Sequential vs. Batch Injection Question...
09-Jul-2003, 07:58 PM
#1
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Sequential vs. Batch Injection Question...
Does anyone know the difference between sequential and batch injection?
From what I've read, batch injection means that the injectors are fired in banks, so for a 4 cyl engine, the injectors are fired in pairs.
Sequential injection means that the injectors are fired individually, ie, during the intake event of each cylinder.
I read somewhere that honda's are use batch injection, and not sequential injection. This implies that gas is squirted on the intake event and an exhaust event... Isn't that a wasted of gas?
Do I got this right? Am I totally out to lunch? If so, can someone tell me what exactly the difference bettwen seq. and batch injection and how it applies to honda engines?
From what I've read, batch injection means that the injectors are fired in banks, so for a 4 cyl engine, the injectors are fired in pairs.
Sequential injection means that the injectors are fired individually, ie, during the intake event of each cylinder.
I read somewhere that honda's are use batch injection, and not sequential injection. This implies that gas is squirted on the intake event and an exhaust event... Isn't that a wasted of gas?
Do I got this right? Am I totally out to lunch? If so, can someone tell me what exactly the difference bettwen seq. and batch injection and how it applies to honda engines?
09-Jul-2003, 09:09 PM
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You're absolutely right about the definition, but all honda's have used sequential injection since somewhere around 1990. Just about every production car right now uses sequential injection, since it's difficult to pass federal emmissions standards using batch injection.
Injecting during strokes other than the intake stroke doesn't waste gas, because the gas just sits on the back of the intake valve until the valve opens. Even with sequential injection with high load, the injector doesn't have time to inject all the gas needed while the valve is open, so it sits behind the intake valve. This is beneficial since it cools the intake valve, and aids the atomization of the gas before it enters the cylinders.
Injecting during strokes other than the intake stroke doesn't waste gas, because the gas just sits on the back of the intake valve until the valve opens. Even with sequential injection with high load, the injector doesn't have time to inject all the gas needed while the valve is open, so it sits behind the intake valve. This is beneficial since it cools the intake valve, and aids the atomization of the gas before it enters the cylinders.
10-Jul-2003, 06:39 PM
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Thanks for the answer.
Now, I some more questions.
So even in sequential injection, (under heavy load) the inject will spray gas onto the closed valve?
Are all modem EFI cars made with seq. injection?
How does the build up of gas on the valve aid fule atomization? To me, logically, this would hinder atomization...
Now, I some more questions.
So even in sequential injection, (under heavy load) the inject will spray gas onto the closed valve?
Are all modem EFI cars made with seq. injection?
How does the build up of gas on the valve aid fule atomization? To me, logically, this would hinder atomization...
Originally posted by DirtyLude
You're absolutely right about the definition, but all honda's have used sequential injection since somewhere around 1990. Just about every production car right now uses sequential injection, since it's difficult to pass federal emmissions standards using batch injection.
Injecting during strokes other than the intake stroke doesn't waste gas, because the gas just sits on the back of the intake valve until the valve opens. Even with sequential injection with high load, the injector doesn't have time to inject all the gas needed while the valve is open, so it sits behind the intake valve. This is beneficial since it cools the intake valve, and aids the atomization of the gas before it enters the cylinders.
You're absolutely right about the definition, but all honda's have used sequential injection since somewhere around 1990. Just about every production car right now uses sequential injection, since it's difficult to pass federal emmissions standards using batch injection.
Injecting during strokes other than the intake stroke doesn't waste gas, because the gas just sits on the back of the intake valve until the valve opens. Even with sequential injection with high load, the injector doesn't have time to inject all the gas needed while the valve is open, so it sits behind the intake valve. This is beneficial since it cools the intake valve, and aids the atomization of the gas before it enters the cylinders.
10-Jul-2003, 09:26 PM
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I believe that it does not help fuel atomization at all ... reason being is simple you get a "puddle" build up on the intake valve and when the valve opens that pool of fuel will want to stay together and not atomize...(split apoart and mix in the air uniformily) so the end result is a mixture in the combustion chamber that is not uniformly mixed resulting in areas that are "rich" and areas that are "lean" which is not the best of conditions....
