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EFI duty cycle question

Posted By: jcc

EFI duty cycle question - 07/22/14 04:09 AM

I'm confused ( as normal )
So a 4 cycle motor has 720 crank rotation for each power event. Typical cam has intake open, say for arguments sake, 250 Degrees. Assume air intake pre valve is moving or turbulent for a slightly longer period then when valve is open. I don't think the exact amount is crucial to my question. Typical Seq port injection has injector approx 5" from backside of intake valve. If when designing an EFI system, target is never, under full load/WOT, to have injector open/flowing more then 90%? of the time, correct?

So the question is, what is happening to all that fuel being sprayed in at 50?psi 5" from an intake valve in a relatively stagnant air intake tract?

Seems like it would really want to puddle upon hitting any surface other then the hot? intake valve, and it's doing this for over 300 degrees of crank rotation while the intake valve is closed?

Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/22/14 05:07 AM

It really doesnt puddle to easy but it only fires
the injector just prior to the valve opening so you
have very little time when there isnt any air flow..
for production we didnt like going past 85%.. I flowed
a FEW THOUSAND injectors when I was working.. I'm
setting my injection up at 55 psi.. I'm use to that
pressure
EDIT
I'm drilling 2 manifolds tomorrow for my injectors
Posted By: go green

Re: EFI duty cycle question - 07/22/14 05:21 AM

What do you think a carbureted engine is doing during the closed intake intermission ?How about mechanical fuel injection ? If your injector is at 90%, its time to buy bigger injectors.

You have a thingy in EFI that is called a "injector phase angle " it is where you tell the injector to fire in relationship to the valve opening .Just think of it as example of the law of diminishing returns . When you are idling around ,the EFI has a measured fuel delivery at precise times and all is happy , but when you are a 8000 RPM its pretty much just blasting fuel in at precise times .

The reality is not the slow-motion lazy fuel hanging around the valve mental image that you are imagining .
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/22/14 05:57 AM

Also thats why you have a few sensors to tell the
injector when and how much
Posted By: jcc

Re: EFI duty cycle question - 07/22/14 04:15 PM

So the consensus is the injector on seq, is only firing around when the time when the intake valve is moving?
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/22/14 04:34 PM

Yep... thats part of the reason injection is better
on fuel economy, no waste of fuel
Posted By: herkamer

Re: EFI duty cycle question - 07/22/14 04:37 PM

Information about wall wetting/puddling:
http://www.megamanual.com/ms2/xtau.htm

I would think the goal would be to fire the injector at the open valve, but at high speed and long PW times it may overlap with a closed valve.
Posted By: bigtimeauto

Re: EFI duty cycle question - 07/22/14 05:07 PM

its amazing for years we were using batch without any issues....
Posted By: herkamer

Re: EFI duty cycle question - 07/22/14 05:17 PM

Quote:

its amazing for years we were using batch without any issues....


Batch or bank is fine for something that is not emissions critical. Sequential performance gains are very minimal; emissions is where sequential wins.
Posted By: Mopar_Rich

Re: EFI duty cycle question - 07/22/14 05:24 PM

Sequential wins for idle control with a radical camshaft, because you can start the injection pulse just after the intake reversion pulse ends. Air is now flowing in the right direction and the fuel pulse itself is short. Once up in RPM batch works just about as well.

richard-nedbal.com
Posted By: Mopar_Rich

Re: EFI duty cycle question - 07/22/14 05:32 PM

Back "in the day" when I was part of an EFI research team, we assumed spraying into an open valve would be the best approach. This was true at idle (see reversion above), but at higher RPMs when the pulse got so long that it was spraying some portion of its cycle on a closed valve we saw no negative effect. It turned out that spraying on the back of a hot intake valve gave the mixture time to atomize so it was ready for the next cycle. Same thing happened with a carburetor. The manifold design affected this because the runner length helps the charge stay to its assigned cylinder.

richard-nedbal.com
Posted By: jcc

Re: EFI duty cycle question - 07/22/14 08:10 PM

Quote:

Information about wall wetting/puddling:
http://www.megamanual.com/ms2/xtau.htm

I would think the goal would be to fire the injector at the open valve, but at high speed and long PW times it may overlap with a closed valve.



