Single channel O2

[Ed Wright]

Originally Posted by Michael Beard

FAST XFI. Currently running in Alpha-N, closed loop, Target A/F at 12.5. Got it to 13.3 on Run #3 of the weekend at MIR, and it wouldn't get out of it's own way.

Question is, is 13.3 to 13.2 a big jump, is 13.3 to 13.0 a big jump, or is 13.3 to 12.5 a big jump? How much is 1,000' DA change likely to affect the A/F ratio (ballpark)?

Subtract 8% at the RPM that is 13.3 to get 12.5. Some guys have 1000' tunes, 2000' tunes, etc. Many simply adjust fuel pressure. 1 to 2 psi per 1000' is pretty common.

[Signman]

Ed & Michael

Michael: Do you have internal Data Logging?

Ed: Used to run the Accell Gen 6 Alpha N. Drove me up the wall when moving from track to track. The best info I ever got was to have a map for each Baro reading you will see. Had some other issues with EFI and have since made wholesale changes for the better.

[Ed Wright]

Frank, I run mine in speed density mode. Almost nobody else does. I set my maps to 3 Kpa and 500 RPM break points. It runs off a different row when the baro changes. It takes a while to run it in that many different conditions, but once you have it pretty much adjusts it's self. Everybody else I know uses Alpha N. It's for sure simpler.

[Signman]

"Frank, I run mine in speed density mode. Almost nobody else does. I set my maps to 3 Kpa and 500 RPM break points. It runs off a different row when the baro changes. It takes a while to run it in that many different conditions, but once you have it pretty much adjusts it's self. Everybody else I know uses Alpha N. It's for sure simpler."

Am now using Fast XFI 2.0 Set it up on chassis dyno to run Speed Density. Last weekend tried Load Based Speed Density but will more likely go back this weekend. Your comment about needing to let it see different conditions over time makes sense.
Many are using Alpha N for simplicity but if you go on the right chassis dyno (tuner) your high gear map will be good from the start. All the runs and data logging necessary to get close will cost you more than the day on the dyno!!!

The issue am having a lean spike when it leaves (footbraking) Then it goes rich and then lean again. Tough deciding how much acceleration enrichment is too much or not enough, and with the short time it takes to go from stage RPM to stall to shift point, exactly which cells in the map need to be leaner and richer. Considering the delay that has to exist from the actually event, when the O2 sees the ex gas plus the electronic delays. On the data log the event is well under 2 seconds. Even with my slow s**t.

[Ed Wright]

Frank, when you play your log back, if you will pull up your fuel map, put it at the top, make it about half the screen size, then the log at the bottom, when you click the left arrow to scroll through it, there will be a "bubble" appear on the cell the ECU is looking at as you scroll through it. I don’t use load indexed speed density, that always goes to the top row, just like AlphaN. I mean regular speed density, Baro changes your manifold vacuum and MAP values. Load indexed will not. May as well use AlphaN as that, imho. On the dyno all you can do is tune for the weather that day. The Great Bend Kansas points race recently is the first time mine has used the 3rd row down in the map. Start out with 2% difference per row, dropping as you go down, in the top 3 or 4 rows of the fuel map for a starting place. Won't be all that far off. When you tune in different air, just tune the row at which it's looking. Your numbers will be bigger around the torque peak. That is normal. Leave the already tuned cells alone. Then log driving down the return road, with it warmed up. Shoot for about 14-1 to 14.5-1 there. Mine likes to leave in the mid-12s. Yours may be different. The return road tuning should also apply to AlphaN. That part can be done on a variable load dyno. A couple of feet of collector extension will make idle and low speed tuning accurate. Open collector will causes bogus lean numbers. Might look right, but hardly ever are.