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Slipper Clutch - How it works.

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tapmyhed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Topic: Slipper Clutch - How it works.
    Posted: 23 Oct 2012 at 09:21
Dammit.  I knew 'how' it worked, but without the detail.  Heres the detail and the reason you have the T-piece and the one-way valve.  This has so eluded me for such a long time!

I hope that helps a lot of you out there when your clutch is slipping on the gas and 'why' it would.
One test to do is remove the vac pipe off the clutch cover, and plug up the hole in the rubber pipe..use a bolt or something.  If your clutch still slips, you have air in the hydrolic lines or your clutch is worn.

The later RSVRs 06 onwards I think, changed the design of the TB to improve the slipper action....the hole through the throttle valve.

Also, the 'slipper' was designed to lighten the clutch action by taking some of the clutch pressure; PPC vacuum assisted clutch....as it is known.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote fusebox Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2012 at 09:37
good one dude!!
i havent seeen that drawing in a while!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2012 at 12:55
I've been thinking about this all day so far and the check valve can have only one function, and that is to hold vac at the clutch until you open the throttle to go.

Youve closed your throttle, PPC operates, the revs come down, tickover can not generate enough vac as compared to higher revs running down against a closed throttle.

Once you open the throttle, you vent the vac lines from the airbox, however....hard on the gas must generate low pressure at the TBs, which instead of creating vac to the clutch, just bleeds through from the airbox.

If you did not have the check valve, you would not have enouigh vac at tickover????
So that has to be its only job.  So what is confusing me is with a busted check valve, just how does this give clutch slip hard on the gas?  As you cant have VAC.

Anyone got an idea??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2012 at 12:57
Thats it...I'm going to fit a vac gauge and measure it on a ride out.  I'll see if I can get a digital one.  This is annoying me now!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pieman Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 15:54
Great stuff!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kiwi_rsvr Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 20:16
Interesting, very interesting. I wonder how my "cocked" up version affects thing's.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 21:24
I'll try and explain how i see it.

With the throttle open the vac in the venturi on an intake stroke is lower because the venturi is open to the air box peventing the vac building. That lower vac cannot overcome the force needed to open the check valve and so no vac feeds through to the bladder.  Any residual pressure in the PPC bladder is bled away via the valve venting to the airbox.

When you close the throttle the air box valve is closed no longer venting the bladder and because the venturi is mostly closed the vac builds as it is in a confined space in relation to the airbox. As soon as it builds enough to open the check valve the bladder is activated.

Now the confusing bit. If the check valve fails the bladder is constantly open to the venturi and if the vac builds faster than it is venting to the airbox (at high revs) then the bladder will inflate. There is always vac in the venturi whatever when running otherwise there would be no induction but all the time the check valve is working it is only powerful enough to open the check valve when the throttle is closed.

Make sense ?



Edited by Spoonz - 25 Oct 2012 at 21:25
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wayne'o' Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 21:55
Originally posted by Spoonz Spoonz wrote:

I'll try and explain how i see it.

With the throttle open the vac in the venturi on an intake stroke is lower because the venturi is open to the air box peventing the vac building. That lower vac cannot overcome the force needed to open the check valve and so no vac feeds through to the bladder.  Any residual pressure in the PPC bladder is bled away via the valve venting to the airbox.

When you close the throttle the air box valve is closed no longer venting the bladder and because the venturi is mostly closed the vac builds as it is in a confined space in relation to the airbox. As soon as it builds enough to open the check valve the bladder is activated.

Now the confusing bit. If the check valve fails the bladder is constantly open to the venturi and if the vac builds faster than it is venting to the airbox (at high revs) then the bladder will inflate. There is always vac in the venturi whatever when running otherwise there would be no induction but all the time the check valve is working it is only powerful enough to open the check valve when the throttle is closed.

Make sense ?

NoWacko, i was right with you upto the "with the throttle open" bit !!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 22:20
Originally posted by wayne'o' wayne'o' wrote:

Originally posted by Spoonz Spoonz wrote:

I'll try and explain how i see it.

With the throttle open the vac in the venturi on an intake stroke is lower because the venturi is open to the air box peventing the vac building. That lower vac cannot overcome the force needed to open the check valve and so no vac feeds through to the bladder.  Any residual pressure in the PPC bladder is bled away via the valve venting to the airbox.

When you close the throttle the air box valve is closed no longer venting the bladder and because the venturi is mostly closed the vac builds as it is in a confined space in relation to the airbox. As soon as it builds enough to open the check valve the bladder is activated.

Now the confusing bit. If the check valve fails the bladder is constantly open to the venturi and if the vac builds faster than it is venting to the airbox (at high revs) then the bladder will inflate. There is always vac in the venturi whatever when running otherwise there would be no induction but all the time the check valve is working it is only powerful enough to open the check valve when the throttle is closed.

