OK, here's where I got to with Dynamics and MAFless......
For the record, I've tried full OL-SD, OL-MAF and CL-MAF. All were tested over a considerable period of time each, with at least 3 or 4 months of driving in each mode. OL-SD was run for around a year while looking at many different settings. The current mode, CL-MAF is what I'll be staying with for now as I find it gives the best "all round" results for the driving that I do.
Ok, on to dynamics...
My View On Dynamics
Delving into the settings and how the amount of dynamic fuel was calculated, I came to the conclusion that dynamics and MAF measured airflow went hand in hand. The main table involved here is B2013, "Impact Factor, Airflow", this being a "Factor" effects the final calculation for dynamic fueling.
B2013 uses "Airflow ( gm/Sec in my case )" to provide a multiplier for the final amount of "dynamic" fuel to add when stomping on the throttle. If the MAF is disabled, then the table will always read "0 gm/Sec" and use that figure for all dynamic fueling calculations. There is no way to do fine tuning of the dynamics in this case because the airflow will never change.
OL-SD
In this mode, I found that the dynamics were a very fickle setting. They were sometimes working well and other times way too rich or too lean. This was where my views on B2013 really came from. I could set the dymanics up to work well for stomping on the throttle and moving up through the gears, but then had rich spikes when just cruising around. If I got the cruise settings working well, then I was lean if I gave it a bit. This resulted in a rough feeling change that felt like the car hesitated slightly when getting back on the throttle after a gear change.
My views on this are that you have 4 options....
- Set the dynamics up for WOT and live with the richness when cruising. This would be fine if you do a lot of track work or have a specific track only car / tune.
- Set the dynamics up for cruising, and live with the roughness of the gear change. If you really wanted, you could flat change between gears and hope you don't miss shift.........
- Set the dynamics up as a mix of both and be stuck in a position where neither is optimal, but neither is way off. It would be like getting some of the worst of both without really getting any of the good points though.
- Set the dynamics up for WOT and get an auto :p
So my thoughts were that while OL-SD worked very well for me most of the time, the dynamics issues were enough for me to go looking for something better.
OL-MAF
Enter the OL-MAF era. Given my thoughts on the MAF being the key to controlling the dynamics, I figured I should turn it back on and see how things went. After a year of OL-SD tuning, it took a very, very short time to dial in the MAF and get the dynamics close to perfect. With the MAF signal back and B2013 adjusted, I was able to control how much dynamic fuel was being applied. It was quite easy add more or less by looking as the MAF signal and the WB-O2 together. Shifts were noticeably better across the board and the car was more "fun" to drive. 0-100KMH times were on par with OL-SD and the best economy was achieved at 8.6Lt/100km or 26mpg. At this time I was also playing with lean cruise and seeing how things worked out there.
CL-MAF
On to CL-MAF, where some interesting results were observed. I originally went back to CL to work on some light throttle, low speed surging I had. I soon found that CL mode had some other benefits that helped dynamics, specifically with throttle close. Many people are only concerned with the initial stomp, to get the best power out of the motor. Not many care about the throttle close, but this can have significant effects on gear changes in a manual.
For example, if you go very rich on throttle close, than stomp on the throttle again for the next gear, you may end up way too rich and flood the motor for a second. This could see a hesitation in the motor as the clutch is let out making the change feel rough.
When the STFT's were turned back on, they helped control the return to "stoich" for the fueling. This helped control dynamic fueling on throttle close, not only on gear change but any time the ECM went back into CL mode after being in PE mode. The WB-O2 showed a much faster return to stoich than when STFT's were not being used.
I mentioned "lean cruise" earlier and should mention something about that, though it is a bit OT to dynamics. I think that lean cruise is a bit of a "misnomer" in the E38 - Gen IV due to the way the engine makes power. While the car can run fine at 15.5:1 AFR, it feels stronger if it runs a little richer. I've played with PE settings and found the car to pull up hills better when...
[list][*]lean cruise is active at 15.5:1 afr.[*]there is no change in the throttle possition[*]the ECM detects a rise in MAP readings and enables PE mode[*]commanded mixture becomes 13:1
[list]
The idea I have is that while you can run a leaner mixture, the engine will produce less power. This results in you using more throttle and therefore, more fuel. Running slightly richer results in a little more power, so you use less throttle.... The end result is that the final economy figures for both are similar, but the car feels more "effortless" when running a tad richer.
I just got back from a trip to Eden New South Wales, while towing a very full trailer. Running CL-MAF, I got a total average of 12.8Lt/100KM @ 98kmh, or 17.8mpg. That was a pretty good result given the size of the trailer.
Simon.