Injector data...its ALL what its cracked up to be!

[Meister]

Ok I am going to bring a little life back to this thread. I have question for Phil, Greg, Howard, and anyone else.
What effect does fuel pressure have on all this?
The standard operating pressure for the LS is 58psi (4bar). Now I have ID1000 injectors and am considering running one fuel pump instead of dual stock style pumps for simplicities sake. Using Magnafuel 4303 without a controller. This is a turbo charged engine with a boost referenced return style fuel system. Magnafuel reccomends using 35psi (2.4bar) as my base pressure. They say this will keep load on the pump down and have plenty of room to meet my 800hp base goal.

The difference in the Flow Base easy enough to calculate.

But what happens in the other tables and settings?
I would guess the the minimum pulse would stay the same along with the break point.
Would the small pulse adust change?
What about the voltage adjust? If manifold pressure effects it surely fuel base pressure does?

You are going to use the value at the base pressure you are running (whatever you decide it is) and use that for the entire table. This will work assuming you are using a regulator with a vacuum line on it. Your min pulsewidth and small pulse values will stay the same.

[eficalibrator]

Pressure will have a noticeable impact upon injector offset as well as linear flow rate. The short pulse phenomena are the question here. If this were a Ford, we'd be looking at applying a similar Bernoulli correction to the low slope as we did to the high slope for the change in pressure. Since GM uses a time adjustment to correct for short pulse errors, this requires a bunch more math and interpolation _or_ a whole new set of characterization tests at the new pressure. The latter would be my preferred method.

[Meister]

Pressure will have a noticeable impact upon injector offset as well as linear flow rate. The short pulse phenomena are the question here. If this were a Ford, we'd be looking at applying a similar Bernoulli correction to the low slope as we did to the high slope for the change in pressure. Since GM uses a time adjustment to correct for short pulse errors, this requires a bunch more math and interpolation _or_ a whole new set of characterization tests at the new pressure. The latter would be my preferred method.

Well said. I have always done this maintaining the factory base pressure. Injector Dynamics, if asked nicely, would be more than happy to provide this data for you if they have time available. If you will have enough range in your fuel system to keep 58psi I would do so.

[ASNUPHIL]

Hi John,

Before you do anything with the fuel pressure, take your injectors along to an ASNU owner and have him flow them at 4 bar under the Auto Cycle, this runs the injectors at 3, 6, 12mS @ 600, 2500, and 5000 RPM, look at them and see what a difference it will make to the spray patterns and the flow rates, the droplet will increase in size dramatically for when they are run at 4 bar, you will certainly have a difference with the air/fuel ratios compared to when they are run at 4 bar pressure, they do not have an orifice plate, so the fuel relies on the seat to distribute and atomize the fuel and lower fuel pressure will change the spray pattern characteristics.

You need to be sure you want to do this modification and have all the issues attained to the change. My suggestion is that when you are sure you can get the basics right, then you can start adjusting for the injectors characteristics.

Hope this helps.

[ASNUPHIL]

John,

What you need is the data like this that we now supply with our ASNU Injectors, we have the data at 3, 4 & 5 bar settings.

What you need to decide is where you make the settings, for example, look at the 12v data, you will see that the delivery at 1.4mS is minimal, increasing at 1.5mS and then getting a full belt @ 1.6mS, now do you set your parameters as the injector is opening, part open or fully open?

1.4 0.15
1.5 0.73
1.6 2.75

You also need to be sure what the linear range is for the injectors at the pressures you are planning to use.

[slows10]

Ansuphil, Where do we/I go for injector pricing and available sizes and styles information?

[JOHNBOY]

Thanks guys. Your confirmed what I thought. Strike one on the the Magnafuel tech guy LOL. I have no plans of running fuel base that low. Injector Dynamics provides wonderful data for there product at 58 psi. That is what I intend to use. I know I could simply ask them to help if I really wanted to change the pressure base. I really see no need to change the base pressure/ Things said by the tech at Magnafuel got me thinking and I figured this was the best place to get some answers.

[PRAY]

This is great stuff. So for us non smart guys trying to become better than your average tuner, is there a link to adjusting all the injector tables and what they do? Also, everyone keeps saying to get the data on the injector from who ever you get it from. How does that data translate to adjustments in the injector tables in EFI live? Sorry for the "beginner" questions in such an advanced thread but I am just trying to learn. Point me to a tutorial or thread and I will gladly read away. Thanks.

[Redline Motorsports]

Pressure will have a noticeable impact upon injector offset as well as linear flow rate. The short pulse phenomena are the question here. If this were a Ford, we'd be looking at applying a similar Bernoulli correction to the low slope as we did to the high slope for the change in pressure. Since GM uses a time adjustment to correct for short pulse errors, this requires a bunch more math and interpolation _or_ a whole new set of characterization tests at the new pressure. The latter would be my preferred method.

Well stated....

[eficalibrator]

Time for another lesson, gents. Today, we learn about how some fluids change properties with aging. Particularly, the injector test fluid provided with some stands. I ran a test to back up some of my original data and got some interesting results. I grabbed the very first set of injectors that I tested on the stand, a set of STOCK LS3 Bosch ev14 units, all of which matched very well on the first test. I ran them again under the same conditions (13.4v, 400kPa) and got different results:

Moral of the story? The provided fluid has a limited pot life in the test stand and changes with age and usage. How rapidly does it change? I'm not sure, but I don't like ANY change here since it makes scientific comparison very difficult when I can't reproduce the baseline test. I have a few more things to check, but the next step will likely be to drain the test stand and refill with a known test fluid. Next up, an actual batch of N-Heptane, which is what we probably should have been using from the start on this bench... Good thing test grade N-Heptane is only ~$200/gal.