injector-duty-cycle discussion simple style

[LandSpeed-DSM]

So why don't you enlighten all of us on how the whole injector duty cycle works but please don't tell me the same old shit that everyone else has said. So far none of you here have posted any solid evidence that shows that my way of thinking is wrong. Only thing I've seen so far is a simple explanation that says IDC is a calculation of IPW which we all know.

I'm not saying that I'm right but I want to be proven wrong, and if it turns out that I'm wrong then I will admit that I'm wrong. I want to see some facts that show that car manufacturers have designed injectors to spray on the closed valves and that roughly 25% IDC is actually spraying fuel when the valves are open and the other 55% (80-25=55) is sprayed when valves are close.

Because you disagree and/or don't understand is not equivalent to the explanations given to you being wrong.

So the both of you can spare me walls of semi-coherent text.

IDC, as you acknowledge, is a function of pulse-width in relation to engine speed and the intake cycle. That''s pretty much it. The faster the crank speed for a given IPW, the greater the IDC.

Sometimes the demand for fuel requires that the spray start just before the intake valve starts opening. Because the ECU doesn't actually have any sort of feedback for when IVO/IVC occurs it may not only start before IVO but continue well beyond IVC.. just loading the port up with fuel.

How about instead of this childishness that seems to follow the both of you.. you guys first shut up, grab an oscilloscope, find an injector lead, watch it and then shut up some more when you finally figure out that you are entitled to your own opinions and not your own facts..

This isn't a debate or something that is a poorly understood phenomena.. this is integral to EFI. I would hate to have been your professor in anything more mentally taxing than remedial english.

Or, FFS - try researching the differences and prevalence of batch, bank or sequential injection. Or "injection angle" on cars using full stand-alones with crank triggers controlling both spark and fuel.

Even with a descending piston adding to the pressure differential.. you are not going to get a >0.1mL mass worth of fuel (in mist form) accelerated out of the injector and sent several inches down the port into the cylinder in only ~10ms (or less depending on crank speed and valve timing)

 

[bastarddsm]

Jesus christ, my first post should have ended this. It's not rocket science it's simple math. Figure out how long an intake valve is open, then tell me if your injectors could be injecting enough fuel in that time.

There is no discussion, it's pretty cut and dry.

Don't listen to 90% of people on forums. Hell don't listen to me. It's not like I'm a professor of combustion or anything.

 

[LandSpeed-DSM]

This is a big reason we have had to account for "wall-wetting" fuel film evaporation in port injected engines..
Evaporate prediction and compensation of intake port wall-wetting fuel film for spark ignition engines fueled with ethanol-gasoline blends - Springer

There are a ton of SAE papers on this too, but a subscription is required first. This one just had a convenient little diagram in the abtract.

 

[dsmcurse]

okay bastard, I still dont quite understand? And by no means does this make me any less of a tech or mechanic or person or anything, I perform big huge crazy jobs as a mechanic everyday. Me, along with many others reading along dont quite "get it". So i guess were ALL dumbasses with the exception of you and LandSpeed...

On a serious note, the above explanations just dont "click" with my head, and instead of being a typical teacher at highschool who ignores the student in question, why dont you take 15mins out of your day and teach me (along with others reading along) the BASIC princible? I participate in this forum to learn and teach. There have been many other threads where a noob just couldnt quite grasp the concept of something rather simple, and I took the 20 or 30 mins out of my day to provide detailed information in a simple to understand sorta write up.

Now maybe this is just SO-O-O-O simple to you and LandSpeed, BUT, im still in the class room scratching my head... I have nothing to prove to any of you as far as my "mechanical" skills go as I can slot up into just about ANY auto, diesel or marine shop and land a job no problem. I have attended EFI 101 class hosted by Brian Macy of Home Brian Macy is a reputable tuner who teaches EFI and tunes 2000HP racecars and 3000HP off-shore race boats, during the class I asked him to explain this IDC phenomenon and he NEVER mentioned spraying on a closed valve. In-fact, his explanation sounded closer to mine than any of yours.

Im almost at a loss for words here, my intentions are good, I WANT TO understand this concept as easy as I understand how to tie my own shoes. Can LSD or Bastard please take 15-20mins of your important day and type up a lamens terms explanation? Pretty-please? I know me, along with many would love to grasp the same understanding concept as you guys (not being a smartass in any way shape or form)

 

[Boostdriven]

Because you disagree and/or don't understand =/= the explanations given to you being wrong.

