I'm almost ready to buy an AF-XIED but getting the 8GS out for the first rides of the spring, I'm reminded how flat low RPM feels. At around 5000RPM, there is a significant increase in torque that is felt all the way to fuel cut. Is this the change over point from Close to Open loop fuelling, or is it just a point where VE/intake resonance really comes into play? Bike is bone stock (except Uni foam filter and Iridium plugs). Does this unit help flatten out that torque curve? It has plenty of pull in the to end, but almost feels like the DR up to 5000.
First question is hard to narrow down. Really the only way is if you dyno the bike hooked up to a gs-911. Personally I dont think so. Imho..... the 8GS have some aggressive cams, and it is designed as such. The HP/TQ curves do mellow out, and power is more stable, mostly due to correct fueling, not a starved engine close the OEM stock AFR of 14.8.
I could go and dig out some GS-911 data on the closed/open loop question but the point at which the BMSK changes over is based on throttle angle and TPS combined. Above half throttle, or above 5-6000 rpm and you'll likely be running open loop with long term fuel trims applied. The mixture is richer and the spark advance is different. Any lambda-shifting device (LC-1/2 or AF-XIED) will add fuel at low and mid RPMs and flatten the torque curve. Below are a couple posts from earlier in the thread that are typical of many similar comments I've seen.
Mixture yes, but I was not under the opinion that the XIED changed the ignition advance on the 8GS...... What did I miss Roger.....
Hey Erling, You didn't miss a thing. The first paragraph isn't talking about the LC-1/2 or AF-XIED, it's only referring to what happens as throttle angle widens and RPM increases.
Well for the price, I'm just going to have to try one. Thanks to all the contributors for your time, research and patience in repeatedly trying to explain the basics of how EFI works . good old fashioned book learnin https://books.google.ca/books?id=KZSbG-dVT3YC&printsec=frontcover&dq=motorbooks+workshop&hl=en&sa=X&ei=kNMnVbyPJpK0sATPp4D4Dw&ved=0CE8Q6AEwBzgK#v=onepage&q=motorbooks%20workshop&f=false http://books.google.ca/books/about/How_to_Tune_and_Modify_Motorcycle_Engine.html?id=r4CcIjtDU5QC&redir_esc=y I know none of that above applies specifically to our machines, but the principals are all the same. As I've been mulling this over, it occurred to me that this unit will actually add some knock resistance. The fact that the BMSK has NO knock feedback is a bit scary, and leaves a great deal of timing/power on the table. Too bad. This little gizmo will make me feel a bit safer if I'm stuck in the bush with nothing but purple farm gas.
Mixture Adaptation, Short/Long Term Trims, ECU Learning Exposed by the GS-911! The Short Version The GS-911 now reports long term trims for the BMSK which show beyond a shadow of a doubt that the BMW fueling strategy includes Long Term Trims, learned in Closed Loop by using the stock O2 sensor, which are applied to the entire fuel table. This means that the ECU learns about all fueling errors and most attempts to alter fueling on a stock bike. It learns about fueling changes (other than those made to the O2 sensor, e.g. LC-2 or AF-XIED) and brings fueling back to stock AFR. Although this data was taken on an R1200GS with BMSK, I also have a data set from an F800GS in Colorado, showing the same Long Term Trims. The Long Version For the past four years I've been explaining how the Motronic, BMSK and BMSX use the narrowband O2 (lambda) sensor to control combustion AFR in the Closed Loop area of the fuel table to accurate achieve lambda=1 (14.7:1 AFR for gasoline). It also allows those ECUs to learn how much correction is required throughout the Close Loop area and to therefore "learn" long term correction factors (mixture adaptations) that are applied throughout the fuel map--at idle, acceleration, all the way to full throttle--all the time. Measurements reported throughout this thread have demonstrated the effects of this "learning" and many readers here have come to realize that our BMW motorcycle ECUs perform this powerful function. It allows the ECUs to adapt to changing conditions in the engine as it wears, as the fuel injectors and air filter accumulate deposits, imperfections and errors in all sensors, voltage deviations (even due to a failed alternator), fuel pressure changes, and even adapt to gasoline with ethanol. This mixture adaptation also limits the ways in which you can alter fueling: modify the air temperature sensor and the ECU corrects fueling. Change the fuel pressure regulator and it learns about and fixes that too. Even modify values in the ECU fuel table in the onboard chip, and it corrects