# Formula to get correct afr? could use some help tuning

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**1**3.0 BAR

Thread Starter

Join Date: Dec 2005

Posts: 2,081

**Formula to get correct afr? could use some help tuning**

Say I'm between 15.5-16.5 afr at idle, and i would like to make it about 14.5-15.0, is there a formula I can use to find the percent I should add in for the values on my map in crome? Or do you just guess and screw around with it for awhile until the afr's are good? I'm a newb to tuning and would like some pointers on how to get a decent afr.

Its in the mid 15-16 range in most of vacuum and high 12/low 13's in boost, I know this is lean and would like to know the percent to add to my fuel tables.

If you know of any good read's could you post up links please, i've read through xenocrons, and another one on uberdata, but this is all still a little confusing to me. Any help is appreciated thank you.

Its in the mid 15-16 range in most of vacuum and high 12/low 13's in boost, I know this is lean and would like to know the percent to add to my fuel tables.

If you know of any good read's could you post up links please, i've read through xenocrons, and another one on uberdata, but this is all still a little confusing to me. Any help is appreciated thank you.

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**4**0.0 BAR

Join Date: May 2005

Posts: 0

**Re: Formula to get correct afr? could use some help tuning**

Originally Posted by

********8.6% change= 1 AFR point change.

Originally Posted by

**MADMAX**
Originally Posted by

********8.6% equals 1:1 AFR change, so if you're at 10.5:1 AFR and you pull 8.6%, you would then be at 11.5:1

For fuel since the values are inverted to the A/F

(Current A/F - Target A/F) / (Current A/F) = % Change in fuel

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**5**3.0 BAR

Join Date: Apr 2004

Posts: 9,802

**Re: Formula to get correct afr? could use some help tuning**

Originally Posted by

**MADMAX**I thought I went over this with you once already. Go back to math class ****.

Go back to math class buddy. 10.5 to 11.5 is 9.5% difference. The only time a 1.0 A/F change would happen with 8.6% change in fuel would be if you started at 11.63 A/F.

For fuel since the values are inverted to the A/F

(Current A/F - Target A/F) / (Current A/F) = % Change in fuel

Go back to math class buddy. 10.5 to 11.5 is 9.5% difference. The only time a 1.0 A/F change would happen with 8.6% change in fuel would be if you started at 11.63 A/F.

For fuel since the values are inverted to the A/F

(Current A/F - Target A/F) / (Current A/F) = % Change in fuel

it must feel so great to be right on the internet...even got to repost something from a post in a thread that i never read.

im so envious.

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**6**3.0 BAR

Thread Starter

Join Date: Dec 2005

Posts: 2,081

**Re: Formula to get correct afr? could use some help tuning**

I guess that's the formula i'm looking for, damn its gonna take a long time to tune this bitch. there has to be an easier way to do it without crome pro, I'm using crome and ecu control.

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**7**0.0 BAR

Join Date: Jun 2005

Location: WA

Posts: 0

**Re: Formula to get correct afr? could use some help tuning**

you dont even need to datalog to tune.

do it by feel, lol. its not too hard. just watch your afr's and rpms and how much throttle you're at, and adjust it by that.

do it by feel, lol. its not too hard. just watch your afr's and rpms and how much throttle you're at, and adjust it by that.

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**8**1.5 BAR

Join Date: Apr 2006

Posts: 676

**Re: Formula to get correct afr? could use some help tuning**

Get a damn Ostrich. Setup Crome to run in real time, then have a buddy drive the car while you look at the wideband. Make small changes often and you can have a pretty solid tune in about an hour.

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**10**0.0 BAR

Join Date: May 2005

Posts: 0

**Re: Formula to get correct afr? could use some help tuning**

Originally Posted by

********---- yourself dickstick.

it must feel so great to be right on the internet...even got to repost something from a post in a thread that i never read.

im so envious.

it must feel so great to be right on the internet...even got to repost something from a post in a thread that i never read.

im so envious.

You're one of the biggest ******** on here, so when I see a time to clown you, I will.