Alfa Romeo Owners Club of Australia Forum

Technical => 932 Series (156, GTV, Spider, 147, GT, and 166) => Topic started by: johnl on August 29, 2018, 03:25:17 PM

Title: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on August 29, 2018, 03:25:17 PM
These things are generally known to cause problems with the clutch action, because they create a degree of disconnect between what the pedal does and what the clutch itself actually does. For a long time now I've been 90% convinced that the delay valve has been 'interfering' with with gear changes because the clutch is a bit vague and 'numb' in the way it works. It's harder than it should be to consistently perform clean gear changes, i.e. getting the timing just so.

So, today I pulled the battery tray to have a gander at the suspect problematic valve, to see how it might be deleted, bypassed, or in some way 'sabotaged'.

Firstly, I now want to shoot the person who designed the battery tray attachment, what a stupid way to do it. It's not so much that it's necessary to remove the fuse block from the fuse box, and to also disconnect wires from it to do so, and it's not so much the 10mm nut inside the box carefully hidden beneath a little plastic cover, it's the utterly hidden and not easily accessible 10mm nut beneath the the rear of fuse box itself. What a pain, but I digress...

I was initially hoping it might be possible to disconnect hoses and in some way be lucky enough that they could be reconnected in a manner that bypassed the valve, but of course it's not going to be that easy. One thing is clear, it will be necessary to retain the hard line on the outlet side of the valve (that is connected to the rubber hose that goes to the slave cylinder), because the hose is permanently attached to the hard line, and can't be unscrewed from the rubber hose (there is no threaded fitting, just a clamped fitting).

The hard line is also permanently attached to the delay valve, and can't be unscrewed from it. If one were to ever need to replace the rubber hose, then it looks like the hose, hard line, and valve would all need to be replaced as a unit. The valve can be unscrewed from the hard line that leads to the master cylinder (though it seems to attach to flexible braided hose near the MC rather than directly to the MC itself).

I'm now thinking that the path of least resistance might involve taking off the valve, rubber hose and hard line as a unit. It might then be possible to cut the end of the valve body off, delete its' guts, then weld a plate onto the end of the valve body, leaving an empty cylinder. The empty cylinder should then just fill with fluid, and cause no problems.

I'm thinking it would be best to purchase a used valve (and associated hard line and rubber hose), and modify this instead of risking encountering a problem while modifying the only valve etc that I currently have...

Any thoughts or red flags on this idea?

I have done something similar to this with the clutch delay valve in my old Accord, which did improve the clutch action and gear change precision (though the Accord delay valve was externally quite different to the Alfa one).

Regards,
John.

Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on August 29, 2018, 03:45:32 PM
Why not bypass it with new bubble flares in the existing hardlines and a short bridging length of flared tubing with female flares?
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on August 29, 2018, 05:45:39 PM
Thanks CB,
Possibly.

This had crossed my mind. The hard line in and the hard line out of the valve are different OD, and I don't know if this would limit the availability of adaptors(?). I'll measure more exactly and make some enquires, when I can find time.

The 'in' hard line will already have a flared fitting, so I'd like to use that if possible. So I'd need to disconnect it to establish exactly what kind of flare and thread is used to ensure it fits an adaptor. The hard line that is attached to the rubber hose would need to be cut as close to the valve as possible, and then be flared to suit a fitting and adaptor.

I doubt it would be neccesary to add any extra hard line to bridge a gap, as I think it should be possible to bend the existing lines to meet each other end on, even if this might mean needing to make a supporting bracket, though I suspect a support isn't required since the valve is currently unsupported other than by the 'in' hard line (though I wouldn't consider this 'best practice'...).

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on August 29, 2018, 06:17:21 PM
It's a clutch, much less a life-or-death instrument than brakes. You could just cut, sleeve and hard solder too.

FWIW anyone with a Sele knows the battery tray routine, it's not that hard and is a good chance to clean up stuff around there from general accumulated grime.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on August 30, 2018, 12:55:20 PM
Quote from: Citroënbender on August 29, 2018, 06:17:21 PM
It's a clutch, much less a life-or-death instrument than brakes. You could just cut, sleeve and hard solder too.

A few possibilities.

I had another look at the connections, it's a bit hard to see in poor light and shadow but the hard line going to the valve isn't (as I first thought) attached to a braided hose near the firewall, that's one of the brake lines. The clutch hard line screws into a metal fitting that itself attaches to what appears to be a plastic fitting protruding from the firewall. This then has a fitting that appears to be the same as (or very similar to) the fitting where the rubber hose attaches to the slave cylinder, i.e. a 'push - pull' fitting with a securing wire clip. So, to remove the hard line from the firewall; pull the clip out and then just pull out the hard line (I assume...).

This would be a good thing because there isn't much room to swing even a small spanner between the firewall and the inlet manifold (to undo the threaded fitting on the line itself), let alone get ones' hands in there. So, it seems like removing the hard line between the firewall and valve should probably be relatively quick and easy (where have I heard that before...), as should be taking out the valve and it's undetachable hard and rubber lines. Once all the lines and the valve are out it should be easy to unthread / cut the valve from the lines and then solder the lines together.

I'm not convinced that this would be less work than taking the valve off, cutting, gutting, and resealing it with a welded plate. It is however a viable Plan B if Plan A (eviscerating the valve) doesn't work out for whatever presently unkown / unexpected reason. I kind of like Plan A if for no other reason that it involves less dimantling (i.e. avoids removing the hard line from the firewall), thus less risk of something breaking, or refusing to re-assemble, or re-assembling but then leaking...

Quote from: Citroënbender on August 29, 2018, 06:17:21 PMFWIW anyone with a Sele knows the battery tray routine, it's not that hard and is a good chance to clean up stuff around there from general accumulated grime.