Yea, that's what I talking about, the link might take a few rereads to digest.

This leads into another related topic, seems like any intake tract coatings would have a downside regarding the wall wetting/evaporation issue, either by causing worse puddling with a slick coating, or slow down evaporation with an insulating style coating.
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/22/14 08:52 PM

Quote:

Quote:

Information about wall wetting/puddling:
http://www.megamanual.com/ms2/xtau.htm

I would think the goal would be to fire the injector at the open valve, but at high speed and long PW times it may overlap with a closed valve.



Yea, that's what I talking about, the link might take a few rereads to digest.

This leads into another related topic, seems like any intake tract coatings would have a downside regarding the wall wetting/evaporation issue, either by causing worse puddling with a slick coating, or slow down evaporation with an insulating style coating.



Thats why we spray the fuel in at higher pressures..
it will atomize much quicker.. the fuel particles
are much smaller.. and the pattern of the spray makes
a big difference also.. most all of the injectors now
spray a cone shape with different amount of fuel in
different areas of the cone.. I had to measure the
amount of fuel in each section of the cone... vs
the straight spray of fuel.. this type of injector
would puddle and as said, was hard on emissions..
you dont just spray in a certain amount of fuel but
how its sprayed in
Posted By: Thumperdart

Re: EFI duty cycle question - 07/22/14 09:04 PM

Quote:

Also thats why you have a few sensors to tell the
injector when and how much




Yep, pulse width............lower r`s less fuel wider width higher r`s more fuel tighter width or so I heard.
Posted By: BobR

Re: EFI duty cycle question - 07/22/14 09:32 PM

Quote:

What do you think a carbureted engine is doing during the closed intake intermission ?How about mechanical fuel injection ? If your injector is at 90%, its time to buy bigger injectors.

You have a thingy in EFI that is called a "injector phase angle " it is where you tell the injector to fire in relationship to the valve opening .Just think of it as example of the law of diminishing returns . When you are idling around ,the EFI has a measured fuel delivery at precise times and all is happy , but when you are a 8000 RPM its pretty much just blasting fuel in at precise times .

The reality is not the slow-motion lazy fuel hanging around the valve mental image that you are imagining .



If you could see the 9500 rpm event in slow motion the injector isn't closed much. Also, you really don't even need a cam position sensor on a race car.
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/22/14 09:41 PM

Quote:

Quote:

What do you think a carbureted engine is doing during the closed intake intermission ?How about mechanical fuel injection ? If your injector is at 90%, its time to buy bigger injectors.

You have a thingy in EFI that is called a "injector phase angle " it is where you tell the injector to fire in relationship to the valve opening .Just think of it as example of the law of diminishing returns . When you are idling around ,the EFI has a measured fuel delivery at precise times and all is happy , but when you are a 8000 RPM its pretty much just blasting fuel in at precise times .

The reality is not the slow-motion lazy fuel hanging around the valve mental image that you are imagining .



If you could see the 9500 rpm event in slow motion the injector isn't closed much. Also, you really don't even need a cam position sensor on a race car.



Even at 85% duty cycle(WOT) you would swear its on
all the time. I know it isnt but the sound sure sounds
like it.. its just a buzz(I was testing this stuff
on a test stand built just to test injectors without
any engine in play) so I could flow the injectors at
different duty cycles and we tested at different voltages..
you would be really surprised at how they act at low volts
Posted By: 383man

Re: EFI duty cycle question - 07/23/14 02:10 AM

Heck back in 1989 I was trained on the Dodge Monaco which was not like the old Monaco's as this used a foreign V-6 and it sprayed all injectots all the time everytime an injector fired they all fired. Mopar also did this before they went to ported and sequential injection. The 3.0 v-6 would fire half the injesctors all the time. Which 3 depended on which cyl was fireing. And before that they used throttle body injection as most were 2 barrels and would spray both injectors on every dist signal. Course didn't need a cam sensor on that setup. They finally went to sequential in the early to mid 90's. Mopar also used the 02 just for the fine tuning as the addaptive memory had a larger control over fuel mixture and then once in the right addaptive cell the 02 would fine tune it. Ron
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/23/14 02:24 AM

