User Tools

Site Tools


maftcalibrationbyloggedboost

MAFT Calibration by Logged Boost

The following has been copied from the DSMLink forums. The original (courtesy of Ron Francis) may be found at in this user support forum thread (registered DSMLink users only). The text below has been updated to include 1g-specific info, as well as other minor edits.

Preface

These instructions are for those without a WBO2 who are logging an external boost source. This method tends to produce much more accurate airflow readings. Although tuning by WBO2 works, this method is superior. You can use any accurate external boost source that DSMLink supports with this method. Happy Tuning!

Assumptions

  • Zero boost/vacuum leaks
  • You know the correct deadtime and global fuel settings for your injectors, for your car.
  • If you are using recommended injector settings, your base fuel pressure is 43.5psi.
  • You're not over running your fuel pressure regulator.
  • Your fuel system is adequate for your application.

Items to log

  • RPM
  • LTFT-Lo
  • LTFT-Mid (2g) +OR+ LTFT-Hi (1g)
  • STFT
  • Logged boost source (GM3Bar, GreddyBoost, etc.)
  • BoostEst
  • MAFRaw

MAFT Set-Up

  1. Set MAFT base fuel setting for stock injectors (450's).
  2. Set MAFT idle, mid & WOT knobs to zero.
  3. Clamp IAT/Baro signal in DSMlink under ECU→Miscellaneous.

Idle Tuning (LTFT-Lo) 50hz

  1. Set injector fuel settings to what you were already running them at or what is recommended in the DSMLink guide (or refer to the base injector data page)
  2. While idling the engine watch the LTFT-Lo and STFT.
    • If LTFT-Lo fuel trims are positive, add air at the 50 Hz point in the airflow table.
    • If LTFT-Lo fuel trims are negative, subtract air at the 50 Hz point in the airflow table.
    • Adjust the airflow 1% for each 1% fuel trims are adjusting fuel.

Example: If LTFT-Lo is at a constant +5%, add +5% to the 50 Hz slider in the airflow table. If the LTFT-Lo is at a constant +12.5% and STFT is at +13%, add +26% to the 50 Hz slider in the airflow table. Repeat until you are happy.

Rev Tuning (STFT) 150hz

  1. After you are done with idle tuning, rev the engine and keep it at the 150 Hz level.
  2. Watch your STFT's for needed adjustments.
    • If STFT fuel trims are positive, add air at the 150 Hz point in the airflow table.
    • If STFT fuel trims are negative, subtract air at the 150 Hz point in the airflow table.
    • Adjust the airflow 1% for each 1% fuel trims are adjusting fuel.

Example: If STFT’s are bouncing between +14% and +16%, add +15% to the 150 Hz slider in the airflow table. Repeat until you are happy.

Cruise Tuning (LTFT-Mid +OR+ LTFT-Hi) 250hz

  1. Drive on the freeway at a steady speed to get stable fuel trims.
    • If the fuel trim is positive, add air at the 250 Hz point in the airflow table.
    • If fuel trim is negative, subtract air at the 250 Hz point in the airflow table.
    • Adjust the airflow 1% for each 1% fuel trims are adjusting fuel.

Example: If the fuel trim is at a constant +7%, add +7% to the 250 Hz slider in the airflow table. Repeat until you are happy.

WOT Tuning (Logged boost, BoostEst, & MAFRaw) 400hz, 800hz, 1200hz, 1600hz, 2000hz, 2400hz

  1. It is easier to do this if ““BoostEst”” is right above logged boost in the DSMLink application.
  2. After a 3rd gear pull from 1500rpm to redline study the relationship between ““BoostEst”” and logged boost at each ““MAFRaw”” Hz point.
  3. Adjust the airflow at each ““MAFRaw”” Hz point in the Airflow Table using the associated Hz point in the log.
    • When BoostEst is higher than logged boost, subtract airflow.
    • When BoostEst is lower than logged boost, add airflow.
    • Make small changes at one time and then just repeat until the BoostEst matches the logged boost, or it is close enough and you give up.

Notes

  • With this method my fuel trims are both with-in 1% of zero and my A/F Ratio are WBO2 shadow each other with-in 1-2% for an entire pull.
  • LTFT-Lo tends to be slightly unstable, so do not go crazy trying to get it perfect. With-in 3% of each other and with-in 5% of zero is acceptable.
  • Some changes to the Airflow Table at the 150 Hz point maybe needed when “cruise tuning.”
  • Adjustment to any slider in the airflow table WILL affect the two sliders adjacent to it.
  • For me, getting the 400 Hz point perfect created a nasty dip at the untunable 500-600 Hz range. Tuning the 500 Hz point using the 400 Hz point in the Airflow Table worked much better.
  • Sometimes tuning using a HZ point 100 more than what you are tuning, works better. So, instead of 1200 Hz sometimes using 1300 Hz works better.
  • This is not the “Ideal, Perfect” way to tune a MAFT, but it was sure easy. As with any tuning the main problem arises with boost leaks and fuel delivery discrepancies. So long as you have no boost leaks and your fuel system is working properly, this is an extremely easy and viable way to tune a MAFT.
maftcalibrationbyloggedboost.txt · Last modified: 2008/01/24 07:34 by twdorris