The battery tray will be a lot easier next time, now that I know exactly where that damned 10mm nut is and how to get at it...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: bazzbazz on August 30, 2018, 03:22:12 PM
Quote from: johnl on August 30, 2018, 12:55:20 PM
The clutch hard line screws into a metal fitting that itself attaches to what appears to be a plastic fitting protruding from the firewall. This then has a fitting that appears to be the same as (or very similar to) the fitting where the rubber hose attaches to the slave cylinder, i.e. a 'push - pull' fitting with a securing wire clip. So, to remove the hard line from the firewall; pull the clip out and then just pull out the hard line (I assume...).

The plastic fitting protruding from the firewall is the back end of the Master Cylinder. And yes, pull clip out and pop off the line fitting, and yes, as usual, there is bugger all room. I suggest to save a lot of swearing when working here to undo upper, lower & front engine mounts and swing the engine forward to give some room.

Saves having to apologize to the neighbors for the language.  ::)
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on August 31, 2018, 12:51:12 PM
Quote from: bazzbazz on August 30, 2018, 03:22:12 PM
The plastic fitting protruding from the firewall is the back end of the Master Cylinder. And yes, pull clip out and pop off the line fitting, and yes, as usual, there is bugger all room. I suggest to save a lot of swearing when working here to undo upper, lower & front engine mounts and swing the engine forward to give some room.

Saves having to apologize to the neighbors for the language.  ::)

I have no neighbours near enough to disturb with the language and general loss of ones' 'cool' that can occur while battling with the stupidities inflicted upon us by car designers, but the family (including the dog) are a different matter...

It sounds as if my preference to avoid, if possible, disconnecting the hard line at the firewall is well enough founded.

Thinking about these 'delay valves', it has occurred to me that there is a possiblity that they could be implicated with cases of the clutch hydraulics 'sucking' air into the system. My theory is that the valve might in certain circumstances create a momentary low pressure inside the master cylinder that might allow air to enter the MC past a worn / marginal piston seal.

How does such a loss of 'normal' pressure in the MC occur? These delay valves are designed to be free flowing when the fluid is passing from the MC to the slave cylinder, but restrictive when flow is reversed. If the pedal is released quickly enough then the restriction at the valve could be great enough to cause a substantial drop in pressure between the valve and the MC, even if pressure is still fairly high between the valve and the slave cylinder. This could concievably result in an aged MC seal that starts to leak air into the MC well before it might have done if the valve didn't exist...

The MC will have a 'directional' piston seal, i.e. one that is far better at containing a high pressure inside the cylinder than it is at preventing air from entering the cylinder, if the internal pressure were ever to be low enough. This is because, due to the geometry of the seal shape, the seal will expand tightly against the cylinder wall when internal cylinder pressure is significantly higher than atmospheric, but doesn't seal nearly as strongly if the internal pressure is quite low (especially near to zero).

When there is only a small internal pressure, the seal has to largely rely upon the inherant tightness of its' fit inside the bore, and if the seal is old it will have hardened and compressed to some degree, and no longer statically press against the bore wall as strongly as it did when it was more youthful. Nor, due to age hardening, will it so readily expand with internal pressure, so internal pressure now has to be somewhat higher to push the seal lip against the bore as effectively.

If the valve didn't exist, then the MC piston seal would be exposed to the full system pressure for the entirety of its' return stroke, so there will be significant internal pressure acting on the seal nearly all the way to the pedal being completely 'up', assisting to prevent seal leakage by expanding the seal against the bore until the reservoir port is exposed. Of course the pressure would reduce the closer the pedal is to being fully released so that the affect (seal expansion) is relatively small near the end of piston motion, but it is still there until the piston seal passes the port into the reservoir.

On the other hand, if a delay valve is present and if the pedal is released quickly enough, then the internal MC pressure could potentially drop to near zero well before the pedal is fully released (due to the restiction at the valve). This would mean that the piston seal is moving in the bore for some distance without significant internal pressure acting to expand it against the bore wall, so the likelihood of air bypassing the seal would be increased. With a good seal this wouldn't be an issue, but if the seal is compressed and hardened by age, it might be significantly more likely...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: bazzbazz on August 31, 2018, 08:33:39 PM
This may be of some interest -

https://www.competitionsupplies.com/clutches/tilton-clutch-flow-control-valve (https://www.competitionsupplies.com/clutches/tilton-clutch-flow-control-valve)
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 01, 2018, 03:01:50 PM
Quote from: bazzbazz on August 31, 2018, 08:33:39 PM
This may be of some interest -

https://www.competitionsupplies.com/clutches/tilton-clutch-flow-control-valve (https://www.competitionsupplies.com/clutches/tilton-clutch-flow-control-valve)

I can't imagine why anyone might actually want to fit one of these things if they are lucky enough to have a car not fitted with one. My experience with them is that they cause problems with gear shifting, albeit relatively subtle ones.

The story, possibly apochryphal, goes that some car makers started to use them as a result of drive train breakages during test drives by mechanically unsympatheitc journalists brutally abusing the clutch, and then writing that the drive train was a weak point on the car...

All they are supposed to do is retard / slow the re-engagement of the clutch, which can cause additional clutch slippage, and presumably wear over time. If the clutch is used sensibly then they fix a problem that doesn't really exist. Before I disabled the delay valve on my Accord, I found that the clutch re-engagement was somewhat erratic, sometimes fine, sometimes there would be unexpected slippage, sometimes it just felt a bit weird. I'd lose confidence that the clutch would do what I expected it to, and get a bit 'lost' in the pedal travel.

Oddly, considering that these valves supposedly don't affect flow from the MC to the slave cylinder (supposedly only the reverse flow), the disengagement point seemed to also change erratically. Sometimes the clutch would disengage with only a short pedal push, sometimes the pedal needed to go all the way to the floor before the gear would cleanly release or cleanly engage.

After disabling the valve this all got a lot better. The clutch behaviour became less erratic and significantly more predictable.

