[johnlear]

For quite a long time the variator on my 147 TS has rattled for a few seconds after start up, as seems common with older variators. I didn’t think this a significant issue since it quickly quietened and the engine performed well enough, and, accepted wisdom seems to be there are no adverse affects from a noisy variator other than the rattley start up.

However, sometimes the engine would feel a bit ‘off’, more so some times than others. This would usually be after driving for a while or later in the day, and I wasn’t sure might not be a figment of my tiring imagination. The engine would go from feeling fine to just seeming a bit ‘flat’ and lacking ‘enthusiasm’. The next morning it would seem ‘refreshed’, so maybe it was just in my head...? But, later it would again start to feel a bit lacklustre. In the end I decided something seemed to be wrong...

The question crossed my mind; could it be that the variator might possibly be causing an erratic problem, even when it wasn’t being overtly noisy at the time? If so, then why exactly might that be?

So I decided to investigate...

My spare variator (from the spare parts car) was externally rusty, and obviously not useable in such a state (how did it get like that...?). I pulled it apart to see if I might be able understand exactly how it works and what might possibly go wrong with these things.

First impression was that it seemed in excellent internal condition. There are relatively few moving parts, most of the components are hardened (probably) steel operating in a very well lubricated environment, and exposed to only relatively light loadings.

There appears to be very little that could actually fail. The fact that variator ‘repair kits’ consist only of a new spring and plastic thrust washer tends to support this, i.e. that not much goes wrong, and that if it does then the spring and / or plastic thrust washer will most likely be the problem.

Next I dismantled the variator from the road car, and after very careful examination this too appeared in similarly excellent internal condition to the other, as far as I could tell (and not rusty on the outside...). So what was wrong with it, why the diesel like rattling?

But, before I go further into this, the happy ending here is that this variator has been successfully ‘reconditioned’ and is now completely silent, zero diesel like rattle at any time, not even momentary. And, I’m sure the engine is now running more smoothly and performs far better than it previously did.

And the cost, other than my free labour, only $0.00...

The variator components look like this:

End part one...

Regards,
John.

 

[johnlear]

Part two:
But how to correctly assemble a variator isn’t entirely obvious, there is a hidden trap:

In the diagram below (Figure 6), notice that there are three holes in disc D (‘the disc’). Two have a 2.5mm diameter, ignore these (I have no idea why they exist and seem to serve no purpose I can discern). The third hole has a diameter of 3mm, which is not to be ignored.

Piston C (‘the piston’) also has a 3mm ‘blind’ hole that corresponds with the 3mm hole in the disc. When the disc and piston are correctly aligned these 3mm holes line up perfectly, and a 3mm rod (e.g. a drill bit shank) will pass through and into both holes. However, mysteriously the helical splines seemingly don’t align when the holes are aligned...

Initially I was at a loss to understand why it was that with the disc and piston in contact and the 3mm holes aligned, it was impossible for their helical splines to align properly. It seemed obvious that the 3mm holes ought to align, but when they did the spline alignment was way off. If this hole misalignment were ignored, then I could find several rotational orientations of disc and piston at which the helical splines did align, sort of, but not exactly. It seemed to me that the holes must exist for a reason, what if not alignment of disc and piston...?

I found this very puzzling , until I found this:

Using the TS Variator Repair Kit - My experiences

The OP is one ‘rathkennades’. He (I’m assuming...) states that the variator should be assembled NOT with the piston and disc in contact (as seems intuitive, and as I had initially assumed), but that there must be a GAP between the disc and piston faces...

This was a penny dropping moment, and explained why it is that with piston and disc in contact I hadn’t been able to find any orientation at which the helical splines were in perfect alignment (close yes, perfect no). But, if an approximately 2mm gap existed between disc and piston then perfect spline alignment was easily achievable (with the 3mm holes also in perfect alignment). Still, this seemed a bit weird, why a gap, and why the disc for that matter...?

Rathkennades couldn’t explain why the gap exists, nor the purpose of the disc as a separate component to the piston, but, with a sudden epiphany I think I might have intuited the reason for the disc as a component, and why a gap between the disc and piston...

