injector flow rating

[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

[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.

[stevemgb]

Grammes per second?Steve..

[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.

[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!

[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.

[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.

[jcarruthers]

Those who object to metric units should feel free to contact these folks: http://www.bipm.org/en/si/

Made me chuckle