To me the clutch in the 147 feels quite similar to how the clutch in the Accord felt before I gutted the valve, which is why I have some hope that deleting or disabling the Alfas' delay valve might improve it... 

Regards,
John.


Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 01, 2018, 09:20:02 PM
Coming soon... Conversion to twin Stromberg CD175s and mechanical advance only dual point distributor?

More seriously, what if the clutch system is just deficient through age, wear or trapped air? The fact you can buy replacement hydraulic dampers for various other marques, suggest it may be a known failure point.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: poohbah on September 02, 2018, 09:43:10 AM
QuoteComing soon... Conversion to twin Stromberg CD175s and mechanical advance only dual point distributor?

Going slightly off topic (and because I have no technical input to this discussion), I watched a video the other day of Edd China helping some Scandinavian guy restore his Mk 1 Golf GTi, which included replacing the "i" with twin carbs. (Can't recall if Strombergs or Webers). Some people do the strangest things.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 02, 2018, 03:37:24 PM
Quote from: Citroënbender on September 01, 2018, 09:20:02 PM
Coming soon... Conversion to twin Stromberg CD175s and mechanical advance only dual point distributor?

CB, are you suggesting that these valves are a major advance in automotive technology that we now can't do without? Respectfully I strongly disagree (the word 'bollocks' comes to mind, respectfully of course!).

Strombergs? What are you smoking?

Maybe a brace of DCOE Webers, or even DHLA Dell'Ortos (more or less a DCOE clone). Properly set up you'd get the same power (or at least near to it, though the graph might not be quite so smooth), and, they would sound fantastic! (compared to the muted and uninspiring induction sound of the EFI single TB). Keep the ignition timing as controlled by an ECU though.

With good carbs, the butterflys would do exactly what the driver wanted them to do, not what the ECU decides it will allow them to do. In particular the throttles would close sharply when the driver lifts off, not the lazy / slow closure (causing 'rev hang') that emmissons control requirements force upon us in order to reduce nitrogen oxides...

Call me a Luddite, but throttle response and 'drivability' would be much improved (Webers and Dell'Ortos specialise in throttle responsiveness), at the expense of a possible slight reduction in absolute power, and idle speed control (AC and electrical loads would affect idle, a small price to pay, though you could get around the worst of it with a throttle solenoid activated when the AC is on).

Quote from: Citroënbender on September 01, 2018, 09:20:02 PMMore seriously, what if the clutch system is just deficient through age, wear or trapped air? The fact you can buy replacement hydraulic dampers for various other marques, suggest it may be a known failure point.

The clutch itself works fine, no slippage or other issues other than what seem attributable to the delay valve. It was bled recently.

BMW drivers whinge about these things a lot, deletion is common, you can buy kits to do it.

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 02, 2018, 04:28:05 PM
BMW drivers also think the cure for a flat SMG accumulator is replacement of the pump relay.  ::)

I wasn't suggesting wear in the clutch friction but possibly seal wear in the master cylinder, assuming they also have a good shaft seal this might go unnoticed for a while.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 03, 2018, 03:56:24 AM
Quote from: Citroënbender on September 02, 2018, 04:28:05 PM
BMW drivers also think the cure for a flat SMG accumulator is replacement of the pump relay.  ::)

I'll just pretend that I know what an SMG accumulator actually is (since my car has a manual gearbox and I'm pretty sure doesn't have one, I'm guessing something to do with semi automatic gear selection and the clutch?).

Quote from: Citroënbender on September 02, 2018, 04:28:05 PMI wasn't suggesting wear in the clutch friction but possibly seal wear in the master cylinder, assuming they also have a good shaft seal this might go unnoticed for a while.

A reasonable thought. Which prompts a speculation re a possible cause of the clutch engaging and disengaging at variable pedal heights:

If the main MC seal were to be marginally effective and as a result 'sucking' air on the pedal upstroke (but not neccesarily actually leaking fluid out, though it might), then considering that the MC is very high up in the system, some or all of this air might self bleed into the reservoir whilst the pedal is fully 'up'(?). Sometimes it might all self bleed out of the cylinder, other times it may not have time to completely self bleed...? As a result there could possibly be a variable amount of air present in the system on each pedal stroke, so clutch engagement and disengagement points in the pedal travel would become somewhat erratic. If such a leak became bad enough then not all air would self bleed regardless of how long the pedal is 'up', and so air might get pumped farther 'down' into the system, and become more permanently entrapped.

Re my earlier speculation about delay valves creating a momentary lesser pressure in the hydraulics between the MC and the valve (than would be the case if no valve were present); this may well make such a problem more likely, and / or more severe. It might be more likely because the  internal MC pressure would be lower for a greater distance in the piston back-stroke, and the longer a lower pressure exists in the MC the more likely it is that air will leak past a dodgy seal into the cylinder, especially while the seal is still moving in the cylinder bore...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 09, 2018, 02:54:27 PM
So I did it today, that is, I disabled the clutch delay valve (CDV). On the face of it, this has worked very well. The clutch is now much nicer to use, seeming to disengage more fully and without subtle 'delays' in engagement and disengagement. Gear shifting is significantly improved with a more predictable clutch action. The pedal now feels noticeably 'springier', which is quite evident especially on the pedal upstroke.

There are of course two things that have occurred, the valve has been disabled so no longer does what it was designed to do (hooray), and the system has been bled as part of re-fitting it. Bleeding may account for what I'm feeling, but it was bled a couple of months ago and this did not have the same affect (a slight improvement in clutch action, but only slight). I suppose time will tell if the clutch action deteriorates from here due to ingress of air...

To disable the valve; firstly I did the tedious preliminary removal of the battery and tray. Then clamped the rubber hose leading from the reservoir to the MC. Then disconnected the single threaded hard line attachment at the valve. Then disconnected the fitting at the slave cylinder (removed wire clip and pulled it off). Now I had the valve and its' permanently attached hard line and rubber hose on the bench.

