04BlackSilverado

iTrader: (6)

That looks sweet!!!
Is that just a scanner?
Can you edit with it?

parish8

iTrader: (6)

not sure what you are talking about but when IDC hits 100% you are out of injector. the computer can comand the injector to be open more than 100% but that just means it will be open all the time. 100% or 120% or 130% is all the same, wide open. efilive and these other scan tools do the calculations for you .

also raising your fuel presure may give you slightly more injector but will also reduce your fuel pump output. the flow from your fuel pump is inversely proportional to your presure.

unredeemed

iTrader: (2)

What's not to understand? This common misconseption that "IDC's over 100% tell you your out of fuel," should be addressed and it's my best practice to not concentrate on that number alone. Infact, It's one of the lower ones on my list.

Granted you don't want to assume that 100% is okay. But it's really not the number(IDC) that means the most when comparing to IPW.

For everyone that still reading, the Injector Pulse Width (IPW) is the amount of time (in milliseconds) that the ECU wants the injectors to be open between compression strokes. The injector duty cycle (IDC) in percent is determined by multiplying the RPM times the IPW and dividing by 1200.

So in other words, the IPW is the number your really concerned about as IDC is derived from that.

In my own vehicle I'll shoot for under 85% IDC's. But also know that if I'm pushing 100% IDC's with a short IPW, I can still keep going with those particular injectors. a new fuel pump and higher fuel pressure will fix those IDC's pretty easily. I don't even want to get into the prequisutes(higher output pumps, injectors, etc) of what you should have in a FI vehicle as that will spur another debate


*One note to the formula I gave above in that it may not be accurate as I'm not sure that the 1200 factor is correct for our motors.

Flyer

iTrader: (1)

The motor on the hot plate here is not FI, in fact, it's just a cammed 4.8, no juice, now charger, just old fashioned HP.

Please enlighten us on how the IPW should be looked at to judge when your out of injector. What would you consider safe and not safe.

Either way ... the general assumption that when the motor gets tuned better, the injectors will be fine.

Maybe 01 will come in and give some particulars about the logs he was looking at.

BigTex

iTrader: (16)

Ask yourself, apparently you don't fully grasp the concept.

Yes IDC is derived from the pulse width. But you have to know how much time you have to physically open the injector before the pusle width means anything, hence the IDC.

Keep going LEAN you mean? Who cares if the pulse width is small or large, if the available time to inject fuel is less than the pulse width, then you are under fueling.


Injector duty cycle is simply a ratio showing the amount of time physically available to inject fuel VS the amount of time the PCM is wanting the injector open. Its simple, either there is enough time to get all the fuel injected that the PCM asks for, or not. IDC is that ratio.

FACT: If you are over 100% duty cycle, you are out of injector for that rpm.

ThunderZ28

iTrader: (7)

well I tried to get it fixed tonight, and wound up going the wrong way..
now my o2's are above .980, and my Ltrms went to 16.4
also my Knock retard went up to 8*
need to go the other way..
will have to try tomorrow.. it's a bit difficult to take care of a sick wife, and kid, and go out and tune all night...

goshawk23

damn you got sicks ones there too? i thought i was the only one dealing with that right now. hope you get your tune right. i know you will.

parish8

iTrader: (6)

bigtex, thanks for explaining that better than i could have.

IPW doesn't mean much till you take rpm into acount. out scan tools with do the math for us and convert IPW and rpm into IDC. duty cycle is the important number here.

i have seen comanded duty cycle at 150% before with the whipple. the whipple computer lets the stock injectors go static and then adds fuel with 2 extra injectors.

ktmrider

I had also heard of the 85%+ factor indicating larger injectors but again it was a guideline not a rule.
Thanks for all the input and info!

tooquick2beslo

When I am spraying my 125 shot I am at 89% but that was with only 600 psi in the bottle. Do you'll think with more pressure in the bottle that it make go down some.

Also on a side note if I sprayed more do you think I would run out of injector ?