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Sequential injection with only crank position sensor


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 Crank rotates twice for every cam rotation. To get true sequential you need to know the timing of when the intake valves are open which is dependent on the cam. If you shut off your car or roll it the computer won't know which location your cam is in if it is in intake or exhaust so it needs a cam sensor.

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Edit: Sequential injection requires a Crank and Cam position sensor. Cam signal is often called " Home " signal. ECU needs to know when #1 piston is at TDC on the Compression/Power stroke, other wise it can't do sequential Fuel injection  or Coil On Plug ignition.

 

Edit: Multipont ( all injectors fire at once, twice per 720 degrees ) or Batch fire Fuel injection with a Dizzy Ignition can be done with a only the RPM signal ( crank sensor) . Spark plugs and injectors fire twice in 720 degrees. One at TDC on the compression stroke and once at TDC on the Exhaust stroke. Since there is no compression ( Exhaust stroke )  and no Air/ Fuel mix, no combustion occurs. That is why it is called " Wasted Spark ".  Fuel doesn't have to be timed any near as accurately as spark.

 

Ford EDIS can do wasted Spark with only a crank signal. Fuel will still only be Multipoint or Batch fire. 

Edited by Chickenman
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But the ECU knows TDC from #1 piston from the Crank sensor. Same as reading it with the timing light from the crank pulley. 

 

 

A complete combustion event in a 4 cycle ( OTTO cycle )engine consisted of Intake Cycle, Compression Cycle , Power Cycle  and Exhaust Cycye. Each complete cycle takes Two revolutions. 720 degrees. During a complete combustion event, the piston comes up to TDC at BOTH the Compression cycle and the Exhaust cycle. For sequential Fuel and COP Ignition the ECU has to know what CYCLE the piston is on when it hits TDC.  Compression or Exhaust cycle. And that requires a Cam sensor.

 

Read about 4 cycle engines operations as suggested please...  I've edited post number #4 to make things a bit clearer for you.

Edited by Chickenman
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Yea it is kind of odd to think about, glad you got it. 

 

While yes it is possible for a computer to keep track of where you are just based off the crank assuming 720 for a full cycle. You have to remember if the car rolls or it forgets and looses track of the crank rotation once then you would be in a lot of trouble. There are some ways of doing it very simply with a sensor that reads the spoke/spaces between the cam gear/pulley, you just have to make one of them stick out more or less to give a variable signal for the sensor.

 

Overall the benefits seemed pretty small. Would be pretty cool if you were controlling each individual cylinder on standalone, but other then that Tony's explanation to the fuel pool using aftermarket injectors and readings on the MS forums makes it seem fairly minimal benefit for the effort involved.

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Overall the benefits seemed pretty small. Would be pretty cool if you were controlling each individual cylinder on standalone, but other then that Tony's explanation to the fuel pool using aftermarket injectors and readings on the MS forums makes it seem fairly minimal benefit for the effort involved.

 

The key benefit for running sequential is that you get twice the injector pulsewidth.  For those running large injectors this makes a HUGE difference in controllability of fuel delivery at idle and other low-load conditions.

 

Also, you absolutely can run sequential without a cam sensor (if your controller will let you) - you'll just be on the wrong phase about half the time.  This really doesn't make much difference in how the engine runs and you still get the advantage of increased injector pulsewidths.

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^ However, the opposite is true in the upper RPM ranges. Participated on a Web seminar hosted by HP Academy last nite and managed to stump the moderator on a question regarding required differences in injector sizing between Batch Fire and Sequential. 

 

For a given HP range batch fire has more time to inject the amount of fuel needed than sequential. Say you are running Batch Fire or Multipoint and your engine makes 200 HP. Not going to do the Math but that requires XX cc/min of fuel. Batch and Multipoint gives two sprays per 720 degrees ( OTTO Cycle ) to inject the required amount of fuel. Batch and Multipoint are referred to as untimed injection. They basically squirt tow big whacks of fuel into the Intake manifold and let the engine sort things out. Juts like a carburator and Plenum manifold. 

 

Edit: Full Sequential is timed injection and it only gives one squirt per 720 degrees and that squirt is usually timed to the Intake cycle when Intake flow is established. Thus you have a far shorter time to inject the same amount of fuel. It can That can cause issues with converting from Batch Fire to Sequential fuel injection if you do not take into account that you have may have to use a larger injector when upgrading to sequential.

 

Simple Digital Systems has a very good Tech article on why you have to watch injector sizing when upgrading from Batch Fire/Multipoint to Sequential. Interesting reading:

 

http://www.sdsefi.com/techseq.htm

Edited by Chickenman
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Fortuantely, large pulse widths at low RPM's are not the issue that they used to be. Injector fidelity has increased immensely over the last few years. Guys running E85 with 1,000 cc or larger injectors are having no issues running pulse widths as low as 1 to 1.5 ms. USRT Genesis and Genesis 2 injectors are a favorite of the Big Turbo VW/Audi crowd ...or really anything that uses a modern Bosch injector. Common Big Turbo rail pressures are now up to 4 and 5 bar. Higher rail pressures = better fuel atomization .

