| control is primarily based on engine RPM and MASS Airflow. In high load conditions, the ECU is in open loop and does not read from the O2 sensors in this condition. It is operating strictly on a calculation that measures the mass of air entering the engine (via the MAS), calculates how much of that is entering per stroke (through the load calculation of airflow divided by RPM), and references the fuel map to see how much "extra" fuel you want from a 14.7:1 A/F mixture. At higher elevations such as where you are at, even at 15psi, you are operating at the equivalent of around 12.5-13psi of air massflow into the engine at sealevel. Although the gauge says "15psi", you aren't flowing the equivalent air mass of 15psi if you were at sea level. At lower air mass flow levels, the ECU isn't going to run the car as rich since it isn't necessary to do so. It isn't until you increase the air mass flow that you will see the mixture fall more towards 11.5:1 or so. If you were to continue to raise the boost level until you were operating at a sea-level 15psi equivalent air mass flow, the trend you see in your A/F curve would continue to drop into the 11's. In addition to this, the SAE correction factor works pretty well for naturally aspirated vehicles, but it fails with forced induction intercooled systems. The readings are typically higher at high elevations simply because of the correction that their formula calculates into the actual numbers. The formula doesn't take the fact that a forced induction intercooled system will not lose nearly as much efficiency as a naturally asspirated setup will as you begin to thin the atmospheric air (higher elevation). So, it overcorrects and puts the numbers considerably higher than it should be. What I would suggest you guys do that are way up there is to NOT correct the dynochart numbers - get the uncorrected values and then make your own correction based on the difference in the actual airmass flow level that your gauge is equivalent to at sea level. As an example:
If your uncorrected values at 15psi (on your gauge up there) are 310RWHP/330RWTQ, you are actually only pushing the equivalent of about 12.5-13psi of mass airflow at sea level. So in this case, you would say that your car is making 310RWHP/330RWTQ at 12.5-13psi. Take the numbers for what they are - uncorrected numbers are what the car is actually making to the wheels. Then simply say "I was running "X" boost pressure and this is the power it made" , substituting "X" for the corrected boost pressure. I have seen other dyno charts from my programs that do the same exact thing. This leads other people in your area to believe that my programs are "too lean" and that they aren't suitable for high elevation operation, which is an incorrect statement. They aren't taking the fact that the air is thinner and you are moving less of it into the engine at typical boost levels, so the ECU isn't going to deliver as much fuel because it simply isn't necessary - you aren't making the power that the corrected dynocharts are saying you are, which misleads people even further to say that the programs are too lean. In this case, I see you have a JWT ECU in your car, which I would hope people will factor into their understanding of what I am saying here. It really doesn't matter if you have a JWT ECU or one of mine, or any other ECU upgrade - you are still going to see the same trends of "higher than normal corrected values tied in with some scary-lean looking A/F curves. Just dont be concerned unless you see A/F levels significantly leaner - it isn't as it appears.
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