I didn't say the explanation given to me was wrong, I just said it contains no detail except that's its a generic statement that we all already know and agree on.

IDC, as you acknowledge, is a function of pulse-width in relation to engine speed and the intake cycle. That''s pretty much it. The faster the crank speed for a given IPW, the greater the IDC.

This is the information that we all agree on.

Sometimes the demand for fuel requires that the spray start just before the intake valve starts opening. Because the ECU doesn't actually have any sort of feedback for when IVO/IVC occurs it may not only start before IVO but continue well beyond IVC.. just loading the port up with fuel.

Partially I agree with this as well but this still does not explain how the damn theory of 720* of crank rotation would some how equal to 100% +/- IDC. I agree that the IPW is based off of the time it takes an engine to make 720* of ration because the new engine cycle would begging after 720* therefore demanding fuel to be sprayed in the cylinder again. What I don't agree with is that 100% +/- IDC is somehow equal to 720* +/- of crank rotation. Even though new IDC has to begin after 720* of crank ration that don't mean that the injector has full 720* time frame to get fuel in to the engine. I think the IPW is only calculated from a 1/4 +/- of the time it takes the engine to rotate 720* which would only be the intake cycle of the engine. Meaning that the injector opens somewhere at the top of the intake stroke and would have 100% IDC somewhere at the bottom of the intake stroke. Due to the fact that every make of car has a different cam duration that 100% IDC could be at a different degree of crank rotation but it would be somewhere around 180* +/- of crank rotation from the top of the intake stroke. Of course the top would vary as well due to cam setup from the factory.

How about instead of this childishness that seems to follow the both of you.. you guys first shut up, grab an oscilloscope, find an injector lead, watch it and then shut up some more when you finally figure out that you are entitled to your own opinions and not your own facts..

Just because you can not explain something that you don't know yourself don't mean you have to get your panties in the wad and tell people to shut up

 

[Boostdriven]

Jesus christ

Don't get Jesus involved in this, He has nothing to do with this discussion

 

[hotrodssnova]

Here's how I understand it. Idc is a number given to an event by a calculation. This calculation is set up in your LOGGINGssoftware and NOT in the code that the ecu processes. The ecu injects fuel when the cas tells it to. Then it calculates the air coming in, and holds the injector open. The logger translates this amount of given time, by the formula in the logging software, and spits out an idc.

 

[LandSpeed-DSM]

It's pretty obvious enough time has been wasted here. The information is there, go find it.

As far as "proving you wrong" - as a logical matter, proving a negative is impossible.

You guys are not looking to learn or discuss, and never do in these "discussions."

Time for you to do some research. I gave you some keywords.. batch, bank, sequential, injection angle, etc.

The two of you circle-jerking one another in every thread that you participate in gets tiresome. Some things can't be dealt with by busting out the crayons, the onus is on you to comprehend the basics that lead to the more "complex" bits.

The time frame is a full 720*. If at X rpm it takes 20ms to run through all 4 cycles, and the injector is supplied power for 15ms.. you are at 75% IDC. If you have the vaguest understanding of how the valves behave during that 720* you know that there is a comparatively long period of time that fuel is being squirted into a port with a closed valve.

 

[Boostdriven]

It's pretty obvious enough time has been wasted here. The information is there, go find it.

As far as "proving you wrong" - as a logical matter, proving a negative is impossible.

You guys are not looking to learn or discuss, and never do in these "discussions."

Time for you to do some research. I gave you some keywords.. batch, bank, sequential, injection angle, etc.

The two of you circle-jerking one another in every thread that you participate in gets tiresome. Some things can't be dealt with by busting out the crayons, the onus is on you to comprehend the basics that lead to the more "complex" bits.

Thank you for your vivid explanation

 

[bastarddsm]

okay bastard, I still dont quite understand? I have attended EFI 101 class hosted by Brian Macy of Home Brian Macy is a reputable tuner who teaches EFI and tunes 2000HP racecars and 3000HP off-shore race boats, during the class I asked him to explain this IDC phenomenon and he NEVER mentioned spraying on a closed valve. In-fact, his explanation sounded closer to mine than any of yours.

