Throttle body synchronization procedure

[Hogges]

Hi,

I am looking for information on throttle body synchronization procedure. I do have the BMW service manual DVD which describes the procedure which includes the dealer specific tool to park the throttle body stepper motors.
 

Over on the ADVRider forum people are usually quick to say it’s not necessary to park the steppers before synchronizing but I never found a technical reasoning why this may be so. 
 

I have motoscan but this particular “actuator”  feature doesn’t seem to work right on my bike. 

[dirtrider]

35 minutes ago, Hogges said:

Hi,

I am looking for information on throttle body synchronization procedure. I do have the BMW service manual DVD which describes the procedure which includes the dealer specific tool to park the throttle body stepper motors.
 

Over on the ADVRider forum people are usually quick to say it’s not necessary to park the steppers before synchronizing but I never found a technical reasoning why this may be so. 
 

I have motoscan but this particular “actuator”  feature doesn’t seem to work right on my bike. 

Evening  Hogges

 

You can park the steppers or leave them operational. You actually ride it with the steppers responding so parking them to sync  is kind of up for debate. 

 

If I don't park the steppers I usually shut the engine off, then restart, then do the part throttle sync as soon as possible (while the steppers are still linked). If you take too long on a warm engine the steppers will probably go independent before you are done. 

 

If you want it sync with the steppers parked then find a GS-911 & park them (or figure out how to get your Moto Scan to park them).

 

On the other hand if want your sync to reflect how it will be when actually riding down the road then leave them active during the sync. 

 

Probably the only time you will notice a difference is if the curb idle sync is way off with the steppers locked at the same steps. But if it is off that far then find out why, don't try to sync around it.  

[Hogges]

Thank you, dirtrider. I do have Motoscan but this function doesn't seem to work right on my bike. It increases my idle to something like 3000rpm! 

 

After reading your post, I realize that I don't understand what the steppers do and when. If I understand you right, when one starts the bike the stepper motors link to the same value initially and then only later start adjusting. What is actually measured to calculate this adjustment, and is the main purpose of all this for idle or for higher power settings?

 

Is unplugging the steppers before startup a bad idea for the sync as it would lock them at whatever setting they were at when the bike was last shut down? If so, would it be advisable to start the bike and then unplug the steppers so that they remain linked? As long as they are linked the synchronization should work out but maybe the adjustment range is not the same as it would be with parked stepper motors. 

[KDeline]

On 7/24/2023 at 6:29 PM, Hogges said:

 

 

Is unplugging the steppers before startup a bad idea for the sync as it would lock them at whatever setting they were at when the bike was last shut down? If so, would it be advisable to start the bike and then unplug the steppers so that they remain linked? As long as they are linked the synchronization should work out but maybe the adjustment range is not the same as it would be with parked stepper motors. 

My understanding without 911 is on a cold bike, turn on the ignition, do not start, then turn off. Unplug the steppers as they should now be in the same position. Start bike, warm up and sync, when finished don't forget to plug them back in.

[dirtrider]

On 7/24/2023 at 7:29 PM, Hogges said:

Thank you, dirtrider. I do have Motoscan but this function doesn't seem to work right on my bike. It increases my idle to something like 3000rpm! 

 

After reading your post, I realize that I don't understand what the steppers do and when. If I understand you right, when one starts the bike the stepper motors link to the same value initially and then only later start adjusting. What is actually measured to calculate this adjustment, and is the main purpose of all this for idle or for higher power settings?

 

Is unplugging the steppers before startup a bad idea for the sync as it would lock them at whatever setting they were at when the bike was last shut down? If so, would it be advisable to start the bike and then unplug the steppers so that they remain linked? As long as they are linked the synchronization should work out but maybe the adjustment range is not the same as it would be with parked stepper motors. 

Morning  Hogges

 

I don't use a Motoscan so can't comment on it's stepper holding function. 

 

BMW calls the idle stepper an   (Idle Control Device). 

 

As far as the idle steppers go, those are just computer controlled devices that are in the throttle bodies, they allow the fueling computer to control the amount of air that by-passes the throttle plates.  The idle steppers (Idle Control Devices)  have a movable pintle (that is tapered valve on a screw like stem) the fueling computer can run the pintles in & out to open or block the air by-pass hole in the throttle body (allowing more or less air into the intake on the intake-valve side of the throttle plate. Think of them as computer controlled BBS screws.

 

The idle steppers serve a few functions, their main function is to control the engine idle RPM's. The fueling computer looks at a number of things to determine how many counts to set the idle steppers to, like engine temperature,  intake air temperature, cylinder head temperature, altitude, pre engine start or after engine start, TPS, etc (it looks at a LOT of things).

