Interesting throttle body synch

[Hati]

Since finding that lost E-clip and finishing the valve clearance adjustments on my little camhead, I had two jobs left. 

 

Change the clutch fluid as the bike still has the original fill, but more importantly the colour of the fluid was black and no longer transparent. I had some mineral hydraulic fluid from  topping up my bicycle  hydraulic brakes, so the exercise went without a hitch. Thanks to the Mytivac setup I have, it took a couple of minutes and didn't even have to pump it. Magic :D

 

The last job was to do the throttle body sync, and this is the reason for the topic.

 

I got a GS911 updated to the latest release software and firmware. As per instructions, the bike was warmed up after the throttle cables were checked for slack and that the butterflies return to their stops with an audible clunk. 

 

The idle was around 1200ish before this exercise.

 

The software than calls for locking the idle actuators, starting the engine and making the appropriate adjustments to get the vacuum differences under 25 and 15 mbar respectively. 

 

Before it locks the actuators, it performs and actuator calibration that I could easily hear as they were moved through the range of their travel.

 

Once I was happy with the vacuum readings, I proceeded as the software called for to finish. then turned the bike off .

 

Soon after, and this is the interesting part, I turned back on the bike to check that everything is working as it should. To my surprise the idle was right down to 900ish, very lumpy as expected that low in the rev range and it even stopped a couple of times. Twisting the throttle gave me a nice and smooth increase in revs as expected, but it then returned to that lumpy idle until a minute or so later when the actuators begin to follow the throttle cams. Then the idle increased a little, smoothened out and was much like before the sync.

 

A test ride confirmed that the bike runs better then ever, it pulls like a steam train and other then that initial minute or so of idling when the ECU runs the actuators to whatever parameters it wants to, it is better then ever. This is my first camhead, I currently have a shiftcam and had a hexhead before that, so no other camhead to compare to. I did not have a chance yet to try a cold start.

 

The question I have is what is the reason for that very low idle. My understanding is that the ECU controls the idle and it cannot be changed by the user. I did not touch the idle adjusters, I am aware that those are set in the factory, or more precisely by Bing and need to be left alone.

 

 

 

EDIT: Since I wrote this, the bike had a chance to cool down to hand warm. I started it and it idled like it used to, nice and stable above 1000 rpm. Very puzzling...

 

[dirtrider]

2 hours ago, Hati said:

Since finding that lost E-clip and finishing the valve clearance adjustments on my little camhead, I had two jobs left. 

 

Change the clutch fluid as the bike still has the original fill, but more importantly the colour of the fluid was black and no longer transparent. I had some mineral hydraulic fluid from  topping up my bicycle  hydraulic brakes, so the exercise went without a hitch. Thanks to the Mytivac setup I have, it took a couple of minutes and didn't even have to pump it. Magic :D

 

The last job was to do the throttle body sync, and this is the reason for the topic.

 

I got a GS911 updated to the latest release software and firmware. As per instructions, the bike was warmed up after the throttle cables were checked for slack and that the butterflies return to their stops with an audible clunk. 

 

The idle was around 1200ish before this exercise.

 

The software than calls for locking the idle actuators, starting the engine and making the appropriate adjustments to get the vacuum differences under 25 and 15 mbar respectively. 

 

Before it locks the actuators, it performs and actuator calibration that I could easily hear as they were moved through the range of their travel.

 

Once I was happy with the vacuum readings, I proceeded as the software called for to finish. then turned the bike off .

 

Soon after, and this is the interesting part, I turned back on the bike to check that everything is working as it should. To my surprise the idle was right down to 900ish, very lumpy as expected that low in the rev range and it even stopped a couple of times. Twisting the throttle gave me a nice and smooth increase in revs as expected, but it then returned to that lumpy idle until a minute or so later when the actuators begin to follow the throttle cams. Then the idle increased a little, smoothened out and was much like before the sync.

 

A test ride confirmed that the bike runs better then ever, it pulls like a steam train and other then that initial minute or so of idling when the ECU runs the actuators to whatever parameters it wants to, it is better then ever. This is my first camhead, I currently have a shiftcam and had a hexhead before that, so no other camhead to compare to. I did not have a chance yet to try a cold start.

 

The question I have is what is the reason for that very low idle. My understanding is that the ECU controls the idle and it cannot be changed by the user. I did not touch the idle adjusters, I am aware that those are set in the factory, or more precisely by Bing and need to be left alone.

 

 

 

EDIT: Since I wrote this, the bike had a chance to cool down to hand warm. I started it and it idled like it used to, nice and stable above 1000 rpm. Very puzzling...

 

Morning Hati

 

Not that puzzling, when you lock the steppers with the GS-911 the fueling computer loses control so it loses it's base learning. It can take a short time after next engine start to catch up to stepper counts matching commanded counts. 

 

The fueling computer re-calibrates the steppers at each key-on (so it knows where home is) if you don't give it a chance to fully home the steppers then run them back out to proper starting counts at key-on, or don't revv the engine after start up (to allow the steppers to follow the throttle), it can take a short time to re-learn (adjust to) correct curb idle.     

 

The steppers on the BMW camhead are simple 4 wire steppers, that means no pintle position feedback to the fueling computer. The computer ONLY know where the pintles are now based on where they were last & how many counts have been commanded from the last COMMANDED location. This works great until a stepper pintle isn't where the computer thought it was.  

 

This is also why, at each new key-on, the computer runs the pintles into fully seat to re-calibrate home so it knows where "0" counts actually  is.

[Hati]

Thanks DR, that explains it.

[6speedTi]

I went through the same thing when I replaced my throttle body pulleys. I ran all the tests before and after the throttle synchronization and adjustments.  I too had the low idle at one point.  I realized I did not give the bike and or the GS-911 a proper shutdown or power down procedure. I rushed it. So anyway same thing on my part. I just let everything cycle through. Bike runs awesome now. Glad your up and running and very glad you found the E-clip. 👍

[Hati]

1 hour ago, 6speedTi said:

Glad your up and running and very glad you found the E-clip.

 

Thank you, me too. My independent BMW trained master technician  responded to my email asking if I could borrow his chain timing tool. He said yes, on return from his break.  I am looking forward to getting that done too because on my 1250 the timing adjustment made a noticeable difference to how the bike runs, and this camhead is already running better then I could ever imagine.