Make sense ?

NoWacko, i was right with you upto the "with the throttle open" bit !!

Ha ha, think of it like this. You hold a tube in your hand (this is the venturi (humour me)

If you suck on the tube all you do is draw in air but if you put your hand over the other end you create a vacuum inside the tube. Yes.

That is what happens when the throttle plate is open, it partially vents the venturi vac but when it's closed it can build and overcome the force to open the ppc check valve. The Valve is in effect sucked open by vac.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote edelliott Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 23:11
One reason I like the EVO airkit is with the Renegade I seemed to loose all engine braking!
 
And I love backing the bike into roundabouts
Kinda how a twin should beBig smile
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 23:29
Originally posted by edelliott edelliott wrote:

One reason I like the EVO airkit is with the Renegade I seemed to loose all engine braking!
 
And I love backing the bike into roundabouts
Kinda how a twin should beBig smile
 
 

First time i rode a Ducati (999s) of my mates i slid sideways into a wet roundabout because of the rear locking on a closed throttle.

It wasn't until that point that I realised how much the PPC was doing. Now i ride a Ducati full time i don't miss it but it deffo does work assuming everything is in order mechanically.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wayne'o' Quote  Post ReplyReply Direct Link To This Post Posted: 25 Oct 2012 at 23:40
Read this thread about ten times now and each time i understand a little bit more i think, is of interest as i was getting slip at high revs on my falco, if i keep reading it i might one day get it or maybe not. Apologies for being a bit thick but am i right in thinking that it may not be the clutch on it's way out but could be the check valve malfunctioning or my favourite prognosis there's no problem at all i'm just spinning it up like Stoner......cough"BULLsh*t"ahemLOL 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 00:08
Originally posted by wayne'o' wayne'o' wrote:

Read this thread about ten times now and each time i understand a little bit more i think, is of interest as i was getting slip at high revs on my falco, if i keep reading it i might one day get it or maybe not. Apologies for being a bit thick but am i right in thinking that it may not be the clutch on it's way out but could be the check valve malfunctioning or my favourite prognosis there's no problem at all i'm just spinning it up like Stoner......cough"BULLsh*t"ahemLOL 

Take the check valve off, see if it passes air both ways. If it does it's knacked.
If it doesn't take out the clutch plates and rough up the steels with fine wet and dry.

Then go ride and whinge like Stoner if it still slips.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 10:33
Spoonz!!!  You da man!!!

I had not considered the 'hysteresis' of the check valve.  Now it makes sense.
It isn't as simple as having the check valve operating or not operating as like you said, venturi effect still generates vacuum.

Low level vacuum cant over come the check valve, so cant 'charge' the PPC with vacuum.  High vacuum is achieved by closing the throttle, then the valve opens then the PPC operates.

Now I get it.

Which leads to my next observation.....if you take the check valve out and suck both ways <cough>
you should feel a blockage in both directions except in only one direction you can overcome it then the valve operates.  This is an interesting observation as its not as simple as being able to blow through it one way and not the other way.  Some might think its 'sticking' when it is not.

The other observation is this, if you could adjust this hysteresis, then you could change how the slipper works....or can you, not really...once it has operated the PPC is functioning, there is no middle ground....other than when it starts to operate and the whole point of the valve is to prevent it operating hard on the gas....as you need to prevent it operating by having this restriction or limit.  Some have replaced the plastic one way check valve with a metal equiv, used in diesel systems......it would be interesting to test the difference in vac pressure that operates this valve as compared to the original plastic one.....

It so happens I have both and in the post yesterday arrived a simple electronic boost sensor with vacuum sensor, t piece and pipes all for less than 20 quid.  I might be doing a bit of testing soon.

The metal equiv valve thats been frequenting the forum of late, I took it apart.  Its a spring loaded check valve, which has a hysteresis to operation, what I dont know is at what pressure it would operate.  The 'blow' test I did found it very similar....but thats purely finger in the air.

If you wanted to be able to tune the PPC, then it gets complicated.  On the USA forum, a chap called 'theknurl' explains how you could do this....but its conveluted, involves vac tanks, control valves and  other stuff, and not really worth doing at the end of the day.

Everyone....back on yer heads. LOL



Edited by tapmyhed - 26 Oct 2012 at 10:40
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 11:32
You could tune the PPC via the valve resistance. The lighter the force to open it, the sooner it opens and the further it opens or vice versa.

Probably Aprilia tested a resistance that prevents any vac scenario other than a closed throttle from generating the force needed to open it. If you make it open sooner it may trigger on a full throttle.

Noel (the knurl) i think wanted to generate the vac by other means than the venturi opening the check valve. Generating a vac probably isn't that hard but matching how much you apply to to any given throttle situation might be a nightmare.

