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Post by katt on Sept 3, 2018 1:34:00 GMT -5
Month ago my speed was 30mph @ 8000 RPM, after installing Gates PL20507 neoprene belt (699x18.1x30) max speed went up to 38mph @ 8000 RPM. After 500 miles max speed went down to 36mph @ 8000 RPM. Marked variator with marker today and here's how far belt travels, it has to do with belt stretched or variator weights (currently 8.3g)
Does it look stretched, is it normal wear for 500 miles of ride? |
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Post by diynuke on Sept 3, 2018 5:46:17 GMT -5
Could be the rollers or the rear pulley not sliding all the way in.
Does look like the belt doesn't travel far enough up. ive done the same thing and mine always remove all the marker. so yeah it isn't traveling far enough.
First thing. check the rollers. ive had some rollers where the metal inert was sliding out of its sleeve so it was rubbing against the side and this explained the high rpm
and no it shouldn't wear that much. or you got an really bad bad belt but I assume you don't have that kind of one.
I normally drive around with an belt for 8000km/4970miles and the I replace it just to be sure.
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ratdog
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Post by ratdog on Sept 3, 2018 7:50:57 GMT -5
The thing that comes to mind at once is ther you say you were at 8000rpm at each speed. At top speed you should be at full lock up ( overspin). So if you were going 30 at 8000 and also 38 at 8000, it would suggest you are not getting full lock up. I would try some slightly heavier sliders or roller. ( I happen to like the sliders, but I’m also putting a lot more power into the CVT then you are.
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Post by Happypancake! on Sept 3, 2018 8:09:57 GMT -5
A lot of things can effect speed. Low air pressure in tires can drop you 2mph.
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Post by snaker on Sept 3, 2018 11:07:23 GMT -5
Katt, didn't you just have another post where someone pointed out to you that your belt was sitting too low in the driven pulley at stop? If so and assuming that your pulley's are maintained then:
A belt that doesn't ride all the way up the driven pulley at stop and doesn't ride all the way up the drive pulley at full shiftout equals a belt that is too short.
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Post by katt on Sept 4, 2018 3:50:13 GMT -5
The thing that comes to mind at once is ther you say you were at 8000rpm at each speed. At top speed you should be at full lock up ( overspin). So if you were going 30 at 8000 and also 38 at 8000, it would suggest you are not getting full lock up. I would try some slightly heavier sliders or roller. ( I happen to like the sliders, but I’m also putting a lot more power into the CVT then you are. What's overspin and full lockup? Katt, didn't you just have another post where someone pointed out to you that your belt was sitting too low in the driven pulley at stop? If so and assuming that your pulley's are maintained then: A belt that doesn't ride all the way up the driven pulley at stop and doesn't ride all the way up the drive pulley at full shiftout equals a belt that is too short. Not me, but my belt is 685mm instead of 669mm and also width shrinked to 17mm instead of 18.1mm. My next thing is to get new belt i will go for EPDM belt by Gates PL30508 i found it even cheaper than my current Neoprone belt @ srockauto just $12 shipped, its 660mm, but i want to try it.
I rebuilt clutch today, i also have a lot of belt dust in the CVT so i suspect belt sips at clutch, will observe my CVT operation and measure belt travel now and after i get new belt.
A lot of things can effect speed. Low air pressure in tires can drop you 2mph. That i forgot, thanks for tip i will check, my last settings were around 3.0psi, will monitor the speed changes at different tire pressures and select one that good balance between handling and max speed. |
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ratdog
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Post by ratdog on Sept 4, 2018 8:38:52 GMT -5
Why are you using a longer belt? In theory, a longer belt would never get the clutch side pullies to the bottom of their travel. Also, at any given rpm, you rear pulley would be a larger then the design of the CVT. In effect, a "lower" gear
In a correctly set up CVT (with the correct belt) you start out with the front drive disks apart, in effect giving a small front pulley and the rear drive disks are close together to create, in effect a large pulley. As you give the bike gas, the weight move out and act against a lever that forces the front drive disks together. As they get closer together they effectually make a larger front pulley and the belt is a fixed length so it forces the rear drive disks apart. effectively making a smaller rear pulley.
at some point, the front drive plates get as close as they can together and make the largest pulley they can make. At the rear, they make the smallest pulley they can make. at this point the CVT is in "top gear" but if the bike has the HP to still go faster, now the CVT no longer has effect on speed. It is at full lock up or overspin and many call it. So on an unmodified CVT the bike jumps up to 7500 rpm and stays there from 5mph to 35mph. When it gets to lock up, the only way its going to go faster is if the rpms go up. so at 8000 rpm it might go 40 mph and at 8500 rpm, it might go 45mph.
Now all of this assumes that you have the correct length belt that the people that spent thousands of hours designing the system designed it for. If you have a too long belt, the rear can only get so close together and the outside dia of that pulley can only get so big, so when you are taking off, it would have to slip like a bitch. only after the front pulley was big enough would it start to get "traction". With a correctly sized belt, there would be no slippage and when you get close to top speed, the belt would be forced into the drive disks to make the smallest rear pulley possible.
