Weird Bob
Registered user
Were you using the quick shifter? I often get a pop on my 1200 going up through the gears with the shifter. I have an aftermarket can so it’s a little more obvious.
First impressions of my new R1250GS
- Thread starter fred_jb
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Were you using the quick shifter? I often get a pop on my 1200 going up through the gears with the shifter. I have an aftermarket can so it’s a little more obvious.
fred_jb
Registered user
No, I don't tend to use the quickshifter on upshifts, mainly out of mechanical sympathy for the transmission, and only occasionally use it on downshifts. Having got a few miles on the bike I was starting to accelerate harder while going up through the gears manually, and that was when I heard it.
It seemed to happen as I re-opened the throttle after momentarily closing it while changing up a gear, which is why I wondered if the closing and then sudden re-opening of the throttle was causing the shiftcam to do an audible double shift, down to the low cam then back up to the high cam.
However, I would have thought the ECU would have some sort of timer on this to avoid flipping for short lived changes in power demand such as for gear changing.
The other reason I am thinking it might be the shiftcam is that it is exactly the same single pop and quite subdued noise every time, without the variability you would get with fuel popping in the exhaust.
Weird Bob
Registered user
Ok not the same as mine then.
It may be an oddity of the shiftcam. It is the first generation of it and more importantly the first generations of the controller software for it so it may well be making the occasional bad decision on cam change.
It may be an oddity of the shiftcam. It is the first generation of it and more importantly the first generations of the controller software for it so it may well be making the occasional bad decision on cam change.
fred_jb
Registered user
Yes, could be - maybe they should have given us an indicator light which flashes whenever the can shifts so we know what is going on!
It might be worth trying to use the quickshifter -- just hold it on either a steady or open throttle when upshifting and it will change smoother\faster than you can with the clutch. (don't close the throttle when changing up or it will be jerky\clunky) . Similiarly when changing down but this time make sure you are on a closed throttle.
Ive done about 3000 miles on my 1250 now and find it much more relaxing and easier to not use the clutch most of the time. Still use the clutch at slow speeds and junctions\roundabout etc. Even 1st to 2nd is smooth when the engine is cold, not so smooth when it has warmed up, for some reason?? So I use the clutch 1st to 2nd.
Never heard any noise that I thought could be the shiftcam -- mind you I'm half deaf with helmet on
, don't feel the shiftcam changing or feel there's any need to know when it is changing.Weird Bob
Registered user
fred_jb
Registered user
It might be worth trying to use the quickshifter -- just hold it on either a steady or open throttle when upshifting and it will change smoother\faster than you can with the clutch. (don't close the throttle when changing up or it will be jerky\clunky) . Similiarly when changing down but this time make sure you are on a closed throttle.
Ive done about 3000 miles on my 1250 now and find it much more relaxing and easier to not use the clutch most of the time. Still use the clutch at slow speeds and junctions\roundabout etc. Even 1st to 2nd is smooth when the engine is cold, not so smooth when it has warmed up, for some reason?? So I use the clutch 1st to 2nd.
Never heard any noise that I thought could be the shiftcam -- mind you I'm half deaf with helmet on
Thanks for the suggestion, well intended I am sure, but I do know exactly how to use the quickshifter, it's just that I prefer not to use it. While I don't want to start a big debate on this, the reason I don't use it is that I feel that unlike DCT type gearboxes, quickshifters are a bit of a bodge solution and put additional strain on the transmission, especially on upshifts. On downshifts the engine gets blipped which assists with matching road speed to engine rpm - but you can't do a negative blip to reduce engine speed when changing up a gear!
When you change up a gear the engine revs need to drop to match the current road speed to the new ratio. When you use the clutch to do this you disconnect the engine from the transmission and rear wheel, and allow the revs to fall appropriately before reconnecting them. Do this right and you get a smooth change with no undue strain on the transmission, and even any slight mismatch between engine revs and road speed is smoothed out by a little clutch slip as the clutch reengages.