Next I ground off the swaged flange at the base of the valve body, until the steel disc came out (this disc is what you see when looking at the bottom of the valve, held in place and sealed by the flange, it has a hole in the center). There is an internal plastic cylinder that can now be extracted (this cylinder was held and sealed by the steel disc). Next I welded a steel plate onto the base of the valve body to reseal it. The valves' external cylinder is now empty, and the valve is disabled. Lastly, the valve was re-installed and the system bled (using my home made pressure bleeding thingamy). It was all very straightforward, nothing went wrong it and took about two hours from start to finish.

The CDV seems a very simple device, yet it's principal of operation isn't obvious (at least not to me...). It's just a cylinder with an inlet (from the MC line) at the top / side of the cylinder. The outlet tube (leading to the slave cylinder) projects about 1cm into the top of the cylinder void, with an open end that bears against the end of an internal hard plastic tube. You can see where the open end of the inlet tube presses against the end of the plastic tube, there is a tell tale 'ring' shaped mark in the plastic made by the open end of the inlet tube. The junction between the inlet tube and the plastic tube must be partially sealed because they are pressed against each other (hence the tell tale mark), but I can't imagine that it's a positive seal. The inlet tube must have some holes in it near where it starts to project into the cylinder void (above its' open end), because I could hold my finger over the fully open end of the inlet tube and was still able to blow air into the void (a hole or holes must exist in the inlet tube wall, but are not actually visible in there).

On the disc which can be seen at the end of the valve body, there is a hole which opens onto a void in the internal plastic cylinder, this void consequently being exposed to atmospheric pressure. The valve action must be associated with this void being exposed to atmosphere, and possibly by deformation of the plastic tube due to hydraulic pressure, but I'm not at all sure exactly how...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 10, 2018, 02:20:50 PM
So with further driving / familiarity with the now disabled CDV; the clutch action is now noticably somewhat lighter than it was before. The action now has a 'mechanical springiness', rather than a 'rubbery springiness', which is apparent on both the down and up strokes of the pedal. Pedal weight increases as the pedal moves toward the floor, but in about the last quarter of pedal travel it now decreases noticably, i.e. there is a now feeling of the pedal / clutch going 'over centre' that wasn't there previously. The shift action is cleaner, lighter and more consistent than before, and shift action is generally improved. This is all good.

However there is a slight down side. When 'rev matching' the car is now less tolerant of ham fisted throttle 'blipping' (ham footed?). If the rpm are a bit high or a bit low when I change into a lower gear, then the car will 'lurch' (momentarily accelerate or 'decelerate' slightly) as the clutch pedal is released. This wasn't as big a deal when the CDV was operating. It's obvious that when the CDV was unmolested it allowed a degree of extra slippage as the pedal was released, so if the rpm were not quite right then there was some 'blurring' of the clutch engagement that to some degree masked clutzy technique. Without this extra slippage the clutch engages more positively and strongly, so rev matching has to be better.

Clutzy technique is I think a by-product of becoming habituated to the original vagueness and erraticity in the clutch action, i.e. technique was hard to hone because the clutch action was less than consistent so it was harder to get the timing exactly right. I'm sure my technique will improve with more practice / familiarity, it's already getting better.

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 10, 2018, 10:34:41 PM
People seem to have lost interest in this, but I've become rather curious to know how these valves actually work and how this might affect the clutch action. I haven't found any specific explanations anywhere, so can only speculate based on what I found inside mine:

Firstly, there are no obvious valving arrangements inside the CDV, i.e. no springs or spring loaded components, or other obviously moving parts. It's a bit mysterious.

The CDV has a cylindrical body with a fluid inlet (from the MC) at the top of the side of the cylinder. At the very top is a centrally located outlet tube leading to the slave cylinder. There is a hard (ish) but still somewhat pliable largish OD (about 16mm) hollow 'rubber' tube inside the CDV, which fills much of the internal space (I initially thought this was made from a semi pliable plastic, but it is actually some kind of rubber-like polymer).

This rubber tube is closed at the end that is highest inside the CDV, but open at the other end. The open end is exposed to atmospheric pressure via a small hole in the base plate of the CDV. Fluid is pumped into / through the cavity between the rubber tube and the outer cylinder.

The outlet tube projects inside the top of the cylinder by approximately 1cm, and has an open end inside the cylinder. It also has at least one small orifice in its' wall very close to the internal roof of the cylinder (higher up than the fully open end). The length of the rubber tube seems to be such that normally its' flat internal end is pressed against the open end of the outlet tube, thus sealing the open end of the outlet tube.

When the pedal is depressed, pressurised fluid enters the CDV via the inlet tube. The fluid passes out of the CDV through the small orifice in the outlet tube wall (that is near the roof of the cylinder), and from there toward the slave cylinder. The clutch itself now creates a resistance to fluid flow, so fluid pressure increases above atmospheric.

I'm guessing that the rising pressure now causes the rubber tube to deform in a manner that causes its' effective length to become slightly shorter (i.e. effectively contract, 'crushed' by the pressure). This could occur because the rubber is somewhat pliable, the ID of the hollow rubber tube is only exposed to atmospheric pressure, but, the pressure on the tube OD tube is exposed to a substantially higher system pressure. If so, then this would cause the end of the rubber tube to move slightly away from the open end of the outlet tube, and so 'unseal' it. This would then permit a less restricted flow of fluid as the pedal is further depressed, once internal CDV pressure reaches X psi.

When the pedal is released, the internal pressure will fall, and the length of the rubber tube will again become slightly longer, thus resealing the open end of the outlet tube. Fluid flow backward from the slave cylinder will now be constricted to whatever flow is allowed by the restricted orifice at the top of the outlet tube, thus impeding the rate at which the pressure acting inside the slave cylinder drops, and so slowing the rate at which the clutch re-engages.

Well it's a theory...

