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Ok - I am finally going to sit down and try to spell this one out as best I can.
With our MAF based car tuning you have two “running numbers”; the fuel flow and the airflow. Once you start to play around with these (or even from the factory) they start to vary from their intended Volts to Value tables.
Before we address the Fuel Scaling - the first step in tuning a MAF car is to Scale the MAF. This involves correcting the MAF table from the g/sec or lb/min values and the voltage readings.
Here is a screen shot of a sample MAF Scale.
Step One: Cruising
- On your Base Fueling MAP; set the Lambda Values in the cruising range to 1 (AFR 14.7). Be sure to use the LOW LOAD areas in order to avoid engine damage. Additionally; you will need to ensure you are in Open Loop.
- For Closed Loop areas; set the lambda to 1 and compare your Fuel Trims to the % changes you are making in open loop. See more info on this below.
- Go find a flat level surface or dyno and get your car into a stable cruising speed and RPM. Hold it long enough for your AFR’s to become stable. Document the Volts, g/sec, measured Lambda like in the picture above.
- You can also log these runs and go over the average (like Baseline Does).
- Adjust your g/sec based on the % deviation from your target. Using a Target Lambda of 1 makes the math easier.
- Hit as many voltage cells as you can in your Low Load cruising areas and look for trends. If your 1-3 Voltage range is all trending low by 10%; go ahead and scale the ENTIRE MAF by that percentage in order to get closer to your targets when you do your WOT MAF Scaling.
- Once you get all your cruising areas within 1-2 Percent then you should be pretty good.
Step Two: WOT / Boost
- The process is basically the same but your obviously NOT going to set your Lambda to 1…. set your target Lambda to a safe number (this AFTER you may have already scaled the entire MAF by the percentage trend in the Cruising Area.)
- Zero the Throttle Enrichment Maps out - you just want to see the Base Map Fueling.
- Be careful about stabbing the GO Pedal; since your gonna get lean spikes without Enrichment.
- Get to your higher Load Areas - Boost and WOT; but don’t Punch the pedal, slowly get to WOT and hold it as long as you can.
- Use the same Math Process as Cruising but with a richer Lambda.
Step Three: Connect the Dots.
- Now that you have maybe 40-60% of your MAF scale done; connect the dots by filling in the blanks using the overall shape of your MAF curve.
- Try to make a nice smooth line. You can go back and re-tune the blanks later if you need to.
- Ideally you want to test each voltage in your table; but some interpolation is not going to be a big deal.
Step Four: Idle
- With radical cams / porting idle can be an issue…. the best way to go here is to get a g/sec trend for your car. Like the RX8; all 10-20 stock and boosted ones I have seen, all idle really close to 5 g/sec… so if your car idle g/sec is 7-8 then you can adjust it down to a known approximate value of (in my case 5). If your MAF numbers never get stable; you need to address the turbulence. If your engine is modified to the point you can never get it stable; then just do your best and shoot for best idle quality.
- You always do idle last because it can be the most challenging; but again if your % changes were all pretty much the same across the board then you can start with that % change at idle as well.
* Remember you don’t have to have the same numbers or trend line; if your cruising is scaled at 3-5% and your WOT areas end up being scaled at 15%; that is fine.
* Closed loop actual lambda readings can’t be used since the car will hit the target Lambda using Fuel Trims. So in closed loop cruising; look at your logged and stable LTFT instead.
Tuning ANY FUEL MAPS without first knowing your airflow readings are good is a waste - get your sensors right FIRST; then start in on your actual tuning.
*** With the new version of Baseline this process is now done automatically for you; simply drive in the same manner mentioned above and build as many logs as you can - then load them into Baseline and Select the button to Scale the MAF instead of the Autotune button. You will receive a table with MAF Volts and the % (M-Value) to apply to that airflow readings to scale your Mass Airflow Sensor. ***
Scaling Injectors: As for the primary injector; use your “known” MAF g/sec value and look at your fuel trims… if your MAF idle is 5 g/sec (good based on known similar cars) and your LTFT is +5%; there is a good chance that is the Fuel Injector scale…. go back and scale the P1 injector a bit and see if it cures it.