Higgs Boson

iTrader: (3)

duty cycle is a named conversion related to the amount of fuel sprayed in a set amount of time. after all, that's the difference between a smaller and bigger injector - the amount of fuel sprayed, not the length of time it sprays. the time remains the same.

as mentioned before, many posts up, being over 100% duty cycle just shows how much fuel the injector lacks, not the amount of extra time it needs to spray.

JonCR96Z

iTrader: (33)

So duty cycle over 100% and just calculations made by the PCM based on what how long it thinks the injector should be, but it can't actually go over 100%?

Higgs Boson

iTrader: (3)

right. an injector can't flow more than 100%.

think about it. why do you buy bigger injectors. because they flow more fuel in a given time period. duty cycle doesn't measure time. it measures fuel.

it measures fuel as a function of time. but you still alleviate the problem by flowing more fuel in the same time period rather than flowing fuel for a longer time period..... if you extended flow for a longer time period, you would be spraying after the valve closes and have fuel sitting on the valve for a full cycle. you don't want that....

JonCR96Z

iTrader: (33)

And there are no downsides to over doing your injector sizing, assuming the tuning is right?

Higgs Boson

iTrader: (3)

Well, bigger injectors are harder to tune on an engine that isn't really big enough for them. When you back the flow (electronically) off an injector that is (mechanically) designed to flow much more you lose a good spray pattern, etc and it just doesn't work right. Think about turning your shower pressure way down and what happens to the water flow.

How much HP are you planning on making?

JonCR96Z

iTrader: (33)

Hopefully in the 450-470rwhp range. I was considering running the SVO 30#s and 255lph pump, and now it seems like that might be the best idea.

Jon

Higgs Boson

iTrader: (3)

That should be good.

TAQuickness

iTrader: (28)

Negatory ghost rider. Injector duty cycle is the amount of time the injector has to to flow relative to the crank shaft speed. The cam dictates how much flow the injector must be capable of.

ssheets

iTrader: (1)

Yes, that makes much more sense. The "window" is based on speed of the rotating group. The specs of the crank shaft and the piston will determine when the piston is on the intake stroke and thus when and for how long it can draw fuel into the combustion chamber. If it starts early, the intake valve may be closed, but that's irrelevant when determining the size of the "window." You have x amount of milliseconds to get a charge of fuel in based on the location of the piston in its cycle. If you have to spray longer than that window affords you then you have exceeded 100% DC and you're likely spraying fuel on your exhaust valve after it has closed and fuel on you intake valve (not as bad) before it opens.

A big cam will give you a bigger window of time while the valves are open...so ideally you need to consider both windows, piston stroke and valve timing events and how the injector duty cycle works within them???? I think I'm getting an understanding. Hopefully I can see more when I hook up my EFI scanner and look at injector duty cycle.

RedHardSupra

iTrader: (1)

http://redhardsupra.blogspot.com/200...se-widths.html

here's a program i wrote some time ago that accounts for a lot of variables. play with it and you will understand what the pulse width you need at what rpm

ssheets

iTrader: (1)

I downloaded your program and hopefully the EFILive V1 will provide me with enough information to utilize it.

Excuse my ignorance, but what is IFR? [edit; Injector Flow Rate]

I appreciate the assistance with my education.