This is where it starts to get interesting, but confusing and hard to describe...

When the piston and disc are correctly assembled onto shaft B (‘the shaft’), the two 3mm holes should line up perfectly, such that it is possible to insert a 3mm rod through both disc and piston holes. There is only one orientation of disc re piston rotation where the two 3mm holes do perfectly align (though the straight cut splines will insert in any orientations of disc, piston and shaft rotation).

If the 3mm holes are not aligned, then the helical splines will be misaligned in varying degree depending on the exact ‘misrotation’ of disc and piston. With the holes misaligned there are several relative disc and piston rotations at which the splines are very nearly aligned, but not perfectly.

It would seem intuitive (and what I initially assumed...) that the helical disc and piston splines ought to be in precise alignment with each other when the two 3mm holes are also in alignment, and ALSO when the faces of piston and disc are in physical contact with each other. But counter intuitively this is not so, a trap for the unwary....

See diagram 4A below. Note the slanted red guide lines which illustrate the angle of the helical splines. Now note that the piston and disc are in physical contact with each other, but the splines are not quite in alignment. Piston and disc are shown in correct rotational alignment but in the wrong linear position relative to each other, i.e. both 3mm holes are perfectly aligned, but there is no gap between disc and piston.

Now look at diagram 4B. Note the approximately 2mm gap between disc and piston. When the 3mm holes are perfectly aligned and this gap also exists, then the helical splines do align across the gap, not only with each other but also with the internal splines in cylinder A (‘the cylinder’).

This is how the relationship between piston and disc must always be in an assembled variator, a gap must always exist between disc and piston. Theoretically the gap doesn’t need to be 2mm wide, a gap of some width just needs to exist, with the disc and piston not in actual contact. The gap is nominally 2mm (give or take), but due to clearances (between the splines on disc, piston and inside the cylinder) it will vary just a little during operation.

In use the gap will not disappear regardless of the linear position / movement of the disc and piston. It can’t disappear because for this to occur the helical disc and piston splines must become substantially misaligned with each other. This can’t happen because the clearance between the disc / piston splines and the cylinder splines is too small to permit more than a tiny degree of misalignment of the disc and piston splines, too small a clearance and too little misalignment for the gap to ever become zero.

Clear as mud? Sorry, doing my best here...

End part two...

Regards,
John.

 

[johnlear]

Part three:
But what purpose does the gap serve? And, why is the disc a separate component?

My epiphany strongly suggests that the gap is most probably a noise reduction feature, intended to reduce spline rattle when the variator is at full retard.

Full retard occurs when no oil pressure is supplied, and the force of the spring pushes the piston and disc to the front of the variator, until the disc comes into contact with the plastic thrust washer and cannot move further (and neither can the piston, even though a gap still exists between it and the disc).

I think it would be quite possible to design the variator without the disc being separate from the piston. The variator would still vary the cam timing with the helical piston splines alone. However I suspect such a variator would tend to be noisy due to fluctuating torque loading that occurs within each individual camshaft rotation. These fluctuating rotational loads are transferred through the splines from shaft to piston to cylinder, and cylinder to piston to shaft, and conceivably could cause rattle due to the existence of operating clearances between the splines (as the splines cyclically load and unload). This would I think be most likely at low rpm, at and near idle speed.

It is also easily possible to assemble the variator so that the disc and piston are in contact, i.e. no gap. This is possible at several orientations of disc rotation relative to the piston, but in any orientations the the 3mm holes will be misaligned (if the disc and piston are in contact with each other). I speculate that if assembled without this gap, the variator would behave as if the disc did not exist (as a separate component), and so may also be noisy at full retard, but still work to alter timing.

On the internet I’ve seen mentioned instances of rattley variators having been ‘rebuilt’ with a ‘rebuild kit’ (basically a new spring and thrust washer), but that this reportedly didn’t cure the rattle. I suspect this might possibly maybe and perhaps be as consequence of the variator having been assembled without a gap separating the disc and piston. As above, it is easily possible to do this, and far from obvious that it might be wrong.

