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injector flow rating
Posted: Mon Jun 20, 2011 5:15 am
by thr3shold
Under General Settings in TunerStudio the injector flow rating units is g/s, what units are those? I've searched the web,forum and help files, but can't find any mention of it anywhere.
Thanks
Re: injector flow rating
Posted: Mon Jun 20, 2011 5:43 am
by LT401Vette
That appears to be a new setting added to the 2.90 firmware. I don't see any documentation on it yet. So I can not say.
Re: injector flow rating
Posted: Mon Jun 20, 2011 6:15 am
by stevemgb
Grammes per second?Steve..
Re: injector flow rating
Posted: Mon Jun 20, 2011 7:05 am
by Bernard Fife
Yes, the fuel flow rate is in grams/second. Injectors are usually rated in pounds per hour, or cubic centimeters per minute.
There are 454 grams is a pound, and 3600 seconds in a hour, so:
grams/second = (pounds/hour) * 454/3600 = (pounds/hour)/7.93
For cc/min, one cc of gasoline is roughly 0.737 grams/milliliter = 0.737 g/cc and 60 seconds in a minute, so:
grams/second = (cc/min) * 0.737/60 = (cc/min)/81.4
I will add a javascript calculator to the docs when I get a chance.
Lance.
Re: injector flow rating
Posted: Mon Jun 20, 2011 9:44 am
by thr3shold
I recognized the units as grams per second, but wasn't sure since it didn't seem to be units used by anyone for sizing injectors. Thanks!
Re: injector flow rating
Posted: Mon Jun 20, 2011 11:35 am
by Bernard Fife
thr3shold,
Yeah, grams/second is used so that the calculations for mass air flow are more straightforward in the code (actually, in the code it's milligrams/second to avoid the decimal places).
This could easily be changed in the INI. Currently there's a line (~#497) like this:
Code: Select all
fRate = scalar, U16, 768, "g/s", 0.00100, 0.00000, 0.00, 60000, 3 ; * ( 2 bytes)
where 0.001 changes the value from grams to milligrams.
To change the units to pounds per hour, the INI could be edited to something like this:
Code: Select all
fRate = scalar, U16, 768, "pph", 0.00793, 0.00000, 0.00, 300, 1; * ( 2 bytes)
To change the units to cc/min, the INI could be edited to this:
Code: Select all
fRate = scalar, U16, 768, "cc/min", 0.08141, 0.00000, 0.00, 3000, 0 ; * ( 2 bytes)
However, I won't change the 'official' INI until I have consulted with Al.
Lance.
Re: injector flow rating
Posted: Sat Jun 25, 2011 4:03 pm
by Bernard Fife
All,
I have put a javascript injector flow rate calculator here:
http://www.megamanual.com/mt29.htm#s
We will leave the INI in grams/second, as these are the 'natural' units for this quantity (pounds per hour being non-metric, and cc/min requiring the fuel density to know the mass of the fuel injected). Those who object to metric units should feel free to contact these folks:
http://www.bipm.org/en/si/
Users can change their own INI to use their preferred units as above, of course. Or they can use the calculator in the manual to convert from pph or cc/min.
Lance.
Re: injector flow rating
Posted: Sun Jun 26, 2011 7:49 am
by jcarruthers
Made me chuckle