Im almost at a loss for words here, my intentions are good, I WANT TO understand this concept as easy as I understand how to tie my own shoes. Can LSD or Bastard please take 15-20mins of your important day and type up a lamens terms explanation? Pretty-please? I know me, along with many would love to grasp the same understanding concept as you guys (not being a smartass in any way shape or form)

Carefully read my posts and come back with specific questions as to what is confusing you. As far as Brian Macy, I don't know who he is, but I learned this when I was 8yrs old with my dad. He has an Accel DFI on his 65 mustang since 1992, back before anyone was doing EFI. Guess who was riding shotgun plugging numbers in. Exactly. More currently I tune the durty deere, a 3.0 turbo prostock diesel truck. We have one of the highest horsepower duramaxes ever, with 2 seasons, 4 dyno sessions, and over 150 hooks on the same engine. Making over 1500 hp the entire time. We run a Bosch MS15.1, and it is so complicated it would make even the most accomplished tooner on here cry for their teddy bear and suck their thumb.

 

[dsmcurse]

Carefully read my posts and come back with specific questions as to what is confusing you. As far as Brian Macy, I don't know who he is, but I learned this when I was 8yrs old with my dad. He has an Accel DFI on his 65 mustang since 1992, back before anyone was doing EFI. Guess who was riding shotgun plugging numbers in. Exactly. More currently I tune the durty deere, a 3.0 turbo prostock diesel truck. We have one of the highest horsepower duramaxes ever, with 2 seasons, 4 dyno sessions, and over 150 hooks on the same engine. Making over 1500 hp the entire time. We run a Bosch MS15.1, and it is so complicated it would make even the most accomplished tooner on here cry for their teddy bear and suck their thumb.

Well thats VERY impressive, I almost envy you in a way, I had no one to show me the ropes so to speak or to pass down the tourch of mechanical knowledge. Your very lucky guy, but theres still questions to be asked, I guess at this point and time I'll do my own research (on differant sites and differant sources of information) and maybe Ill be back with something "intelligent" to say as LSD would put it...

Sorry im not on the same understanding level as you LandSpeed

 

[LandSpeed-DSM]

CTRL + F "Intelligent" - Results 1 of 1... and it's your post.

You started this as a discussion.. though it never read like you planned to do anything but preach what you believe to be occurring.

Then, when said knowledgeable members chimed in (as requested) you guys dug in your heels and shit went pear-shaped.

The hang-up here seems to be what the time frame the duty cycle is generated from.

You guys are rejecting the well established fact that the injector sprays on a closed valve. This would indicate you feel that the time frame is from precisely when the IVO begins and lifts from the seat to IVC.

To which I still refer you back to an earlier post of mine:
Even with a descending piston adding to the pressure differential.. you are not going to get a >0.1mL mass worth of fuel (in mist form) accelerated out of the injector and sent several inches down the port into the cylinder in only ~10ms (or less depending on crank speed and valve timing)

This would require an enormous injector, of several times the capacity that we use currently to service a given fuel and airflow figure.

As well as what casper and bastard shared. At no point have I claimed knowing this makes me "smart" .. it just means I researched this sh!t.

 

[Xploitn]

Thank you wisemen for providing some good info!

 

[dsmcurse]

CTRL + F "Intelligent" - Results 1 of 1... and it's your post.

You started this as a discussion.. though it never read like you planned to do anything but preach what you believe to be occurring.

Then, when said knowledgeable members chimed in (as requested) you guys dug in your heels and shit went pear-shaped.

The hang-up here seems to be what the time frame the duty cycle is generated from.

You guys are rejecting the well established fact that the injector sprays on a closed valve. This would indicate you feel that the time frame is from precisely when the IVO begins and lifts from the seat to IVC.

To which I still refer you back to an earlier post of mine:
Even with a descending piston adding to the pressure differential.. you are not going to get a >0.1mL mass worth of fuel (in mist form) accelerated out of the injector and sent several inches down the port into the cylinder in only ~10ms (or less depending on crank speed and valve timing)

This would require an enormous injector, of several times the capacity that we use currently to service a given fuel and airflow figure.

As well as what casper and bastard shared. At no point have I claimed knowing this makes me "smart" .. it just means I researched this sh!t.

informational post's like this (minus the smartassism) is what people are looking to read.

