86 IROCZ28

Wanted to ask for the last time what is the way to go if the car is running a lot on the lean side.

Say BLMs are around the 140-150 mark.

Would you lower the injector constant to fix the problem and then tune the VE table?

Or would you leave the Injector constant as it is and adjust the VE table?

I have read a lot of posts and some say do the injector constant and others tune the VE Tables.

But why would you want to lower the Injector constant when running 19lb injectors and the constant is set to 19lb?? Should it not be set to the correct size of the injectors and left as is. Or is it normal practice to lower or raise the injector constant to the way the car is running and then hit the VE table?

ski_dwn_it

86Iroc,

The rule of thumb I use is:

If you are universally rich or lean then use the injector constant, then fine tune certain areas with the Ve tables.

For your situation, I am assuming you are 140-150 across the boards, you want to make the injectors look smaller than they really are, this will make the ecm add more fuel.

What I found is that you will go back and forth doing this a few times and when EVERYthing is were it should be you will be back to darn near 19# (or the actual inj constant).

Hope this answers your question....if you need anything else let me know...

Grumpy

Enter the injector constant for what your running.
Tune as necessary.

Then you change the injector constant you change all the fueling, not just the VE table. EVERYTHING.

Sometimes, the right way is more work, but thats what it takes to get things CORRECT.

86 IROCZ28

So Grumpy you are saying that if the injector constant is set correctly to what I am running I should leave it and tune as necessary.

Just want to give you an example what I am finding out from my data logs. Below is an example of firstly the stock VE table values.

Second table is with the VE values adjusted to be around the 128 mark. I've read that the VE values should be incremint in value as you step up in KPA well in my case that is impossible as you can see.

STOCK VE VALUES 1300RPM

20KPA 25KPA 30KPA 35KPA 40KPA 45KPA 50KPA 55KPA 60Kp

47.6 51.89 58.13 63.2 65.93 67.49 68.66 69.83 69.4


ADJUSTED VE VALUES TO OBTAIN 128 BLMs

20KPA 25KPA 30KPA 35KPA 40KPA 45KPA 50KPA 55KPA 60Kp

48 52.34 58.58 70.85 73.65 78.56 79.9 81.2 71


What I am trying to show is that at 60KPA my VALUE is 71 which is smaller then my value at 40KPA (73.65).

This happens in many more RPM ranges is this a problem is what I am really trying to find out?

Thanks for any help.

Dominic Sorresso

86,

As Grumpy says, the injector constant is just that. Its a constant that's used by any number of parameters. You have a 3d VE table so you can fine tune. If you are universally rich, then maybe consider leaning out the fuel pressure or if you are universally lean, then bump up the FP. But I am not a proponent of that type "shotgun" approach. That's why you undertake ECM tuning in the first place. And depending on your setup, it is possible to have a greater VE at lower RPM. Hopefully its not too out of whack. You'll find a "knee" in your fuel table that generally indicates where the cam is "coming in". For instance, I have an area at the 1700-1850 rpm region that's a bit "hinky". Cam starts to come in right after that point at about 2000rpm. Another area to look into is the SA table as a means of adjusting VE requirements. I try to get the Fuel Table close first, then get into the SA to tune a little closer. And RBob has suggested using the SA table to tune for the rpm cells that are "in between" the cells on the Fuel Table since the SA table goes in increments of 200rpm and 5 kPa. I am describing the 7747 tables at this point, not any others. Some of the above may be appropriate for your ECM.

IroczInOz

Thanks for the info everyone, I am runing a stock set-up but like said by Domenic it is not uncommon to have a higher VE value at lower KPA in the same RPM band. Guess I will go ahead and see how I go