For tuners, a Holy Grail of Injector voltage Offset

[XfireZ51]

Gentlemen,

The Holy Grail of Injector Voltage Offset:

http://injector-rehab.com/shop/lag.html

If you look through this you can see how different injectors act under varying voltages. You can compare the Bosch v Accel and RCs for example. With longer opening times you get less fuel for the same calc'd pulse width. That's why it's important to get this offset right since it makes tuning fuel more accurate. If you have ever felt that your car has idled roughly after a long hot run, this is one of the reasons why. Once you modify this parameter, you'll need to re-check your fuel tables by datalogging.

[mike100]

I like the listing to use for comparison purposes, but they neglected to show the unit of time.

[scottfab]

Originally Posted by mike100

I like the listing to use for comparison purposes, but they neglected to show the unit of time.

Must be milliseconds.
Interesting the variance in resistance from unit to unit even
within one vendor per part number.

[XfireZ51]

Originally Posted by scottfab

Must be milliseconds.
Interesting the variance in resistance from unit to unit even
within one vendor per part number.

Scott,

Yes, its msec. And the variance is the point of posting this. An injector isn't just an injector. Swapping different brands, although same fuel flow rating, has consequences in the tune. This is especially true at idle and short pulsewidth situations where the opening time is a proportionately larger part of the total calc'd pulsewidth.
Now some on this board might say, "yeah but.." when you tune to 14.7:1 or to a 128 BLM, doesn't the ECM overcome this. Without the correct injector offset, you'll undershoot or overshoot the actual calc'd pulsewidth the ECM is looking for. In some cases, you may "run out of injector" or have too high a duty cycle. By using the correct offset, you may find that you can lower the overall VE% and have a smoother VE map which means the motor operates more smoothly and predictably in varying conditions.

[mike100]

Originally Posted by scottfab

Must be milliseconds.
Interesting the variance in resistance from unit to unit even
within one vendor per part number.

yeah, I fired up my TunerPro file and checked the usec values against the table here assumed as msec. Looks like the RC Engineering 23 lb injector falls into the stock table very closely.

I have the Lucas ones- I can't recall if they are 19 or 21 lb rated though.

[XfireZ51]

Originally Posted by mike100

yeah, I fired up my TunerPro file and checked the usec values against the table here assumed as msec. Looks like the RC Engineering 23 lb injector falls into the stock table very closely.

I have the Lucas ones- I can't recall if they are 19 or 21 lb rated though.

Not sure but when I look at the stock table v the RC values, they're off but 300msec or so. At 14v, its double the stock time of 300 v 620 for
RC injectors.

[mike100]

This was the example I was comparing to:

__________cc. lbs/hr. ohm -> 10v 11v 12v 13v 14v 15v

RC Engineering: 240 23 16--> 1.31 1.10 0.97 0.77 0.62 0.46

[XfireZ51]

Originally Posted by mike100

This was the example I was comparing to:

__________cc. lbs/hr. ohm -> 10v 11v 12v 13v 14v 15v

RC Engineering: 240 23 16--> 1.31 1.10 0.97 0.77 0.62 0.46

Yes that's right. And at 14v the stock Inj. Offset is .3msec compared to .62. You would note a difference if you made that change in the cal.

[VetteVet]

For anyone wondering what this thread was all about, I just stumbled upon this, which explains it very nicely.


http://www.injectordynamics.com/GMDATA.html

Jep

[Hib Halverson]

Being that this is a tuning thread, let me hijack it a bit.

What do you guys do for engines forced to run on E10?

Do you work with E10's different stoich or do you just tune for a certain lambda value from your wideband?