Tweaking a ThunderMax for Cruising AFR

[superglide]

Hi,
I run a Thundermax with Autotune on my fairly stock 09 Sportster 883L - and love the thing!
I get good mileage from the engine at a consistent 47 miles per gallon.
I must spend about 95% of my riding @ 3 speeds (60km/h, 80km/h and 100km/h) and all with a steady throttle position.  I have marked the throttle with tape and pen and have a very good idea of the Throttle and RPM range I operate in, so thought why not tune for a more lean and closer to 14.7 AFR.

I am playing with the Air/Fuel Ratio @ TPS settings for the 2500, 2800, 3000 and 3300 RPM range, but not seeming to make any headway.

Has anyone actually done an exercise like this?  The attached is the map tweak I run for those 4 rpm settings.You cannot see attachments on this board.

[superglide]

I'm gutted...gonna have to put this one in the too hard bin as obviously EFI is so complicated that no one does this stuff at home.

[irishrover]

I'll take a stab at an answer, from what I've been taught the near perfect AFR for power and engine efficiently is between 12-13 AFR any leaner and you risk burning a valve lower and thats when you start carboning things up. you've heard the term running rich when your plugs are all black, and running lean when there all white and overheated looking, correct Fuel mixture (AFR) not only makes an engine run efficiently it helps keep it cool and a lot of other things     

[mayor]

I'll take a stab at an answer, from what I've been taught the near perfect AFR for power and engine efficiently is between 12-13 AFR any leaner and you risk burning a valve lower and thats when you start carboning things up. you've heard the term running rich when your plugs are all black, and running lean when there all white and overheated looking, correct Fuel mixture (AFR) not only makes an engine run efficiently it helps keep it cool and a lot of other things     

AFR for best power is around 12-13 AFR, but efficiency is closer to stoich of the fuel. Most of the modern efi calibrations are running 14.5-14.7 afr at cruise. 

It's been a long time since I ran a T-max, but I would generally set my lighter to mid cruise TPS afr around 14.2.  Much like what is shown on the chart.  I never trusted the T-max system enough to run any leaner than that. Another option you can try is to see if adding a degree or two of timing in that same area would improve milage and responsiveness. 


When you are looking at each RPM range chart, keep in mind that since these charts are throttle position based, the lower rpm chart sees peak engine load faster than the higher rpm chart so the curves for both timing and afr in these charts should likely not be the same. 

47 miles per gallon doesn't sound too far off to me.  I've had two 883's over the years (both carb bikes), and I think I was in the 45-54 mpg range most of the time depending on riding conditions. 

[q1svt]

 

except... unless you truly know the fuel you are using, I would not set lean in the 14.anything % on a performance engine.
[newer vehicles that require premium fuel have sensors and switch fuel mapping... TM you'll need to know and reflash a map]

Fuel   A/F   Lambda ()

Pure Gasoline Stoichiometric   14.7   1.000
Pure Gasoline Max Power Rich   12.5   0.8503
Pure Gasoline Max Power Lean   13.23   0.900

E10 Stoichiometric   14.08   1.000
E10 Max Power Rich   12.0   0.8523
E10 Max Power Lean   12.7008   0.9020

E15 Stoichiometric   13.79   1.000
E15 Max Power Rich   11.75   0.8521
E15 Max Power Lean   12.4362   0.9018

An old friend [salt racer] would test his street cars gasoline though out the year for fun... and years ago when the fuel pump began listing the gas pump containing up to 10% ethanol, his tests showed they generally had 6-7% for decades. 2019 his data showed they were @10% +-2%.