Whatever, that the hollow inner tube is demonstrably made from a pliable (and non-reinforced) rubber, is exposed to hydraulic pressure on its' OD, and only exposed to atmospheric pressure on its' ID, means that the rubber tube must suffer some degree of deformation when the clutch pedal is depressed. This explains quite a lot.

Today I went for quite a long drive, and was noticing that with the CDV now disabled (i.e. the rubber element deleted) the engagement and disengagement points in the pedal travel were now consistently at the same height, whereas before disabling the CDV they generally weren't.

It would also explain changes in the engagement and disengagement points that seemed to be temperature related (the pedal becoming mushier on warmer days and after longer periods of driving). The rubber must get softer the hotter it happens to be, which must be affected by ambient and under bonnet temperature.

It would explain why the pedal action is now generally less 'mushy' and more 'defined'. It would explain why the pedal 'weight' has become noticeably lighter (the rubber no longer abuts the open end of the outlet tube at any time, so can never obstruct it).

It would explain why deleting the rubber would increase the pedal height at which the clutch engages and disengages, as it has done, i.e. pedal motion is no longer 'lost' due to the tube deformation.

Having this relatively soft tube in the system is analogous to having a rubber hose a portion / length of which that has at least partially failed, and so swells with internal pressure (causing a mushy pedal), except that instead of expanding with pressure, the tube partially collapses. This must surely be a cause of 'mushiness' in the system, as my experience with this supports...

The more I drive the car without this BS valve in operation the more I'm liking how the clutch is now working, and the improvement in gear change quality that this has created. If you have a manual gearbox then your car will have one of these damned things, my advice is get rid of it, I don't think you'll regret it...

Regards,
John.


Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 11, 2018, 02:58:34 PM
No comments or questions, or even interest? Maybe if I say that disabling the CDV has turned out to be one of the most effective modifications I've yet made to this car (and I've made some other very effective mods...). It's been even more effective than a similar modification I made to my old Honda Accord. And, it only took a couple of hours and cost zero dollars (if I don't count half a welding rod and having to buy a bottle of brake fluid...).

I'm now on an anti CDV crusade, in case you hadn't noticed...

Regardless of the car to which they are fitted, these CDV devices are seemingly always generically described as having zero restrictive effect on the pedal downstroke, and to only 'work' on the pedal upstroke. Assuming that my newfound understanding of how these things might actually function is correct (at least the ones fitted to the 147), then this just can't be true.

According to my understanding, in a static state (pedal undepressed) the internal rubber tube abuts and blocks the largest orifice at the end of the outlet tube (its' internal open end), leaving only a more restricted orifice for fluid to pass through. As the pedal is depressed and fluid pressure rises to X psi this changes, with the largest orifice becoming opened by the rubber tube becoming compressed and 'withdrawing' from the open end of the outlet tube, and flow capacity thus increasing (i.e. flow out of the CDV to the slave cylinder, as well as back into the CDV from the slave cylinder).

So, as the pedal is depressed there is an initial flow restriction which then 'de-restricts' with further pedal motion. I can't imagine that the pliable rubber tube moves all that far away from the open end of the outlet tube, so it's likely that though the end of the outlet tube becomes 'unsealed', the proximity of the closed end of the rubber tube to the open end of the outlet tube may still tend to be at least somewhat restrictive (which would explain why with the rubber tube deleted my pedal now feels at least a little bit lighter throughout the pedal strokes, i.e. there is no restriction at all at any time).

This all happens in reverse as the clutch pedal is released. The internal CDV pressure falls to X psi and so the rubber tube expands (de-compresses), and so the end of the rubber tube reseals the open end of the outlet tube (through which fluid is now flowing in reverse direction), and creates a more restrictive path for the fluid pressure to release from the slave cylinder, but only after the pedal has been partially released.

So as I understand it, these valves create a significant increase in restriction in both directions, but only when the pedal is in the upper part of the pedal travel. When the pedal is lower than this (i.e. closer to the floor), then the restriction decreases (though doesn't necessarily disappear completely), and this is the case whether the pedal is being depressed or being released. So, the 'softening' of the clutch re-engagement only occurs after the clutch has already become partially re-engaged, not from the beginning of the re-engagement.

It's less noticeable and has less affect on the pedal down-stroke because the pedal pressure is not limited, other than by the speed with which the pedal can be depressed (so the pedal will be a bit stiffer the faster you push it, but fluid will still flow through the restriction). However, on the up-stroke the clutch springs (diaphragm) can only push against the fluid pressure with X force, and if the fluid has to pass through a restriction then the rate at which the clutch itself can fully re-engage will be impeded, but only after the pressure has dropped below X psi...

This would be much easier to explain with accompanying diagrams...

Whatever, these things add a rubbery elastic element into the system, which compresses and de-compresses with changes in pressure. This causes mushiness in the pedal. If that's not bad enough, the elasticity of the elastic element will be variable depending on the temperature of the elastomer...


Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 11, 2018, 04:52:52 PM
Further (over of this yet?), the atmospheric air cavity inside the CDVs hollow rubber tube must in effect act like there is a large air bubble in the system, one that is at best only partially isolated from the hydraulic system by the stiffness of the wall of the rubber tube. The rubber is kind of 'hardish', but I can squeeze the tube walls significantly closer together between my fingers, so it's not all that rigid.

If there were an actual air bubble trapped in the system, at least its' pressure would rise (and fall) in step with system pressure, rendering the bubble increasingly less compressible as the pressure increases, but the pressure in the rubber tubes' cavity never rises above atmospheric...

Did I mention that the clutch engagment and dis-engagement points in the pedal travel are now not only each at the same consistent pedal height, but also are now significantly higher off the floor than they were with the CDV in operation? It's no longer essential to fully depress the pedal all the way to the floor to fully release the clutch (as it often was before, though this was something of a variable...). I'd say that removing the compressible rubber tube probably has a big part to play with this, i.e. less deformation of the tube equating to less 'lost' pedal motion, and a more consistent action.

