right ball park.
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I like sums. :)
Try crash reconstruction.
Pedestrian throw.
Partial braking.
Critical speed.
Pedestrian slide.
I like sums...... :P :'(
:)
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for those cases programming is easier than doing calculations :P
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Aye, volume to mass which is why I was a factor of about 1000 out.
Makes sense now :y
Wonder what worries will strike me during tomorrows 'rituals' ;D
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I will send you some old copies of the Daily Mail to keep in there to save you doing all that thinking. :y
::) :D ;D ;D ;D
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I will send you some old copies of the Daily Mail to keep in there to save you doing all that thinking. :y
::) :D ;D ;D ;D
::) I didn`t think there could be a poorer quality paper in a toilet, than Izal! ;D
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I will send you some old copies of the Daily Mail to keep in there to save you doing all that thinking. :y
::) :D ;D ;D ;D
Prefer to wipe with Andrex.
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
Stopped doing that when.... ....nah, not suitable for OOF ;D
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
Stopped doing that when.... ....nah, not suitable for OOF ;D
;D ;D
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
You can't beat the red circles on the tops of your knees and pins and needles in your legs ;D ;D
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
You can't beat the red circles on the tops of your knees and pins and needles in your legs ;D ;D
Reading heavy reference books, as I often do, results in such bad pins and needles, you can't stand when 'finished' ::)
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Its amazing the crap that goes through your mind when sat in the little boys room, pondering life...
read the paper like most others ;D :y
You can't beat the red circles on the tops of your knees and pins and needles in your legs ;D ;D
Reading heavy reference books, as I often do, results in such bad pins and needles, you can't stand when 'finished' ::)
Yeah, Razzle is quite thick these days :D :D
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Okies .. to "redo" TB's calculations ... as best I can and hopefully I've got it right .....
1500 cc of air per revolution @ 600 rpm (idle) = 900000 = 900 ltrs air /minute
Relative density of air is 0.0013 kg/ltr
so 900 X .0013 =1.17 kg of air /minute
"perfect" ratio of 14.7:1
so 1.17 / 14.7 = .07959 kg fuel/minute
Relative density of petrol is 0.72 kg/ltr
.07959 / 0.72 = .11054 l/min
.11054 l /min = 6.6326 l/hr = 1.46 galls/hr
HTH :)
This is the "theoretical case" as it assumes a full swept volume and a 14.7 ratio ... as Kevin says .. this just won't happen ....
In reality less volume will pass the MAF so less fuel needed, but ratio will be lower so more fuel needed .... :(
good approach Entwood :y as I understand you take the density of air at 0 meters altitude , 15 celcius and standard atmospheric pressure.. in my job, assumptions are made from time to time to prepare a base calculation.. However, inside engine, air temperatures will change seriously (depending also on weather temp,humidty etc also combustion efficiency may highly change the values) so real injection amounts corrected by ECU from lambda combustion result readings..
so real values may change even 30% from calculated.. :-\