Batch vs Sequential injection for turbo application

[MazterDizazter]

I've been reading up on the similarities/differences between batch/sequential injection and how it would relate to my L28ET setup. This all came up when I was researching how to custom make a crank-angle sensor in order to run Denso individual coil packs. Certain crank triggers do or don't allow sequential injection so I wanted to see which would be ideal.

 

To my understanding, or according to my sources, there is very little difference between the two. It seems that sequential injection runs smoother on idle and possibly low-RPM operation, but at high RPM's there is little to no difference between the two, which seems understandable given how quickly valves are opening/closing and injectors are firing. Here are my sources, I'll make reference to them next:

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

http://members.rennlist.org/951_racerx/SequentialVsBatchFiring.pdf

 

Since I will be running a fully-programmable ECU, I have the option to do either. I will be paying for dyno-tuning, so I am concerned that the extra parameters needed to tune the engine for sequential injection may translate to extra cost on top. However, if there is an advantage to running sequential injection, be it lower fuel consumption (pretty sure there wouldn't be) or a significant reduction of emissions (with no reduction in performance, of course), I would like to do that.

 

Something interesting I noted that may actually lend credence to batch-firing: according to the second link, it appears that batch-fired injection may help the turbo to spool under low RPM's because of an extra little boost in combustion. I could be wrong, but that almost looks like pre-ignition (or detonation, or something like that) to me.

 

Another interesting thing I noted (read second link under "Variation 1: Double fuel output on sequential system) is this:

"Another scheme for sequential fuel-injection is to dump in twice as much fuel during a single 360-degree

cycle of the batch-fired system. This requires using injectors that are TWICE as large and a fuel-pump that

can deliver TWICE the volume at the same pressure. With this arrangement, the difference in fuel-delivery

between the two methods is again 50%."

 

This means that if I run injectors and pump that are twice as large as normal (ex. 1100cc instead of 550cc), I could maximize the amount of fuel being used while the intake valves are open and reduce (or eliminate) fuel being dumped onto closed intake valves, correct? If so, that seems like a much more efficient system.

 

Please let me know if I'm missing anything here. I am a complete n00b when it comes to fuel delivery, so any and all help is appreciated. I'd really like to have my mind made up on which system to use well before I get to the dyno. Thanks everyone!

[MazterDizazter]

Don't tell me I stumped you guys...

[RTz]

Certain crank triggers do or don't allow sequential injection so I wanted to see which would be ideal.

 

No crank trigger alone will allow sequential injection (or multi-coil ignition). There must be a cam reference of some type.

 

To my understanding, or according to my sources, there is very little difference between the two. It seems that sequential injection runs smoother on idle and possibly low-RPM operation, but at high RPM's there is little to no difference between the two, which seems understandable given how quickly valves are opening/closing and injectors are firing.

 

Your not far off. It is somewhat dependent on the package as a whole, but overall, the differences are usually subtle, not groundbreaking. Keep in mind, most sequential systems will also allow you to trim each cylinder independently. Depending on the application/use, this could be quite substantial (mainly with very high specific output).

 

Since I will be running a fully-programmable ECU, I have the option to do either.

 

Only if its capable. You need a channel for each cylinder. What EMS are you using?

 

 

Another interesting thing I noted (read second link under "Variation 1: Double fuel output on sequential system) is this:

"Another scheme for sequential fuel-injection is to dump in twice as much fuel during a single 360-degree

cycle of the batch-fired system. This requires using injectors that are TWICE as large and a fuel-pump that

can deliver TWICE the volume at the same pressure. With this arrangement, the difference in fuel-delivery

between the two methods is again 50%."

 

This means that if I run injectors and pump that are twice as large as normal (ex. 1100cc instead of 550cc), I could maximize the amount of fuel being used while the intake valves are open and reduce (or eliminate) fuel being dumped onto closed intake valves, correct? If so, that seems like a much more efficient system.

 

I think there is some slightly flawed logic in their presentation. I'll read it a little more closely when I get a chance.

[woldson]

Don't tell me I stumped you guys...

 

Me yes, Rontyler probably just getting started:)

[Careless]

"Another scheme for sequential fuel-injection is to dump in twice as much fuel during a single 360-degree cycle of the batch-fired system. This requires using injectors that are TWICE as large and a fuel-pump that can deliver TWICE the volume at the same pressure. With this arrangement, the difference in fuel-delivery between the two methods is again 50%."

That doesn't sound right. correct me if i'm wrong, but upon firing that one cylinder, there is still the same amount of fuel in there, you're just preserving your injector's life cycle by having the electromagnetic element only open once per cycle rather than twice (as you said, squirting on a closed valve).

 

Also, you'd probably see a gain from having less wash on the ports/valve because they are filled when open, and not when closed. But at that speed, it only makes a difference when air is moving slower (ie. idle), and at high speed, the velocity of the incoming air would just force all the fuel into the chamber.

