Tuning FAST using datalog runs

[Johnny5]

Hi! Well, after numerous hurdles including a bad IAC driver chip (replaced under warranty) I am idling at 900 RPM and on the road. My next question deals with interpreting log data. I was expecting to be able to smooth out the 02 Correction and Actual A/F Ratio swings by making corrections to the VE table. I am correcting but still getting radical swings (datalog readings available on request). I don't know how smooth I can expect to get this graph so I'm looking for some experience in this area. Any other tuning tips are greatly appreciated.
Thanks, John

'99 Dakota, 318 5 spd, KRC 210 cam, 1.6 roller rockers, M-1 manifold, FAST w/WBO2, Vortech S2 blower, MSD6 ignition, 52mm throttle body, ported R/T heads, Gibson cat-back duals.

 

[Otto J]

when setting idle air fuel ratios ,especially with an aftermarket cam you make need to fatten it up to get it to idle smooth,my air fuel at idle is aroun 12.8 and it idle great,any leaner and it wonders, but also you may need to play with timing at idle also to get it real good, set me the file ill take a look
Otto

 

[bobc455]

Here's my experience-

For tuning WOT, record the run then overlay the run on your VE table and see where the O2 sensor is making corrections. Three or four trips down the track and you should be darn close. Be sure that you are recording target A/F, actual A/F, and O2 correction as part of your log.

Tuning regular "driving around" conditions is easier done with someone else at the wheel - have them drive on the highway (up hills, down hills, etc.) and just sit there and fiddle with the VE table to get those parameters right. Traveling between 55 and 75 MPH (depending on your local speed laws) will get you most of your critical driving parameters. You might also take it out of OD to get some of your higher RPM stuff done. After that, do the same thing at 35 MPH on back roads - a bit tougher, but you'll nail it after a few minutes.

If there are any cells that you don't hit while driving, you can kinda guess where they should be by just looking at the numbers in the adjacent cells.

Most cars will do fine once you are below 6-7% correction in most cells - some people will try for 5% correction or less, and some will take the time and effort to get the whole table to less than 3% correction. 3% is about the best you can ask for.

-Bob Cunningham
bobc@gnttype.org