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Author Topic: Air/Fuel Ratio  (Read 5089 times)

Offline ktlstar

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Air/Fuel Ratio
« on: December 30, 2011, 09:50:55 am »
What is the AFR guideline for the GTi's ? I always thought 11.8 AFR is the true ratio in any turbo car, however reading on audi forumn and reading data logs there Lamba value is showing around 0.85 at full WOT x 14.7 = 12.5 AFR.

Is this not too lean for the car ?

I understand the leaner it is the more power can be made, SO if you can run 12.5 AFR lean, you just go to look out for the (Cylinders) CF timing being effected ?

^ Is this correct ?

Thanks



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Offline heavyd

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Re: Air/Fuel Ratio
« Reply #1 on: December 30, 2011, 10:37:20 am »
From what I've read, tuners tend to try to run on the rich side to cool the cylinders down. heres one of the AFR logs from one of my first shark stage 3 maps

« Last Edit: December 30, 2011, 10:48:08 am by heavyd »
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Offline ktlstar

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Re: Air/Fuel Ratio
« Reply #2 on: December 30, 2011, 10:47:10 am »
Yours is bang on  11.8 if not richer at higher revs. However My log (revo) and some S3's logs that iv seen are around 12.5afr at full WOT. I'v always used the 11.8 at full WOT from my previous turbo cars.

Richer is always gonna be safe however less power is gonna be made! But what would you rather a broken engine or an engine that will last ?

 If you are taking fuel out does this show on the Correction factors on the cylinders so you can put more fuel back in if its effecting your cylinders ?.

I mean you can proberly run 13afr make loads of power but it does not show up on your cylinders. (engine knock)

You mentiond that your broken engine was because of running to lean. It might make sense ?

Have you got a log on Revo software i.e stage 2 or 2+?









« Last Edit: December 30, 2011, 10:52:06 am by ktlstar »
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Offline heavyd

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Re: Air/Fuel Ratio
« Reply #3 on: December 30, 2011, 10:58:28 am »
I was getting timing pull like this shows below.
I wasnt running lean.
I havent got any AFR logs from when I was running revo stage 2+ unfortunately
If you are going to run lean, your best off checking your EGTs.
I would rather run a safe map and keep the engine stable than run loads of power and going through what I have....

« Last Edit: December 30, 2011, 11:00:25 am by heavyd »
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Offline ktlstar

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Re: Air/Fuel Ratio
« Reply #4 on: December 30, 2011, 01:34:32 pm »
So do we know what AFR we should be aiming for ? As it seems 12.5 maybe ok ?
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Offline bacillus

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Re: Air/Fuel Ratio
« Reply #5 on: December 30, 2011, 02:09:11 pm »
I like to see a lambda value of ~0.8 at wot...
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Offline PDT

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Re: Air/Fuel Ratio
« Reply #6 on: December 31, 2011, 01:11:15 pm »
Quote from: ktlstar on December 30, 2011, 01:34:32 pm
So do we know what AFR we should be aiming for ? As it seems 12.5 maybe ok ?


This is where dyno testing comes in, by logging egt's, afr, ign advance and torque you can optimise your afr's. Without use of the dyno you wont find optimum AFR.
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