Pedal feel has been substantially improved, I can now feel with my foot the engagement and dis-engagement points in the pedal travel, which was previously quite 'numb'.

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 11, 2018, 10:19:46 PM
QuoteNo comments or questions, or even interest?

Well, I had two days off for a cultural occasion.
I await the next instalment of automotive retrogression. Will it be a power steering delete?
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 12, 2018, 12:13:16 AM
CB,
From a position of having actually experienced back to back how the 147 clutch behaves both with this device operating and without it, and how this affects the driveability of the car, I assure you that disabling / deleting it is a fairly substantial step forward into the past, and not in any important way a downgrading of the engineering of the car. Not every manufacturer uses these, even today.

That these newfangled gizmos have been adopted only relatively recently by some manufacturers doesn't ipso facto make them a good thing. They aren't the solutuion to a significant problem, rather they are a band-aid for a potential problem and the creater of a significant real problem (or chain of problems). I strongly suspect that they were forced upon drive train engineers from above as a crude means of reducing drive train shock if drivers abuse the clutch (i.e. avoidance of potential warranty claims...).

I can imagine the way it might have gone; the 'powers that be' inform the engineers that there have been some drive train claims under warranty, and that therefore they are instructed to come up with some means of mitigating the possibility of more claims, and while you're at it, make it cheap to implement. The engineers grumble, but comply...

I do think I've put forward a reasonable case for why CDVs are not such a good thing to have. I've detailed my personal experience, and develped a cogent explanation (I think) as to how exactly they must do what they do, based on a reasonable analysis of the internal components that exist inside them (at least the ones in the 147). I've described the problems created by having an elastic element in a hydraulic system, and how this must adversely affect the dynamic behaviour of the system. If this isn't enough then I don't know how I could convince you, unless you could drive my car...

PS, and off topic, if even fairly small modern cars weren't so damn heavy (kerb weight), then manual steering would be fine by me. Over the years and numerous cars that I have driven, by far the most communicative, lively and fun to use steering that I have experienced has been with non PS systems (though not all manual systems are that good). It's all smiles, until you want to park it (but then I have very strong arms and shoulders...).

At least part of the issue with heavy (manual) steering is the trend to zero scrub radius (or very near to it), especially with FWD. Along with high kerb weight, this can make PS more or less a necessity (unless you can live with maybe five or so turns lock to lock). With zero SR, at low speed as the front wheels are turned the contact patches must be 'scrubbed' around the point at which the steering axes intersect the ground, which adds substantial 'weight' to the steering (more so at low speed, the effect diminishes as speed increases). If the SR were to be e.g. about 100mm or so, then instead of the contact patch 'scrubbing' around the steering axis, the entire wheel will roll along an arc centred on the offset steering axis, with very little 'scrubbing' at the contact patch, and so the low speed steering effort will be a lot lighter. Unfortunately this isn't all that good for FWD cars, as substantial SR is a major contributor to 'torque steer' affects.

I once owned a BMW 2500 with PS and a fair dose of SR. One day the PS died, but this made very little difference to the steering weight. I happily deleted the PS pump rather than spend the $s to replace it, and my wife didn't complain about the steering becoming heavy......

Regards,
John.

Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 12, 2018, 01:03:48 PM
Quote from: Citroënbender on September 11, 2018, 10:19:46 PM
I await the next instalment of automotive retrogression.

CB,
Maybe if we approach this from the other end. Rather than me continuing to attempt explaining why I think CDVs are inherently a bad thing that significantly degrade drivability and therefore ought to be ditched, can you say what it is that a CDV actively does that improves the clutch functionality? Why exactly is it that deleting it is an act of "retrogression"? How does deletion make the clutch function and driving experience worse? Why are we better off with a CDV than without?

I accept that a CDV will to some degree protect the drive train from abusive treatment (other than the clutch itself, which is not unlikely to wear at least a bit faster because of additional slippage), so let's assume that the driver isn't an idiot, has at least some mechanical sympathy and won't use the clutch in a brutally stupid manner...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 13, 2018, 08:23:45 AM
I have indeed, not driven a 147 with the clutch damper removed.

The present manual car's clutch bears a slightly disconnected feeling, it is no particular concern to me. How effectively the gears actually engage is of more interest, as syncros are never cheap to buy, nor easy to replace. (Excluding surprises, I try to not brake from more than 30km/h in a manual car - preferring to read the conditions, use my throttle and gears.)

If I had reason to consider the damper as suspect I would first try a genuine new item, and bleed the system fully.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 13, 2018, 02:45:07 PM
Quote from: Citroënbender on September 13, 2018, 08:23:45 AM
I have indeed, not driven a 147 with the clutch damper removed.

I thought it unlikely. Respectfully I suggest it's untenable to criticise this particular modification if you haven't experienced the results of it.

Quote from: Citroënbender on September 13, 2018, 08:23:45 AM
The present manual car's clutch bears a slightly disconnected feeling, it is no particular concern to me.

So you recognise that some problem exists, but you don't find it to be an issue for you. That's fine, but it might not be for others, it certainly wasn't any longer acceptable to me. Your car may be less affected by the CDV action than was mine, maybe down to the state of the clutch itself, or some difference between brands of clutch, who's to say...

Quote from: Citroënbender on September 13, 2018, 08:23:45 AM
How effectively the gears actually engage is of more interest, as syncros are never cheap to buy, nor easy to replace.

My main issue wasn't so much the actual feel of the pedal (though I didn't like it much, it just didn't feel 'right' or anywhere near as good as many other clutch pedals in my experience, even ones that used a cable). It was more how the erraticity in the hydraulic system adversely affected the shift quality in a rather random fashion. It was obvious that sometimes the clutch was fully disengaging, and sometimes not quite fully, the gears would sometimes be easy to shift, sometimes a bit resistant. This was not synchromesh related (which feels different). However, the feel of the clutch pedal and the quality of the shift action are interrelated. 