10-Jul-2003, 10:38 PM
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The hot intake valve evaporates some of the fuel. Injection time actually changes as RPM's increase and injection will occur earlier (before the intake valve opens) during high RPM's in order to start the evaporation earlier.
If you look at some pictures of heads that have been removed you'll see the exhaust valves are discoloured while the intake valves have a colour similar to the rest of the combustions chamber (usually dark with carbon) the heat sucked away by the fuel is one thing that keeps them cool.
In the old carbs, evaporation of the fuel could actually freeze a throttle plate open.
EDIT: I got the high/low rpm's backwards.
If you look at some pictures of heads that have been removed you'll see the exhaust valves are discoloured while the intake valves have a colour similar to the rest of the combustions chamber (usually dark with carbon) the heat sucked away by the fuel is one thing that keeps them cool.
In the old carbs, evaporation of the fuel could actually freeze a throttle plate open.
EDIT: I got the high/low rpm's backwards.
10-Jul-2003, 11:40 PM
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DirtyLude,
Yes, I can see that the injector "on" time increases as the RPMs go up... but, it doesn't really show me that the injectors squirt while the intake valve is still closed. ( or am I missing something here? )
How do you know that injectors are pulsed on while the valve is still closed.
And even if the injectors are pulsed while the valve is closed, since gas takes some time to travel from the port to the valve opening, the valve maybe open by then.
Sorry if some of my assumptions are not correct. I'm still learning about the finer points of EFI and engine tech.
Yes, I can see that the injector "on" time increases as the RPMs go up... but, it doesn't really show me that the injectors squirt while the intake valve is still closed. ( or am I missing something here? )
How do you know that injectors are pulsed on while the valve is still closed.
And even if the injectors are pulsed while the valve is closed, since gas takes some time to travel from the port to the valve opening, the valve maybe open by then.
Sorry if some of my assumptions are not correct. I'm still learning about the finer points of EFI and engine tech.
Originally posted by DirtyLude
This is the current injection phasing map for my Prelude.
You can see the end of injection times are advanced as the RPM's increase.
This is the current injection phasing map for my Prelude.
You can see the end of injection times are advanced as the RPM's increase.
11-Jul-2003, 06:12 AM
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This is an injector phase map, not the fuel map. It specifies at what crank angle the injector has to finish it's injection by for the current engine cycle. This map actually makes sure that the no injection happens while the intake valve is open.
The vertical access on this graph is degrees Before Top Centre on the intake stroke. It's hard to judge, but the far left bar above 0 rpm is set to 180. So the ECU will calculate to finish it's injection for that engine cycle before the crank reaches 180 degrees before the intake stroke, which is right when the intake valve should be opening, if not already open.
The vertical access on this graph is degrees Before Top Centre on the intake stroke. It's hard to judge, but the far left bar above 0 rpm is set to 180. So the ECU will calculate to finish it's injection for that engine cycle before the crank reaches 180 degrees before the intake stroke, which is right when the intake valve should be opening, if not already open.
11-Jul-2003, 09:09 AM
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You would probably find that, as the intake on one cylinder is closed, and another intake cycle is starting, there is a period of negative movement in the intake runner. There would be a period of suspension.
And the hot valve will also cause a flash evaporation, cooling the valve as well.
As the engine is reving the valve will be opening by the time the fuel spray gets there.
And the hot valve will also cause a flash evaporation, cooling the valve as well.
As the engine is reving the valve will be opening by the time the fuel spray gets there.
11-Jul-2003, 12:57 PM
#11
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If you're really interested in this stuff, you should buy a book on it. I can recommend a couple, but if you try to take everything into account that happens around the intake valve it's too complex to put all down here. The speed of the air in the induction system is fast enough that you need to know a little about finite amplitude wave theory and some fluid dynamics to start understanding what's going on.
12-Jul-2003, 12:50 AM
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Okay. I understand. The bar is not really specifying a duration, but a value. Yes, it all makes sense to me now.
