KingK_series wrote:
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Yes they run at 85% duty but not much above idle they are sized to fire before the inlet opens - which is bad for emissions and torque because the fuel falls out of suspension in static air
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I am not sure this is 100% accurate.
You do not want to squirt before the intake valve opens if you have a lot of overlap, as you then have a lot of fuel going straight out the exhaust.
So it accurate that it is bad for emissions, but mostly at low RPM.
If you do not have a lot of overlap then it does not matter, and I suspect the VTEC solves some of those overlap issues.
At RPMs past where significant intake get drawn into the exhaust, then it debatable as to how good or bad it is. But with a poorly atomising injector the statement may be accurate. And one does not ant sheets of fuel raining off the intake walls, so it also matters as to how hot or cold the intake tracks are.
Another school of thought is that you want to squirt the fuel onto a closed intake valve to both cool the valve as well as more of the atomised fuel can be converted to be vaporised the fuel from picking up the heat of the valve.
And yet another school of thought is that injecting higher up in the intake provides more time for vaporisation as that also cools the intake charge which makes it denser, hence more power. But that also results in wetted out runners, which are not easy to dry out for emissions without moving some air through them.
Scuffers wrote:
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To spec injectors that are big enough to achieve max required flow without going over ~35% duration would be catastrophically stupid for several reasons, in no particular order:
1) emissions
2) fuel pulp/reg sizing (and increased cost)
3) idle/low load performance
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I am not sure that this is 100% accurate either.
I believe that the ideal is to have the injectors sized for duty cycle (in phase or degrees) at something around the intake timing duration in degrees. Then the fuel gets delivered when the air is flowing.
But this means very small injectors for partial throttle, leading all the way to massively sized injectors for WOT - where at high RPM the cycles is "short in time".
There is only two solutions
1) Run the car at either high RPM high-load with big injectors
2) Optimise it for cruise., and do not allow it to get to high RPM high load.
3) Size the injectors at the 85% DC as a compromise.
4) Or the more elegant solution of Dual injectors. But neither the K-series nor K-20 have that as OEM option, whereas some of the toyotas have the 5th injector which does take that approach.
Maybe this is headed into why people like Toyotas
