Changes to Injector Offset in LT 1 Edit

White Tiger · 07-25-2002, 05:05 PM

Recently I upgraded to 36# injectors and made the change in LT1 edit but noticed that it did not change my injector constant. They are still at the stock settings.

Is there a formula for adjusting these and can someone provide me that formula if it exists?

Any guidance is appreciated.
Thanks

Dr.Mudge · 07-26-2002, 02:09 PM

Injector offset and constant are not the same thing.

What PSI are your injectors rated at, are they SVO?

If they are SVO you could use around 39/39.5 for the constant.

White Tiger · 07-26-2002, 05:56 PM

Thanks for responding Dr. Mudge.

I am trying to adjust the constant for the Blue Tip 36# injectors (they are not SVO). The injector constant in one of the setting in LT1 edit that tells the the injector how long to stay open at various Ms pulse width's.

The constants in my computer are still at the stock settings and since my injectors flow more (36# vs 24# (stock)). I would like to have them only open the necessary amount of time.

I have tried to adjust the other items that could affect my richness issue without any success and believe that the 36# injector should not be open as long as the stock injector was to flow the same amount of fuel under normal driving conditions.

I'm not looking to change the pressure, but just the time that the injector opens.

Thanks
Ed M.

[This message has been edited by White Tiger (edited July 26, 2002).]

LWM · 07-26-2002, 06:50 PM

LT1 editor

open file

edit ... fuel

there is a box on that page with injector size on it. Tick the lbs/hr circle and then enter your injector size ... save the file and then up load it.

If you find you are excessively rich or lean, then you can adjust the injector size accordingly.

Worked for me with SVO 30# injectors

LWM

------------------
95 A4, SLP catback, KBDD sfc, airfoil, Vortech S-trim, 30# SVO injectors, Autometer electric FP guage, boost guage, Hotchkis STB, AS&M headers, AFPR, Vortech Aftercooler, 3.125" blower pulley, 7" crank pulley, Vigilante 2,800 stall, MSD 6 BTM, SLP 35mm front bar, SLP 21mm rear bar, LT-1 editor ...

, 437hp at the wheels. --- members.shaw.ca/mackenzl/LWMsZ-28/LWMsZ-28.html ... 01 vert in the making ...

iwon · 07-27-2002, 03:20 AM

Quote:

Originally posted by LWM:
LT1 editor

open file

edit ... fuel

there is a box on that page with injector size on it. Tick the lbs/hr circle and then enter your injector size ... save the file and then up load it.

If you find you are excessively rich or lean, then you can adjust the injector size accordingly.

Worked for me with SVO 30# injectors

LWM

but thats not the correct and safe way to do

White Tiger · 07-27-2002, 06:54 PM

Quote:

Originally posted by LWM:
....there is a box on that page with injector size on it. Tick the lbs/hr circle and then enter your injector size ... save the file and then up load it.

If you find you are excessively rich or lean, then you can adjust the injector size accordingly. LWM

From what I've noticed, is that changing the injector size there does not changes any other visible settings in the program. I noticed nothing in the VE tables, Inj Constant table, PE tables, etc.. And the only item I haven't tried to correct is the millisecond settings.

The car is heavily modded, and even negative numbers in the PEvsRPM table couldn't bring me leaner. Really I'm interested in finding the formula for correcting the injector constant throughout the volt range.

Thanks

[This message has been edited by White Tiger (edited July 30, 2002).]

LWM · 07-27-2002, 07:58 PM

How about trying this link.

http://carprogrammer.com/Z28/PCM/Injector/injectors.htm

Not a formula, just a table, but it might set you in the right direction.

From what I've seen in my travells, with these MAF enabled cars, the greatest tuning tools are the "injector size" and the PE table.

