Flip-Flop switching between two injectors

[AnalogKid]

Also he's firing 2 injectors at a time - quite a normal thing that was done before sequential injection came out.

OK, since you seem to know what you're talking about,

FIRE - do the two FIRE phases (one for each injector) have to be perfectly matched, or can they vary with respect to each other by +/-10%?

ak

 

[malc9141]

Hi guys

I am most grateful for your helpful comments. It has been suggested that I approach a company called Motec, which might have an adaptable ECU. Of course, my hopes are not high. But let me wait to see how they reply before I tie you up further with this thread.

 

[augustinetez]

FIRE - do the two FIRE phases (one for each injector) have to be perfectly matched, or can they vary with respect to each other by +/-10%?
ak

Not really, the total open time is the most important bit as it is relative to speed/rev rate of the motor.

The length of the FIRE time is more related to energy use and heating of the injector solenoid (to stop burnout).

 

[shortbus=]

He said earlier it is a 4 cyl 2 stroke.

Also he's firing 2 injectors at a time - quite a normal thing that was done before sequential injection came out.

And he also said, quote, " It worked fine (for our single cyl engine)." I couldn't find in the thread where he said 4 cylinder 2 stroke though.

Can you give an example of 2 injectors per intake track? None that I'm aware of in car engines do that.

I still say just taking a fire command from an opto sensor isn't going to give any real usable performance. If you just need an engine to run at one set speed maybe, but there also needs to be a reference to throttle position, this is what sets the time duration of injector activation. And to do that the whole system needs a brain. Concentrating on only one point and not looking at the whole system is just going to keep things from being solved.

 

[AnalogKid]

NOTE: This is a CONCEPT schematic. It uses parts grabbed from my design libraries, not components recommended for a prototype.

Concept schematic of where I think we are. LX is the injector, CX sets the FIRE time period, and RX sets the HOLD current. U2A and B form a monostable that is adjustable from something less than 2 ms to approx 5x that.

A real circuit probably needs a real gate driver rather than U3. Also, there might be a very short (less than 1 us) period when the previous injector fires again, caused by the propagation delay through U1 relative to the propagation delay through the monostable circuit. This can be fixed with a short delay network at the output of the monostable.

ak

 

[augustinetez]

Can you give an example of 2 injectors per intake track? None that I'm aware of in car engines do that.

Possibly some confusion here - I think (not having seen any pictures or other info) - the OP is firing 2 injectors at a time - 1 injector per cylinder intake, not 2 injectors per cyl intake track, on a 4 cyl engine. This was a common way of doing it in earlier days (check early GM injected vehicles - they used to divide the number of injectors in to banks of two and fire one lot all at once and then the other lot) I haven't been hands on for a long time now, but it wouldn't surprise me to find it still being done that way in some vehicles.

Post #9 is where the OP mentions the engine they are trying to get this running on.

Car engines - yes - high performance/high horse power stuff have used 2 injectors (or more) per cyl, although not that common now that bigger injectors are available (my mechanic of long standing is a high performance engine builder and I did work with him for a period).

 

[shortbus=]

I think (not having seen any pictures or other info) - the OP is firing 2 injectors at a time - 1 injector per cylinder intake, not 2 injectors per cyl intake track, on a 4 cyl engine. This was a common way of doing it in earlier days (check early GM injected vehicles - they used to divide the number of injectors in to banks of two and fire one lot all at once and then the other lot)

The also had throttle body injection that basically never shut off, more like a electronic carburetor.

But getting back to what I bring up about a "brain" to run this. No ijection or carb system works(that I'm aware of) just by a signal from the flywheel. Added fuel by that means alone will just end up flooding the engine out, it's (as most probably know) the throttle butterfly and amount of fuel in combination that allows it to increase RPM. Unless were talking a diesel engine, that has no butterfly just an open intake track.

The fact this is a two stroke adds some communication to the mix though. A 4stroke has a cam that allows a distributor to get the position of each cylinder firing point(I know, overly simplified). So a multi cylinder 2stroke would need a trigger from the flywheel, one for each cylinder, to tell when to fire or open the injector on that cylinder. It needs the same signal for the ignition timing so why not use that to signal injector opening?

 

[shortbus=]

I think (not having seen any pictures or other info)

That's why I asked for those. Chrystal ball engineering doesn't go very far.