The phase map just tells how many degrees btdc the injection pulse has to end. The injection pulse must end sooner for higher RPMs because more fuel is needed??
Correct me if I'm wrong, but doesn't the intake valve open before tdc?
The phase map just tells how many degrees btdc the injection pulse has to end. The injection pulse must end sooner for higher RPMs because more fuel is needed??
Correct me if I'm wrong, but doesn't the intake valve open before tdc?
Originally posted by DirtyLude
This is an injector phase map, not the fuel map. It specifies at what crank angle the injector has to finish it's injection by for the current engine cycle. This map actually makes sure that the no injection happens while the intake valve is open.
The vertical access on this graph is degrees Before Top Centre on the intake stroke. It's hard to judge, but the far left bar above 0 rpm is set to 180. So the ECU will calculate to finish it's injection for that engine cycle before the crank reaches 180 degrees before the intake stroke, which is right when the intake valve should be opening, if not already open.
This is an injector phase map, not the fuel map. It specifies at what crank angle the injector has to finish it's injection by for the current engine cycle. This map actually makes sure that the no injection happens while the intake valve is open.
The vertical access on this graph is degrees Before Top Centre on the intake stroke. It's hard to judge, but the far left bar above 0 rpm is set to 180. So the ECU will calculate to finish it's injection for that engine cycle before the crank reaches 180 degrees before the intake stroke, which is right when the intake valve should be opening, if not already open.
12-Jul-2003, 12:52 AM
#14
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So are you saying that at no point in the RPM band will the fuel arrive at a closed intake port?
I would think that the injector pulse is timed so that throughout the RPM band, the intake valve will open just before the fuel gets there. Am I right?
I would think that the injector pulse is timed so that throughout the RPM band, the intake valve will open just before the fuel gets there. Am I right?
Originally posted by donesixer
You would probably find that, as the intake on one cylinder is closed, and another intake cycle is starting, there is a period of negative movement in the intake runner. There would be a period of suspension.
And the hot valve will also cause a flash evaporation, cooling the valve as well.
As the engine is reving the valve will be opening by the time the fuel spray gets there.
You would probably find that, as the intake on one cylinder is closed, and another intake cycle is starting, there is a period of negative movement in the intake runner. There would be a period of suspension.
And the hot valve will also cause a flash evaporation, cooling the valve as well.
As the engine is reving the valve will be opening by the time the fuel spray gets there.
12-Jul-2003, 12:55 AM
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Sure, recommend a couple of books to me.
I'm currently reading internal combuestion engine fundatmentals by John B. Heywood. It's pretty technical... which I like.
It's going to take me a while to read and digest everything, but I will eventually get through it.
Finite amplitude wave theory? You sould like you know fluid mechanics very well. Fluid mechanics wasn't my strong point in school. How I wish I paid more attention in class now!
I'm currently reading internal combuestion engine fundatmentals by John B. Heywood. It's pretty technical... which I like.
It's going to take me a while to read and digest everything, but I will eventually get through it.
Finite amplitude wave theory? You sould like you know fluid mechanics very well. Fluid mechanics wasn't my strong point in school. How I wish I paid more attention in class now!
Originally posted by DirtyLude
If you're really interested in this stuff, you should buy a book on it. I can recommend a couple, but if you try to take everything into account that happens around the intake valve it's too complex to put all down here. The speed of the air in the induction system is fast enough that you need to know a little about finite amplitude wave theory and some fluid dynamics to start understanding what's going on.
If you're really interested in this stuff, you should buy a book on it. I can recommend a couple, but if you try to take everything into account that happens around the intake valve it's too complex to put all down here. The speed of the air in the induction system is fast enough that you need to know a little about finite amplitude wave theory and some fluid dynamics to start understanding what's going on.
12-Jul-2003, 12:56 AM
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Yeah, I totally agree with you.
BTW, how well are you conversant with fluid dynamics?
Every hear of the Navier Stokes equations??? =)
BTW, how well are you conversant with fluid dynamics?