In contrast, when using a quickshifter there is no disconnection, so the rear wheel, via the transmission, instead of just matching the speed of the gearbox internals to the new ratio, also has to forcibly, and almost instantaneously, slow down the engine with all of its all heavy rotating masses as the new gear engages. The only help it gets to reduce the extra strain this puts on the transmission is that the quickshifter cuts the ignition for a few milliseconds, so that at least the engine is momentarily unpowered, though to slow it down the inertia of all that rotating and moving metal still has to be overcome.
Regarding the odd popping noise, I am not worried by this, more just interested to find out if the ShiftCam operation might be audible, though I agree with all the roadtesters that you cannot feel it happening through the engine response. If it is happening on each upshift during hard acceleration then you would think the system would just keep the fast cam engaged to avoid excessive cycling between the slow and fast cams. This would be similar to a technique called hysteresis which is commonly used in electronics, whereby to avoid excessive cycling between two states you avoid the switch happening at the same point in both directions.
I see what you're saying but I really don't think that it's as much of as issue as you may think. Sequential boxes are known for having the ability to shift by just lifting off the throttle a bit and slipping it into the next gear, some handling far more torque than our bikes put out. At the end of the day, I don't think that so many manufacturers would equip bikes with the equipment and then warranty it for 3+ years if they thought that it was going to prematurely wear everything down?
fred_jb
Registered user
I'm sure you're right, but knowing what is happening mechanically when using a quickshifter just grinds my gears (pun intended!) to the point where I don't want to use it. In any case I'm quite happy to use the clutch, and I'm not on a racetrack so saving a fraction of a second on each upshift while accelerating is not necessary to me.
Hi, sorry if my comment sounded patronizing.
I respect your choice not to use the quickshifter.
you must have had some bad experiences with broken gear boxes
. If this one goes in the next 3 years, using GSAP or not, BMW can fix it . If it's fitted to the bike may as well use it rather then feel any sympathy for the internals of the gearbox. It is easier and more fun riding using it.
Know what you mean about not punishing the gearbox too much though, sometimes if the loading on it is too heavy for it to change easily it won't change so I don;t force it. Sometimes happens when you are going down a steep hill and there is a lot of engine braking in use, use the brakes and clutch to change down.
SmaRTrxxv
Registered user
Actually the "popping sound" yo can hear when using the quickshifter that's the engine/ignition cutting off for a very short time to allow the gear change - which also means that the gearbox isn't fully engaged through the gear shift..
fred_jb
Registered user
When using the quickshifter, the ignition cuts out momentarily to reduce the torque output of the engine so that changing gear without the clutch puts less load on the gearbox than if it remained under full power. It still means more load on the gearbox than when using the clutch, as not using the clutch means that the gearbox remains fully engaged with the engine and hence experiences the extra load of forcing the engine revs down to match the road speed as the next gear is engaged. This extra loading does not occur when the clutch is operated to disconnect the gearbox from the engine during gear changes.
The pop when using the quickshifter is probably due to the momentary ignition cut out allowing a small amount of unburnt fuel to escape into the exhaust. The pop I was hearing occurred during manual gear changes under hard acceleration so was not caused by any quickshifter initiated cut out in the ignition, which is why I wondered if it might just be the sound of the shiftcam operation.
lkyphl
Registered user
pbbanks;5332969 sometimes if the loading on it is too heavy for it to change easily it won't change so I don;t force it. Sometimes happens when you are going down a steep hill and there is a lot of engine braking in use said:
Just a thought Fred. After listening to your description of the popping noise. Could it be that even though you are engaging the clutch, the quick shifter is occasionally cutting the engine?
I have to say that I have experienced this once in a while on my 2017 whereby I get the feeling the quick shifter has operated even though I used the clutch. Maybe a sticky switch on the clutch (as I believe that the clutch switch disengages the quick shifter which is on as default).
Just a thought.
I have to say that I have experienced this once in a while on my 2017 whereby I get the feeling the quick shifter has operated even though I used the clutch. Maybe a sticky switch on the clutch (as I believe that the clutch switch disengages the quick shifter which is on as default).