So what I call "full lock up" is when the CVT is in its highest "gear" and no longer effect the speed. for practical purposes its a "direct drive". the CVT is locked up, the clutch is locked up. its just the motor to the rear wheel.
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Post by snaker on Sept 4, 2018 16:31:08 GMT -5
There is no sort of lock up or lock out on these GY6 type CVT's.
With the Torque Sensing function they are alway's subject to backshifting (forced downshifting) due to abnormal loading.
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ratdog
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Post by ratdog on Sept 4, 2018 19:47:02 GMT -5
Ok, I guess I didn’t explain it well. Assuming you have the HP, at some point the variator get as large as it can get. The clutch side gets as small as it’s going to get. Your in the upper RPM range, so we can assume the clutch is locked up. This is the point I call full lock up. As you continue to accelerate the variator no longer has effect on the overall ratio and to go faster, the engine has to spin faster.
Of course as soon as you back off the gas, the RPMs drop and when your speed gets back down to the “ lock up” point, the variator will start separating and once again vary the gear ratio. If you come to a hill, the engine can no longer push let’s say 8500 rpm so it starts dropping the RPM to a point that the variator will start allowing the plates to separate.
Maybe calling it full lock up is not comfortable for you. That’s just my term because wenn we were on CVTs for cars we called it full lock up. I guess that why a lot call it “overspin”. For all I care, you can call it “Fred”.
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Post by snaker on Sept 4, 2018 21:03:49 GMT -5
Doesn't bother me what you what terms and names you want to use. That's one of the challenges with these systems, several names used for the parts. For example the use of clutch describing the driven pulley when there is actually a mechanical clutch piggybacked on to the driven pulley. The clutch handles the stop and go and has nothing to do with the high rpm's (provided its healthy and doesn't slip).
Translating your nicknames I believe that your talking about running the CVT to full shiftout plus what ever additional acceleration that can be squeezed out of the engine.
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Post by snaker on Sept 4, 2018 21:12:32 GMT -5
If you come to a hill, the engine can no longer push let’s say 8500 rpm so it starts dropping the RPM to a point that the variator will start allowing the plates to separate. What you describe here is what would happen on non-Torque Sensing CVT's and is exactly what the Torque Sensing is intended to prevent. The TS forces a down shift (backshift ) in that situation to keep the engine in its power band. The machine does slow down but the engine isn't falling on its face. |
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ratdog
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Post by ratdog on Sept 4, 2018 23:12:02 GMT -5
“Shift out” is a team I don’t use, because, of course, there is no shift in the normal sense. To the non CVT world, a “shift” is a change in gear ratio. Of course when the CVT is accelerating, there is no shift as in a change of ratios, it’s really a lack of shift. At that point the CVT stops changing ratios. But like I say, call it what you like, it’s the point where the CVT no longer effects the final drive ratio. Makes me half wondering what they call it in the snowmobile world.
At least we both know what I was talking about. I was trying to explain to the orginal poster what I was calling lock up, but it works just as well calling it shift out.
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Post by benji on Sept 5, 2018 9:13:36 GMT -5
To the non CVT world, a “shift” is a change in gear ratio. Of course when the CVT is accelerating, there is no shit as in a change of ratios, it’s really a lack of shift. you have this almost COMPLETELY backwards. Cvt's change ratio. And just like a ten speed bike (that also has no gear cogs), it shifts. Shifting is not limited to the world of Manual gearboxes. Shit, my tool box shifts around in my trucks bed all the time. The term "shift" Is much broader than your assuming. |
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ratdog
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Post by ratdog on Sept 5, 2018 10:14:02 GMT -5
one again Benji, you butt in where you don't understand what is being talked about, or just don't understand how a CVT works.
there is a point where the CVT no longer changes ratios the point where the variator is as large as its going to get, so the rear drive plates are as far apart as they are going to get. the other poster called this "full shit out" but the important thing is from this point to the top speed of the bike, the CVT is no longer changing ratio. you can call it shift out, or lock up, or overspin, but at that point the CVT no longer effects the final gear ratio. So CVTs continuously adjust the ratios until they are in as "high" (actually lowest final ratio) a "gear" as possible. then they no longer change ratios as the both the RPMs and speed continue to increase
and by the way, I also know a whole lot more about bicycles then you do too. Although for me its 22 speed or 24 speeds not ten speeds. the last time I had a ten speed, I think I was about 14 years old.
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Post by snaker on Sept 5, 2018 10:32:44 GMT -5
Ratdog, I think I know what your getting at. I don't get bent out of shape when people use different lingo then me. The snowmobile world uses terms around shift all the time: upshift, downshift, backshift, shiftout. I don't understand your aversion to shift, seems clearcut to me, but as you said, call it what you want.
You make comparisons to automotive CVT systems. These small engine CVT's have virtually no similarities to car CVT's other than sharing the same letters and a bit of the same overall function. Here you have a rpm sensing drive pulley (variator) using flywheights , a rubberized belt and a torque sensing (TS) driven pulley. Won't see anyhing like it in a Volvo.
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