escort_ford84

What exactally does this add to? open loop, closed loop. does this differ from base pulse width?

D's89IROCZ

also to add how many injector bias resistors do we have .

RBob

iTrader: (1)

It is a value that is added to the injector PW. This is done just before the ECM hardware is programmed for injection PW. The purpose is to help linearize the injector at small PW's.

RBob.

escort_ford84

Ok, i have found what injector bias does, it adds BPW to "SYNC" only
the "746" ecu has this " Injector bias added to pw (sync)"

RBob

iTrader: (1)

The bias is added to both aync and sync fuel pulses.

RBob.

escort_ford84

I may have to relabel this or something, but this is what its labeled with the $61 hac, "PW - Injector bias added to pw (sync)"

escort_ford84

OK, i think i see what this injector bias is. Looking at the pulse width at the injector with an oscilloscope, there is a spike right at the begining of the pulse width, its very slight, but its there. I see how that would help the injector firing at low Pulse widths.

HaulnA$$

The spike you are seeing is the "peak" portion of a "peak and hold" injector pulse. This is a hardware function and has nothing to do with injector bias. The reason for the bias is because the injector requires a set amount of time to open to the point where fuel flows. This time can be as short as a few hundred microseconds for a TBI injector to over one millisecond for a saturated port injector. Say for examplethe ECM calculated that on a port injected setup, it requires a 1.5mS pulse width. Since it takes 1mS for the injector to open, fuel will only flow for .5mS or only 1/3 of what is needed. If a bias of 1mS is added to the final pulse width, a 2.5mS pulse occurs minus the 1mS for the injector to open and fuel flows for 1.5mS. Just what the ECM commanded. Make sense?

escort_ford84

That was a really good explanation of that. Makes perfect sence. Thnaks man.

69 Ghost

iTrader: (1)

Does anybody know if the reported PW in a datalog is the calculated or the actual? Also does anybody know how to tell if it is off? The reason for my question is all injectors are different so if you put in a different set with a different rate how do you calibrate this?

escort_ford84

You could change the Base Pulse Width constant, there is a formula for that.

HaulnA$$

It probably depends on the mask in use. You should consult the hack to find out for sure on your particular application.

escort_ford84

You know, i was thinking. The 305,350 bins are set to 396.50 (Injector Bias), 454 is set to 274, and the 6 cylinders are set to 480. these times are in microseconds. If i set my injector bias up (like 520) i get a rich smell. The engine seems to run a little smoother to. If what is explained is true, then Pulse widths at larger duration would be extended to. Since im a taqd lean in the upper r's being at 100% VE, then more bias should help there.

Dominic Sorresso

Escort,

If you re-read Haulin's post you'll understand why more bias causes a richer mixture.

Pre-Tuner

iTrader: (2)

I know this post is a little old, but is there a way to tell what the correct amount should be? Do you just adjust up or down until the idle is smoother?

I guess I understand what it does, I just don't understand how to properly set it.

Dominic Sorresso

I don't think you do understand. You don't use the IB for setting a smoother idle. Lowering the IB will generally cause a leaning of the mixture and vice versa.

Pre-Tuner

iTrader: (2)

I understand it isn't for making the idle smoother, but I'm not seeing any other way to tell if the bias is set too little or too much. If the bias tends to lean or richen the mixture, how do you find the proper amount of bias?

1tpi

Pre-Tuner

iTrader: (2)

OK, forget what I said about the whole idle thing.

How do you properly set the injector bias?

getsideways

ive been messing with this myself. not sure if its doing much for me. from what ive read, the way to tell if you need to raise the bias is by looking at the ve tables in the low map areas where your p.w. are generally at ther lowest. if you are needing to raise your ve higher in those areas creating an upside down bathtub shape on the graph, you may need to raise your bias. the bias allows for the injector opening time. if you have raised your fuel pressure the injector probably needs more time to open. this would be a reason to play with the bias. i have 65lb injectors at 24psi and have my bias set at .656 usec right now. my idle p.w. are about about .8-1.0ms. im struggling more with surging at low map under light throttle deceleration. my afr's are swinging 12.0-16.0. lowering prop gains and prop counts havent helped enough yet.

Dominic Sorresso

The best way is to simply set the IB at a level that matches the injector opening interval. With TB injectors its around 700msec. Then tune from there.

getsideways,

Lower the Prop Gains further. You'd be surprised at how little PG you need with 24 psi particularly in the 0 -16 gm/sec airflow area.

Pre-Tuner

iTrader: (2)

Oh, OK. Thanks guys.

vernw

iTrader: (2)

If you were running SVO 30's in a Miniram at approx 48PSI, what would you use for the INB?