Silly question: why would I want my A/F ration to be leaner as I give the bike throttle?

The map I'm looking at starts at a 13.0 and 12.50 at no throttle, but leans, to 14.6 out, for everything untile basically WOT 90-100%, where it goes back to 13.2 or lower...

Is that for fuel economy? If I lowered everything over, say 2k rpm to around 12.5 A/F ration would I get more power through the powerband? Instead of just down low and at WOT?

Thanks

 

14.6 in A/F screen uses the Closed Loop Bias mode which use the O2 sensors in cruiseareasjust be sure to raise the CLB table to richen it up
past the EPA friendly stock map settings put it in the 700 neighbor hood

 

K, so I put it in the 700 heighborhood, keeping the settings higher, but relative...on the CLB talble... but leaving the A/F at 14.6 sounds right?...

What do the closed loop bias numbers mean?
That 14.6 is as lean as it goes? Do i really want that?

 

I'm not sure I understand the CLB menu. I set the values higher than in the canned map, with the higher levels around 700 like you suggested, and the lower ones relative to that. What do these numbers mean? The defualts on the canned map matching my config were mid 500s (now replaced with about 700) to low 400s (now replaced by numbers in the 500s). Can you explain what I did?

Also I heard that a slightly lean (not as lean as it comes stock, just slightly lean) will deliver more power than a slightly rich mix. What do you think? Given I don't have a dino, am I'm, going to be off, which side should I err on?

Just picked up the cables today. Will be downlaoding my map when I get home from work!

 

Those numbers in the CLB tables are in millivolts as I recall. The max you can go is 798. If you max out each entry in the CLB tables with 798 or 7xx as you desire, it has the overall effect ofimproving the lean 14.6 EPA A/F ratios to 14.1. You will still see 14.6 in the A/F tables but the CLB values override these A/F ratios.I would try that move and see how your bike runs. Mine has the798 CLB entries and it runs great. I will get a dyno run later which is the proper time to adjust the A/F ratios and timing and not before then IMO.

 

Sorry, Herr Monk, I forgot to complete my answer. The stock 14.6 A/F ratio on the '07 and '08 bikes is what makes them run too hot.That's the EPA's doing and not something Harley dreamed up to make our rides less comfy. Getting a richer A/F mix within reason will cool down the heat and reduce potential pinging. If you went whole hog, so to speak, and got the A/F ratio down to 10 or so, you might start to wash down the cylinder walls and get SUV-like gas mileage. On the other hand, going toward a more lean condition than the already lean 14.6 might lead to a not so nice hole burned in a piston or burned valves if taken too far. Most tuners like to aim for something in the low to high 13's. So richer is the way to go.

 

Fow WOT wouldn't you want it a little lean? A little lean will give it more power than a little rich.

Lets pretend I'm tunning for drag racing

If I'm going WOT through all RPMs wouldn't I want that in the 14.1 range?

Why would the tuners be aiming so low?

 

Monk: At the lower rpms the fuel doesn't atomize efficiently, so the richer settings for lower rpm range; andleaning them as the rpms rise.

Also, by richening the a/f you can bump the timing a bit (2-3*) for a better burn up to the point where pinging occurs.

The SERT has good software explanations on the basics; makes for excellent reading.

 

Pingman gives the reason why the A/F ratios are put in the 13's by tuners: The richer mix is used in conjunction withtiming advance to max out performance up and down the RPM range. They advance the timing until it starts to ping on a dyno runthen back off a little. If you set your A/F at say13.2 without any timing advance, you probably wouldn't see any change in performance - just lower gas mileage and cooler running.

I agree that a little leaner will often get good performance but at the expense of more heat and possible pinging. It's a balancing act.I am using map 100 on my '08 Ultra with the CLB tables maxed out to 798 which gives 14.1 A/F. I have a SE AC and SE street performance mufflers in addition to the SERT. The bike runs good and gets low 40's for gas mileage.I am not going to mess with any other things like timing and A/R ratio changes. I'll let my tuner do that when I get a dynotune.

 

Monk: HD a/f SERT maps in '07 and '08 show lots of red for EPA compliance purposes: 14.7 a/f is the theoretical point at which all combustible gases are burned, so zero emissions of hydrocarbons. But one of the important functions of fuel is also to cool the combustion chamber.

Maximum torque is created at 13.6-13.8 a/f.

And, lastly, ignition timing effects the burn and therefore the emissions.

So, you can be at 14.1 (or any other a/f for that matter), with a given ignition timing event, but then add more fuel (richening the mixture) and advance the timing and get a burn that produces more power but yields the same 14.1 a/f in the example. SERT tuning done well is, in large part,a process of adding fuel and advancing timingto achieve the power the engine can provide, but avoiding pingingand the point where adding fuel and/or advancing timing don't improve performance.

TNBagger makes an excellent point for those of us, myself included, who are not qualified SERT tuners: use the map closest to what you have, max out the CLB tables so you aren't at 14.6 a/f and cool the motor; then let a competent tuner adjust the timing and a/f if you want more performance.

If you would like to see how EPA compliance has effected HD's tuning recommendations, take a look at the maps for '06 and earlier engines; you will see farfewer red cells demonstrating the richer a/f's they recommended for those older engineswithout the more restrictive EPA emissions constraints for the newer models.