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CVT Tuning

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Vladmir123 View Drop Down
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    Posted: Dec/29/2012 at 8:07am
I've researched a lot about this, and have never really fully realised this. Till last year, we had a small set of weights and springs and used to keep interchanging them until it looked visibly faster , and obviously till when the tachometer showed us a good result. But we failed to include the road feedback into tis equation (when checking the cat with a tachometer) and therefore never conclusively "tune it properly". This year we first tied designing a Matlab system but sadly failed. So we're back to square one. So could everybe please tell me what techniques they use to tune their CVT and how they know that it's "tuned to optimum settings" ?
We use a Polaris P85 by the way
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LPIdaho View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LPIdaho Quote  Post ReplyReply Direct Link To This Post Posted: Dec/29/2012 at 6:36pm
Originally posted by Vladmir123 Vladmir123 wrote:

I've researched a lot about this, and have never really fully realised this. Till last year, we had a small set of weights and springs and used to keep interchanging them until it looked visibly faster , and obviously till when the tachometer showed us a good result. But we failed to include the road feedback into tis equation (when checking the cat with a tachometer) and therefore never conclusively "tune it properly". This year we first tied designing a Matlab system but sadly failed. So we're back to square one. So could everybe please tell me what techniques they use to tune their CVT and how they know that it's "tuned to optimum settings" ?
We use a Polaris P85 by the way

Let me know if you guys have a good starting point set-up or if you find one as we will be using this clutch too and for the first time.
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Priyank View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Priyank Quote  Post ReplyReply Direct Link To This Post Posted: Dec/30/2012 at 8:55am
Could you please tell what exactly the problem was with the MATLAB setup ?
You never stop learning.
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Vladmir123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladmir123 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/30/2012 at 10:12am
Just too little time. We barely had a sem to get it right. So we've kept that on hold for now and atleast for this season, we'll just report to hit and trial .. But I wanted to know a good starting point to that.
Will probably pursue the MATLAB Program again in my 8th semester
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Priyank Quote  Post ReplyReply Direct Link To This Post Posted: Dec/30/2012 at 9:40pm
Well, 15 days with a running car is all you need.
With the car in the running condition, you can easily find the values which you can't by calculation, simply by repeated testing.

To start with, use the standard weights from CVTech. That is probably for shifting at a low RPM. Start drilling holes and milling the internal surfaces in accordance with the weight reduction you need.
You never stop learning.
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Priyank View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Priyank Quote  Post ReplyReply Direct Link To This Post Posted: Dec/30/2012 at 9:42pm
Speaking on a practical note, you simply need to play with the spring coefficient and weight, other values can be done away with for a while, if the car is running.
You never stop learning.
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Vladmir123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladmir123 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/31/2012 at 11:59am
Ok. That sounds great. We use a Polaris BTW. The problem I face is .. How do You ever know what's exactly right ? There are a million combinations possible with the weights, 2 springs and helix ramp Polaris offers. It's just hard to start. That's what I need to know. How does everybody use the process of elimination ? Or do u guys fix a weight, and then machine that ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ballast Quote  Post ReplyReply Direct Link To This Post Posted: Jan/05/2013 at 11:59pm
i ve read in a cvt tuning book that the 'shift-out point' depends on the weight of the vehicle. that is if the vehicle is heavy for the motor the shift out point has to be set higher than the max engine power so that the cvt settles at the max power rpm in straight shift.Similarly if the vehicle is lighter for the motor, the shift out point should be lower than the engine max power.

my question is that "how to determine if the engine is heavier or lighter for the vehicle?"
as far as i figure, it can be determined only outdoor while testing. 
Is there any analytic method ?
jacking with the screw
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Priyank View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Priyank Quote  Post ReplyReply Direct Link To This Post Posted: Jan/06/2013 at 10:46am
Not i have heard of.
I am not sure if i agree with that concept you read in that tuning book.
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Vladmir123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vladmir123 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/07/2013 at 8:58pm
yeah i dont think thats true either. Road feedback and weight do affect the torque output. But im not sure it affects the shift out point in a way you've mentioned. I think its just variable inertias which obviously have some affect on the CVT shift out point
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Priyank Quote  Post ReplyReply Direct Link To This Post Posted: Jan/09/2013 at 12:07pm
Vlamidir, BTW, i kinda perfected the tuning using analytical method.
I used force balance.
Energy balance was kinda difficult to work with.
You never stop learning.
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