Quote from: ajpturbo on March 12, 2015, 08:27:43 PM
Quote from: FoMoCoSHO on March 12, 2015, 01:26:03 PM
Quote from: IHeartGroceries on March 11, 2015, 12:09:41 AM
Anybody had the OE injector flow tested?
You lose pressure (with ethanol or whatever) becasue your injector pulse width decreases with engine speed, your duty cycle increases, your injectors are staying open near continuously and so the high pressure pump struggles to compress fuel, as the restriction eases.
Unless I am mistaken, the rail pressure in these engines is dependent on engine speed, correct? The HPFP is cam driven. It could potentially be responsible for some pressure drops or lean conditions, high load, low in the RPM band.
So, as stated by aj, your injectors can potentially flow well enough, but your limitation is with the HPFP. If there is replacement availability for that, then you open up more headroom for fuel. Until you max the injectors out. O_o
So looking at this, if we were get get a +25% injector that can run at a higher pulse width that closes like a normal injector, wouldn't that at least help restore rail pressure?
It may not be the ultimate fix but it would help wouldn't it?
Nope....Only a pump can help pressure....The larger and higher flowing injector will only deliver more fuel at a given pulsewidth....That's why you always see flow rates for injectors in cc/min or lbs/hr at a given pressure...usually 43.5 psi in the non direct injected world.
if the injector pulsewidth is 2 milliseconds and both injectors are operating at the same pressure then the larger injector will deliver more flow.
Someone said earlier that as rpm increases then injector pulsewidth decreases...That's wrong...Pulsewidth in just the duration of time that the injector sprays fuel...So when load is higher and you are making more power then the fuel demand is higher and will require a longer pulsewidth
Oh, yes. You're correct. Load increases, fuel demand incrases, pulse width increases, DC increases.
I'd intended to say that your window of injection timing for optimal performance during high RPM, high load homogeneous operation decreases on GDI engines, as you're limited to injection only during the induction cycle. A PI system could of course inject during any of the four cycles.
If you're looking at injectors, it's critical that they are produced very precisely and are well made. Spray patterns are important. The ability to atomize fuel is hugely important. The newest GDI injectors are really pieces of art. So, I'd be slightly sceptical of anything remotely affordable.
If somebody has a set of the stockers, you can have them flow tested to learn exactly what you're working with, what kind of headroom you have. Unless that information is already out there.
The HPFP is almost certainly the bottleneck. Which is what I don't get about developing injectors. Even if you've maxed out injector DC, you can still invariably reduce your injector workload with a fuel pump upgrade and likely have what you need for your modest power goals.
This is apart of why I've preached an auxiliary PI system. I know 4DR did it. But never learned what his shortcomings were. It is easiest solution and easiest to get support for...