 

The steppers are also used as throttle followers, so as the throttle is opened (running engine)  the steppers open farther as the throttle is opened (not all the way to WOT but for ways).  This is to prevent engine stalling if the throttle is suddenly dropped (closed).

If they didn't do this you could get an engine stall at a quick throttle close. (think of this throttle following function as a computer controlled dash-pot)

 

The other thing the steppers do is to increase air flow around the throttle plates at engine starting so you can start a cold engine without holding the throttle open a little. They act like the choke (fast idle lever) on the old 1100/1150 engines but they do it automatically & based on engine sensor input). 

 

On a cold engine, when you turn the key on, the fueling computer looks at all the input sensors then runs the idle stepper pintles into their seats (fully closes them) then sets that fully closed position to "0" counts, then based on the sensor information & other baked in programming opens the steppers to a given number of counts that allows enough air flow around the throttle plates for engine starting & cold idle.   The fueling computer does the same basic thing for a warm engine, or partially warm engine, etc only on a warn engine it doesn't open the steppers as far for engine starting.  

 

Once the engine is started & running the fueling computer continually adjusts the idle stepper counts to keep the engine running at an RPM determined by sensor input & fueling computer programming. 

 

As you can see it's somewhat complicated in theory but not that complicated in actual operation. 

 

The big thing with the BMW idle steppers (Idle Control Device) is they are only 4 wire steppers (2 wires for fast response & 2 wires for slower more precise control). With only 4 wires the fueling computer doesn't always know the precise location of the steppers, the fueling computer ONLY knows where it last commanded them to be & where it just commanded them to go. So if the stepper pintles are where where the fueling computer last commanded them then all is good, if they are not where the computer thinks they are then they are lost.  

 

There is one last little confusing thing about the 1200 hexhead steppers, most of the time they are linked side to side so a commanded  60 counts for the left side means the same 60 counts goes to the right side. They are always linked to the same counts for starting &  linked to same counts after engine starting & for a time after engine starting. But at some point the can & will go into independent control so at that time they are not linked to the same counts side to side. This seems to happen on an engine up to operating temperature, & especially when the evap canister purge function is open (the 1200 hexhead only purges into one throttle body  so that is a calibrated vacuum leak into that side only). 

 

There is more to the stepper operation but the above is the basics & enough to understand operation. 

 

 

 

  

[dirtrider]

Is unplugging the steppers before startup a bad idea for the sync as it would lock them at whatever setting they were at when the bike was last shut down?--- Not a good idea, the steppers are not where you would think they are, when the ignition switch is turned off the fueling stops but the steppers are still active for a second or two so no idea on where they end up. That is why when you turn the ignition switch on the steppers always re-home & re-set to "0" counts at seated. 

 

If so, would it be advisable to start the bike and then unplug the steppers so that they remain linked?--- This could work but those darn steppers are very fast in response so unless you unplug both at exactly the same time there could be a couple of counts difference between them by the time you get the second one disconnected.  Once you disconnect neither you or the fueling computer have any idea of where their counts really are. 

 

As long as they are linked the synchronization should work out but maybe the adjustment range is not the same as it would be with parked stepper motors.--- This is a very debatable thing. You don't ride it with parked steppers so why would you skew your above idle balance. But you would ideally like to balance the above idle with both side steppers linked, not independent & not moving.  They typically link at above idle throttle following so actually balancing above idle allows even side to side stepper position.

 

The gain in locking the steppers at hot curb idle is the BMW  manual calls for first verifying that the held stepper side to side variance is within specifications, THEN if within specs carry that variance up into the above idle cross side balance. This is the debatable part, IF the hot engine curb idle (linked stepper) cross side balance is off far enough to be an issue then FIND & FIX the reason for that hot curb idle cross side balance discrepancy do not just try to skew your above idle cross side balance to cover it up!

 

The BMW warm engine curb idle spec is about 25 mbar (about 10"of H2o), that is a lot of side to side variation, do you REALLY want to carry that much discrepancy up into your above idle balance? Or would you rather find out WHY the hot engine cross side vacuum is off by 10" of H2o? 

 

Bottom line here___ if your hot engine side to side balance at curb idle is under 5" of H2o with the steppers showing the same counts on each side then no need to lock the steppers for doing the above idle balance. Hopefully your Motoscan should be able to see the stepper counts (if they are the same side to side then you know they are still linked). 

 

The big decision is IF you find (lets  say 5" H2o side to side variance at curb idle) do want to carry that up into the above-idle balance, or  just set the above idle balance the same side to side?  The good news is I have tried it both ways & can't seem to tell any difference in how the motorcycle rides.  

 

If I find the hot engine curb idle off more than 5" H2o with linked steppers then I try to find the reason  (coked up throttle bore or coked up throttle plates, or coked up stepper air passages, or intake leaks, or valve adjustment problem, or compression issue, or ????? 

