funstick

thanx for catching that.for some reason when i read it it just didnt click ?

as far as i know there arent any injector out there in saturation IE the 1227165 or the 1227730 that have such a short rise time and such a cshort closing time.

also the longer that injector stays open the more current is has to dissapate. but the point im making is that with a varied injector strategy you could easily use upto a 18 msec pw.

so thing are not what they appear to be. this might be the reason the OEM's are all running SEFI becuase you can easily use more PW per cylinder allowing smaller faster injectors. and using cheaper saturated injectors at that.

the last thing to consider here is something no bodys talked about yet. for the ecm to use asynchronys fueling the pulse width would fall under 2.5 msec. thats if it was firing based on the fact that in asynchronys fueling mode it would fire at every ref pulse.

heres my take on the whole shebang in a nutshell. when ever the ecm has a PW that has a longer dwell period then the async ref pulse domain would allow it simnple holds the injector state until it reaches x number of ref pulses. this would explian why Ski down it is able to run that injector pulse and not run out of fuel. but going static would ential running less then a 2.5 msec pw based on the asynchrons fueling model.

thats simply rediculous.

figure 8 ref pulse per 20 msec at 6000rpm thats 2.5 msec per ref pulse. you injector sizing formula doesnt apply here.

Kingtal0n

dont know if this applies here, but i figured i would ask anyways.

does idle and/or part throttle change your BSFC dramatically?
and does this help or hurt your idle PW with huge injectors.
usually my carbed car likes to idle rich. i bet the extra fuel required to "smooth" the idle out helps add PW to a high PPH low PW injector while idling around or at part throttle.

thing is, the bigger the injector the lower you have to move your PSI to keep the PW reasonable and the spray pattern as atomizied as possible right?

so i guess what im really asking is, when an engines idling, say a 350 with a procharger. the thing would need big injectors (72-82 pph) to keep up with the 850~ horsepower its making (assuming a D1-SC and like 15 PSI etc...)

so with these huge injectors, that 350 would need "about" the same fuel at idle as most any other N/A 350 right?
So does PW or FuelP drop off so dramatically as to change your BSFC at low rpms, and does a huge injector cause problems at part throttle because of low FP and / or PW, and does this affect fuel economy or (BSFC) in a significant way. oh heck. i dont know what im saying.

Grumpy

BFSC moves all over the place.
Idle often being the worst. Peak Torque the best.
(Talking about street 3rd Gen engines).

With a bigger then stock cam, it begins to self EGR the engine, from the increase in overlap, so you usually have to add some fuel and timing to most stock calibrations to get the idle right.

72s is getting into serious injector catagory,
They are also Peak and Hold, ie low impedance. So while the general operating range of saturated drives is 2-10 msec, the P+Hs suggested times are 1-5. So they inherantly are able to run at shorter PWs.

Tuning is tuning.
I'm running 55 PPH injectors in my little 231, quite nicely. And there are some guys running 72 just fine.

funstick

i totally debunk pw limatations and firing strategy. not a word. that was a nice dodge.

Kingtal0n

<b>So while the general operating range of saturated drives is 2-10 msec, the P+Hs suggested times are 1-5.</b>

are you saying that 72pph injectors at 100%DC can only be run 5msec? why are the suggested times half as long... what happens if you go 10msec?

funstick

i got no idea WTF hes talking about. jesus 72pph injectors should be enough fuel for a pro stock motor. your fuel pump had better be the shiznitz.

im not sure wheres hes comming up with 5msec. i think hes lossing his mind again.

funstick

has anybody done anymore work to figure out how a 12.8 msec pw is working ? i mean i have my thoery but im going bust looking at the code to figure it all out. im not sure what im looking for.