for that. However, alter the O2 sensor for richer or leaner fueling and the ECU obligingly shifts the entire fuel table automatically--e.g. LC-2 or AF-XIED. (Another way to alter fueling successfully is to disconnect the O2 sensors & add a piggy back controller. This approach puts the ECU into a Limp-Home mode.) In spite of the Bosch and BMW documentation mentioning mixture adaptation and long term trims, and even given the measurements of it shown in this thread and others, there are still many riders who aren't fully convinced. After all, until now there haven't been any gauges or displays which explicitly show the long term and short term trims at the heart of this "learning" capability. Recently Hexcode SA, maker of the powerful GS-911 diagnostic tool, have added new realtime values to the long list reported for the BMSK ECU. In addition to the short term trims shown for the Closed Loop area (Lambda Correction Factors 1&2), the GS-911 now reports four new long term trims: Additive Trims 1 & 2 and Multiplicative Trims 1 & 2. The "1" trims are for the right cylinder and the "2" trims are for the left cylinder. A colleague in the UK who has an R1200GS and owns a GS-911 and dual LM-2s (which can record AFR data and other info for both cylinders) with Wideband O2 sensors added to each exhaust. He took a ride the other day and sent in the LM-2 and GS-911 data, which includes a 13 second wide-open-throttle (WOT) run in 6th gear. This 6th gear "pull” shows for certain that long term trims exist and that they are applied to open loop fueling, right up to WOT. Have a look at the table below. The data clearly shows the BMSK going open loop (highlighted in yellow) where the lambda control factors set to 1 (set to 1 there is no increase or decrease in fuel due to the immediate values of the O2 sensor) and clearly shows the application of the Long Term Multiplicative Trim at WOT. To understand the Multiplicative Trim, the number in the Injection Time column is multiplied by the number in the Multiplicative Trim column. Taking the first highlighted row, the 10.56 mS injection time is multiplied by 1.12 for the right cylinder and by 1.03 for the left cylinder resulting in Injection Times of 11.8 mS for the right cylinder and 10.9 mS for the left cylinder. In other words, the long term trim learned at lower power levels has been applied to this Open Loop area of fueling. If you’re surprised that there is this much difference between the left and right cylinders, he confirmed that left and right cylinders had AFRs which tracked each other very closely by making an actual AFR measurement on both cylinders at the same time the GS-911 data was gathered. Going a bit further, the multiplicative trim is not a single value for the whole but map but a table of values (how many have not yet been determined). There are 5 different long term multiplicative trims in this "pull" between 1800 and 4700 RPM. So the long term trim table is quite a bit larger than we'd expected. There are also two long term additive trim types, for which there is a corresponding table of values. These additive long term trims affect small throttle angles and idle. The multiplicative trims affect cruising, acceleration and wider throttle angles. [Summary] This new GS-911 capability is an exciting development in the understanding of BMWs fueling strategy. It demonstrates clearly the complex ways in which its ECUs process data gathered in the Closed Loop fueling area and apply it to the entire fuel table, including acceleration and starting. At the moment, Hexcode has not added the collection of this data for the newer liquid cooled Boxers or for the older Motronics but the effect of the trims has been accurately measured on all bikes. If you care about this make sure to let Hexcode know that you’d like to see this data for your bikes too. (The BMSK is used on many different BMW bikes including the F800GS.) As I receive more data from the field, I will add any important insights that are found.
Hi Roger. I have had the AF-Xied for about 18 months and 5,000 miles now. I am still impressed. The engine has gotten smoother and it feels like the power curve has improved into the higher RPM range. Early on I tried a 17 tooth sprocket and liked it so much that I kept it. It is not for the hard core, but the bike will do some pretty steep dirt grades because the engine will lug and the abrupt throttle is all but gone. I am riding to Utah in 2 weeks, I will get to test for mileage at higher speeds. Not much effect so far. I got a question about open loop fueling ratio's with the AF-Xied. Since they adapt to whatever is added to closed loop, is it logical that the same percentage increase in closed loop is added to the stock maps in open loop?