Disabling the CDV resulted in a complete cure for both the pedal feel, inconsistency of clutch action, and the resultant shifting issues. Changing gears is now a predictable pleasure, whereas before it just wasn't.

Keep in mind that my car doesn't have a stock 147 shifter, but a very modified Honda shifter that shortens the lever throws and is much more precise in its' action. It also has modifications at the gearbox end which further reduce the shift lever throws (my cars' shift lever movement is very 'tight', by which I don't mean stiff). This reduction in lever throw means that the lever has substantially less leverage on the gearbox internals associated with shifting gears, and so any resistance to changing gear that might be caused by say a slightly dragging clutch will be more obvious with my car than a car with the OE long throw shifting mechanisms.

I'm suggesting that your shift mechanism will have a lot more leverage than mine, so where I can feel untoward resistances when shifting gears, you may not be able to feel them? If so then this doesn't necessarily mean that such resistances never occur...

Quote from: Citroënbender on September 13, 2018, 08:23:45 AM
If I had reason to consider the damper as suspect I would first try a genuine new item, and bleed the system fully.

FWIW, there were no signs inside my cars' CDV that it was in any obvious way worn or damaged.

Because of pedal 'sponginess' I had already bled the clutch previous to disabling the CDV, which made no difference to the "disconnected" feeling and the issues associated with this. I used a pressure bleeder, and bled it a lot, several times because the pedal didn't improve, there were no bubbles coming out. After disabling the CDV I bled it again (of course), but due to a limited supply of fluid on hand only did a very quick job, i.e. I didn't put much fluid through the system, about one third of a bottle. Regardless, the pedal feel, clutch function and shift quality were immediately much better than with the CDV in operation.

I'm just trying to share this very effective and virtually free modification with others. Maybe someone has similar issues to the ones my car had, will try it, and reap the multiple benefits of my pioneering work...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 13, 2018, 04:01:11 PM
It is not a "problem" in my eyes.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 13, 2018, 05:10:25 PM
Quote from: Citroënbender on September 13, 2018, 04:01:11 PM
It is not a "problem" in my eyes.

CB,
If you're happy then I'm happy for you to keep your car totally stock, whatever works for you.

I've argued my corner on this ad nauseum because you seemingly want to dismiss this simple modification out of hand as being in some unclear manner and in principle worse than pointless, when my direct experience of it is that it is in reality a very worthwhile improvement.

The simple inescapable fact is that my car is now hugely more enjoyable and easier to drive with this 'thing' disabled. The more I drive it the more I get used to the improved characteristics and the more I like it. It's 'before', and it's 'after', no other changes. The positive affects are way more than placebo, much too distinct for that...

Regards,
John.

Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: bazzbazz on September 13, 2018, 07:10:10 PM
Now look you two . . . . . don't make me come back there . . . . . !   >:(

;D
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 14, 2018, 12:42:01 AM
Quote from: bazzbazz on September 13, 2018, 07:10:10 PM
Now look you two . . . . . don't make me come back there . . . . . !   >:(

;D

Bazz,
I'm not looking to have an unfortunate argument with anyone, just a disussion. I've learned to rate and respect CBs opinion on most things Alfa related, and am sure there are areas where he knows more than do I. But, in this instance I'm struggling to understand what seems a stubborn possibly ideological recalcitrance to consider that there are obviously very positive aspects to disabling or deleting the CDV, and no real downsides. Just a bit frustrating...

Regards,
John.

Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 15, 2018, 12:31:01 PM
I do feel a bit like a 'prophet in the wilderness' on this, considering the apparent lack of interest. It's not just me who has found CDVs to be a sugnificant issue, I've lifted these reported experiences from a Honda site, they match my experience with my Alfa:

https://www.civicx.com/threads/clutch-delay-valve-delete-prl-ss-clutch-line-install-review.21587/

"After deleting the CDV, it made a world of a difference! It honestly feels like I have a whole new clutch inside the car, almost making it feel like I have a Stage 1 clutch...That noticeable of a difference. :yes: The Clutch bites instantly with no slips during normal driving and aggressive high RPM operation MUCH better and RPM's drop between gears and shifting motion became much more fluid and natural. Best part is, it cost me $0. Only thing I bought was a bottle of brake fluid to top of the reservoir during the clutch bleeding process."

"Few pumps of the pedal and you notice a huge difference. Drove the car for a bit and it's amazing having that natural clutch feel again."

"I notice a big difrence going from stop->1st->2nd. Alot smoother. Shifts are quicker."

"pulling away in 1st on a normal start is much quicker
pretty sure I chirped the tires at 2k rpm
if I didn't know any better, the pedal feels more "direct" and slightly stiffer
you can definitely feel the difference where the CDV "assisted you" vs without it."

"Just removed the delay valve and it was highly worth it. Much faster response on the clutch and even better at higher RPM."

It's easy to find plenty of similar reports from drivers of Hondas, Bimmers, VWs, Subies, and other marques. The CDVs in these cars (including Alfas), are all similar in what they do (if perhaps not in the detail of how they do it?). If they commonly cause issues with other cars, then Alfas won't be immune either (mine wasn't).

Have I become obsessed with these things? Maybe a bit, but I am rather annoyed that they are fitted in the first place, and that I've had to go to the trouble of disabling mine just to have a clutch that works properly, as it should have done from the factory. I'm not specifically targeting Alfa for this, it seems like a pandemic infecting more and more cars...

If you have a manual car, then IMO it is causing problems for you, even if you have become so habituated to crappy 'modern' clutch action that you aren't aware of it. Disable it and you will notice a positive difference, I promise...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Vne165 on September 15, 2018, 08:51:52 PM
How do I know if I have one fitted? Would my 2002 916 TS Spider have one?
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Vne165 on September 15, 2018, 08:53:42 PM
I do have a whistling brake booster though...a little sort of high pitched sigh emanates from under the dash when you push the brake pedal.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Citroënbender on September 15, 2018, 09:09:10 PM
I think a persistent whine from near the passenger seat is more common than a whistle in the brake booster. Does the pedal feel "right"?

