Moving from batch fire to fully sequential

[rob@vems.co.uk]

It starts on the trigger tooth.

[SamSpade]

So for sequential ignition, is it correct that the injectors will start firing 40°-60° BTDC on the compression stroke (depending on the setting) since the VEMS manual suggests limiting the 'TDC after the trigger' setting to between 40°-60°?


http://www.vems.hu/manual/html/ch09.html#Detailed.Sensor.RPM.Config

[rob@vems.co.uk]

That's what I assume.

[mattias]

And IIRC timed or phased is when they're fired at specific degrees during the cycle, this usually requires an injection start map and would be beyond the ability of most of us DIY'ers to tune.

There's a long running argument with claim and counter claim that timed sequential gives more power and better emissions than sequential, one thing for sure is that it gives better HC and CO emissions, but the power thing is is proven and disproven daily it seems.

I've asked for this feature for a long time. At least I'd like a fixed angle instead of at the trigger tooth, then I could get the timing to occur later in the intake stroke.

Timed/phased injection is a very good idea when you have a aggressive cam profiles as there is more or less intake reversion at the beginning of the intake stroke. Timing the injection to END before the closing of the inlet valve means you can reach a much more stable idle and low load behaviour. The majority of engines are not helped by this feature much, but you can detect stronger vacuum at a certain injector phase on almost any enging. The effects of intake heat soak and such things are minimized too, also helping the ease of tuning.

[Arthur]

Hi. I'm preparing for a mot test in the near future. This means I started thinking about my injection again.

I have a wasted spark 4 cyl.

Now running Semi sequential with injector table h(0) 0 set to 9 and 1 set to 6. This means 1&4 and 2&3 are paired.

My Peugeot trigger is 60-2 and trigger is 120 deg BTDC so I set trigger settings like:

TDC after trigger (deg)          60
Number of teeth                   58
Trigger tooth                       10
Next trigger                         30

This means in my config the injection starts 120 deg BTDC.

The following post (rob) is confusing me a lot.

(((Stick with the crank sensor alone for the time being.  You set the injectors to fire sequentially but they will not be in phase with the engine, but this does not matter as long as you inject when the inlet valve is closed.  The inlet is closed when ever the coil is firing (as the cylinder will either be on its ignition or exhaust stroke) so in the case of a 1, 3, 4, 2 engine
Ignition occurs: 1&4, 2&3, 1&4, 2&3 ...  so injectors will fire 1, 3, 4, 2 ... or as you don't have the sync pulse from the cam the engine may be firing in the sequence: 4, 2, 1, 3 which isn't a problem as the ignition still remains: 1&4, 2&3, 1&4, 2&3 and the injectors will still fire onto closed valves.)))

When the cyl 1 is ignighting, cyl 4 is traveling down to and in inlet so the inlet valve is open.

[rob@vems.co.uk]

When the cyl 1 is ignighting, cyl 4 is traveling down to and in inlet so the inlet valve is open.

You know - you're quite right.
Lets see...

Induction	Compression	Ignition	Exhaustion
1	3	4	2
2	1	3	4
4	2	1	3
3	4	2	1

In the first case 4 is igniting, so you want to inject on 3 or 2

[Arthur]

Oké.

I just read in in a way that made me think you ment different. 

Just for the complete picture. Not injecting on open inlet is only applicable under low load and rpm. Isn't it?

On high 7500 rpm, 1.2 boost, 70% duty cycle and 285 deg cam you will always inject to fuel in a same way as emtying a bucket of fuel in the header.

[rob@vems.co.uk]

I just read in in a way that made me think you ment different. 
[/qoute]

Well what it comes down to is when the injection event occurs, and that is on the trigger tooth - which is 100 to 60 deg BTDC.
So 1 will be compressing, and 4 will be exhausting.

Just for the complete picture. Not injecting on open inlet is only applicable under low load and rpm. Isn't it?

On high 7500 rpm, 1.2 boost, 70% duty cycle and 285 deg cam you will always inject to fuel in a same way as emtying a bucket of fuel in the header.

Exactly right, although reports vary on the effects of timed/phased injection at higher RPM regarding improved power and lower emissions, but thats not something that we can worry about.

Rob

[Arthur]

Hello


Sorry for bumping this very old topic, but it has a lot of info in it on which I have new questions. Also my last project was in it, which was also peugeot and looks a lot like what I'm doing now. Also this info could be nice for the archives I think.

About (semi) sequential injection without camsinc:

Peugeot uses flywheels on which the 1st tooth is 120 deg before tdc. So it would be logical to take 60 deg btdc and teeth 10 and 40 as triggers, right.

Actually I have a TU engine now with BE4r gearbox. On this gearbox the sensor is in a different place (2 teeth) so you need 60 deg and 12, 42 trigger as trigger teeth. So for BE4r 1st tooth is 132 deg btdc. (22 teeth)

Now I see that Vems recommends 80 to 60, max 40 deg before TDC for the trigger. But why is 120 deg with triggers 0 and 30 not allowed? Wouldn't this mean the injection starts at 120 before tdc making 100% sure you inject on closed valves? (assuming inlet is closed 60 deg after BDC)

Does this mean I can play with this 132 degrees as long as the total is 132 degrees?

132 degrees with trigger 0 and 30 --> inject at 132 btdc (I guess it needs at least some time to calculate)
60 degrees with trigger 12 and 42 --> inject at 60 btdc
90 degrees with trigger 7 and 37 --> inject at 90 btdc

IMO it would all work. Let's say I take 132, 0, 30 and the inlet valve opens 10 degrees btdc. This would mean injection starts 132 degrees btdc and only when the pulsewith exceeds the time it takes for this 122 degrees to pass, it will be injecting on open valves, which doesn't hurt because this will only happen at high rpm and WOT anyway.

Isn't injecting as far btdc as possible the ideal way to inject sequential without camsinc and without worrying you inject on open valves at low load rpm?