Think it would be easier to fit a genuine mechanical slipper if it were that important.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kiwi_rsvr Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 11:47
The problem as I see it as most people would not be aware of it working or not. I have taken apart the valves and to be honest they are rubbish (ducks bill type) and on the older bikes 10 years+ they would have stopped working a long time ago.
 
I have one of these spring loaded check valves connected to both throttle bodies and have had some interesting issues around clutch slipping and engine breaking.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 11:52
Originally posted by kiwi_rsvr kiwi_rsvr wrote:

The problem as I see it as most people would not be aware of it working or not. I have taken apart the valves and to be honest they are rubbish (ducks bill type) and on the older bikes 10 years+ they would have stopped working a long time ago.
 
I have one of these spring loaded check valves connected to both throttle bodies and have had some interesting issues around clutch slipping and engine breaking.
 
I thought they had updated the design but maybe not, can't remember.

If it were me i would just use the Aprilia item and consider it a high maintence part and replace with each major service.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kiwi_rsvr Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 12:01
I may revert to a "new" Aprilia one and see if it changes any thing or at least returns a predictable response.
With my setup as is now when you close the throttle from high rpm and then open it again very quickly you get momentary clutch slip (as indicated by a rapid but brief rise in rpm), however on the plus side you can definatley downshift (much easier) into lower gears without even a hit of locking. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 15:29
Kiwi, If I have it correct.....your feeding the PPC with both TBs through 2 check valves?

Do you have the second one venting through the original route through the butterfly and into the airbox?

I would think then your getting a quicker increase of vac using 2 cylinders on shut throttles, bringing on the PPC much quicker???

If your feeding 2 cylinders through one check valve then I'm guessing youve halved the effort needed to turn it on, so effectively halving the 'stiction' of the check valve....ie its like doubling the vac effect from on cylinder.....so the balance between operating the PPC and venting it has been moved....

I did wonder about this with the differance between the standard and the spring loaded valve....if you could use a spring loaded valve that you could adjust the 'pre-load' on, you could tune operation a bit, and equally adjust the TB vent route through the butterfly arm, you could control the point at which you lose vac to the PPC, even restrict the rate of reduction.

2 tuning points......some say you have to have the throttle fully shut to benefit from the PPC, but in later models of RSVR, the TBs were changed slightly to prevent it venting so soon on partial throttle openings....perhaps thats the thing to do:

setup the initiation point by adjusting the spring in the valve
setup the release point against throttle position by adjusting the TBs.....

I can see some fettling advantages to this, but for a normal joe, road riding with occasional track days I dont see the point....as long as it works!  If my bike was track dedicated, I would most likely look into this.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote kiwi_rsvr Quote  Post ReplyReply Direct Link To This Post Posted: 26 Oct 2012 at 19:12
I have both TB's feeding into a y piece (equal length) then a longer pipe down to a single valve , the other side of which has a y piece for the fuel pressure and other side of the valve then onto the clutch diaphram tube.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2012 at 12:56
Interesting.  I'll have to look at mine and see how that goes.  I wasn't aware of the connection to the fuel pressure..........
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tapmyhed Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2012 at 13:00
I also tested a replacement OEM check valve......it hardly needs any effort to operate in the right direction, which brings me back to the hysteresis thing.....not sure about it....other than it would have to operate with a closed system behind it and that would take vac effort to overcome...akin to the differance of sucking air or water through a straw....one takes more effort, so that would be the hysteresis aspect of pulling against the PPC which would hold back the valve when the throttle was closed. ????  I understand it anyway.....

I almost got to testing the vacuum this weekend except it started to bloody rain, so I had to knock that on the head.

Hopefully next weekend.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Craigr1977 Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr 2017 at 12:41
Hi Guys,
I posted about havinmg some issues with the clutch in the gerneral section as i couldnt find a dedicated thread, then I found this one in the RSVR thread this morning. Simple really, i was just searching for Tuono related threads doh.
 
Anyway, Gen 2 2009 Tuono. I've discovered from exploded diagrams of a standard configuration should be as follows.
 
1 vac line from rear TB to check valve with the other vac line joining below the check valve before routing to the clutch casing.
 
On my bike both lines are tee'd above the check valve, meaning both TB's are creating vacuum rather than just one as is the case in the standard configuration.
 
Would I be right in thinking this would create the clutch slip at high revs as i know the clutch is good as with lines blocked it doesn't slip at all.
 
Cheers Craig
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Post Options Post Options   Thanks (0) Thanks(0)   Quote damo46 Quote  Post ReplyReply Direct Link To This Post Posted: 07 Sep 2017 at 13:33
On the new check valve, when fitting it does the arrow point up towards the throttle bodies.
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