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Optimal time for injector to squirt.
Posted: Thu Jun 21, 2007 1:12 pm
by FIntruder
I will be converting a Japanese motorcycle to microSquirt some day. Its timing pickups are on the crank so if I use them to control the mS the injector will fire just before the intake stroke and just before the power stroke which will not immediately be taken into the cylinder. I guess this works fine as many do it this way.
If I were to mount a timing pickup on the cam somewhere so as to avoid the dual squirt, at what point is it optimal for the injector to be triggered? I would think just before the intake stroke like the spark plug gets it but I may be wrong.
Does a missing tooth wheel mounted on the crank provide for this same kinda timing, I don't see how as the crank is spinning at two revs per cycle.
Re: Optimal time for injector to squirt.
Posted: Sun Jun 24, 2007 11:10 pm
by slabbielad
FIntruder wrote:I will be converting a Japanese motorcycle to microSquirt some day. Its timing pickups are on the crank so if I use them to control the mS the injector will fire just before the intake stroke and just before the power stroke which will not immediately be taken into the cylinder. I guess this works fine as many do it this way.
Engines aren't as fussy as you may imagine. They don't mind that small bit of air fuel mix being held in the inlet port. If you want super clean emmissions then sequential is the way to go but you need to remember that it will seriously affect your injector sizing.
If I were to mount a timing pickup on the cam somewhere so as to avoid the dual squirt, at what point is it optimal for the injector to be triggered? I would think just before the intake stroke like the spark plug gets it but I may be wrong.
The actual injector event timing varies depending on a lot of factors. Inlet port design, cam profile, engine speed/load etc all have an effect.
Does a missing tooth wheel mounted on the crank provide for this same kinda timing, I don't see how as the crank is spinning at two revs per cycle
No, it won't. You would need some form of "phase" sensor, usually from the cam which would allow the ECU to work out which cylinder is on TDC (firing).
This is the way I see it anyway - I'm not hugely au fait with the Mega.Microsquirt system but I believe the basic FI principles are the same!
Stewart
Posted: Tue Jul 03, 2007 12:08 pm
by mrbell
to reinforce what slabbielad quoted("Engines aren't as fussy as you may imagine") think of this: Engines have run on carburetors for more than 100 years and carburetors can almost never run "properly". They run "well enough" tho, which is the most important part...
Posted: Tue Jul 03, 2007 3:42 pm
by FIntruder
Can I buy a Hall Sensor or make one? How do they work exactly. I understand that as two parts pass each other a signal is triggered etc. Is it magnetic? What type of sensors/triggers are the stock pickup coils that trigger the coils on my Suzuki? They are mounted with the stator, one per cylinder/coil.
Posted: Sat Jul 07, 2007 12:07 pm
by mpanther
I would just split your fuel needs in two and inject once a spark. this will give you all the fuel you need and any missed will be there for the next intake.
If you inject at the intake or just before you might have the valve close before it can get the whole fuel charge, with multi injections per intake the injector times are shortened and the fuel is either waiting to be pulled in or injecting during intake. any fuel injected during the power stroke should stay attimized or evaporate on the hot valve.
at least, so it seams to me.
anybody else have some thoughts?
Posted: Sat Jul 07, 2007 5:29 pm
by FIntruder
I guess I'll try it the simple way first and then go from there. Thanks for the input fellow squirters.
Posted: Sat Jul 07, 2007 11:52 pm
by mpanther
K.I.S.S. it and make it All better.
*grin*
Posted: Sun Jul 08, 2007 6:46 am
by FIntruder
So fuel injection systems that only squirt once per cycle do so at how many degrees before the intake valve opens? Spark is soo much faster and shorter in duration I would guess an injector would need more time and have to fire sooner.
Posted: Mon Jul 09, 2007 2:27 am
by newtyres1
The number of degrees the inj is open before the intake valve closes would depend on how much fuel needs to be injected, and if that system wanted to inj all the fuel before the intake closes. Maybe have a read about injector duty cycle, where the injector at WOT and engine at high revs may be open for most of the cycle period, i.e. 2 crank revolutions. At that stage sequential is meaningless.