when is the injector triggered ?

[briney]

hi guys. i'm looking at injecting a single cylinder 2 stroke. i'd like to be able to set it up so the injector squirts into the transfer port when the exhaust port is almost closed. i'm assuming the computer fires the injectors when the ignition triggers. i'm quite happy to run it fuel only, with an extra sensor added to get the injection timing right.

[Helical]

Subscribing to this.

I have been pondering messing around with a small single cylinder 2 stroke.

Troy

[The1]

all that rain your getting must be making that grass hard to mow.

[VL400]

The start of the injection pulse is in sync with the falling edge of the reference pulse. This can be changed in 12P using "Injector - Injector delay Table (% of Ref period vs RPM & TPS)". As an example, a value of 50% will put it halfway between the ref pulses.


Here are some scope caps of a TBI setup with 0% delay, the yellow is the reference pulse and green is injector (injector pulse low is injector on)...

TBI Double Fire Zoom.png (23.03 KiB) Viewed 4827 times

TBI Double Fire.png (24.84 KiB) Viewed 4827 times

The above two shots are in double fire mode, if the pulse width becomes too small then the pulse only happens once per engine revolution so you get the skipped injection like this..

TBI Single Fire.png (24.18 KiB) Viewed 4827 times

And to show how different cyl selection changes how often the injectors fire. These are all double fire, single fire mode means the skipped pulses are double (ie 8 cyl goes from every 4th pulse to every 8th)...

8cyl Double Fire.png (23.66 KiB) Viewed 4827 times

6cyl Double Fire.png (23.68 KiB) Viewed 4827 times

4cyl Double Fire.png (24.06 KiB) Viewed 4827 times

[briney]

that's exactly what i was after. thank you very much.

[briney]

well, it's actually an experiment to get some better economy. if i can squirt the fuel into the transfer port just before the exhaust closes, hopefully all the fuel will stay in the cylinder. now i've got the electronic part of it sorted, i'll have to look at how in the bloody hell to actually make it work.

[briney]

after some more looking on the internets, i've been looking at going direct injection. the systems i'm looking at are air assisted. there needs to be a squirt of the injector (usually during the power stroke.) then the air is used to fine atomise the fuel into the engine. i was looking at using the standard cdi ignition. then using the fuel injector output to control the fuel injector. then using the ignition signal to fire the air injector. it gives me massive adjustability of the time and the ability to vary the point of injection with speed and load. i've ordered some manuals off ebay to see how it all works, and if i can make it work.