Edited by Chickenman
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Timz: I think you are talking about the semi sequential mode I think it is called in megasquirt? I have it enabled on my tune, basically fires the injectors once per crank rotation, so twice per 4 stroke cycle. 

 

I didn't think about that, but that would indeed allow one to run a lot more fuel at a lower duty cycle. 

Edited by seattlejester
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Timz: I think you are talking about the semi sequential mode I think it is called in megasquirt? I have it enabled on my tune, basically fires the injectors once per crank rotation, so twice per 4 stroke cycle. 

 

I didn't think about that, but that would indeed allow one to run a lot more fuel at a lower duty cycle. 

I'm not a MS expert, but I don't think this is what I was referring to.  I'm talking about running full sequential and simply not caring whether you were injecting on the "correct" phase or not.  So each cylinder would get one twice-as-long pulse every other revolution. The phase relationship to the 4-stroke would stay the same for the duration of a given key cycle, but it would be "wrong" on roughly half the key cycles.  And I'll bet you would never know the difference.

 

 

^ However, the opposite is true in the upper RPM ranges. Participated on a Web seminar hosted by HP Academy last nite and managed to stump the moderator on a question regarding required differences in injector sizing between Batch Fire and Sequential. 

 
For a given HP range batch fire has more time to inject the amount of fuel needed than sequential. Say you are running Batch Fire or Multipoint and your engine makes 200 HP. Not going to do the Math but that requires XX cc/min of fuel. Batch and Multipoint gives two sprays per 720 degrees ( OTTO Cycle ) to inject the required amount of fuel. Batch and Multipoint are referred to as untimed injection. They basically squirt tow big whacks of fuel into the Intake manifold and let the engine sort things out. Juts like a carburator and Plenum manifold. 
 
Sequential is timed injection and it only gives one squirt per 720 degrees and that squirt is usually timed to the Intake cycle when Intake flow is established. Thus you have a far shorter time to inject the same amount of fuel. It can That can cause issues with converting from Batch Fire to Sequential fuel injection if you do not take into account that you have may have to use a larger injector when upgrading to sequential.

 

I'll have to respectfully disagree.  From this description it appears that you are confusing/conflating Sequential Injection with Direct Injection - they are not the same thing at all.  While it is true that most sequential injection setups time the injection at TDC on the intake stroke, Sequential Injection has absolutely no requirement that the injection pulse has to finish before the intake valve closes.  On the contrary at full load the injector pulsewidth is pretty much always longer than the valve open period.  By a lot.  As it turns out the timing of the beginning of the injector pulse is pretty much irrelevant at higher load/rpm.  

The only place it can make a difference at all is at low load, where the injector pulsewidth can be short enough to fit inside the valve open period, and even then the benefits of this timing are going to be extremely hard to detect for the purposes of anybody tuning their own MegaSquirt.  The advantages of the longer pulsewidths at low load/idle, on the other hand, are pretty obvious.

 

 

Fortuantely, large pulse widths at low RPM's are not the issue that they used to be. Injector fidelity has increased immensely over the last few years. Guys running E85 with 1,000 cc or larger injectors are having no issues running pulse widths as low as 1 to 1.5 ms. USRT Genesis and Genesis 2 injectors are a favorite of the Big Turbo VW/Audi crowd ...or really anything that uses a modern Bosch injector. Common Big Turbo rail pressures are now up to 4 and 5 bar. Higher rail pressures = better fuel atomization .

Again, respectfully disagree.  

First, E85 is not a good supporting example, since it requires roughly 30% more pulsewidth for a given lambda (i.e., it's easier).  So yeah 1000cc injectors at 1 to 1.5mS isn't an issue.  Try to run gasoline at that same lambda and you'll be looking at more like 0.75 mS pulsewidths which aren't so easy.

 

I also don't see how 4 and 5bar rail pressures are going to help this situation - higher pressures typically drive lower pulsewidths for a given lambda and simultaneously don't help the injector achieve those short pulsewidths.

 

Even if you can get injectors to work at 1 to 1.5mS PWs, you will always have better control over idle/low load fuel delivery if you can run at 2 to 3mS instead.

Edited by TimZ
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1: I'm not a MS expert, but I don't think this is what I was referring to.  I'm talking about running full sequential and simply not caring whether you were injecting on the "correct" phase or not.  So each cylinder would get one twice-as-long pulse every other revolution. The phase relationship to the 4-stroke would stay the same for the duration of a given key cycle, but it would be "wrong" on roughly half the key cycles.  And I'll bet you would never know the difference.

