LTFT adjustment

[eboggs_jkvl]

Do you guys realize how much a person can get confused in here with a search on LTFT adjustment?

Ok, no wide band right now so I know I'm a sinner yes, I'll do penance in the morning but...

Trying to do this crap correctly. I loaded a stock MAF setup into the car (I've been using the MAF to adjust LTFTs and from what I see, that's a mortal sin... sigh...)

Ok, I drive and I average my LTFTs and get +8.0

Without doing SD or the other mumbo jumbo, can I simply highlight the VE (both) table and multiply by -10%? Will this pull the LTFTs down to the negative (or start to the negative) range.

Elmer

[eboggs_jkvl]

Yes or No.

[dfe1]

Yes or No.

Frankly, it's anybody's guess. I haven't ever seen a 1:1 correlation between fuel trim percentages and VE numbers. I've modified the VE table in areas where the trims were 6-7% on numerous occasions and VE changes of 3-4% were sometimes not enough and sometmes too much. I think this is actually normal because if you look at you data logs closely, you'll find different trim values for the same cells at different points in the log. The same is true of BEN data. Look at a cell in a BEN map and you'll see a significant difference between maximum and minimum values-- and that's in speed density, open loop mode.
I don't think you'll ever see dead consistency unless you can control ALL the variables, which is virtually impossible outside of a test lab. For what it's worth, I've had the best results by making small changes, testing and making further small changes until I achieve the desired results. And don't worry about tuning with the narrow band sensors. As long as you're working with 14.63 AFRs the narrow band sensors will get you really close.

[eboggs_jkvl]

Well, that was certainly a long "yes or no"

Ok, we'll give it a whirl and use the same logic -% to go leaner +% to go richer.

Thanks for the reply.

Elmer

[johnsZ06]

I've found the same thing as dfe1 and basically approach tuning the same way. I make adjustement small increments at a time until my VE table is close to where I want it. Then I attack other areas such as timing etc. to see if I can improve upon anything.

[Joel_SS]

Well, that was certainly a long "yes or no"

Ok, we'll give it a whirl and use the same logic -% to go leaner +% to go richer.

Thanks for the reply.

Elmer

FWIW. My LTFT were in the +20 range on average. I added 10% to my main ve table across the baord and got my LTFT down to about +11 on average. But from what I unerstand +11 is still way to high..

[BACKinBLACK]

if i remember correctly you actually want your ltft's to be around -12.

[dfe1]

Actually, LTFTs should be in the 0 to -4% range. Try working the areas that are the furthest off by adjusting 4-5% at a time. Once you make the corrections indicated by the scan logs, go back and blend in the adjacent cells. The overall map should be relatively smooth. If it looks like the Rocky Mountains, you have more work to do. Keep in mind that the values in each cell have a relationship with the values in adjacent cells.

[Joel_SS]

Good info, but I think my LTFT are off becasue I have an intake leak.

[BACKinBLACK]

well you are having better luck then i am. My ltft's were at least 14 and
15+% so i added 30% to the entire VE table and it really didnt help at all. It appears to have helped in some ranges and other ranges the LTFT's went even higher. So what do you guys recommend in this situation. I can send some one the copies of my logs and my tune if some one would look at them for me. i would post a link but i have no idea how to host it.

I would really appreciate some help here, this is really frustrating me and im about ready to park the car for long term bc of this. Also this seems to have been a problem since i changed my ypipe but the only leak i can find is about 3 feet down past the collectors and the O2 sensors so i didnt think it would affect it that much. Also i cant get it to idle worth a crap either anymore. I have logged and changes my RAFIG according but each time i add the amount it shows i need, the next time i log it, it goes up more so i keep adding. Im in the 33 range now at 20C.

Thanks for any help you guys can give, its really frustrating me

I have a 00 SS
F14 cam (232,234 .598,.598)
Fast 90 NW 90
Mac mids, ORY
and a bunch other supporting mods.