anybody know where i can find good write up on VE tuning. I want to get my fuel trims on point.

 

Are you running speed density mode?
If not, dont waste your time doing it.

 

MAF dosen't kick in until 4k. Tweaking your VE tables will help.

 

??? What vehicle are you talking about? In a typical '94-'95 OBDI F-body, the MAF is used all the time.

Dan

 

The way to adjust your fuel trims is:

1) Get rid of or at least minimize split BLM's.
2) Check and set your actual fuel pressure for the correct value.
3) Fueling adjustmens:
a) Injector constant for overall fueling (affects all cells)
b) Injector offsets (affects mostly idle)
c) Alter the MAF calibration table (affects specific cells of your choice)

You should seek for slightly negative fuel trims if you dont have a the WOT BLM LOCKER feature active in your tune.

You need scanning software with logging capabilities to do that, of course.

 

thanks ricardo. i was looking for a little more detail. i see those are the genaral steps but unfortunately i don't know enough about tuning to go off just that. i have VE master which i know helps once you have a log of all your fuel trims. do i have to put the car into SD when adjusting fuel trims?

 

sorry, I was in a hurry.
http://redhardsupra.blogspot.com/200...on-part-1.html

The above quote says what I meant to say. I was merely trying to relay the fact that even in MAF mode, VE tables need to be properly tuned for idle-4000rpms, as MAF mode is really a MAF-SD hybrid.

 

I can't help you with VE master. I have not used it. My car is OBDII.

What I did to get my VE tables in line was the following:

Made a tune with the following changes:
Triggered speed density mode on
Set it to run open loop all the time (raised closed loop enable to 150 deg)
Filled my open loop AFR vrs coolant vrs map for a fixed value of 13.8 for the operating temp range.

Logged a lot of information with an LM1 wideband (AFR/MAP/RPM)

Made the proportional corrections for the values in the VE tables corresponding to the observed and logged data.

I went thru this logging-correcting cycle a lot of times, until the logged AFR would be close enoughto the commanded AFR.

My objective was to be able to run SD in order to get rid of the MAF meter. I ran into a problem with a tip-in hessitation that was extremely hard to overcome. It is much better now, but still not perfect. I did notice that my car would idle much smoother in SD, but never raced it in SD due to this.

 

thanks guys for the help. i'm going to have to try it out because my fuel trims are off.

 

Okay so I installed my LC1 wideband finally and my afr is all over the place at low rpms. I want to get started with the VE tuning but want to make sure I have the steps right.

First I have to get the car into speed density mode and have it run in open loop. I understand how to tune to have it run in open loop all the time. Is that speed density mode or do I have to unplug the MAF as well?

Then I have to do a lot of logging to and make the appropriate changes to the VE table to get the values as close to 128 as possible. The log has a left and a right fuel trim column. These columns have different values. what do i plug into the VE table? Do i get an average of both left and right for a given rpm and then add and average those two? I'm not too clear on how do i get the number that i use to make the change in the VE table.

 

Back from the dead.

Question. Are the VE tables used in open loop? I thought they were only used in closed loop. Or is triggering speed density the reason they are used?

 

That is the exact reason they are used. When in speed density mode the PCM calculates fueling by based upon the MAP sensor reading.

Open loop or closed loop it will allwas refer to the VE tables for fueling. (In speed density mode). It will adjust for the O2 sensor readings if running closed loop. It won't adjust if in open loop mode.

 

"My objective was to be able to run SD in order to get rid of the MAF meter. I ran into a problem with a tip-in hessitation that was extremely hard to overcome. It is much better now, but still not perfect. I did notice that my car would idle much smoother in SD, but never raced it in SD due to this."

You can disable MAF which will trigger SD mode... it will run better (if VE's are tuned in right... sometimes have to wait till 02's correct it).
I had severe Tip In lean stumble for long time... cure it and cured it for a few others as well in one mod!!...
If it doesnt run better in SD then simply tune in your VE #'s. All the work will be worth it. I was a diehard MAF guy due to the concept but once I got rid of it I couldnt believe how much more responsive.

Not trying to redirect... but my Tip In problem resolution was fixed/solved while working on something else.. Long story short.. I tricked the PCM into increasing the "Pump Shot/Accel Shot" by lowering the actual injector flow rate considerably... (20%?). Since I was in SD mode I compensated/removed excess fueling by subtracting ~20% from the VE %. I did this with only hope it would work simply because there is no Pump Shot/Accel Shot setting anywhere. It worked and I noticed it right away (yes I tried EVERYTHING to get rid of lean Tip In - this is the only thing that worked for me - 83lb injectors w/AEM Driver - was OK with 42lb'ers).
if your interested in reading a book, link below...
https://www.camaroz28.com/forums/sho...d.php?t=560089

 

Yes, I have been reading a lot of your posts lately. My car is now boosted, and I would like to run the 2 bar setup in SD open loop mode. Im worried the waste gate and cross over pipe would fudge o2 readings.

Thanks for the post!


Do you think you could email me your SD 2 bar tune for me to check out?

 

Sure, PM me with your email.

I cant comment on open loop SD since there wont be any corrections made, but I would like to hear how it runs without correction... so let us know!

Keep in mind I notice this tune runs a little shaky the FIRST TIME closed loop mode takes over but only for a minute.. actually I think it's smoother in initial open loop.. when it enteres CL mode and I keep gassing it I can usually feel one hickup shortly after it hits closed loop... followed by a little leanness... then it snaps back into shape during the next few miles of spirited Closed Loop (non-PE mode) driving. Once a few miles pass it's smooth sailing. Seems like no matter what happens if I gas it soon after it enteres closed loop it will cough only once.
THis also means the initial open loop is uncorrected.. so the second time you drive it (assuming you ran for awhile in closed loop) the open loop is usually even smoother than it is the first time you drive it (corrections).

Point = I dont know what will happen with continuous open loop. Automatic trans will probably be unnoticeable... I have a manual with an aluminum flywheel and Mcleod springless dual clutch so I tend to feel ANY imperfection in the firing sequence.