Engine injector and spark timing questions

group is also known as "batch firing"... which is the term used more often..... and actually, if you have a controllable fuel management, you can adjust how many injections per cycle the injectors spray.....

also, with fuel injection the pulsewidth and rate are important..... starting, warmup, idling, acceleration, deceleration, and cruise all have different figures for each

injector and spark timing questions

The tachometer is operated on the tach signal which comes from the #1 cylinder coil, right? Meaning if the #1 cylinder is firing 1000 times per minute, then that corresponds to 1000rpms, which corresponds to 1000 power strokes of the #1 cylinder per minute, right?

If so, then at 1000rpms - that's 1000rpms of the camshaft, which translates into 2000rpms of the crankshaft, right?

Do the 1ZZ-FE fuel injectors fire in batch, group or sequential. Do all 4 fire at once, or 1-3 and 2-4 fire in a group, or 1,2,3,4 in sequence?

How about the coils? Does the ECU fire the plugs only on the power stroke or are do they fire in groups or batch?

Late,
Trav

alot of good questions, i would like to know...

Out of curiousity, why do you ask?

I'm by no means an expert but I'll try to take a stab at it.

The fuel injector fire on their own. The whole idea behind fuel injection was to properly time the release of gas for each cylinder. Thus, the fuel injectors will fire in the same order as the cylinder firing order (which is 1-3-2-4 I believe). The same applies to the plugs - they'll fire in order, at the proper time.

I'm sorry I can't really answer your question about RPMs...my understanding has always been the its the number of Revolutions Per Minute for the engine, not for a single cylinder, so RPMs would be measured for the entire crankshaft. Since your talking about the tach being operated on the no. 1 cylinder coil, I'm probably wrong...hope that helps.

Well, the injectors can be simultaneous, group or independent.

Simultaneous - they all fire at once, and it's twice per revolution (once per crankshaft revolution). E.g., all injectors fire when #2 cylinder is on the intake stroke, then again when the #4 is on the intake stroke. The 2S-E, 3S-FE, 5S-FE and 3VZ-E are just a few that use this method.

Group can be 2 groups (4 cylinders) or 3 groups (6 cylinders). E.g., injector 1 and 3 fire when cylinder 2 is on intake stroke and injector 2 and 4 fire when cylinder 3 is on intake stroke. The 4A-G(Z)E, 7M-G(T)E, and 2VZ-FE are a few that were group.

Independent is explanatory - each injector fires independently one-by-one right before the intake stroke. The 3S-G(T)E, and 3VZ-FE are independent injection.

I think I've discovered that the 1ZZ-FE probably ignites only one plug at once. Some engines (5VZ-FE 3.4L V6 in the Tacomas) have the direct ignition, but there are 3 coils. 1-4, 2-5 and 3-6 are paired to one coil. So, when cylinder 1 fires on the compression stroke, 4 also fires and is called a waste spark. On vehicles WITH a distributor, all plugs fire at the same time, so there would 3 or 5 wasted sparks. The 1ZZ doesn't do this, I don't think b/c it having 1 coil for each cylinder eliminates that. If there's more than one spark plug being sparked by one coil, then they ALL have to fire whenever that coil fires - there's no circuitry in existence to prevent it.

Late,
Trav

Ok, thanks for that. I learned something today.

I've got an answer for you regarding the fuel injectors. According to cars.com, we have Sequential Multi-Point Fuel Injection. The following is from their website:

Sequential multi-port electronic fuel injection
Sequential multi-port electronic fuel injection delivers fuel in precisely timed pulses corresponding to the opening of each intake valve.
Primary Benefit:
This EFI system provides more precise combustion for better performance and improved fuel economy, as well as excellent driveability and cleaner emissions. Sequential port injection is an advanced form of electronic fuel injection that offers performance and efficiency advantages over other EFI systems.

So the fuel injectors operate based on the opening of the intake valves for each cylinder (independent, as you said).