cvt

Chat about all makes of Maxi scoot here!
lenny
Posts: 13
Joined: Wed Mar 21, 2018 5:05 am
Current Ride: Silverwing 600
England
cvt

Post by lenny » Tue Sep 10, 2019 4:19 am

Trying to get my 67 year old brain around this, anyone out there to put me right? I understand the general operation of cvt, but have a question.
When moving on flat road, constant 3000 rpm and constant speed, 1/4 throttle, drive and driven pulleys in equilibrium.
Now increase to 1/2 throttle. My question is, at that point, what happens to the drive, is it the equivalent of a chain drive with a direct connection of engine to rear wheel or do the pulleys suddenly change in some way when the increased power is applied?

Meldrew
Benefactor
Posts: 3666
Joined: Sun Apr 19, 2009 6:23 pm
Current Ride: 2018 Honda Forza 300 A
Location: York, North Yorkshire
Great Britain
Re: cvt

Post by Meldrew » Tue Sep 10, 2019 4:52 am

Wouldn't it be far simpler for you to do a Google Search for CVT and pick through the pages of topics on how CVT actually works.

User avatar
Has been maxi tours
Benefactor
Posts: 1123
Joined: Thu Aug 16, 2018 6:15 am
Current Ride: Sym Citycom 300
Location: Pikeyville
EU Flag
Re: cvt

Post by Has been maxi tours » Tue Sep 10, 2019 5:02 am

The CVT is always trying to get the belt to top of the pulley friont pulley to get best ratio ie higher gear. What holds it back is the spring in rear pulley .More throttle more power will over come the spring belt get to top of pulley you go faster .Once its as far as it can go revs continue to rise to go faster .On you tube there's videos shows how belt moves in front and rear pulleys .

Its better to be a "Has been " than a "Never Was "

MrGrumpy
Benefactor
Posts: 5911
Joined: Wed Apr 08, 2009 3:50 pm
Current Ride: T-max mk6
Location: Teesside UK
England
Re: cvt

Post by MrGrumpy » Tue Sep 10, 2019 5:32 am

In general, a engine with a CVT likes to sit at a fairly constant rpm - say 5000-5500 rpm. At those sort of revs opening the throttle might increase revs a bit, but the main result will be from the CVT pulleys giving you a higher ratio, at least once acceleration has been achieved and the forces and loads through the CVT have balanced out. For low revs like 3000, twisting the throttle will probably cause revs to rise as it wants to get to its sweetspot, but the CVT ratio will also change. When speed has increased so that the CVT is in its highest ratio, then there will be a more direct connection between revs and speed. The CVT is always balancing load / drag from the road and power from the engine - if you meet a gradient on the road without the altering the throttle, the CVT will lower its ratio.

lenny
Posts: 13
Joined: Wed Mar 21, 2018 5:05 am
Current Ride: Silverwing 600
England
Re: cvt

Post by lenny » Tue Sep 10, 2019 5:58 am

MrGrumpy said
'at least once acceleration has been achieved'
This is the specific part of cvt operation I'm trying to get straight in my head.

User avatar
Has been maxi tours
Benefactor
Posts: 1123
Joined: Thu Aug 16, 2018 6:15 am
Current Ride: Sym Citycom 300
Location: Pikeyville
EU Flag
Re: cvt

Post by Has been maxi tours » Tue Sep 10, 2019 7:01 am

Take belt case off put it on centre stand rev it up you'll see it working .I see your on a Silver wing ecu does a cross check between revs and speed at about 60 mph belt light will come on if it doesn't match up .So nothing to worry about really .

Its better to be a "Has been " than a "Never Was "

MrGrumpy
Benefactor
Posts: 5911
Joined: Wed Apr 08, 2009 3:50 pm
Current Ride: T-max mk6
Location: Teesside UK
England
Re: cvt

Post by MrGrumpy » Tue Sep 10, 2019 8:03 am

lenny wrote:
Tue Sep 10, 2019 5:58 am
MrGrumpy said
'at least once acceleration has been achieved'
This is the specific part of cvt operation I'm trying to get straight in my head.
What normally happens when you twist the throttle is that the revs rise a bit, but then stay constant whilst the CVT does its work.

User avatar
StephenC
Benefactor
Posts: 2097
Joined: Sun Apr 12, 2009 6:24 am
Current Ride: Forza 300
Location: Essex
England
Re: cvt

Post by StephenC » Tue Sep 10, 2019 2:04 pm

Which is why, at least how it seems to me, that traditional motorcycle high revving engines are wrong for scooters with a CVT. What we need is peak torque low down so that the box can move up through the "ratios" without eating fuel. Instead what we have now are engines pulling 5k revs the moment you open the throttle.

I'd like to see smaller capacity versions of Honda's 750 in the Integra, etc. Or at least engines with that design concept anyway.

Is that possible?
Expert in Close Quarters Combat Filtering
Can ≠ Should

XMax400Paul
Benefactor
Posts: 1822
Joined: Fri May 28, 2010 7:03 am
Current Ride: XMax400 - SH125
Location: SE London
England
Re: cvt

Post by XMax400Paul » Tue Sep 10, 2019 2:23 pm

With the increse in revs at the crank, the variator weights are thrown further up the ramps... Centrifugal (dont start on the centrapetal...) force...
The squeezes the front pully pushing the belt up... Which by virtue the belt is a fixed length, must open the rear pully against the conti spring... Dropping the belt down...
Think push bike - front chain wheel size v's rear sprocket size...
Search you tube, also take a look at what Dr Pulley rollers do...

User avatar
StephenC
Benefactor
Posts: 2097
Joined: Sun Apr 12, 2009 6:24 am
Current Ride: Forza 300
Location: Essex
England
Re: cvt

Post by StephenC » Tue Sep 10, 2019 2:44 pm

XMax400Paul wrote:
Tue Sep 10, 2019 2:23 pm
With the increse in revs at the crank, the variator weights are thrown further up the ramps... Centrifugal (dont start on the centrapetal...) force...
The squeezes the front pully pushing the belt up... Which by virtue the belt is a fixed length, must open the rear pully against the conti spring... Dropping the belt down...
Think push bike - front chain wheel size v's rear sprocket size...
Search you tube, also take a look at what Dr Pulley rollers do...
Yeah, what he said. Meant to write that myself but got sidetracked by executing some timey-wimey stuff instead
Expert in Close Quarters Combat Filtering
Can ≠ Should


Post Reply