fuel injection timing question

[mowgli]

As most of you will know, I have a strange fascination with e16se engines.

The ignition and injection timing are controlled by a single hall effect sensor inside the dizzy.

My question is: is fuel injector timing actually that critical? The reason I ask is that this engine originally ran on 4star leaded, and to run on unleaded, it needs the timing retarded.

Would it be worth putting a second sensor on for fuel timing?

[brucer]

Depends how it altered the air/fuel mixture in the cylinder, i imagine the later it gets injected on the intake stroke the less efficient/power it would become.

[meritlover]

Ideally the squirt is timed with the inlet valve opening so the atomised spray is carried straight into the cylinder. I dont know if the e16se is batch or sequencial injection. If its batch, only one of the cylinders will be opening at that time of the squirt, so the remaining cylinders has the fuel pooling on the back of the inlet valve on each cylinder until it opens. I say pooling but its more like lingering. Some say this has advantages as its cooling the valve and the inlet charge as it evaporates... maybe so, but anyone worried about these small advantages would be running fully sequential with 2 triggers so each pulse is timed exactly to the cam....
Because you are using one cam trigger pulse per cylinder the ECU doesnt know where no.1 is so you will never be able to get it timed to all of the valves opening anyway. If its semi-sequential you will have 4 pulses per cylinder fill, its still not timed exactly to the valve opening, but because the pulses are devided up it all of the charge isnt waiting around for the valve to open as long so isnt as bad. The problem with this is because there are 4 events per cylinder, you run out of duty cycle really quickly and the injectors will act smaller than they will if it was batch.

The biggest issue is that the valve 'may' close before the injector has had a chance to deliver that calculated duration for that rev, so it isnt fully optimised. Because this is a linear shift across all the cylinders it doesnt matter so much because what doesnt get in at the end, is waiting for when the valve opens next time round.

If the injector wires to the ECU are commoned up it can only be batch. if they are individual or in pairs theres a chance it could be semi sequencial, or 2 sets of batch.

The long and short is no, it wont make any noticable difference unless you're going mental with the change in base timing. You might get slightly higher CO/HC/MPG because the combustion would be slightly worse, but for an engine of this era its not really an issue at all.

Depending on how far you plan on playing with the timing (+20deg BTDC from std) you are more likey to have issues with crossfire in the distributor.

hope this helps...

[Andy]

great post.+rep

[mowgli]

ok, would there be any great gains in fitting something like megajolt? using a standalone sensor & letting the injection run as before

[meritlover]

that would be better but you would go to all that trouble and not be able to change the fueling anyway. so either go megasquirt or stay OE

If the only reason is to retard the ign timing for lead-unleaded reasons, what's that going to be -5deg at the most even on a bad day?
remember 5deg crank is only 2.5 deg cam so its almost negligible.

[Adam]

E16 is batch injected.