 

Unless of course, you're saying that the closed-valve firing instance is wasted fuel. if that's the case, then yes, you'd be wasting 50% of your fuel injector pulses. But that fuel has to go somewhere.

 

I can see batch firing at a low speed for a long duration creating issues when stabbing the throttle abruptly, but after that 2 or 3 second pull, there wouldn't be any residual fuel in the ports if they are designed to flow completely and not have any dead spots where fuel can puddle, even at high velocity (air can create a thin and powerful barrier to hold things up, rather than move them in)

EDIT:

 

goin through my notes, and looking at what I said earlier about the electromagnetic element being used less frequently, there are other points I should add.

 

Low-impedance injectors firing twice per engine cycle will end up killing your injector drivers, as some are not made to cope with that high of a current over and over again so quickly.

 

you get better control in higher RPM's too, since @ say... 8000 rpm, having an injector open and close twice in the same time that sequential system would only tell it to do once... you are increasing the injector duty quite a bit, arent you? Again, I'm not sure, just seems that way.

 

noq i'm not sure if my first paragraph makes sense.

 

where does all the extra fuel from the first trigger go if not in the cylinder, where it would have to be just the right amount to maintain a stoich AFR rather than an excessively rich one?

 

The reason I ask is due to the fact that nissan had an injector campaign for the Z31's that changed the harness from sequential to batch fire mode. How does a standard ECU properly regulate fuel changes without being altered and without being told it is now triggering twice as much fuel per engine cycle?

 

its all a mystery, folks! VOODOO I TELL YOU, JAPANAYZE VEWDEW!

[MazterDizazter]

Don't tell me I stumped you guys...

 

Me yes, Rontyler probably just getting started:)

 

 

I was waiting for him to read this thread, lol.

 

I'm hoping to run a Wolf V4 3D ECU; I had planned initially to use MSII but someone offered to trade me the wolf unit for some parts I'm selling, and it sounds pretty appealing.

[Tony D]

It's a beaten dead horse. That there was any response at all was kinda suprising.

The 'advantage' sequential has over batch fired goes to two times:

Idle Emissions, and Ultimate Competition Power.

 

OEM's use it for idle emissions reductions as injecting precise amounts of fuel with a proper ECU feedback can actually trim fuel to each individual's combustion characteristics. But processor speeds on commercial stuff (OEM) are not that great yet, so most will switch to batch fire once above a given threshold.

 

Now, for the same reasons at idle it's efficient, at Top Power it has an advantage due to being able to alter phasing between injection and valve opening. Meaning if you can calculate the time it takes the injected fuel to travel down the runner to the back of the valve, you can also time it to fuel only enough to fully charge the cylinder. You return a fuel economy dividend by injecting fuel that ALL goes into the cylinder, and doesn't reside pooling at the back of the valve. F1 kinda stuff.

 

Frankly, for 99.999999999% of the people driving on the street, Batch Fire works well enough that there's no reason to consider the complexity of Sequential.

 

Under some conditions, Sequential will offer advantages, but they are extreme cases. And usually it can come down to phasing the injection event in a variable fashion that gives the drivability and emissions/economy dividend in those cases as well.

 

The aforementioned comment about Camshaft sensor is dead on. To do it, you need to know when #1 is TDC on compression stroke---from that point it's all math.

[tannji]

 

The aforementioned comment about Camshaft sensor is dead on. To do it, you need to know when #1 is TDC on compression stroke---from that point it's all math.

 

No crank trigger alone will allow sequential injection (or multi-coil ignition). There must be a cam reference of some type.

Isn't it just plain sequential that requires a secondary trigger to determine stroke? Meaning you can run multiple coils as wasted spark if there is no compression stroke verifying, as EDIS, DIS and other systems do.

[RTz]

It's a beaten dead horse. That there was any response at all was kinda suprising.

 

I guess we were all in a generous mood... even you

 

 

Isn't it just plain sequential that requires a secondary trigger to determine stroke? Meaning you can run multiple coils as wasted spark if there is no compression stroke verifying, as EDIS, DIS and other systems do.

 

I had to re-read that a couple times... I see what you're getting at now. My statement was poorly written. A better way to say it... "No crank trigger alone will allow sequential injection (or sequential multi-coil ignition).". As you said, a crank trigger will suffice for wasted spark, but you'll need a cam reference to fire the coils individually. Sorry for the confusion.

 

 

I'm hoping to run a Wolf V4 3D ECU

 

Ahhh... well there is a catch. Assuming you're fueling a 6 cylinder, V4 is only capable of semi-sequential. As I mentioned, fully sequential requires one channel per cylinder. The base model V4 came with 4 injection channels, and 4 ignition channels. So, wasted spark and semi sequential it best you can do. The Plus model V4 came with two additional ignition channels. The Plus would allow sequential ignition if you're into that stuff (Note: V500 comes with 8 of each).