Its like this, 2 guys can read the same page on the book, maybe one guy dont understand it worth a F, other guy breaks it down and explains it simple style in his own words. THIS IS WHAT I WANNA HEAR. I can read the same link as you, but still not grasp it... So if I ask for a lamens term explanation then it should be a peice a cake for you to put it in your own words as clearly you DO understand it.

And not to be a "smartass" by any means at all, but I sometimes question the way you "talk" in here. I type the same way I would talk, stupid shit and slang and all the good 'ol fashion lazy american english at work here You on the other hand... Do you really talk like this in real life? Its as if you keep a medical dictionary or a encyclopedia next to your keyboad or something?? If you really truly are Doogie Howser than please accept my apologies.

Bastard and LSD, both of you are well acomplished members of our comunity, and I look up to both of you guys for your well done work, sorry if I have come off wrong but Im here to learn and help teach. I have to take time outa my day to explain some REALLY basic things to nooby members on here, and never once did I come off as "better" as we all have to start somewhere. Ten plus years ive spent as a career mechanic and i still cant explain IDC to an absolute tee (im sure theres 50+ year experienced mechanics that cant explain it either so...) Im open for discussion, im open to take in other peoples theories, some of the highest ranked wiseman still havent chimmed in... Offering the explanation isnt as easy as one would think

 

[LandSpeed-DSM]

I'm a cigar smoking, whiskey drinking, outdoors-man that likes to eat the things I shoot or catch and go through cuss words like water on my own time but as a necessity have been forced to wear slacks to the office 5 days a week and as such that language is ingrained with my typing.

Be it professional correspondence to clients or a forum post.. you won't see any sort of non-ironic teenage text speak from me.

 

[dsmcurse]

I respectfully accept your response, and thanks for not correcting my bad spelling

Nah but seriously, thanks for your "back on planet earth" last response.

 

[bastarddsm]

Well thats VERY impressive, I almost envy you in a way, Sorry im not on the same understanding level as you LandSpeed

I don't know if you think I'm trying to be condesending, or a showoff or what, but damn. You came in here trying to discuss a cut an dry topic, with false information. Then several people lay it out very simply and correctly, and you still refute it. Then when asked why you do not understand, you can't answer.

What is your problem dude.

 

[dsmcurse]

No disrespect aimed at you at all Bastard, my only problem is this, when I close my eyes, I can picture the pistons pumping up and down, I can see the valves open close open close thanks to the bump sticks, I picture the spark plug poppin off at the exact moment to ignite, MY PROBLEM is this, I cant picture the injector spraying on a closed valve? Thats my only problem dude.

This is alienated concept to me, I see it puddling up & being all chaotic. I see it spraying as the piston goes down to inhale its fresh air gulp, to ME it seems as if this is the only time it could make its air/FUEL mixture... This is my problem. I dont understand it in my brain. And as a career mechanic, I definatley WANT TO UNDERSTAND!
By no means am I trying to rub you or LSD the wrong way.

If our forum is 10thousand members strong, Id bet my balls on a choppin platter that 9800 of us DONT truly understand it. So this discussion is to shine some light. Nothing more.

 

[hotrodssnova]

The ecu has no clue to when the valves are open or closed. It sees air flow, coolant temperatures and crank angle. With those factors being fed to the ecu, it calculates the fuel needed, and sprays, regardless if the valve is open or closed.

When the calculated air flow exceeds the available fuel mixture in the calculations, set by injector size, you run into idc higher then 100%. It is only a number calculation based on the reported fuel available combined with reported air volume.
So, you end up with fuel on closed valves. Just not enough valve timing to spray it all in.
So, now you have fuel sitting on a closed valve, when the valve opens, a gush of fuel goes in, some is sucked out the overlapping exhaust valve and we start all over again in milliseconds

 

[dsmcurse]

The ecu has no clue to when the valves are open or closed. It sees air flow, coolant temperatures and crank angle. With those factors being fed to the ecu, it calculates the fuel needed, and sprays, regardless if the valve is open or closed.