Every hear of the Navier Stokes equations??? =)
Originally posted by bbarbulo
well put dirtylude... ppl don't understand the complexity of fluid dynamics. some ppl spend 4-6 years in school studying it, you're not gonna learn about it from the net
well put dirtylude... ppl don't understand the complexity of fluid dynamics. some ppl spend 4-6 years in school studying it, you're not gonna learn about it from the net
12-Jul-2003, 08:48 AM
#17
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My problem is I'm not good at math, and it's the reason I'll never be an engineer. I can understand what's in the books, but to verify and do your own research requires some high math skills that bore me to death. Luckily there's engine simulation software out there that will do alot of that for you, but it still limits how much I can learn.
I've never read Internal Combustion Engine Fundatmentals, but I would think it would have some wave theory in it.
Engine:An Introduction by John L Lumley is excellent. Also highly technical and talks about intake manifold tuning and finite amplitude waves.
Desktop Dynos is actually surprisingly good with simplifying wave theory.
Here's a clip out from Desktop Dynos on wave dynamics:
http://www.higginstribe.com/temp/exhaust/exh1.pdf
http://www.higginstribe.com/temp/exhaust/exh2.pdf
http://www.higginstribe.com/temp/exhaust/exh3.pdf
Back to the original topic, but...
Yes, it opens just before 180 degrees TC, which is why the first bar on the graph is telling the ECU to make sure it's finished it's injection before 180 deg TC.
The injection end time that's listed is ignored if the duty cycle is too high. It's set not to inject fuel on the intake stroke, but the intake stroke takes up 25% of the total engine cycle, which means any duty cycle over 75% is going to start moving into the intake stroke.
This is why race cars and drag cars can still use batch injection. At extremely high duty cycles, there's very little difference between batch and sequential injection since the injectors are open most of the time anyway.
I've never read Internal Combustion Engine Fundatmentals, but I would think it would have some wave theory in it.
Engine:An Introduction by John L Lumley is excellent. Also highly technical and talks about intake manifold tuning and finite amplitude waves.
Desktop Dynos is actually surprisingly good with simplifying wave theory.
Here's a clip out from Desktop Dynos on wave dynamics:
http://www.higginstribe.com/temp/exhaust/exh1.pdf
http://www.higginstribe.com/temp/exhaust/exh2.pdf
http://www.higginstribe.com/temp/exhaust/exh3.pdf
Back to the original topic, but...
Correct me if I'm wrong, but doesn't the intake valve open before tdc?
The injection end time that's listed is ignored if the duty cycle is too high. It's set not to inject fuel on the intake stroke, but the intake stroke takes up 25% of the total engine cycle, which means any duty cycle over 75% is going to start moving into the intake stroke.
This is why race cars and drag cars can still use batch injection. At extremely high duty cycles, there's very little difference between batch and sequential injection since the injectors are open most of the time anyway.
14-Jul-2003, 08:13 PM
#18
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Originally posted by DirtyLude
This is why race cars and drag cars can still use batch injection. At extremely high duty cycles, there's very little difference between batch and sequential injection since the injectors are open most of the time anyway. [/B]
This is why race cars and drag cars can still use batch injection. At extremely high duty cycles, there's very little difference between batch and sequential injection since the injectors are open most of the time anyway. [/B]
With those engines reving past 10K, I would think they would have special injectors that are able to inject accurately for high duty cycles.
15-Jul-2003, 10:51 PM
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So far it's not possible to get a reliable injector that is able to inject the full amount of fuel needed in just the intake and compression stroke. If this was possible, the injector could be moved out of the intake and inject directly into the cylinder. This is what alot of engine manufacturers are trying to achieve, Gasoline Direct Injection. F1 engines rev to 18k which makes it significantly harder to do.
This and hydraulic controled valves will probably be the next steps in engine development and there have already been quite a few patents put out on the R&D already. Renault just put a patent down on it's own Hydraulic Actuated Valve design.
This and hydraulic controled valves will probably be the next steps in engine development and there have already been quite a few patents put out on the R&D already. Renault just put a patent down on it's own Hydraulic Actuated Valve design.
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