Setting the injector constant

[SappySE107]

I am using A1 for reference. The table is at 0761 - 0771

Constant = 1461.5 * (EGR Factor)(liters/Cyl)/(Injector Rate)

Injector Rate is in Grams Per Second.

We know that the stock 3.1 is 16.6# and has a Constant of 0.153 at 0% EGR.

0.152 @ 1.6% EGR
0.145 @ 3.2% EGR
0.1396 @ 4.8% EGR
0.1355 @ 6.4% EGR
0.133 @ 8.0% EGR
0.13 @ 9.6% EGR
0.127@11.2-25.6% EGR

The 3.1 has .516 liters per cylinder

1 pound = 453.59237 grams

453.59237 *16.6 = 7529.633342 grams of fuel an hour
125.493889 grams per minute
2.09 grams per sec

1461.5 * (.012)(.516)/(2.09) = 0.152

I used 1.2% because anything * 0 = 0 supposedly. Any way I go about this formula, its wrong. Math > SappySE107

[neophile_17]

The "EGR Factor" from the first equation apears to be the percent of air that's not form the EGR or 1 - %EGR.

~sam

[SappySE107]

1461.5 * (.988 )(.516)/(2.09) = 0.152

That makes more sense other than I still can't make it work as a math formula either.

[Superdave]

Remember, with $A1 you have to be drunk for the math to work.

[SappySE107]

That is probably what it took 10 years ago when I got it to work one time. Even after this formula is done, I need to know how to convert .153 to 224 in hex. Bottle of whiskey might make it happen:P

[Guest]

Remember, with $A1 you have to be drunk for the math to work.

LOL, sometimes not just $A1.

[Superdave]

That is probably what it took 10 years ago when I got it to work one time. Even after this formula is done, I need to know how to convert .153 to 224 in hex. Bottle of whiskey might make it happen:P

Use windows calculator, change it to scientific mode in XP or Programmer mode in win7. 224 is E0 in Hex

You need a multiplication factor, 1464 works but you have to round the result.

.153 * 1464 = 223.992, rounded and converted to hex is E0. It works for the whole table.

[SappySE107]

well that explains the 1461.5 then (1464?) but I still don't get .153 from the equation when i leave the 1461.5 * out of it. Thanks for making sense of the conversion to the hex

[GutlessSupreme]

Constant = 1461.5 * (EGR Factor)(liters/Cyl)/(Injector Rate)

There is no way that this equation can represent the values in that table. This equation says y = m*x. That's linear, and makes a straight line. The data you posted from the table is not.




That's a plot of the full table. The black line represents a 6th order polynomial fit to plot of the table. 6th order is as high as Excel goes, I don't feel like firing up Matlab. But it's still not particularly a good fit.




That's a plot only including up to the first point where the constant levels out. With a 5th order polynomial trendline, the fit is very close, with the exception between the first two points. Note that the coefficients in front of x can somehow represent some of the constants in the supposed equation that we have, i.e. displacement/cylinder, injector size etc. In order to extract these and infer any relation, however, I'd need another table with different constants to plot and compare against. With the base 5-speed TGP bin that I have and whatever xdf I'm using, the constants of this table are all simply 105. I don't know if the .xdf conversion is wrong, but I assume all my table's values are the same due to having vacuum rather than digital EGR.




Here's a plot like the last one, but skipping the first point too. Here, a 3rd order polynomial gives a very good fit, which I could justify using by just assuming that they defined some hard initial constant as well as some constant max value, both of which maybe don't conform to the equation.

Could you post another table? from a DOHC or something?



edit: of course I should mention, that the reason the main part of the plot isn't a straight diagonal could be due to rounding of the constants. 8-bit, right?

[GutlessSupreme]

Constant = (1 - EGR Factor)(liters/Cyl)/(Injector Rate) - 0.094

For being only a linear fit, this equation actually fits the table points very well, until you get down to that 0.127 region anyway. I have no idea what the ~0.094 could represent, I just used that to offset the plot to line up better with the table points.