When the calculated air flow exceeds the available fuel mixture in the calculations, set by injector size, you run into idc higher then 100%. It is only a number calculation based on the reported fuel available combined with reported air volume.
So, you end up with fuel on closed valves. Just not enough valve timing to spray it all in.
So, now you have fuel sitting on a closed valve, when the valve opens, a gush of fuel goes in, some is sucked out the overlapping exhaust valve and we start all over again in milliseconds

Thank you for your interpretation of how it works, I repect your carefully worded response. One question I have tho, in my mind (read original post 1) I see fuel injector givin signal to spray as piston goes down to take in its fresh air gulp (I guess it will receive signal regardless to what the paticular cylinder position is?) now in my understanding, (which im told isnt correct at all and thats ok by me) I see the injector spraying as piston goes down. for how long it sprayed during its piston travel is what gives you the IDC number on our laptop. If it sprays past its "normal window of time" you end up with a injector duty cycle numper greater than 100 percent.

The way you just explained it, you will end up with a IDC number greater than a 100 percent if the given amount of airflow registered is greater than the given amount of fuel that was just provided? Did I ask this correctly? So on a NA vehicle like Honda with no turbo, it to can exceed 100%, is this which-craft? And what part of the "brains" determines this? In conjunction with TPS, CAS, MAF, MAP, IAT, whats the final judge that says "ok now im gonna report back to the data logger that we just exceeded 100% IDC"?

 

[steve]

Very well put and I agree with your statement but that's just a general explanation of how it works. It does not explain how much of the RPM duration is considered to be 100% duty cycle for the ECU, is it the time it takes an engine to make 180* 360* or is it the full cycle of 720*

Here are few links that kind of explain why IDC has to happen before the intake valve closes or roughly with in 180* of crank rotation.

Injector Duty Cycle explained *good stuff* - LS1TECH

Injector Dutycycle explained [Archive] - IGOTASUBARU.COM FORUM

I don't know how smart those guys are and how much they know but to me that makes sense.

Now explain to me how a carbureted engine works when there is no fuel being injected under pressure but its only being drawn in through the jet in the carburetor ONLY when the intake valve is open and the piston is taking air in.

I'm failing to grasp what you're not understanding. bastarddsm got it 100% correct. I tried to lay it out in different words.

The time available to inject fuel is from one complete power cycle to the next. On a 4 cycle engine that's 720* crank degrees. As pointed out in the first link quoted, there is 40ms available at 3000 RPM. If the ECU thinks it needs a 20ms pulse (IPW) to get the correct AFR and enrichment then your IDC is 50% (half of the available time) if the ECU thinks it needs a 40ms IPW then the IDC is 100%. There is an error in the first post of that first link as it relates to DSM ECU's and lots of errors and misunderstandings in that thread. I won't address them here except for the first error, the ECU doesn't turn off injectors that are still open from the last cycle. It programs a new IPW and if that is still longer than the time available the injectors are running static, on all the time and not able to hit the target AFR. Any time the IDC is > 100% the injectors are static.

The ECU starts the injection cycle while the intake valve is closed during the combustion cycle. It's spraying fuel at the back side of a typically hot intake valve which helps cool the valve and vaporize the fuel more. When the valve does open it sucks in all the fuel it can and if the injector is still spraying when the valve closes the cylinder will suck that in the next time it opens.

Again IDC is the ratio of the IPW and the time per power cycle at the current RPM.

The ecu has no clue to when the valves are open or closed. It sees air flow, coolant temperatures and crank angle. With those factors being fed to the ecu, it calculates the fuel needed, and sprays, regardless if the valve is open or closed.

False! Except on the first cycle during cranking, it always knows. It has to or it couldn't fire the plugs at the right time. It has to see the TDC signals to find TDC cylinder 1 and from that point it knows where the engine is.

 

[hotrodssnova]

Idc is a number. That's all. It does not care if the pistons are moving up or down, starts at the time the cas tells it to and ends when the determined amount of factored fuel has been delivered.

It's bud thirty, and I'm 110% thirsty, therefore, I'm going to drink more than what I need, and it has nothing to do with idc whatsoever.
Bastard should throw in equation here shortly.
Please.
Or Steve.