 

 

2: I'll have to respectfully disagree.  From this description it appears that you are confusing/conflating Sequential Injection with Direct Injection - they are not the same thing at all.  While it is true that most sequential injection setups time the injection at TDC on the intake stroke, Sequential Injection has absolutely no requirement that the injection pulse has to finish before the intake valve closes.  On the contrary at full load the injector pulsewidth is pretty much always longer than the valve open period.  By a lot.  As it turns out the timing of the beginning of the injector pulse is pretty much irrelevant at higher load/rpm.  

The only place it can make a difference at all is at low load, where the injector pulsewidth can be short enough to fit inside the valve open period, and even then the benefits of this timing are going to be extremely hard to detect for the purposes of anybody tuning their own MegaSquirt.  The advantages of the longer pulsewidths at low load/idle, on the other hand, are pretty obvious.

 

3: Again, respectfully disagree.  

First, E85 is not a good supporting example, since it requires roughly 30% more pulsewidth for a given lambda (i.e., it's easier).  So yeah 1000cc injectors at 1 to 1.5mS isn't an issue.  Try to run gasoline at that same lambda and you'll be looking at more like 0.75 mS pulsewidths which aren't so easy.

 

4: I also don't see how 4 and 5bar rail pressures are going to help this situation - higher pressures typically drive lower pulsewidths for a given lambda and simultaneously don't help the injector achieve those short pulsewidths.

 

Even if you can get injectors to work at 1 to 1.5mS PWs, you will always have better control over idle/low load fuel delivery if you can run at 2 to 3mS instead.

 

2: Respectfully. Not confusing Sequential injection with Direct injection at all. Quite familiar with operation of both types of systems. This is more of a difference in terminology than anything else. Sequential injection can be different things to different manufacturers. Full sequential injection is timed to the Intake stroke and is only 1 squirt per 720 crank degrees. This is what I was referring to and why it has relevance when changing from a Batch Fire or Multi point system to FULL sequential. Batch fire can use smaller injectors than FULL sequential injectors to achieve the same HP level, because the Batch fire system has 2 squirts per 720 degrees and has more time to inject the required amount of fuel. IDC is not the same as Time in milliseconds to inject the required amount of fuel. They are two entirely separate issues and where people often get confused in injector sizing differences between Batch fire and Full Sequential.  The SDS link covers the difference in injector sizing requirements quite clearly. It is a considerable difference. 

 

 

Adding to the confusion is the difference in meaning of Sequential. My reference was to fully Timed sequential, where you have one squirt per 720 degrees and it is timed to Intake event. This is the common approach to maximize fuel economy, driveability and emissions. There is also a 2 squirt system as you mentioned, but this is not a true timed sequential system. It is more of a Semi-Sequential, which may be what MS is referring to. A modern Fully Timed FI strategy is basically the same as Direct Injection, in regards to OTTO cycle timing. Cam timings of engine are required in both. Only the method of fuel injection varies. Semi or partial Sequential injection is not the same thing as fully timed Sequential.  

 

Relevance to OP situation is that the factory injectors at 188cc may not be large enough if he goes to Fully Timed Sequential injection with his MS 3 ECU. Especially if he has modified the engine for more HP.

 

I contacted " FuelInjectorman " about converting from batch fire to full sequential on my 280Z and they also warned me to up the injector size if I went with the 1 squirt per 720 degrees option.

 

I agree 100% with the your comments about sequential injection at low injector pulse widths. But that's not what I was referring too at all.

 

3:  Comment on E85 was not in rerference to OP situation. Just that injector technology has improved immensely since 10 or even 5 years ago. You can get 1,000cc injectors to operate smoothly and efficiently at 1 ms these days. Done all the time with E85. You'd never need an injector that big in a pump gas car,  unless you had a a big CI Pro Mod motor on gasoline. And for that see #4.

 

#4 : Increase in modern fuel rail pressures was just a general observation. Not referring at all to OP situation. But it is relevant to fuel efficiency and emissions  in modern cars. Higher fuel rail pressures provides better atomization of the fuel . Nothing more, nothing less. Direct injection takes that to the extreme. Modern fuel injectors can safely operate at 5  Bar and well above. Older designs, such as found on a 280Z , could not. You'd get pintle leak and other issues with too high of rail pressures.

 

Edit. Almost forgot to add the HP advantage of higher rail pressures. Higher rail pressures allow you to use a smaller injector on a high boost car than what could previously be used. That plus improved injector designs allow good idle quality, because the more modern injectors can easily handle a 1ms rate. This gives better fuel atomization at idle over a big injector at a lower rail pressure. At the same time, you can run the smaller injector with out running out of fuel at high boost and RPM's. FYI:  USRT is a pioneer on high pressure injectors. Their Genesis 2 injector operating range is 3 Bar up to 8 BAR!!

