dokalanyi
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« on: September 26, 2016, 08:29:40 AM »
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From the link: https://www.quora.com/If-a-2-0-liter-4-cylinder-four-stroke-engine-idles-at-800rpm-how-many-times-a-minute-does-each-of-the-4-spark-plugs-fireComes down to 1,600 firing events per minute, for a 4 stroke engine. So, if it's a 1.8 liter engine, each cylinder displaces: 1.8liters/4 = 450ml at 14.7:1 for Air:Fuel, 450ml/15.7 = 4.28ml per firing event So that should be 1,600 * 4.28 = 6,848 or 6.8 liters per minute? But, I know my display shows about 0.9 km/hr at idle. How are car engines that efficient? |
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daniel2345
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« Reply #1 on: September 26, 2016, 09:32:39 AM »
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You do not succ the full cylinder volume each time the pisten goes down. One reason is because of throttle blade closed, vacuum in intake manifold.
This is called volumetric efficiency.
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nyet
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« Reply #2 on: September 26, 2016, 10:41:22 AM »
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6.8 liters
At what air density? What is the airmass contained in that volume? What do you think "load" measures? |
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dokalanyi
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« Reply #3 on: September 26, 2016, 10:56:45 AM »
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You do not succ the full cylinder volume each time the pisten goes down. One reason is because of throttle blade closed, vacuum in intake manifold.
This is called volumetric efficiency.
I suspect you suck in air to fill the cylinder every time. You can't have a vaccum mixed with air and fuel. And the throttle blade doesn't close completely |
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nyet
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« Reply #4 on: September 26, 2016, 10:58:28 AM »
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I suspect you suck in air to fill the cylinder every time.
And the density of that air is... what? You can't have a vaccum mixed with air and fuel.
What happens when you mix air at standard density with a vacuum in an enclosed, sealed space? And the throttle blade doesn't close completely
You think air comes in only two densities? One more time: what is "load"? |
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dokalanyi
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« Reply #5 on: September 26, 2016, 11:01:07 AM »
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At what air density?
What is the airmass contained in that volume?
What do you think "load" measures?
Airmass contained in that volume would vary with density I guess. I don't know what "load" measures. What does load measure? |
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dokalanyi
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« Reply #6 on: September 26, 2016, 11:03:22 AM »
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And the density of that air is... what?
What happens when you mix air at standard density with a vacuum in an enclosed, sealed space?
You think air comes in only two densities?
One more time: what is "load"?
Air with a vaccum reduces it's density. Air comes in several densities. Temperature should affect density as well. Was typing my second post when you asked about "load" again |
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dokalanyi
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« Reply #7 on: September 26, 2016, 11:05:53 AM »
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But wait,
This 14.7:1, if it's the ratio of densities, that would change the values. Or a ratio of masses. So is it a volumetric, Mass, or density ratio? Haven't bothered to work out what the consumption would be for each since I'm on phone
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nyet
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« Reply #8 on: September 26, 2016, 11:16:21 AM »
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But wait,
This 14.7:1, if it's the ratio of densities, that would change the values. Or a ratio of masses. So is it a volumetric, Mass, or density ratio? Haven't bothered to work out what the consumption would be for each since I'm on phone
14.7:1 is a mass ratio, not volume ratio. Can you guess why chemical reaction ratios are based on mass, not volume? Not sure what you mean by "mass density", that doesn't really have a useful meaning, nor does "density ratio" If you go down this road, you may want to invest in a few basic chemistry courses.. |
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« Last Edit: September 26, 2016, 11:18:20 AM by nyet »
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nyet
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« Reply #9 on: September 26, 2016, 11:19:12 AM »
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I don't know what "load" measures. What does load measure?
Not sure how you lasted this long without knowing. Did you check the s4wiki to see if there might be more information there about load? |
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dokalanyi
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« Reply #10 on: September 26, 2016, 11:46:39 AM »
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14.7:1 is a mass ratio, not volume ratio.
Can you guess why chemical reaction ratios are based on mass, not volume?
Not sure what you mean by "mass density", that doesn't really have a useful meaning, nor does "density ratio"
If you go down this road, you may want to invest in a few basic chemistry courses..
I think I understand now. Mass will measure the weight of the molecules. So 10g of air will always have the same number of molecules regardless of how much volume they occupy. I was never good at chemistry |
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nyet
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« Reply #11 on: September 26, 2016, 11:50:12 AM »
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So 10g of air will always have the same number of molecules regardless of how much volume they occupy.
Perfectly stated! |
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dokalanyi
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« Reply #12 on: September 26, 2016, 11:59:08 AM »
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Not sure how you lasted this long without knowing.
Did you check the s4wiki to see if there might be more information there about load?
Found the wiki defining "load". And I thought I'd read through (atleast skimmed) everything. But it looks like I'd never seen it before |
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dokalanyi
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« Reply #13 on: September 26, 2016, 12:50:58 PM »
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So from the equation on the wiki load page, using 2.72 g/s and 800 rpm at idle (got this from vagcom block 32)
mass-injected = (2.72 * 60)/(800 * 0.5) = 0.312g (for all cylinders)
Or: 0.078g per cylinder
Mass of fuel required: 0.078 * 1/15 = 0.0052.
1 liter of fuel is 0.75kg (from google). So,
Volume of fuel per spark event: (1000ml/750g) * 0.0052g = 0.0069ml
So from my 1,600 firing events per minute
1,600 * 0.0277 = 11.04ml, and per hour it's 0.662 liters/hr.
And the cluster shows between 0.9 and 1.5 when Drive is engaged. If the calculation is right, then engines are still pretty darn efficient
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royce5950
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« Reply #14 on: October 10, 2016, 11:56:43 AM »
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to answer the question in your thread title, An engines efficiency is defined by a properly calibrated ECU as well as routine maintenance and proper care for your engine.  |
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