Explain this fuel injection wiring diagram

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My 1986 Volvo 240. There are the fuel injectors at the bottom left getting constant 12V+ battery power from fuse 4, so I assume the ecu puts out a ground signal to the injectors anytime they are to be activated. But....all the injectors are connected together to pin 13 at the control unit. How is that possible? Why would the injectors operate all at the same time? The pistons aren't all at the same position in the cylinders.

ecu.jpg
 
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My 1986 Volvo 240. There are the fuel injectors at the bottom left getting constant 12V+ battery power from fuse 4, so I assume the ecu puts out a ground signal to the injectors anytime they are to be activated. But....all the injectors are connected together to pin 13 at the control unit. How is that possible? Why would the injectors operate all at the same time? The pistons aren't all at the same position in the cylinders.

View attachment 122636
The injectors are indeed batch fire.
 

atikovi

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So they spray fuel four times a cycle? Even on the exhaust stroke where it gets shoved out into the converter? Even on the power stroke after the plug has fired? Isn't that a huge waste of fuel? Doesn't it dump raw gas into the converter?
 
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So they spray fuel four times a cycle? Even on the exhaust stroke where it gets shoved out into the converter? Even on the power stroke after the plug has fired? Isn't that a huge waste of fuel? Doesn't it dump raw gas into the converter?

No, because the intake valve is supposed to be closed when the exhaust valve is open. The problems you state if they were problems for batch fire like this would also be problems for throttle body injection...they aren't.
 
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Does this mean the biggest fuel savings in direct injection comes from not being batched fired?
 
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Basically you get a fuel wash in the intake runner and this is taken into account along with the fuel injected on the compression stroke.

As said above, fuel/air mix is only getting in during the intake stroke.

As engine RPM and power increase, fuel injectors need to provide more fuel in a shorter window. Batch firing solves this issue.
 
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Imagine if you want to light a room. Do you put one 100-watt bulb in the center of the ceiling or 4x 25 watt bulbs in the corners? Which lights better? I can imagine batch firing leads to better atomization of fuel vs a dribbly TBI unit.
 
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So they spray fuel four times a cycle? Even on the exhaust stroke where it gets shoved out into the converter? Even on the power stroke after the plug has fired? Isn't that a huge waste of fuel? Doesn't it dump raw gas into the converter?
Maybe they are Multiport Fuel Injectors (MPFI)?
 
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So they spray fuel four times a cycle? Even on the exhaust stroke where it gets shoved out into the converter? Even on the power stroke after the plug has fired? Isn't that a huge waste of fuel? Doesn't it dump raw gas into the converter?

You're both correct and incorrect: Yes, in your particular setup each injector opens once per revolution. Intake stroke, compression stroke, power stroke, and exhaust stroke. For 3 of those 4 strokes, the intake valve stays closed and the injected fuel pools on the back of the intake valve, waiting to be inducted on that cylinder's next intake stroke.

As far as the rest of your concern: it's a simple matter of programming. In a sequential injection system, the PCM opens the injector for the amount of time needed to provide a single cylinder the necessary amount of fuel FOR A GIVEN INTAKE STROKE. In a batch fire setup, the pooled fuel on that's waiting on the back of the intake valve is taken into account.

For example: at idle, let's say a single cylinder needs a 4mS injector "on" time to maintain 14.7:1 AF ratios. In a sequential system, the PCM will open each injector for 4.5mS at the appropriate time. In a batch fire, you simply divide that by 4. So the same setup in a batch fire system will fire EVERY injector for 1mS per revolution instead of firing EACH injector for 4mS. That way, in a batch fire system, by the time said cylinder reaches it's intake stroke, it's holding 3/4 the amount of fuel needed behind the intake valve and the last 4th needed is received when the intake valve opens.

The difference comes from efficiency. Liquid fuel flowing in from a closed intake valve doesn't burn nearly as well as a single, atomized charge directly from the injector. So yes, batch fire systems are "less efficient" but not by a gigantic margin.
 
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This is multipoint. The Toyota 22R-E four cylinder also worked that way. The better system which fires the injectors individually in timed sequence was called multipoint sequential when it first came out. Now all cars have it.
 

atikovi

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It all seems bizarre when first noticed. Like the ignition systems that fire the plugs on the exhaust stroke, but there it doesn't effect anything. Here you have fuel pooling in the intake. That can't be too efficient. The computer has dozens of pins on it. How hard would it have been to have a separate one for each injector?
 
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Volvo / Bosch used two ECUs around that time, (I assume they felt that putting fuel control and the ignition system in one box was too hard?)

Batch firing fuel injectors are less complicated vs sequentially.
 
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It all seems bizarre when first noticed. Like the ignition systems that fire the plugs on the exhaust stroke, but there it doesn't effect anything. Here you have fuel pooling in the intake. That can't be too efficient. The computer has dozens of pins on it. How hard would it have been to have a separate one for each injector?

How hard would it have been for an IBM XT to run Windows 95?

The hardware they used is not capable of sequential EFI anymore than an IBM XT is capable of Windows 95.
 
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The computer has dozens of pins on it. How hard would it have been to have a separate one for each injector?
If you feel it is easy to do, feel free to modify yours. :)

Don’t forget, every electronic component in your your car was designed two to five years before, in order to be qualified for automotive usage. Whatever was cutting edge in 1982 is all you are allowed to use.
 
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