[Six_Shooter]

In my research, sequential systems switch over to batch fire at higher RPMs, not due to processor speed, but due to the amount of time available to actually provide an open valve to get all the air and fuel into the cylinder. As RPM increases, the time that the valve is open shortens proportionally, and so the injector must either deliever more fuel in a single open event or use more open events to provide that amount of fuel.

 

Fuel being sprayed at the back of a closed valve does not by any stretch of teh imagination get "wasted". What usually happens is that the fuel that is sprayed will hit the back of the hot valve, and cause the fuel to become vapour and remain suspended in the intake port until the valve opens, to get pulled into the cylinder, at which time the injector is opening again, to provide more fuel.

 

About the only "performance" benefit that is usually seen is the ability to control rather large injectors at idle and low RPM without over fueling.

This ability to control injectors does have emmisions benefits as well, which is why most OEMs use SFI, they definatly aren't running large enough injectors to need it to keep from overfueling. One such example is the GM 60 degree V6. In the generation II set-up, uses a batch fire ECM, with 16 lbs/hr injectors, runs just fine, stable idle, no overfueling, etc. (uns better than SFI IMO) In the generation III set-up, the PCM now uses SFI for anything below about 3000 RPM, still uses 16 to 17 lbs/hr injectors depending on the year and actual displacement. SFI was implimented strictly for emmisions.

I've owned or own both, and prefer the batch set-up stock for stock. My genII 3.1 would fire up quickly and reliably, my genIII 3.1 (3100) has ALWAYS been hard to start and sometimes takes a couple tries at starting. I have noticed this with other genIII SFI cars as well.

 

On a non-emmisions controlled vehicle I would likely keep it simple and use batch fire, unless I was using some very large injectors that over fuel at low RPMs.

[Chemicalblue]

I'm running a Haltech E11 v2 with 6 LS1 coil packs and 550cc injectors in full sequential. Using the 300zx trigger wheel and the original dizzy for crank and cam timing made everything real easy to set up (no fabrication). The tuning is easy with this EMS, it doesn't even sound like a L28 anymore because it idles so smooth. Just make sure whoever tunes your car that they specialize in that EMS, it will save you money tunnig on a Dyno if they already know there way around the software.

 

As said in a previous post, it does make sense that running sequential is allot less taxing on the ignition and fuel components. Not to mention you wont be flushing precious gas down the drain.

[ktm]

The Wolf V500 is a full sequential system as well, and I have my car setup to run both sequential injection and ignition. I actually use the sequential setup to pull timing in #5 and #6 as a measure to reduce detonation in those cylinders and I was contemplating adding a little more fuel to help with cooling.

 

It is not overly complex to wire up a sequential system if your EMS can support it. However, unless you are trying to eek out every last horsepower out of an engine, there really is no performance difference between the two setups.

[MazterDizazter]

Wait, wouldn't we all want to eke out every last horsepower? lol

[woldson]

Just curious Mazter, what threads have you gone through?

 

Mind if you site some of the information on this subject that you have read here already?

[MazterDizazter]

I didn't read up on this particular subject here, I posted the two sources I did get above. I happened upon the idea when I was reading up on how to run the GM LS1 coil packs that rontyler is selling. Since I blindly bought a set without any knowledge on how to make them work, I figured it was a darn good time to find out.

[Careless]

Wait, wouldn't we all want to eke out every last horsepower? lol

 

the point ktm is trying to make is that you could take your time in fine tuning SFI and put it towards working an extra hour or two at your day job for a week, and coming home with extra money for something that may ultimately be a better purchase for power, and give you better results than the minimal hp gains of SFI if that's what you're after.

 

[woldson]

the point ktm is trying to make is that you could take your time in fine tuning SFI and put it towards working an extra hour or two at your day job for a week, and coming home with extra money for something that may ultimately be a better purchase for power, and give you better results than the minimal hp gains of SFI if that's what you're after.

 

 

That is one thing I'm trying to learn. I do not want to burn money on that last 5%, I just have to figure out what that last 5% is and advoid it.

At least till I'm done and get board.

[MazterDizazter]

I dunno about you guys, but 2hrs at my day job nets me $21.90 before taxes. Not gonna buy me too too much extra stuff. Maybe a nice "how-to" book or a polished somethingorother.

[Careless]

I dunno about you guys, but 2hrs at my day job nets me $21.90 before taxes. Not gonna buy me too too much extra stuff. Maybe a nice "how-to" book or a polished somethingorother.

 

well then you can forget about the equipment it takes to get sequential injection... LOL... and you REALLY need to use that money more wisely, so they point still stands.

 

and... you in fact should get the how-to book on sequential injection or electronic engine management systems.

 

there's a good start. its what i did

[Tony D]

How come guys making $10.95 an hour are considering buying top-end sequential injection units...

I make, er... "more" than that, and am still scouring e-bay for used parts to keep my unpainted slog-beasts goin'?????

I KNOW:

No wife, no kids?

LOL

 

Maybe I'm just cheap.