That is what happens the long term trims are used to increase/decrease the stock maps in open loop. Maybe a better way to think about it is like this: 1) Injection Time obtained from Fuel Map based on RPM and TPS -- always used, never changed 2) Injection Time adjusted for Air Temp, Barometric Pressure and Battery Voltage 3) Injection Time further Adjusted by Long Term Trim Table (Multiplicative and Additive) 4) If the ECU can run the Closed Loop program--engine is warm, throttle is below 50% and isn't moving too fast--make a final adjustment to Injection Time 5) Injector Pulse sent by BMSK to Injector So looking at that flow you can see that the Fuel Maps never change, what changes are the adjustments in Steps 3 and 4.
I know that the modifications are all about how long the injectors are held open. The question was, if a setting difference is 3/6% in closed loop, can I expect a like difference in open loop? If for no other reason, every Dyno result I have seen, shows a drop in HP and Torque between 3,500 and 4,500 rpm. If it fixes that, it is well worth buying.
As I mentioned above, that is what happens. If you average the long term trims in the yellow highlighted area of my chart above, they average a 5.5% fuel addition. The bike that is being tested has dual AF-XIEDs on setting 7. The 5.5% is very close to the amount that setting 7 adds. The rest of the difference is specifics of the bike itself.
Do you have a handle on how fast corrections are learned? I'd like to try do some back to back pocket-dyno testing (setting 1, 7, 8, same road, one after the other) but the learning curve will leave a lot on the table (not to suggest that the iphone is an accurate dyno to begin with). Thank you again for all your work on this Roger. I'm still very impressed with the improvement this little bit of kit has made.
The short term trims (LCFs) start moving right away but the long term trims take a good bit of time. I would ride for several tanks of fuel before trying on-road acceleration measurements, which I find much more accurate than inertial dyno runs because the initial conditions are better. The other thing to remember is that much of the improved feel you get from the AF is because you richen the mixture at part throttle. You could try the testing what happens from idle to 20% throttle as follows: on a flat road, no wind, put the bike in 4th gear, and stabilize at 2000 RPM, then open the throttle to 20%. That might show improvement with little adaptation time.
Soooo...as someone who was looking at buying the AF-XIED, and having read through your detailed post (above with table) twice, I get the impression you're saying the ECU will eventually adapt it's way around the "altered" settings. Is that correct?
Thanks for asking for the clarification. Lambda-shifting with an LC-2 or AF-XIED are among the few solutions that the BMSK will not adapt around. EDIT: "It learns about fueling changes (other than those made to the O2 sensor--e.g. LC-2 or AF-XIED)"
Waydo...... It will take several tank full's before the trims are learned to a point you can feel it, let alone dyno it. That is the one thing I did not like. That being said, It works well, and does what it says it will. Snowy...... It will NOT adapt the XIED out. It is sorta an euphoric treatment to the BMSK. Sorta like the same effect a good Aussie chilled fermented beverage have on you after a week in the bush.......
My experience was different and fairly immediate, especially in the first 4 gears at low rpms. I have a 35 mile loop from my house that I ride a lot. It has a section of dirt road connecting 2 paved portions. All of a sudden I am breaking the tire loose at the same throttle settings that I have ridden dozens of time. The last portion is a steep twisty paved grade out a canyon. The legal limit is 35mph with some 20 mph hairpins. For me it is a 3rd gear road. First climb out with the AF-Xied it became a 4th gear road. A couple of other performance tests I did early was to see how slow I could go. Ran the bike in first gear at idle and applied the brakes. I got it down to about 800rpm before the engine started protesting, but it didn't stall. Another was a 5th gear acceleration up a slight grade at around 2,000 rpm. Not full throttle but it pulled it right up the hill. Maybe a stock bike can do that, I didn't do a comparison test, but I was impressed. I did not expect that to happen so soon. The bike already had a temp spoofer on it, maybe my base open loop settings were already higher than stock. Feeling any improvement at higher rpms took much longer and are not as noticeable as was the improvement at lower rpms.
So it'll make me tell the truth about how I feel to people I don't like, and make me start fights with randoms at bars, taxi ranks, and hot dog stands? Cooool. There's nothing quite like a hot cup of tea and vegemite on toast when you wake up in the cells. (You may have been referring to just one or two chilled beverages, not the eleventy jillion I normally ingested after a week out bush in the Army) Thanks guys. Much appreciated.
It would be great if this was found in a condensed form somewhere without all the discussion of peripheral life events. I don't have time to filter 27 pages although there is some great info in here
