Sticky Request - Miata Airflow Spreadsheet
#1
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Please find below, the link to an Airflow spreadsheet I created for use with DIY Turbo Kits, or anyone seeking an upgraded turbo to meet their goals.
If anyone has any suggestions, such as a higher VE to use etc... Please feel free to let me know and I will update the spreadsheet as such.
Also, if anyone notices a problem with my math, please let me know as well.
https://docs.google.com/spreadsheet/...zZGOXQya3p6MGc
If anyone has any suggestions, such as a higher VE to use etc... Please feel free to let me know and I will update the spreadsheet as such.
Also, if anyone notices a problem with my math, please let me know as well.
https://docs.google.com/spreadsheet/...zZGOXQya3p6MGc
Last edited by TheGrim; 07-01-2012 at 11:46 AM.
#3
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These numbers are not for a specific turbo. This simply shows the airflow numbers for a 1.8L engine operating at 80% VE. The numbers you see at different psi is where the motor itself will flow and are meant to be plugged into a compressor map to help with selecting a turbo for any application given "x" boost level.
#7
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#9
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Tech stay off my threads. I have been to a few of yours, and it is clear you lack ANY understanding of how systems work. Also, your grammar sucks, I don't even understand your prior post. Nothing that I calculated is GUESSED (minus volumetric efficiency). It is all SCIENCE and MATH. Baron, thank you for being the first (or second) person to understand my thread and the point of the chart
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#10
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Tech stay off my threads. I have been to a few of yours, and it is clear you lack ANY understanding of how systems work. Also, your grammar sucks, I don't even understand your prior post. Nothing that I calculated is GUESSED (minus volumetric efficiency). It is all SCIENCE and MATH. Baron, thank you for being the first (or second) person to understand my thread and the point of the chart ![](https://www.miataturbo.net/images/smilies/smile.gif)
![](https://www.miataturbo.net/images/smilies/smile.gif)
Then since I'm so ------- stupid and lack understanding. Explain to me how you are gonna use this data to match up turbos. Like I said before I"m always open to learn.
#11
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Quite simple. You match the airflow on the second part of the spreadsheet (LBS/min) with appropriate boost level, and line it up (with pressure ratio) on the maps for the turbo to see if you are in the best efficiency range. There is a great full article here: http://www.mygen.com/users/dbruce/my...sor%20Maps.htm
This will even show you how to use the maps and plot your data. Both our charts are laid out the same way, so it should be easy enough to compare the two. It's really hard to go wrong with listing data in a chart
This will even show you how to use the maps and plot your data. Both our charts are laid out the same way, so it should be easy enough to compare the two. It's really hard to go wrong with listing data in a chart
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Last edited by TheGrim; 07-04-2012 at 12:57 AM.
#12
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Stop being a retard. If you have 8psi in the intake manifold its very simple math to figure out how much air passes through the nozzle of the intake valves given a certain lift and duration. The killer becomes if you try to be accurate and consider the opening and closing times of the valve. This is turbo/sc/na/leafblower independent, the calculations don't care how 8psi is being generated in the intake manifold.
#15
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I figured anything from 80%-85% wasn't going to provide numbers that were way off. I will check out the other spreadsheet when I get home tonight. What is a good VE to assume with the miata motor? I normally just use 80% to keep it safe and (somewhat) predictable.
Last edited by TheGrim; 07-04-2012 at 06:20 PM.
#18
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That number would only be accurate if you had accurate fuel injector data, no ones has that. The people who made the injectors might but it would be for a nominal injector to come off the line and not something on either end of the tolerances. And they would only have it for some pressures and delta-p's. You'll be within 5% though. Assuming that you dont have to fake anything else on the tune, like actually putting in the correct displacement, and setting the iat and ect modifiers to zero for the conditions the engine was tuned in.
#19
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My intuition says the VE for our weak little BP motor is probably closer to 70% or lower. A quick google search shows VE is equal to the actual air flow through the motor divided by the ideal air flow. Given the generally terrible flow characteristics of the cylinder head and stock intake manifold, I would say 80% is probably on the high end.
Some more quick googling turned up a paper that calculated the VE of an F20 motor out of an S2000 to be about 100% average, spanning from 85% ish in low RPM to over 100% on the high end. Given the amount of power/displacement that motor makes vs the BP, my seat of the pants math/engineering intuition says the miata motor would be doing pretty darn well to be at 80% VE. But this is all speculation based on some quick searching and educated guesses. It would be nice to see some actual calculations based on a mass air flow datalog.
Some more quick googling turned up a paper that calculated the VE of an F20 motor out of an S2000 to be about 100% average, spanning from 85% ish in low RPM to over 100% on the high end. Given the amount of power/displacement that motor makes vs the BP, my seat of the pants math/engineering intuition says the miata motor would be doing pretty darn well to be at 80% VE. But this is all speculation based on some quick searching and educated guesses. It would be nice to see some actual calculations based on a mass air flow datalog.
#20
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If we had a calibration curve for the MAF, we could easily read the flow and calculate VE. Never heard of one though.
With a 1.84l engine (NB) each 360deg rotation should pump 0.92l of air. We can easily measure air temp, that, combined with mass air flow would give us volume air flow. We also measure rpm and therefore:
VE = VAF [l/min] / 0.92l * rpm
Or I could be wrong :-)
With a 1.84l engine (NB) each 360deg rotation should pump 0.92l of air. We can easily measure air temp, that, combined with mass air flow would give us volume air flow. We also measure rpm and therefore:
VE = VAF [l/min] / 0.92l * rpm
Or I could be wrong :-)