Computer Diagnostics and Tuning Technical discussion on diagnostics and programming of the F-body computers

Open Loop Speed density, A/F not changing

Thread Tools
 
Search this Thread
 
Old Mar 27, 2008 | 06:45 PM
  #1  
jchevy's Avatar
Thread Starter
Registered User
 
Joined: Oct 2000
Posts: 1,531
From: Tucson, AZ
Open Loop Speed density, A/F not changing

Im not registering any changes on my A/F gauage when I change my VE tables. Right now Im just messing with idle.

With the stock ve tables I was idling at about 12.4. Pull 15% fuel (multiplied values by 85% so they got smaller) and my A/F seems to be the same. What else is it looking at for fuel.

Open loop, so no 02 sensor feed back.
Old Mar 27, 2008 | 10:25 PM
  #2  
dookie454's Avatar
Registered User
 
Joined: Aug 2007
Posts: 573
I had to use Tunercat to lower my "Mimimum Injector Pulsewidth" with my 83lb/hr injectors, not sure if your having similar problems.

Stock file was set to 1.4ms as minimum, Datamaster was reporting something like 1.0ms at idle. I lowered it to 1.0 and immediately saw a difference

Of course this was after months of using LT1_Edit which doesnt have that adjustment and me going crazy trying to figure out why my idle was so rich.
Old Mar 28, 2008 | 12:05 AM
  #3  
jchevy's Avatar
Thread Starter
Registered User
 
Joined: Oct 2000
Posts: 1,531
From: Tucson, AZ
So am i stuck if I am using LT1 edit?

I havent tried actually driving the car to see if changes work or not, i just know its not working at idle.
Old Mar 29, 2008 | 01:00 AM
  #4  
dookie454's Avatar
Registered User
 
Joined: Aug 2007
Posts: 573
Originally Posted by jchevy
So am i stuck if I am using LT1 edit?

I havent tried actually driving the car to see if changes work or not, i just know its not working at idle.
If you send me your datamaster file I can tell you if the min pulse width is affecting your tuning at idle.. that's about all I can say... as far as what degree I dont know.

Or, you can check it yourself. I know stock LT1 file is 1.4ms minimum pulsewidth. If you see Datamaster calculating 1.0 or even 1.3, then that means it's "calculating" less than the minimum pulsewidth which it can never do since it's limited to what the LT1 file says (stock 1.4ms). Now, to what degree 0.1ms makes on your AFR depends on alot of things, but if it's 0.5ms like mine was with 83lb injectors then that makes alot of difference.

One other thing, I think I notice the PCM loses accurate control of the injectors below ~1.0ms... at least with my 83'lb injectors anyway based off of decel AFR's (ranging from ~14.5-30ARF) when datamaster reports below 1.0ms... so I set my minimum pulse width to about 1.0ms and dont have problems like that anymore.
Old Apr 1, 2008 | 08:44 PM
  #5  
jchevy's Avatar
Thread Starter
Registered User
 
Joined: Oct 2000
Posts: 1,531
From: Tucson, AZ
I am having another problem. I run an open loop tune, and seems no mater what I do i cant get the a/f at wot leaner than 10.8. Think this has something to do with the min pulswidth.

The lowest I saw the BPW ms was 1.8

Last edited by jchevy; Apr 1, 2008 at 08:55 PM.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
DirtyDaveW
Forced Induction
13
Dec 1, 2016 05:37 PM
DirtyDaveW
Parts For Sale
1
Mar 15, 2015 07:01 PM
blac94Z
Drivetrain
15
Mar 2, 2015 12:00 PM
chevroletfreak
LT1 Based Engine Tech
202
Jul 4, 2005 05:00 PM
Speeds8erM-1
Drag Racing Technique
1
Jul 28, 2002 06:18 PM




All times are GMT -5. The time now is 07:45 AM.