I recently had my car tuned, and it was tuned on a perfect AF, using LT1Edit. The tuner I am using is experimenting with a new method, deleting the o2s (making the car run in open loop the whole time). He said he has been tuning various cars like this, because sometimes, long tube headers skew the AF, and the o2's give false readings. The problem is this, I need to go to a local dyno shop, and double check that the AF is still right on, Although i doubt it, since we deleted the o2's. I have lt1 edit, how can I adjust the AF ratio, while the car is in open loop? Thanks a Million!

 

my first bit of advice is never go back to that tuner he doesnt know what hes doing, when you make a car run in open loop you prevent it from using power enrichment mode. which is where your wide open a/f ratio comes. and your also tuning not leting the car correct for a lan condition if something happens.

my advice is do dome research on the board and program it yourself, all he did to make the car stay in open loop is up the temp range that the pcm has to see to go into closed loop.

and to coorect the "skewed" a/f ratio just adjust the maf table at the needed area.

are you haveing problems running rich at idle or something, what are the mods on your car, cam specs particulaly

 

oh, the tuner is great, by all means. We are just experimenting with running the car with no o2's. He tuned my car, mod list in sig, and it was great, but we are thinking that the o2's were giving false readings, so he tuned the o2's out, and now I have to get back on a dyno to see if the AF has changed. IF it has, how can I go about correcting the AF, if the car is only running in open loop?

 

There is an open loop AFR table in tunercat so i assume LT1 edit has the same thing.

 

Are the open loop tables tha same ones you adjust for PE mode

 

Nope. There is a seperate table for adjusting PE.

 

it seems the more I read about this, the more confused I get. Some say only adjust the Open Loop AFR vs Coolant Temp, some say Maf tables, some say VE tables. The car was tuned previously in both open and closed loop, like a normal tune. We started noticing that the o2's were giving false readings, therefore the car only runs in open loop now. So the VE tables were already tuned. But now I dont know what to adjust

 

Sounds like the car was running lean. As far as I know and most people who pay attention to these computers, the VE tables are not used during open or closed loop if you are running with a MAF sensor. Adjusting the MAF table affects both open and closed loop functioning. Adjusting the VE table does nothing and adjusting the open loop AFR table will only affect open loop. If you have datamaster logs then Id take a look at them or your .bin file to see where you set the target AFR in open loop.

 

where in datamaster does it state your target AF? is it AFGS? Thanks

 

It doesnt. In open loop the target is whatever the open loop target AFR is set depending on RPM and engine temp. In closed loop the target is always 14.7:1.

 

Thats one of the best posts Ive seen so far. It really explains alot.

 

im sorry...i have to dissagree with you. the ve table is all i use to get the fuel right. i have talked to joe overton about it (it cam when i bought the cam). the ve tables are the main fueling tables, and everything else is a multiplier of the ve tables.

ive tuned this way for about a year and my blms are at 127 or 128 every where accross the board.

i dont understand why peolpe think that the ve tables are not used, i mean in 94 they added the maf and left the ve tables, do you think that they will build a new pcm for added sensors and just happen to leave the ve tables, if its not used, why did they leave it. its used in the ls1 cars, so they put it in all the pcms sence 93 that i know of, but decided to not use it from 94 to 97.

you can check the box in the switch table and turn the maf off and use the ve tableswith speed density, right. so why wouldnt they be used with the maf.

ok heres another example i had a board member here send me a bin file and ask me to work on it for him and he sent me some scans of the car. i never made more than 2 degrees timing adjustments anywhere. and did alot to the ve tables. and the next weekend he droped .4 and picked up 5 mph. in simular weather. now he was cutting high 1.7s and that next time was cutting low 1.8s, so theres some mph but he drop in the et.

the ve tables work if people will use them.


all in all... do what your comfortable with. if you like using the maf then use it.


if you disagree with me thats fine.

on ls1.com the lt1 section there was a formula for everything the lt1 uses for fueling the car, and how to figure it and the ve tables were the main thing used in the formula

 

Well I just got off the phone with my tuner, and he is EXTREMELY knowledgable, and many of the cars he has tuned have made worldwide appearances on GM high tech, and he was an original beta tester for LT1 and LS1 edit. He said that the VE tables are used for the first 15-20 seconds of startup, and if the MAF were to "Crap out" it dafaults to the VE tables. As for a Open loop tune, Everything is in the PE vs. RPM for WOT, and WOT only.

 

Im not following you here. AFAIK there are 3 ways to change the AFR in open loop.. open loop AFR table, MAF scaling and changing the injector constant. PE vs RPM is only used in closed loop(so ive read but cant say for certain).

 

I'm getting confused, can anyone clarify this.

I know that you can change the A/F ratio with MAF tables in closed loop.
PE is considered open loop and is only for WOT, does it not use VE then?
When really is VE used then?

Do MAF table changes effect WOT?