Do the L98 C4's use batched fired port injection or sequential port injection?

 

Batch

 

In batch, do all 8 injectors fire at the same time?

 

I double checked this in the 1989 FSM. The ECM fires all 8 injectors at the same time, using injector driver circuits on ECM pins D15 & D16. Two separate injector power circuits with independent fuses are used to supply power to each bank of injectors left/right, but the two circuits are closed to ground by the same ECM driver to fire the injectors. The driver shows as one switch in the wiring diagrams.

 

So does it fire 8 injectors in a complete ignition cycle (2 crank rotations 720 degrees) or every crank rotation? and does it control fuel volume or is a squirt a squirt?

 

A squirt is not a squirt. The ECM varies fuel volume by changing the length of time that the injector is open / firing fuel into the port, plus the fuel pressure changes as you change throttle / vacuum. The pulse width, basically, means amount of time that the injector is energized to spray fuel for each signal from the ECM.

Injectors fire once per engine revolution. But since each cylinder only has one intake stroke per every 2 crank rotations, this means that the ECM calculates the total amount of fuel needed and then injects 1/2 the amount needed on every rev. So when the intake valve opens, the atomized fuel/air mixture is waiting there in the port above the valve. It's not the most efficient way to inject fuel/air, but it was what they could do given the ECM compute capabilities back in the early 80s (when these were designed and finalized for production testing). Remember, what we see in a car was designed and tested some months/years in advance.

This info I gave above for 1989 is correct - batch fired all 8 injectors simultaneously. But it varies by year and can be specific to one model year. It's covered very well in this other post on the forum here:

https://www.corvetteforum.com/forums...post1568748397

You can see in years 1994-1996, each injector has its own individual driver circuit in the ECM. True sequential multipoint fuel injection.

What are you trying to figure out if I can ask? Just learning about the system or do you have a specific problem you're trying to troubleshoot?

 

Yes sir.

 

He just said "L98 C4s" in his original, and I didn't know his car specifically. I only have an '89 FSM so didn't know if it applied to his year, but figured the other wider thread link would help him as it shows the wiring diagram for all C4s.