Per the clutch damper, simply follow the hydraulic lines from firewall to slave cylinder to see if there's something lumpy in the middle.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 16, 2018, 03:29:48 AM
Quote from: Vne165 on September 15, 2018, 08:51:52 PM
How do I know if I have one fitted? Would my 2002 916 TS Spider have one?
I haven't examined a Spider / GTV closely enough to know that your car would definitely have one, but I'd say it's a fair bet...

If so then I'd imagine it is not unlikey to be located similarly to the CDV in the 147, which is 'hanging in space' above the gearbox, you can just see it under / behind the battery etc. with a torch.

It's a cylindrical object with a hard line in and a hard line out. Only the hard line from the MC can be unthreaded (at the CDV), the hard line to the slave cylinder is soldered directly into the CDV. Also, the hard line from the CDV to the slave cylinder is permanently attached to the rubber hose that plugs directly into the slave cylinder. To take the CDV out, the threaded hard line needs to be unscrewed, and the rubber hose / hard line detached from the slave cylinder and removed with the CDV as an 'assembly'.

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 17, 2018, 04:08:57 PM
For my own amusement as much as anything else, I've constructed some simple diagrams to help illustrate how I think the CDV as fitted to the 147 probably operates, based on the internal components. I've attached these as a Word Doc. with notes.

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Vne165 on September 17, 2018, 08:10:49 PM
Interesting, thanks for the diagram. I would agree that the rubber element would add a degree of 'compressibility' to the system, by design it would appear. Deletion would result in a more linear relationship of pedal travel to clutch slave cylinder actuation. Clever little jigger, but you'd have to wonder about it's durability over the years.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 17, 2018, 09:05:42 PM
Yes I agree, these are impressively elegant, simple and clever widgets. Pity that what they do is so damned counter productive...

Longevity of the rubber may be of some concern, but I have to say that the rubber tube that came out of my cars' CDV appeared to be in truly excellent condition, with no deformation, cracks, excessive softness, or any other obvious issues. It's so clean that it looks like smooth black plastic.

From my experience, removing the rubber tube definitely results in a much more linear relationship between the pedal and clutch function. I still can hardly believe how much better the clutch is to use, how improved its' action is, and consequently how much better the quality of the gear changes are. At first it just seemed a bit better, but the more I use it and the more accustomed I become to the changed characteristics, the more I realise just how much better it actually is (and what I had been putting up with for ages...).

A wierd thing I've noticed since disabling the CDV; since I've had this car its' had what I was interpreting as a chronic significant 'rev hang', whereby the rpm refused to drop sharply when the throttle was closed and the clutch pedal depressed (my old Accord did a similar thing, which I cured by means of disabling the 'Idle Air Control Valve', another story...). 'Rev hang' is a common 'characteristic' associated with emissions control (i.e. a deliberate strategy inflicted primarily to reduce NOx), and degrades gear shift quality.  But, since deleting the rubber CDV tube, the rev hang symptom has largely disappeared...

More thinking needed as to why this has happened...

Regards,
John.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: Vne165 on September 18, 2018, 08:04:11 AM
Is it simply that the crankshaft remains 'coupled' to the transmission for longer when the delay device is in play, thus keeping revs matched to road speed? Remove the CDV and engine is disconnected faster.
Title: Re: Clutch hydraulic damper / delay valve, considering deletion...
Post by: johnl on September 18, 2018, 12:41:54 PM
Something like that, but not sure exactly how this would lessen the 'rev hang' thing.

Intentionally 'designed' 'rev hang' (for reduction in NOx) is generated by the ECU not allowing the throttle butterfly to close as quickly as the throttle pedal is lifted, or with non FBW throttles, by the ECU briefly opening the air valve that is otherwise used to keep idle speed at X rpm (say when AC is activated, or when other variable parasitic electrical loads exist via the alternator). It's an unfortunate electronic thing, not a symptom of a physical problem.

I just can't visualise how the clutch not properly disengaging could create a symptom that mimicks this. Keep in mind that if my analysis of the way the CDV works is correct, then the clutch disengagement isn't 'lagging' by the time the pedal has reached the floor, though it may well fail to fully disengage if too much pedal motion is 'wasted' by the CDV operation (i.e. deformation of the rubber tube).

All I know is that previous to CDV disablement the rpm would tend to 'hang' and as a result would be too high when the next higher gear was engaged and the clutch pedal released. This caused stiffness in the shift action (synchro resistance due to rotational speed differences inside the gearbox), 'lurching' as the clutch was released, and a sense of general ineptitude as a driver. This also caused issues for 'rev matching' while doing 'heel / toe' downshifts (mostly because response to throttle 'blips' was a bit unpredictable). It could be 'worked around', by adjusting shift technique, adding pauses in the process (like depressing the clutch pedal only after lifting off the throttle pedal, or lifting the throttle almost all the way and then pausing briefly before fully lifting off as the clutch pedal was depressed, and, slowing the speed at which the lever was moved), but this all resulted in unsatisfyingly un-instinctive, slow and clumsy gear shifting.

But now, the 'rev hang' has stopped happening, or at least is so improved as to no longer be an issue (bliss...). Gear shifts are now much faster, smoother, cleaner, lurching has gone, the process is instinctive, and I no longer have to actually think about it while doing it. But I can't figure out why, or the how of the why.

If (when the previous rev hang symptom was occuring) the clutch disengaged enough that it was actually possible to change gears (even with some clutch drag), then the clutch should have been disengaged enough that the engine wouldn't be being 'powered' by road speed acting through the still engaged gears. It doesn't make sense to me, a mystery...

In the end it doesn't really matter, I'm just enjoying how the car is now after ditching the Devils' damnable restricter...

Regards,
John.