I am looking for examples of modified injector offset table to compare to my stock file. I have recently installed some 38# injectors. I think I have the flow rate, but now I need some offset data.

Can I just scale the whole table? If so by how much? What is the stock injector flow rating on a 2001 C5?

Thanks.

 

I spent a significant amount of time with this table, and this is what I can tell.

I installed a set of SVO 30#'s and here is what I can tell you.

Can I just scale the whole table? <strong> NO </strong>

If so by how much? <strong> Refer to above </strong>

The stock injectors on an 01 are 28#'s. The injector offset table is something that is determined by the manufacturer.
I have yet to find an offset table for SVO 30#'s for an LS1 application.
I worked at this table for a while trying to get it dialed in, and I actually ended up with something very close to the stock curve with the exception of a few points down low.
I now run the stock injector offset curve with my SVO 30#'s and everything goes fine.
Most other folks with bigger injectors run the stock offset curve as well.

Good Luck,
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

NoGo, thanks for your info. I thought that I had seen ChrisB develop a spreadsheet, curve fitting some data points (I don't remember what exactly), etc.

I also searched on here and thought someone else talked about mapping LTFT's (avg) vs g/cyl and curve fitting that??? Maybe you responded on that thread or that was you.

What the hell does the offset do/represent?

Thanks.

 

Yeah, I was the genius ( <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> ) that thought he would re-invent the wheel and come up with a better offset curve. After a couple weeks of tuning and coutless a-tap data, I basically came up with a curve that was pretty close to the stock one except on the very low voltages.

The Talkshow Version:

The injector offset curve, simply put, gives the PCM the electrical characteristics of the injector allowing the PCM to properly control the injectors for the exceptionally fast cyclical rates that injectors and connected electrical circuits will be subject too. Being the PCM is dealing with such small times when it comes to injection and ignition, the PCM needs to know how to properly "lead" the injectors with each electrical pulse so that the injectors open and close at the proper time.

If you have nothing better to do, keep reading. From here on out, it gets fuzzy for me, so if someone knows better, points out that I am entirely wrong, feel free to chime in and help me out.
The electrical output to each injector is not a simple unit step of the voltage to the injector. The inductive (capacitive?) load of the injector actually induces an E curve or delay in the step voltage, and would hence delay the opening of the injector and injection of fuel. The offset curve provides a measured value of the time the injector takes to absorb and discharge the commanded voltage to the injector and allows the PCM to determine either an offset voltage (I'm not sure on this one) or offset time, or both so that the injector will 'power up' and open at the right time and 'discharge' and close at the right time.

Hope that makes sense.
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

I think I understand what you are saying to a degree, but I am not for sure how the table could represent two values as in both time and voltage.
It would seem reasonable that if a bigger injector were installed, that might require different offset values.

I found the spreadsheet that someone more knowledgeable than myself created. Basically, he curve fit some "given" SVO data to compute the values from 4.5v to 18v. I don't know where the data came from. I believe he said he got it directly from a Ford Lightning.

The computed table is significantly different than the stock table, and in my eyes seems questionable. However, I might not have the correct spreadsheet and/or simply understand it all.

This came about because I installed new injectors (along with a few other goodies), and the injectors seemed overly noisy. Using a stethoscope, it seemed like the injectors, but the shop is going to check a couple of other possibilites. It seemed really bad at idle, almost like a Benz diesel. Any thoughts on what it might be? It does not seem to get worse with throttle, in fact it seems to quiet down.

 

I know which curve you are talking about. Simply put, my car would not run with that curve in it. I set SES codes, rich on both banks and the car was a dog. I immediately took that curve out and started working on my own. After while, as you know, I went back to a stock curve, and everything has been fine in paradise since.

The voltage bleed and charge vs time is really one of those things where a picture is worth a thousand words. Maybe I should make up a diagram to help explain it. This question pops up every once in a while. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

I would have to know what the "few other goodies" is before I can give you a good answer, but on first guess, I am going to say that it is not the injectors. I had a stock injector heading south once and the noise that it was making was a very crisp, sharp tick. What you are describing (a diesel) sounds more like valvetrain geometery. Pushrods, cam, rockers, valveguides, something along those lines.

 

i got sketchy about the numbers i got from the 42# offset table i needed.. so i just changed the flowrate and tried it.. and everything is working just fine with the stock offest.

i wouldnt worry about it. unless you have flooding out at idle or hard starts, it really wont do much at all..

like i say im running stock 28# offset with 42# svo's just fine.