Hope this helps

LWM

------------------
95 A4, SLP catback, KBDD sfc, airfoil, Vortech S-trim, 30# SVO injectors, Autometer electric FP guage, boost guage, Hotchkis STB, AS&M headers, AFPR, Vortech Aftercooler, 3.125" blower pulley, 7" crank pulley, Vigilante 2,800 stall, MSD 6 BTM, SLP 35mm front bar, SLP 21mm rear bar, LT-1 editor ...

, 437hp at the wheels. --- members.shaw.ca/mackenzl/LWMsZ-28/LWMsZ-28.html ... 01 vert in the making ...

gb95zconv · 07-27-2002, 09:16 PM

Quote:

Originally posted by iwon:
but thats not the correct and safe way to do

Wrong...its both correct and safe when changing injectors...especially when going with a different make such as svo . Different makes are rated at different fuel pressures and that must be compensated for. As long as you are rich or lean across the board the fuel inj constant is a good way to tune.

Now if your car is running correctly and all of a sudden is rich or lean you dont want to correct by changing the constant...you need to find the real problem.

------------------
Greg
95 Z28 conv M6
Georgia F-Body Association

Stage 1 heads, 1.6rr, Meziere WP
lt4 hot cam,lt4 timing chain kit,52mm TB,
Hooker Headers, Pro 5 shifter,3.73s,
NX 150 progressive,
Self-tuned via Tunercat

rskrause · 07-28-2002, 09:25 AM

Quote:

Originally posted by gb95zconv:
Wrong...its both correct and safe when changing injectors...especially when going with a different make such as svo . Different makes are rated at different fuel pressures and that must be compensated for. As long as you are rich or lean across the board the fuel inj constant is a good way to tune.

Now if your car is running correctly and all of a sudden is rich or lean you dont want to correct by changing the constant...you need to find the real problem.

I completely agree, having tuned a number of LT1's and similar setups. If the car is rich or lean across the board adjusting the injector size (constant) is a good first step toward getting the AF ratio right.

For example, my cars "main" injecotrs are 50lb and after a lot of tuning I ended up with the injector constant at 42lb. The tune is based on extensive, fully instrumented dyno runs and it is spot on.

Rich Krause

------------------
'95 Z-28 383 with Vortech, nitrous, etc.
"1FASTZ28"

White Tiger · 07-30-2002, 03:13 PM

Thanks for the info!

Yes, my car is rich across the board, thus that is why I was looking for the constants.

LWM...thanks for the link, this should help.

One more question, the 36# injectors I have are Blue Tips, does anyone know how that compares to the SVO table?

Thanks
Ed M.

Luna · 08-01-2002, 09:09 AM

Quote:

Originally posted by gb95zconv:
Wrong...its both correct and safe when changing injectors...especially when going with a different make such as svo . Different makes are rated at different fuel pressures and that must be compensated for. As long as you are rich or lean across the board the fuel inj constant is a good way to tune.

Now if your car is running correctly and all of a sudden is rich or lean you dont want to correct by changing the constant...you need to find the real problem.

Use the pressure differential formula to produce the correct inj constant.

The injector offsets vs voltage is the better table to tweak, not the contant. For the most part, the leg work has already been done for you with regard to the offsets of aftermarket injs.

-CAL

White Tiger · 08-03-2002, 01:04 PM

Quote:

Originally posted by Luna:
Use the pressure differential formula to produce the correct inj constant.

The injector offsets vs voltage is the better table to tweak, not the contant. For the most part, the leg work has already been done for you with regard to the offsets of aftermarket injs.

-CAL

Thanks CAL, this IS the table I am trying to tweak. I use the link posted by LWM above which showed the settings across the voltage scale. I used the 36# SVO numbers, as a starting point, and this did not improve the operation of the car.

Unfortunately mine are the 36# Blue tip injectors (obtained from the old Modern Muscle in Mich) and I don't know how the SVO's compare and what adjustment, if any I would need to make to the inj offset vs voltage table for the Blue tip vs SVO type.

Thanks
Ed M.
1995 Z28