 

http://forums.vwvortex.com/showthread.php?5864051-**USRT-Fueling-Solutions-Presents-The-Genesis-II-Injector**

 

 

 

Good discussion. Better over beers. I think we're just visualizing things a bit different but essentially on the same channel.... beermug.gif  

Edited by Chickenman
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2: Respectfully. Not confusing Sequential injection with Direct injection at all. Quite familiar with operation of both types of systems. This is more of a difference in terminology than anything else. Sequential injection can be different things to different manufacturers. Full sequential injection is timed to the Intake stroke and is only 1 squirt per 720 crank degrees. This is what I was referring to and why it has relevance when changing from a Batch Fire or Multi point system to FULL sequential. Batch fire can use smaller injectors than FULL sequential injectors to achieve the same HP level, because the Batch fire system has 2 squirts per 720 degrees and has more time to inject the required amount of fuel. IDC is not the same as Time in milliseconds to inject the required amount of fuel. They are two entirely separate issues and where people often get confused in injector sizing differences between Batch fire and Full Sequential.  The SDS link covers the difference in injector sizing requirements quite clearly. It is a considerable difference. 

 

 

Adding to the confusion is the difference in meaning of Sequential. My reference was to fully Timed sequential, where you have one squirt per 720 degrees and it is timed to Intake event. This is the common approach to maximize fuel economy, driveability and emissions. There is also a 2 squirt system as you mentioned, but this is not a true timed sequential system. It is more of a Semi-Sequential, which may be what MS is referring to. A modern Fully Timed FI strategy is basically the same as Direct Injection, in regards to OTTO cycle timing. Cam timings of engine are required in both. Only the method of fuel injection varies. Semi or partial Sequential injection is not the same thing as fully timed Sequential.  

 

Relevance to OP situation is that the factory injectors at 188cc may not be large enough if he goes to Fully Timed Sequential injection with his MS 3 ECU. Especially if he has modified the engine for more HP.

 

I contacted " FuelInjectorman " about converting from batch fire to full sequential on my 280Z and they also warned me to up the injector size if I went with the 1 squirt per 720 degrees option.

 

I think this is where our visualizations are differing.  My system's full sequential does indeed limit each cylinder to one squirt per 720 degrees and is timed to start at TDC of the intake stroke.  That one squirt, however, can last up to the full 720 degrees if required.  Does Megasquirt not allow this?

 

 

Good discussion. Better over beers. I think we're just visualizing things a bit different but essentially on the same channel.... beermug.gif  

 

 

Agreed - always better over beers!

Good discussion. Better over beers. I think we're just visualizing things a bit different but essentially on the same channel.... beermug.gif  

 
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To summarize:

 

I think the sequential injection as it seems chickenman and I know it (for me learned through the megamanual and the megasquirt tuning academy videos), refers to the injection event happening only when the valves are open. Granted, I'm not sure how that would work at higher RPM when the duration would be so astronomically short, probably the reason why it starts to be less of an issue up top as it becomes more sloppy. 

 

The sequential injection as you may seem to know it refers to firing once over the full 4-stroke cycle. Technically that is sequential in that it follows a sequence firing each injector at TDC for each piston, but as you say can be indifferent to the valve timing.

 

Direct injection as I know it requires the injector to actually be in the combustion chamber and requires the combustion chamber to have a certain swirl shape whether in the head or the piston since it does not benefit from the turbulent air coming in, so probably not in our discussion.

 

As far as I recall using my version of tuner studio, without a cam sensor megasquirt won't extrapolate to even attempt sequential. It will do batch, and I want to say multi squirt/semi sequential (splits up the injector pulsewidth over multiple cycles, in theory catching more of the cylinders with the valves open). Although to your credit I don't recall having to put in the cam specs so I'm not sure how smart of a sequential setup it is.

 

Based off of some theory study, not sure how useful it really is. Having the intake valve open during injection does allow for fuel to be more or less directly be placed in the cylinder, but requires the injector spray pattern to target the open intake port and one would have to imagine it is going to have minimal time to disperse as it goes in with the flow around the valve, the benefit would be that the cloud wouldn't have a chance to pool waiting for the valve to open. It must work because you can trim fuel at lower RPM using valve timed injection. However I recall someone machining grooves onto the back of the intake valves causing additional turbulence to help disperse the pooled fuel from a non valve timed injection setup and report also a noticeable amount of efficiency increase. 

 

I guess semantically TimZ is correct in his definition of sequential fuel injection, ours maybe would be better known as intake valve timed injection if we were trying to clear up nomenclature.

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