I was thinking over the weekend about injector duty cycle and it has been bothering me.
on this post someone stated they got 105% duty cycle. My question is how is that possible? Does a 100% duty cycle mean that the injector is open for the entire intake stroke, and a 105% duty cycle is open even after the valve has closed on the intake stroke, or even the injector is pulsed before the intake valve is even open?

Any comments would help..

art

 

hey Mr. Rodrigo, do not let small things like that bother you. We are at war right now and your worried about over squirting.LOL just kidding with ya. Hope to be on the road again soon looking at your tail lights. Ask Louie about injector cycle duty and have him modify your oil pump.RIGHT.....

 

You can not have 105% duty cycle....its impossible.

Duty cycle is defined as the on time/ total time.

 

I agree because suppose a injector operates for 1 second, then is shut off for 99 seconds, then is run for 1 second again, and so on. The injector runs for one out of 100 seconds, or 1/100 of the time, and its duty cycle is therefore 1/100, or 1%.

I was just making sure because its been awhile since ive been in school..

art

 

I think since the intake stroke is only 1/4th the total combustion cycle (2 crank revolutions), it is possible to get more than 100% Duty Cycle. Like Art said, the injector is open longer than the intake valve is.

 

I think you get the extra 5% if the injector does extra credit work or answers a bonus question on a quiz.

 

haha, that was funny.

 

that was funny... at least we got some humorous folks on this board its get dull at certain times.

 

Anyone else have an opinion here??

art

 

Yeah if you have 105% of bubble tea coming out of your bubble tea maker than that thing is broke. Take it back..

 

105% duty cycle is impossible for the reasons mentioned above. Duty cycle is not the percent of time it's open during any single cycle of the engine, it's total open time. 100% duty cycle means the injector does not close. You can't get any higher than that.

That was pretty funny!

 

i dont think thats correct. if you are saying 100% duty cycle means the injector is open ALL the time, then the injector is open while the intake valve is closed during: compression, combustion, and exhaust strokes. by then the intake ports would be filling up with fuel!

 

i'm thinking maybe its more of a numbers thing. not really happening but the ecu is calling for more fuel and the datalogger is reading that as more than 100%. the computer isn't smart enough to realize what the information actually means. anyway thats my guess

 

On my zdyne, there's a setting where I can overclock the injector to 10% more, give it a lil boost

 

"Duty cycle refers to the amount of time an injector is held open vs. the amount of time available at a certain rpm before the next injection event happens and is expressed as a percentage. The electrical characteristics of injectors make it undesirable to drive them at 100% duty cycle due to heat distress on the injector windings and drive circuitry"

From this, I guess that you *could* have 105% duty cycle, but you would be spraying into closed intake valves.

Tom

 

That spraying onto closed valves may be a desired effect to cool them a bit...

 

I would think that would be a bad idea, as gas would end up working its way into the upper parts of the head, possibly washing oil off of moving parts...

Tom

 

105% = madd skillzz injectorzzz

 

100% duty cycle means the injectors are open 100% of the time, that's the definition and that's the only definition. Yes, it means that the injector will still be open when the intake valve is closed.

You guys are thinking of this narrow window of sequential injection. Just to let you know, all cars do not use sequential injection. Batch fire and multipoint are very common too and there is no relationship with intake valve lift and injector events with these types of injection. Injecting fuel while the intake valve is closed is very common and many times wanted. The fuel doesn't just sit on the back of the intake valve. The intake valve is VERY hot and fuel hitting it actualy vaporises.

Sequential injection gives little benefit at high rpms specificly for this reason. Duty cycle is high and fuel is being injected over closed valves. Batch fire and multipoint give almost as good a performance.

 

DirtyLude is right. Fuel is /not/ necessarily injected at the same time the intake valve opens. The fuel will, in fact, wait there until the valve opens.

You cannot have higher than 100% duty cycle. It's mathematically impossible.

"Duty cycle" is a term that is not just used in reference to injectors... it is used in reference to many things that oscillate between on and off... and the above is the /only/ true definition. 100% duty cycle = injector held open.

Dustin

 

Hey Dustin,
Looks like you've narrowed it down to Choose any <u>One</u> in your sig, huh? I like it!

 

if i can have a 101% user rating then there can be a 105% duty cycle!

 

Guess theres no chance of that since you have %100 and not 101

 

I hope that there are NOT people here who still believe that a duty cycle of &gt;100% can exist....are there?

I'm all for sarcasm, and pick up on it with relative ease....but this topic is exhausted, and I personally don't want a 'newbie' reading it and then posting a new topic just to "Clear things up"....know what I'm saying guys.

 

I cant comment on what is theorectically possible with the datalogger, my car says 2.2mph when I am standing still. So it could be some kind of calibration issue.

But I have had a 100% duty cycle quite a few times but never gone over that.