 

[bastarddsm]

You mean like 940pm + hotrrodssnova +budwiser = 896% BAC

 

[Seamus]

Okay dude, since this is a DISCUSSION, why dont you explain this in simple terms please? This is aimed towards better understanding, and Ill openly admit, I DONT UNDERSTAND 720* spraying on closed valves? I dont get get it? An earlier attempt to explain things in my own words left me "stupid" right? I have plenty of books and magazines I could open up but a big scientific explanation isnt what im looking for here, I want simple understanding, draw me a picture with a crayon please. No body on here likes to get qoted then called out by a smartassy reply and thats what I did to you in a differant thread and now you wanna be "internet tuff guy"

In a differant thread homeboy claims to sell "exotic" cars for a living with the ocasional high-end boats... Sure you dont sweep the floors at a high end dealership? Claims like "200 thousand dollar boats are life rafts where im from" c'mon dude, get real. Im so sure. Judging by your pictures id say your car aint $hit. And if you were slanging Lambos and Ferraris for a living I highly doubt that you'd even waste your time in this forum as this is for 20 year-old relic cars that have no business being owned by a rich "big shot" Wouldnt you and your pretend Lambo be better off at www.Lambosareforassholes.com?

Im by no means trying to start

I can't even read all this. I think you have the roles reversed. And you are putting a lot of words in my mouth and not quoting me accurately. You are the one bragging about boats and this and that. I just wanted to point out what a fool you sound like. I never claimed to be wealthy or a big shot. Any one with a 3rd grade reading level could comprehend what I said. I pointed out what I did for a living to illustrate how stupid it sounds to brag about super expensive toys that I so not And could not own. I own a dsm because A. I can't afford an really expensive toy car. B. I like them. A 92 Tsi awd was my first car. That's the car in my avatar. And yea ## right I own a couple year old jetta too. I'm sorry I don't want to spend more money on a car that I never drive, because I have other things to pay for like most adults. I definable never claimed to be rich, in fact I was hoping to state the opposite. As far as me sweeping the floors vs. selling high end cars you got me there. I don't technically sell high end cars. I am the finance/business manager. Btw my daily driver is a company car, and although I could drive a brand new Porsche or damn near anything else I want within reason. I usually drive an an a4 or a6 because I don't feel the news to roll around in some flashy car that isn't mine. About the only time ill drive a high end sports car home is if we get a 993 turbo on cause its my favorite car.

So again my point was, you sound like and idiot bragging about some nice boat that you left your grimey finger prints on. You also sound dumb bragging about your dsm that is nothing special in this day and age. 50 percent of this board is a turbo swap awAy from making power like yours. But of course the no it all posts that are full of misinformation take the cake in tool moves. Oh and btw I have owned some kind of fancy cars and built a couple nice track cars when I was younger. Your priorities change when you have a family.

 

[dsmcurse]

I'm failing to grasp what you're not understanding. bastarddsm got it 100% correct. I tried to lay it out in different words.

The time available to inject fuel is from one complete power cycle to the next. On a 4 cycle engine that's 720* crank degrees. As pointed out in the first link quoted, there is 40ms available at 3000 RPM. If the ECU thinks it needs a 20ms pulse (IPW) to get the correct AFR and enrichment then your IDC is 50% (half of the available time) if the ECU thinks it needs a 40ms IPW then the IDC is 100%. There is an error in the first post of that first link as it relates to DSM ECU's and lots of errors and misunderstandings in that thread. I won't address them here except for the first error, the ECU doesn't turn off injectors that are still open from the last cycle. It programs a new IPW and if that is still longer than the time available the injectors are running static, on all the time and not able to hit the target AFR. Any time the IDC is > 100% the injectors are static.

The ECU starts the injection cycle while the intake valve is closed during the combustion cycle. It's spraying fuel at the back side of a typically hot intake valve which helps cool the valve and vaporize the fuel more. When the valve does open it sucks in all the fuel it can and if the injector is still spraying when the valve closes the cylinder will suck that in the next time it opens.

Again IDC is the ratio of the IPW and the time per power cycle at the current RPM.



False! Except on the first cycle during cranking, it always knows. It has to or it couldn't fire the plugs at the right time. It has to see the TDC signals to find TDC cylinder 1 and from that point it knows where the engine is.

I sincerley appreciate your time to say this in your own words on a not so smartassy level. The way you explained this a lil light bulb just lit up above my head, light bulb still aint as bright as I wished it to be but at least its turning on. I still scratch my head at thought of these chevy v8 guys logging 180%IDC?