wickednick911

How is it possible to have a 100+% duty cycle? I mean doesn't an injector that is stuck open truly at 100% duty cycle
I understand that the pulse width and the 2 complete rotations of the crank have something to do with it, I think.
Can someone explain in simple terms please.

XM15

I thought so too.


Subscribed.

an0malous

curious for a detailed explaination of this too.
i have an idea how it works but there are far more knowledgable folks than I who can explain it properly heh.

stonny9

I believe this statement is correct.


The injector only delivers 100% or the lbs it is rated at but the engine is requesting greater than that so the car runs out of fuel so to speak and the afr gets leaner. If u normally run at 13:1 afr you will then get leaner and go to say 13.6:1. The injector can physically only give 100% and the only way to correct the 100%+ is to get bigger injectors, increase the fuel pressure, or lower the max rpm to decrease the fuel demand

Bruski06

I can tell you with data logging on HP tuners I am seeing 130% IDC. I am trying to figure out what is wrong since I am running only a stage 2 kit with reflash and from what I am hearing a above 100% is normal but we are finding that hard to believe because i am also getting a Rich code thrown.

Darkmanx

Sounds like something is wrong with your hp tuners, i will take it off your hands for a good price.

06black

your rich code is LTFT related NOT IDC.

IDC can be any ****** number it wants to be, once you brake into the 90% range or so it truly doesn't matter.

once your cross that 90% range or so your injectors go static (they stay stuck open and on) so say we use 115% IDC that means the car wants a 115% of the fuel its getting at that moment, and as we all should know thats simply impossible.

this is simple stuff here guys....

Littlegoose

Question. So if you are getting 115% IDC and the car wants more than it is receiving, when you are getting 80% IDC does that mean that the car is wanting only 80% of the fuel that it is receiving and therefore running rich? or does it mean that the injectors are running at 80% of their maximum capacity?

OzzyruleZ

I had John data log mine today. Right about 7K mine hit 104% and at 7400?? (not sure how it hit that) but it was 118%

JRelly

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Bruski06

Jrelly when are you back into town. We need more cobalts to data log so we can check someother stuff too.

Area47

what the ecm commands and what the injectors does. usually two different things.

just think. the stage3. when you log it. blocks out the iat2/inj%/kr/msec. go figure.

it's under warranty. have fun with it.

JRelly

Ill be back thnaksgiving weekend, and then ill be back christmas break to, let me know if you wanna set something up then

Littlegoose

Anyone?

07cobaltss

well i'm pretty sure that the ECM/PCM wants to see 14.7/1 air fuel ratio, so when your at WOT and at 100% duty cycle, your computer saying with your current setup, you need to be at 110% which sets the injector to static or something it cant handle. meaning your injectors are to small to handle what your computer wants.

for the above statment, that means your injectors are at 80% of its capacity, this is why when you get bigger injectors your fuel bars need to be adjusted for the bigger injectors.

Witt

No, thats not what it means. If you are commanding 115%, the PCM is requesting 15% more open time from the injector than is possible in a clock cycle. The clock cycle decreases as engine speed increases. If you would increase either the amount of incoming air or the engine redline you have to compensate in such a way that more fuel is delievered over the same or less amount of time.

If your PCM is commnading 80% then its simply requesting 80% of the possible amount of fuel that could be delivered at that given rpm. The duty cycle is simply a calculation of pulse width at a given engine speed. If the pulse width commanded is equal to the amount of time the engine rotates through 4 strokes, 100% duty cycle has been achieved and the injectors are now commanded to stay open. In most cases if the injectors are commanded to stay open at duty cycles greater than 90% they are also still considered open for the entire duration as the amount of time needed to actually open and close the injectors between cycles is not available.

JMHZ2401

That is just stupid!!! Stage 3 ECU could be locked for many reason's. None of those reason we do not know. Only GM knows. Probably so someone does not mess with it and change something and blow it it, or maybe so we can not figure out how GM likes to tune there HP cars, but not because high IDC is normal. It is not. Ask any real tuner and they will tell you this "once your cross that 90% range or so your injectors go static (they stay stuck open and on) ". From info I have gotten even stock SS/SC's are above 100% IDC. Sounds like GM messed up and maybe does not know it. Stock injectors, and stage 2 injectors are just too small. Now it is up to each person who owns the car to decide how to deal with it. YOu can say F it and hope a injector does not fail, and if it does hope you still have warranty left, or fix the issue, bigger injectors.

Area47

they warranty it. got me man.

when did the stage 3 come out, and when did hpt become available for the lsj's. this will give you your answer as to why.

my guess is gm doesn't want to give away the obvious. or the not so obvious. however. if one is good with math, you can figure out what the car is doing.

JMHZ2401

Great if they warranty it, but do you really want to take that big of a risk/hassle of having to use the warranty??? Let me ask you this if you had the choice of wrecking your car and it being fix at no extra charge to you, which would you take? This is the same, but with the engine.