Larger fuel injectors & voltage offset vs flow

[Joseph Upson]

My turbo flows a little over 72lbs of air/ min. A set of 70lb injectors will support a little over 630-650hp. I need the extra fuel volume, so smaller fuel injectors aren't a possibility. Low-Z injectors allow for faster opening and closing rates than a standard saturated injector. (about .5ms faster)

If you have a use for it no problem but my turbo is capable of about the same (T67) and my injectors at maximum allowed pressure flow ~85 lb/hr of fuel but I know I'll likely never be anywhere near the limits of either. Not sure the low impedance injectors being able to open and close faster would sufficiently address the potential problem of flowing too much fuel at idle I've been having. In your case the flow is even more and I suspect you have a smaller displacement motor if it's a 60 degree mill. I think the problem is more a calibration and voltage stability problem on my end though. I'm also planning to drop down one turbine housing size for a dedicated street performer which is mostly 0-60.

[Google Adsense]

[Driver_10]

If you have a use for it no problem but my turbo is capable of about the same (T67) and my injectors at maximum allowed pressure flow ~85 lb/hr of fuel but I know I'll likely never be anywhere near the limits of either. Not sure the low impedance injectors being able to open and close faster would sufficiently address the potential problem of flowing too much fuel at idle I've been having. In your case the flow is even more and I suspect you have a smaller displacement motor if it's a 60 degree mill. I think the problem is more a calibration and voltage stability problem on my end though. I'm also planning to drop down one turbine housing size for a dedicated street performer which is mostly 0-60.

I imagine that you must be spiking the pressure up and maxing the PWM to get that kind of flow.

Problem one... Increasing fuel pressure will cause slower closing times
Problem two... overheated coil windings and potential damage to injectors

The peak-n-hold style injectors have larger windings and lower resistance as a result. Because of this, they handle greater amounts of amperage. They use high amperage to pull the needle away from the opening and then use a lesser current to hold the injector open. (hence the term "peak-n-hold")

The problem with them is that they can burn the transistors out of an average ECU due to the high amperage. They can be used with inline resistors, but that defeats the purpose of using low-z injectors all-together.

[Joseph Upson]

I imagine that you must be spiking the pressure up and maxing the PWM to get that kind of flow.

Problem one... Increasing fuel pressure will cause slower closing times
Problem two... overheated coil windings and potential damage to injectors

The peak-n-hold style injectors have larger windings and lower resistance as a result. Because of this, they handle greater amounts of amperage. They use high amperage to pull the needle away from the opening and then use a lesser current to hold the injector open. (hence the term "peak-n-hold")

The problem with them is that they can burn the transistors out of an average ECU due to the high amperage. They can be used with inline resistors, but that defeats the purpose of using low-z injectors all-together.

I know all about the differences between the injectors but I'm not referring to operating outside of the equipments capability, higher fuel pressure is an acceptable option within the injectors limits and a given with a boost sensing pressure regulator.
85 psi flow rate was listed in the ad for my injectors I don't run pressure anywhere near that.

The offset table would handle delayed openning times related to higher fuel pressure as delayed openning occurs with low voltage as well so there's one more reason to tune that table for your injectors whenever operating outside the specified range.

I'm starting to lean away from the "more than you need camp" in favor of the "make up your mind about what you want" and use just enough to achieve it rule for maximum efficiency.

My turbo is a little oversized for what I need along with the injectors and for a street performer that means slower 0-60 times. There's no practical setting on the street to take advantage of a high end motor for me. My choices were for my stroked motor where these parts are better suited.

[Driver_10]

I know all about the differences between the injectors but I'm not referring to operating outside of the equipments capability, higher fuel pressure is an acceptable option within the injectors limits and a given with a boost sensing pressure regulator.
85 psi flow rate was listed in the ad for my injectors I don't run pressure anywhere near that.

The offset table would handle delayed openning times related to higher fuel pressure as delayed openning occurs with low voltage as well so there's one more reason to tune that table for your injectors whenever operating outside the specified range.

I'm starting to lean away from the "more than you need camp" in favor of the "make up your mind about what you want" and use just enough to achieve it rule for maximum efficiency.

My turbo is a little oversized for what I need along with the injectors and for a street performer that means slower 0-60 times. There's no practical setting on the street to take advantage of a high end motor for me. My choices were for my stroked motor where these parts are better suited.

Im sorry, I wasnt trying to be patronizing or anything. I had the impression that you honestly didn't know about low-z injectors. I guess I misinterpreted what you wrote. I keep forgetting the crowd that Im speaking to at times.
My bad...

[Joseph Upson]

No problem, I learned the difference about saturated and peak-hold injectors years ago when much of this stuff was still a mystery to the open market in regards to interchangeability. I was hoping Sappy would reply in regards to my question about why I shouldn't run lower fuel pressure given my scenario just in case a circumstance I'm not aware of is present and a potential sticking point.

It wouldn't be a bad idea to take the time to crunch the numbers and verify that the 60s can handle higher fuel pressure without loosing the ability to run low enough pulse widths for idle. Considering they already flow more than twice as much fuel as the stock 28s at around 16 psi less than what the stock injectors are run at and they are now set to about 50 psi I suspect I'll have no choice but to lower static pressure.

[Joseph Upson]

Adding fuel to the injector offset vs base pulsewidth took care of the idle hunt in closed loop. I have to investigate to find the next table to adjust to correct the intermittent engine stall when the coolant fan turns on. The USB Extreme ALDL from Moates is necessary to datalog and emulate 8F code mask and it has proven so far a tremendous help in the short time I've been using it.