Just a thought.
I have noticed that there's a pop somewhere between 4-5k under light to medium acceleration on my 1250 as well. It doesn't seem to cause any issues with the power delivery (i.e. a stutter or something) but is very noticeable and completely separate from gear changes. I don't think that it would be the shift cam because it's below 5k revs and also not with a lot of throttle because I'm still in the break in phase so can't even thrash it too much. The first few times it happened I thought that it was maybe doing something similar to the audible notice of TC activating like I'd heard the HP4 Race does, but I've not seen the TC light while it happens and don't think I'm accelerating near hard enough for it to activate anyway. Glad that others are having the same thing happening.
Don't know that the The 1200\1250 will cut just the ignition with the GSAP ??.
Many years ago I was involved with fitting add on quickshifters to race bikes and the system used either ignition cutout OR cut the fuel injection. I would guess the GSAP is more sophisticated and may cut both??. If that is the case it shouldn't inject fuel when the GSAP is used.
fred_jb
Registered user
That's interesting, thanks for posting. I only noticed it while accelerating, but I wouldn't swear it was directly related to gear changes, maybe more to rapid changes in throttle opening, and was always a single isolated noise which was very consistent in nature, which is why I suspected the ShiftCam may be involved. I did a 350 mile round trip on Saturday to meet some biking friends at Loomies cafe and get some running in miles done, as I want to get the running in service done before going away in May, and it was during this ride that I started noticing it. At first I thought it might be something in my clothing or helmet flapping, but it was too consistent and always related to acceleration so I don't think it was that. It is pretty hard to pinpoint the location of sounds while wearing a helmet and earplugs, but I got the distinct impression it was coming from somewhere low down on the left side of the bike.
I didn't hear it on a short 15 minute ride yesterday, but will try to be more systematic in noting the exact circumstances next time I hear it. Not worried by it, but will mention it at the service, and see if anyone else reports it.
fred_jb
Registered user
Yes, I would expect the system to reduce the fuelling as well as cut the ignition, otherwise the catalyser could get polluted, and you would also get some serious detonation in the exhaust, but there may be enough residual mixture getting to the exhaust when GSAP operates to give a single pop each time.
Did come across this info. on a blog. It is in relation to the 1200 GSAP . Seems to say that it works by only cutting the injection. Does mention popping in the exhaust but only on deceleration at low rpm , presumably caused by injecting fuel as it says "in preparation for idle" , , maybe to prevent stalling at idle??.
None of these explain the noise you mention hearing though and I've never noticed it even before I had the first service.
QUOTE FROM BLOG:--
"Electronic operation
During an upshift the system senses the movement on the shifter and when it passes a threshold, cuts fuel injection for 50–100ms to relieve torque on the driveline and enable the next gear to engage.
During a downshift, the system senses the movement on the shifter and when it passes a threshold, adds enough fuel to relieve driveline torque, then readjusts fuelling to match the rev of the next gear down, which occurs over 100–150ms—basically the same principle as double declutching squeezed into a timeframe of about 1/10 second, or two virtually instantaneous blips of the throttle.
System quirk
The R1200GS engine management cuts fuel flow during deceleration, but starts injecting fuel again in preparation for idle as the revs drop below approximately 2,250rpm. You can hear this on the bike as 1–2 slight pops from the exhaust. Downshifting using GSAP at or below that particular point will result in a rough shift."
fred_jb
Registered user
Good find - that is the sort of low level management I would expect to be going on for GSAP, and also generally such as cutting fuel on deceleration until you get fairly close to idle revs.
It hadn't occurred to me that as well as cutting fuel to reduce forward drive torque for clutchless upshifts it also works in the reverse direction, adding fuel on downshifts to relieve torque in the reverse direction from engine braking. Makes sense though. I guess without disconnecting the engine and transmission with the clutch you have to juggle with the fuelling to minimise strain on the transmission, allowing the gear shift to succeed without expensive grating and banging noises!
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