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[killerbob]

OK - lets take this a little from the top

AFR: Air Fuel Ratio ... This is obviously the ratio between air and fuel.. In the different maps you will see pretty much identical AFR tables - alt least for 07 and 08 models. The numbers in the tabels usually goes from 12,5 to 14,6. The number is how many more times air compared to fuel.. So 12,5 means 12,5 times more air than fuel. Actually the term air is incorect as it is Oxygen. To acheive what is calles stoichiometric combustion you'll need 14,7 grams of oxygen for each gram of gas. In other words if you burn one gram of gas it will take 14,7 grams of oxygen for the gas to burn completely.... So as you'll figure out a lower value of AFR means that we supply more gas than the supplied oxygen can burn. If AFR is higher than 14,7 we'll have unburned oxygen in the exhaust and if the AFR is lower than 14,7 we'll have unburned gas in the exhaust....

Why would we want either ?... Well lower AFR than 14,7 is good for cooling of the engine. Gas that passes the engine unburnt hugely helps cooling. For this reason it is good when running wide open throttle to avoid overheating - and it is allso good when idling for long period of times.. However it polutes

Higher than 14,7 is not really good for anything except polution. It will heat up your engine and aircooled engines will have trouble... In liquid cooled engines lower than 14,7 works just fine - as they have no problem transporting the extra heat away - They do however not produce the maximum no of horsepower - but they polute less

On 07 later Harleys we have 02 sensors in the exhaustpipes. They meassure the amount of remaining oxygen in the exhaust and adjust slightly to make sure 14,6 is achieved in real life... (yes 14,6 - not 14,7). For this reason you'll have to set AFR to 14,6 in ranges where you want the O2 sensors to be active... If NOT set at 14,6 the O2 sensors are automaticly disabled

THE PROBLEM is - that to be able to use tha AFR table to ANYTHING you will have to know the amount of Oxygen in the engine under ALL circomstances. An engine with a 96 cu-in displacement will in theory transport 96 cu-in air through the engine pr. revolution (1586 cc's) So an engine with this displacement running 3000 rpm will pump - in theory 3000 times 1,586 litres = 4758 litres of air every minut !!! (IN THEORY) ... Problem is that the intake, the aircleaner, the valves, the speed of the engine, the exhaust and a couple of other factors all influences on the ACTUAL amount of air transported

Therefore you'll see the really big difference in the maps in the supertuner in the tables "VE" VE is Volumetric efficiency and is entered in the supertuner in percent. This is the hard part - and actually THIS is what we want the tuner on a dyno to meassure in real life. When we use the supplied maps from HD we do not take into account that EVERY engine is slightly different and that it gets worse when we add different A/C's and Exhausts. In my map VE for the front cylinder at 3000 rpm and 20% Trottle the VE is 99% ... So actually it is pretty close to the theoretical value - but at 10% throttle the VE is only 84% (throttle restricts the air)

So - what the Supertuner/EFI does is to look in the AFR table for the actual RPM and manifold pressure to know what AFR we want - Then it looks into the VE tables to know how much air the engine can transport at the given rpm and throttle possition. It allso looks at engine temperature and the tabel for enrichment at low temperatures and it looks at the atmosferic pressure to know the amount of oxygen in the transported air.. All these informations are used to calculate how long the fuel injectors should be left open at each air intake in each cylinder. to achieve the desired AFR

If you go fast at 6000 rpm these lookups are performed 12000 times per minut or 200 times per second...do that with your calculator !! ;-)

So the important thing is to find a map that is as close to your engine/A/C/Exhaust setup as possible... Even if you find a perfect match - the actual VE of YOUR engine IS slightly different than the VE's in the map.. THIS is why HD have put in the O2 sensors - to have some feedback how things actually went.

I found a perfect match for my engine (Touring Exhaust, 1690 SE, SE Aircleaner, 255 cams) - however I have modified my AFR map as follows. All cells that were 14,6 (o2 sensor enabled) I have set to 14,0. AFR around Idle is set to 13.0 - the rest is left unchanged

The ideal thing is to get at proper tune at a Dyno to know the actual VE's of your engine. But you really can't do that on a new engine - you'll have to wait untill it is run-in... So I did what I did to ensure NO lean spots and wanted to complete with a proper tune... However now my bike is fully run in (7000 miles) - but it runs so darn good that I have trouble justifying a day on the dyno... I have had it on a Dyno to meassure RWHP --- 88 HP - 97 torque (135 nm) ... Maybe I can get a little more with a proper tune - but I doubt that my butt -dyno can tell...

Downside of my AFR is that it is pretty thirsty .. Will have to do something about that (Higher AFR)

Hope this helps

Boja53 ... I'm running 920 rpms idle - No problems at all.. Try it - if it doesn't work for you something else is not set right