Project Evo Tuning (Got Mitsulogger Working + 4th Gear Pull Data)
I got Mitsulogger to work over the weekend. Awesome! It was a piece of cake and everything worked very well. The driver for the tactrix cable was already installed when I installed the OPENECU software, so the only thing I had to do was connect the cable from the car to the computer, start the program, and click "Start Logging."
The software had to make an "initialize" attempt to connect with the car CPU, and after a good 5 seconds, it creates a new log file and begun the logging of data.
I kept as many variable as I know "on" as I logged, but I've been told that the program will log slower with more values being tracked. I had the RPM, Speed, Load Value, AirFlow, Knock, and Timing Advance turned on. I might have left a few other things on just for kicks, and I went out for a drive.
Apparently in the MR, the advantage of the gear ratio really comes out in its 4th gear. Having heard that when comparing two similarly modified BPU Evo's (exhaust, intake pipes, boost controller, tune), a MR has been known to pull away from a GSR in 4th, I wanted to capture a 4th gear pull as my first significant log.
The night was around 40~50F and I did a 2500rpm to redline pull with 100% throttle committed. Here's the result from the pull:
Load Value vs. NarrowBand O2 Sensor
With the limited knowledge that I have, I have been told that the load value has a lot to do with the boost level of the car. Assuming that is correct, you can see that the full boost hits around a hair after 3000rpm and holds steadily, then starts to drop off as it approaches redline. It is important to understand load value because it will help you locate the "cell" that you will be modifying when you're changing the parameters of the engine maps. Seeing how full boost on a typically stock MR is set at 19psi and tapers to 16psi at redline, for now I will correlate the assumption as follows: 19psi~250Load :: 16psi~210Load. I'm sure there's something else about Load Value I need to know.
The NarrowBand O2, while not the recommended parameter to understand Air Fuel (A/F) ratio, nonetheless provides some insight. From the DSM tuning days, it is recommended for the car to hold a steady 0.940V at full throttle in 3rd gear (they only had 5 gears in the box). It is said that at that voltage, you have the best air to fuel ratio mixture for power. Apparently the stock EVO map is tuned similarly. As you can see, the A/F ratio climbed up as the rpm rose to provide a richer mixture (avoid detonation) to a final 0.940V. Just to note, no knock was detected throughout the pull.
AirFlow vs. Timing Advance
I know something about AirFlow since I have played around with an Apexi S-AFC before! Evo (like DSM) comes with a MAF sensor and will read in unit of Hz (hertz). More AirFlow means more hertz. Typically during a cruise, the AirFlow will read a range between 100-1000 Hz; the value is affected by throttle position, boost, oxygen density, engine efficiency, ect. Under heavy boosting, the Hz level will climb higher and higher all the way to redline.
As a reference, a typically modified DSM (16G with full supporting mods) will pull a 2000+Hz reading at over 21psi of boost. On a cold night the MAF may be overrun and the fuel cut will kick it (meaning the computer believes the car has reached its highest intake capacity with the factory equipped fuel system and shuts down the car before damage is done). The highest AirFlow value I logged was at 1503.31 Hz.
I don't know much about Timing Advance other than the fact that it is measured in the unit of degrees before TDC (top dead center), referring to the location where the spark ignites the fuel. The closer to TDC when the mixture is combusted, the more power is generated which makes sense since it is exploding from a "more" compressed state. More about that later.
AirFlow vs. Load Value
I wanted to compare AirFlow to Load Value because I wanted to see the correlation of how the boost characteristics of the turbocharger affect the two. As I can tell, the AirFlow continues to increase even though the boost (or what I am directly relating, the Load Value) decreases, which makes sense since air intake volume continues to increase as the rpm climbs higher. It does however look like the rate of change in the Load Value has a direct effect on the the slope of AirFlow, meaning more acceleration in "boost" equals steeper AirFlow slope. As the boost tapers, the AirFlow continues to increase but with a decreasing slope.
In Summary: Is the Evo well tuned from the factory?
Now, time to pause and think a little bit. I've been behind stock Evo's and smelled the nasty rich mixture that it spews out from the tailpipe. I've seen many rear bumpers (including mine) coated with filthy layer of black carbon sut, evidence of a poor A/F tune. On the contrary, it does hit a solid 0.940v A/F ratio toward the top RPM range. It should have the perfect fuel mixture right now, which means it is producing the max power with the given air and fuel. Can we squeeze more out of the Evo, Stock?
Next Step
I think there are two questions I will be seeking answers to next. Does the Evo have a poor factory tune afterall? Maybe it is not evident during the "open loop" state under WOT (wide open throttle). It could be possible that it occurs during partial throttle/partial boost conditions. I want to know.
The second question is, is there much to be gained out of a stock Evo without mods? With its existing near "perfect" A/F ratio at WOT, I shouldn't mess with it right? Well, that is true if and only if the air intake volume cannot be changed. How do we change air volume without messing around with bolt-ons? Right off the top of my head, I can think of two: Timing Advance and Boost, both of which can be altered using the OpenECU program.
For now, I'm going to continue to understand the car as much as possible using the Mitsulogger software before I jump into the horsepower game.
