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"Nicholassss, how have you achieved your AFR readings.

nicholas lawrence

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10 Apr 2014
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Frenchmeister said:
Nicholass,
How ,how have you achieved your AFR readings, stoitch is 14.7 I believe, running 17ish when cruising is pretty lean :eek:


This question was just asked by Frenchmeister in another topic. I started a new thread so I don't ruin the original post.


Frenchmeister you are correct. Most cars run (or should run) 14.7.1 AFR which is known as perfect Air Fuel mixture. If you look into the manufacturer software, you will see on cruise Porsche have set my engine to run a LOT leaner than the figures I am running at cruise.


This is the original fuel map by Porsche (Bosch) for 911 Carrera 2S 3.8 Litre 355hp
 

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You can see from factory the car runs 'leaner' than Stoich and is fine for most people.


What I have done is increased fuel slightly.. but it is still leaner than 14.7.1 AFR
 
You will see here 15.73 AFR - slightly leaner value than my signature, I must have changed it recently.
 

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If you can see the figures in the original fuel table - you can see how lean Porsche run the engines at cruise.


Not a good idea - ideally I would run 14.7.1 AFR but it really ruins economy. I could adjust this for good economy on cruise, but if EGT (Exhaust Gas Temperatures) rise after booting the car around, it will run exactly 14.7.1 AFR until the temperature falls back to what I would say is a safe level.



I hadn't thought of that before - thank you! (gets notepad).


The cars don't have functions like my last idea from factory - if we don't take the software apart and study the instruction we never know how it works. I like that new idea - maybe I will keep it lean and 'cheap' but not when temps are above 700deg for example. Keeping the car at 14.7.1 if I suddenly 'cruise' after thrashing its breasts (I hope that isn't a bad word mod? sorry) makes good sense.
 
To adjust software you use WinOLS. It is the only professional software out there.


Some people find it difficult, and opt for 'tick box' tuning software but you can never get inside the engine properly unless you buy DAMOS and search through every map - or enter the map names (in German) to find what you need.
 
When you have finished adjusting your software file, you need a programmer. For these engines I prefer AMT Cartech MPPS and you have two main buttons.


READ and WRITE :)
 

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For anybody interested in this boring stuff - here is a 'general' AFR guide for you to browse!
 

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The Stoiciometric (by mass) thread your doing is always going to be interesting Nicholasss.

:thumb:
 

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