Quote:

Heck back in 1989 I was trained on the Dodge Monaco which was not like the old Monaco's as this used a foreign V-6 and it sprayed all injectots all the time everytime an injector fired they all fired. Mopar also did this before they went to ported and sequential injection. The 3.0 v-6 would fire half the injesctors all the time. Which 3 depended on which cyl was fireing. And before that they used throttle body injection as most were 2 barrels and would spray both injectors on every dist signal. Course didn't need a cam sensor on that setup. They finally went to sequential in the early to mid 90's. Mopar also used the 02 just for the fine tuning as the addaptive memory had a larger control over fuel mixture and then once in the right addaptive cell the 02 would fine tune it. Ron



I use to flow the throttle body injector(note singular)
back in the beginning of Chrysler injection.. I
built the first flow stand at Chrysler years ago
for testing injectors... I've flowed a FEW injectors
over the years
Posted By: jcc

Re: EFI duty cycle question - 07/23/14 03:07 AM

You mentioned different spray patterns, is there an injector that sprays at closer to a 90 degree angle,ie downstream, instead of the floor of the intake opposite of the injector?
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/23/14 03:20 AM

Quote:

You mentioned different spray patterns, is there an injector that sprays at closer to a 90 degree angle,ie downstream, instead of the floor of the intake opposite of the injector?



None that I have heard of
EDIT
also in the way a injector is designed it would be
real are to get one to fire at 90*.. if you look at
it, its got a long needle and seat per say.. the needle
is called the pintle which is pulled upward by the
electro magnet when fired and if the fuel touches
anything it would puddle so you cant just put a 90*
on the end of the injector
Posted By: 383man

Re: EFI duty cycle question - 07/23/14 05:37 AM

Quote:

Quote:

Heck back in 1989 I was trained on the Dodge Monaco which was not like the old Monaco's as this used a foreign V-6 and it sprayed all injectots all the time everytime an injector fired they all fired. Mopar also did this before they went to ported and sequential injection. The 3.0 v-6 would fire half the injesctors all the time. Which 3 depended on which cyl was fireing. And before that they used throttle body injection as most were 2 barrels and would spray both injectors on every dist signal. Course didn't need a cam sensor on that setup. They finally went to sequential in the early to mid 90's. Mopar also used the 02 just for the fine tuning as the addaptive memory had a larger control over fuel mixture and then once in the right addaptive cell the 02 would fine tune it. Ron



I use to flow the throttle body injector(note singular)
back in the beginning of Chrysler injection.. I
built the first flow stand at Chrysler years ago
for testing injectors... I've flowed a FEW injectors
over the years




Dont know why but I had the 318 on my mind as many of the ones I worked on were the 4 cylinders with 1 injector and the low pressure (14 lb) fuel inj system. Course the turbo cars had 4 injectors. I actually have a real good book on the four cylinder Mopar eng from the late 80's and early 90's that is a very good book and got deeper into details then any Mopar training books before it. Ron
Posted By: jcc

Re: EFI duty cycle question - 07/23/14 02:49 PM

Quote:

Quote:

You mentioned different spray patterns, is there an injector that sprays at closer to a 90 degree angle,ie downstream, instead of the floor of the intake opposite of the injector?



None that I have heard of
EDIT
also in the way a injector is designed it would be
real are to get one to fire at 90*.. if you look at
it, its got a long needle and seat per say.. the needle
is called the pintle which is pulled upward by the
electro magnet when fired and if the fuel touches
anything it would puddle so you cant just put a 90*
on the end of the injector




I agree, it would be hard to get a functioning design to emit fuel properly at 90 deg, but if you could, would it be much of a plus?
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/23/14 02:56 PM

Quote:

Quote:

Quote:

You mentioned different spray patterns, is there an injector that sprays at closer to a 90 degree angle,ie downstream, instead of the floor of the intake opposite of the injector?