 

If you can see your active stepper counts on your Motoscan then  just make sure they are at the same counts side to side when looking at your initial curb-idle balance & doing your above idle balance. If you can't monitor the active stepper counts then do an engine re-start after balancing to verify that the side to side above idle balance is still good (you have some time after hot engine re-starting where the steppers will stay linked). 

 

  

 

 

[Hogges]

Thank you very much for the detailed explanations. I think I’ll start by trying the motoscan one more time (it’s been a few years that I attempted it) and if this doesn’t work follow the full procedure to set the idle adjusters manually for the calibration. I do have a twinmax in the meantime.

 

By the way: you brought up the carbon canister. Mine has been removed. But the solenoid (?) switch at the underside of the tank is still there and plugged in. Is the computer still going to run occasional imaginary purge cycles and in doing so de-tune the right side throttle body for a short time, even if nothings comes into the now capped vacuum port?

[dirtrider]

9 hours ago, Hogges said:

Thank you very much for the detailed explanations. I think I’ll start by trying the motoscan one more time (it’s been a few years that I attempted it) and if this doesn’t work follow the full procedure to set the idle adjusters manually for the calibration. I do have a twinmax in the meantime.

 

By the way: you brought up the carbon canister. Mine has been removed. But the solenoid (?) switch at the underside of the tank is still there and plugged in. Is the computer still going to run occasional imaginary purge cycles and in doing so de-tune the right side throttle body for a short time, even if nothings comes into the now capped vacuum port?

Morning Hogges

 

The fueling computer should still run the purge cycle. If the purge solenoid valve is still plugged in then it will open the purge valve.  If the purge valve intake fitting is plugged off then no air will be introduced to the throttle body.

 

If the purge valve intake-side is still open to ambient air then it will suck ambient air into the throttle body when the purge valve is open.  (unless the throttle body fitting is plugged off)

 

With no evap canister on that motorcycle you should remove the hose between the purge valve & the throttle body then use little rubber plugs  (or short pieces of hose with a screw or something) to plug off the throttle body nipple & also plug off the purge valve fittings (you can leave the purge valve in place & electrically hooked up)

 

That evap canister WAS the fuel tank vent so make sure that the vent hose coming from the top of the fuel tank is now hooked directly  to the evap hose that ends up behind the riders L/H foot peg area. 

[Hogges]

1 hour ago, dirtrider said:

Morning Hogges

 

The fueling computer should still run the purge cycle. If the purge solenoid valve is still plugged in then it will open the purge valve.  If the purge valve intake fitting is plugged off then no air will be introduced to the throttle body.

 

If the purge valve intake-side is still open to ambient air then it will suck ambient air into the throttle body when the purge valve is open.  (unless the throttle body fitting is plugged off)

 

With no evap canister on that motorcycle you should remove the hose between the purge valve & the throttle body then use little rubber plugs  (or short pieces of hose with a screw or something) to plug off the throttle body nipple & also plug off the purge valve fittings (you can leave the purge valve in place & electrically hooked up)

 

That evap canister WAS the fuel tank vent so make sure that the vent hose coming from the top of the fuel tank is now hooked directly  to the evap hose that ends up behind the riders L/H foot peg area. 

Good morning to you as well, dirtrider.

 

My throttle bodies now have OEM rubber plugs on both sides, replacing a makeshift solution. My BMW dealer had it in stock for a buck or so. The purge valve is plugged in to avoid any potential complaining from the computer, but it just sits in the open air. The drain hose is going to the foot peg area as you describe and hasn't given me any trouble in 20k miles, except it did its job once when I filled the tank and then had to wait for my buddies while the bike sat in the full sun, making a very small puddle. I have been careful to avoid this since. One rider in our group has an R1100R or R1150R with a metal tank which has big dents from an implosion caused by a plugged evap canister.

 

Anyway, it's an interesting fact to know that the idle actuator on the right side(?) will still occasionally adjust for a "virtual" purge cycle on my bike. 

[dirtrider]

59 minutes ago, Hogges said:

 

 

Anyway, it's an interesting fact to know that the idle actuator on the right side(?) will still occasionally adjust for a "virtual" purge cycle on my bike. 

Morning Hogges

 

If the vacuum nipple on both throttle bodies are plugged then there is nothing for the computer or idle actuator to adjust to. 

 

It doesn't change anything when it actually opens the purge valve (see below****), the fueling computer just reacts to the o2 sensor input when it sees fuel vapors being sucked in & burnt.

 

**** The thing that can happen when the fueling computer opens the purge valve then runs a purge cycle  (whether it is actually sucking in fuel vapors of not) is it will probably put the idle steppers into independent mode at that time as the BMW 1200 hexhead only  purges into one side throttle body (even if it can't actually do that due to plugged off TB nipples).