None that I have heard of
EDIT
also in the way a injector is designed it would be
real are to get one to fire at 90*.. if you look at
it, its got a long needle and seat per say.. the needle
is called the pintle which is pulled upward by the
electro magnet when fired and if the fuel touches
anything it would puddle so you cant just put a 90*
on the end of the injector




I agree, it would be hard to get a functioning design to emit fuel properly at 90 deg, but if you could, would it be much of a plus?



Sure it would.. it would be directed at the valve
and it would already have velocity
Posted By: redmist

Re: EFI duty cycle question - 07/23/14 06:50 PM

I have found that my car likes injector phasing to fire at the back of the closed valve just before it opens, instead of firing as it opens.

It's a difference you can feel.

I am using off the shelf Mustang GT-500 injectors, @ $24 a piece. The spray pattern is setup for a dual valve design, but they work better than my old non-split injectors I had in it.

My duty cycle is 65% at WOT, on a car with 500 HP, and 542 Ft-Lbs.
Posted By: MR_P_BODY

Re: EFI duty cycle question - 07/23/14 08:59 PM

Quote:

I have found that my car likes injector phasing to fire at the back of the closed valve just before it opens, instead of firing as it opens.

It's a difference you can feel.

I am using off the shelf Mustang GT-500 injectors, @ $24 a piece. The spray pattern is setup for a dual valve design, but they work better than my old non-split injectors I had in it.

My duty cycle is 65% at WOT, on a car with 500 HP, and 542 Ft-Lbs.



Those injectors are probably split cone for the dual valve
Posted By: ntstlgl1970

Re: EFI duty cycle question - 07/24/14 07:22 AM

the injectors edelbrock supplies have 4 spray nozzles, not sure it's any better or worse than others just interesting. Pretty sure they are magneti marelli. The cam sensor allows you to do individual cylinder mixture if your controller supports that with sequential....
Posted By: BobR

Re: EFI duty cycle question - 07/24/14 03:32 PM

Quote:

the injectors edelbrock supplies have 4 spray nozzles, not sure it's any better or worse than others just interesting. Pretty sure they are magneti marelli. The cam sensor allows you to do individual cylinder mixture if your controller supports that with sequential....



With BS3 you can do individuals without a cam sensor.
Posted By: TRENDZ

Re: EFI duty cycle question - 07/24/14 07:09 PM

Quote:

Quote:

the injectors edelbrock supplies have 4 spray nozzles, not sure it's any better or worse than others just interesting. Pretty sure they are magneti marelli. The cam sensor allows you to do individual cylinder mixture if your controller supports that with sequential....



With BS3 you can do individuals without a cam sensor.


Please explain how it does this without knowing what cylinder is firing.
Posted By: jcc

Re: EFI duty cycle question - 07/24/14 07:26 PM

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?
Posted By: BobR

Re: EFI duty cycle question - 07/24/14 08:07 PM

Quote:

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?



At about 5000 RPM it matters ZERO and very little at any speed. We used one until it took a crap and prevented our engine from starting. On the advice of a very knowledgeable heads up racing tuner we disconnected it. Engine started and idled fine. Threw the sensor in the trash. This is not direct injection. When the injector fires means little-especially as the RPM climbs. It all happens so fast it just doesn't matter.
Posted By: OUTLAWD

Re: EFI duty cycle question *DELETED* - 07/24/14 08:09 PM

Post deleted by OUTLAWD
Posted By: Blusmbl

Re: EFI duty cycle question - 07/24/14 08:41 PM

For something other than a 100% race motor it is best to inject on a closed intake valve. Depending on spray pattern and orientation you can run into bore wash issues and have long term ring durability issues.
Posted By: 383man

Re: EFI duty cycle question - 07/24/14 09:06 PM

Mopar used a few different injection systems as some had to have the cam sensor to run and some would run without it. I know on V/8's with a dist it used the dist hall effect as the cam sensor and it only looked at it while starting as once it started you could unhook the dist and it would run fine. Some 4 bangers use the same basic type as if you cranked them with no cam sensor the PCM would start trying different firing orders until it got it right and it started. The V/8's and V/6's cranked longer then the 4 cyl did when trying to start with no cam sensor signal because of the longer firing order. Course these are ported or sequential inj as throttle body inj does not need a cam sensor at all. Ron
Posted By: TRENDZ

Re: EFI duty cycle question - 07/24/14 09:21 PM

Quote:

Quote:

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?



At about 5000 RPM it matters ZERO and very little at any speed. We used one until it took a crap and prevented our engine from starting. On the advice of a very knowledgeable heads up racing tuner we disconnected it. Engine started and idled fine. Threw the sensor in the trash. This is not direct injection. When the injector fires means little-especially as the RPM climbs. It all happens so fast it just doesn't matter.


My question was how you do individual cylinder tuning with no cam sensor.
As far as injection timing events.... No system is capable of spraying on an open intake at all rpms.
Posted By: BobR

Re: EFI duty cycle question - 07/24/14 10:28 PM

Quote:

Quote:

Quote:

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?



At about 5000 RPM it matters ZERO and very little at any speed. We used one until it took a crap and prevented our engine from starting. On the advice of a very knowledgeable heads up racing tuner we disconnected it. Engine started and idled fine. Threw the sensor in the trash. This is not direct injection. When the injector fires means little-especially as the RPM climbs. It all happens so fast it just doesn't matter.


My question was how you do individual cylinder tuning with no cam sensor.
As far as injection timing events.... No system is capable of spraying on an open intake at all rpms.



As I stated before with BS3 you can. It doesn't matter where the valve is when the event occurs. You just add or subtract fuel from the appropriate runner at any given RPM. Believe me...it works.
Posted By: TRENDZ

Re: EFI duty cycle question - 07/24/14 10:50 PM

Quote:

Quote:

Quote:

Quote:

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?



At about 5000 RPM it matters ZERO and very little at any speed. We used one until it took a crap and prevented our engine from starting. On the advice of a very knowledgeable heads up racing tuner we disconnected it. Engine started and idled fine. Threw the sensor in the trash. This is not direct injection. When the injector fires means little-especially as the RPM climbs. It all happens so fast it just doesn't matter.


My question was how you do individual cylinder tuning with no cam sensor.
As far as injection timing events.... No system is capable of spraying on an open intake at all rpms.



As I stated before with BS3 you can. It doesn't matter where the valve is when the event occurs. You just add or subtract fuel from the appropriate runner at any given RPM. Believe me...it works.


OK, so you have 8 injector channels. without a cam sensor you are still controlling the channel that is hard wired to the cylinder you want to change, but the injection event could happen at any point in the cycle. I get it now, but this must not work for ignition events. So I see how fuel trimming would work, you just loose individual ignition control.
Posted By: BobR

Re: EFI duty cycle question - 07/25/14 03:36 PM

Quote:

Quote:

Quote:

Quote:

Quote:

I have no idea, but does the cam sensor only really matter and reference upon start up, or does it verify cyl #1? every time?



At about 5000 RPM it matters ZERO and very little at any speed. We used one until it took a crap and prevented our engine from starting. On the advice of a very knowledgeable heads up racing tuner we disconnected it. Engine started and idled fine. Threw the sensor in the trash. This is not direct injection. When the injector fires means little-especially as the RPM climbs. It all happens so fast it just doesn't matter.


My question was how you do individual cylinder tuning with no cam sensor.
As far as injection timing events.... No system is capable of spraying on an open intake at all rpms.



As I stated before with BS3 you can. It doesn't matter where the valve is when the event occurs. You just add or subtract fuel from the appropriate runner at any given RPM. Believe me...it works.


OK, so you have 8 injector channels. without a cam sensor you are still controlling the channel that is hard wired to the cylinder you want to change, but the injection event could happen at any point in the cycle. I get it now, but this must not work for ignition events. So I see how fuel trimming would work, you just loose individual ignition control.



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