When disassembling a variator, as soon as the circlip is removed the internal parts ‘pop’ out of the cylinder, propelled by the spring. The spring pushes the shaft fully out of the disc and piston, and once apart there is no way to tell just how the disc and piston rotation was originally aligned. The only clue is the 3mm holes, which will align perfectly in only one position of rotation, but with the splines apparently misaligned (if disc and piston are touching...), so it’s all a bit confusing.

Yet why else would these two holes a) exist, and b) align so perfectly at only one specific orientation? It’s a clue to a very clever and elegant design feature, the anti rattle gap...

There is an internet page (won’t mention which one) giving very clear instructions (with photos) re how to assemble a variator after having installed a new spring and washer. Mostly the advice is good, but one of the photos depicts the disc and piston about to be installed with the splines in correct alignment (seemingly...), but also in physical contact each other, which is wrong. Once installed in the cylinder, the splines will become invisibly misaligned (i.e. misalignment hidden inside the cylinder). I don’t think this would stop the variator working to alter timing, but may well result in it being noisy, or maybe not, toss a coin...

If the disc and piston are fitted onto the shaft without a separating gap, then careful examination reveals that even at the orientation of best possible spline alignment, the alignment can be pretty close but not actually perfect (at least it isn’t with the variator parts I have on my desk). At some relative rotations the splines are far from aligned, at a few other rotations they are very nearly in correct alignment.

It can be confusing because when assembled with no gap and at the rotations where spline alignment is very close to correct, the disc and piston can be manually manipulated into and then artificially held in seemingly correct alignment, but in reality it is not quite perfect.

This is possible if a slight rotational force is manually applied, rotating the disc and piston very slightly in opposing directions (until the straight splines contact straight shaft splines, preventing any further rotation). However, if the directions of the applied forces are reversed, it becomes apparent that the alignment is actually not quite correct. When the direction of manually applied forces is reversed the splines visibly misalign, even if they did align when the forces were applied in the other direction. This is due to the spline clearances not being ‘equally clearanced’ on both sides of the spline teeth, i.e. more clearance on one side of the splines than the other.

When a gap is present (as it should be...), then as the spring pushes the piston axially it must also be trying to close the gap between piston and disc. But, any narrowing of the gap must also cause the disc and piston splines to become misaligned, being because the splines can only be correctly aligned when a gap of approximately 2mm width exists.

The spring pushes the piston toward the disc, and in response the disc then moves away from the piston without the piston coming into contact (not by magic, this is elegant engineering...). The disc stops moving when it reaches the limit of its’ forward travel (when it contacts the thrust washer). Because there are small clearances between splines, the piston now moves very slightly closer to the disc (but not into contact). As the gap beigns to decrease width just a tiny amount, the helical piston splines start to misalign with the helical disc splines.

Clearance between the helical cylinder splines and the helical piston / disc splines is fairly close, so the disc and piston splines can only very slightly misalign before the cylinder splines prevent any further misalignment. This prevents the piston / disc gap from closing to zero.

The gap width doesn’t ever change more than a tiny amount because linear movement between the disc and piston in effect becomes ‘jammed’ by the spline misalignment, which effectively eliminates operational clearance between the disc / piston splines and the cylinder splines (in the direction in which the loads are transferring from spline to spline, clearance still exists in the other direction but the loading is not in that direction).

Note that all of this only happens when the spring has pushed the piston as far as it will go toward the front of the variator, and so the disc is being pressed against the immovable object that is the thrust washer.

When an influx of oil pressure pushes the piston in the opposite direction (toward rear of the variator) , the piston ‘pulls’ the disc away from the washer (indirectly via the angled flanks of all the helical splines). When the disc loses meaningfully forceful contact with the washer it becomes more or less ‘fee floating’ on the shaft.

The gap still remains largely unchanged at 2mm or so, but the splines will easily and lightly move into and out of alignment very slightly, enough to create a small rotational force that partly vectors into a small linear force acting on the disc splines, causing it to ‘follow’ or ‘precede’ the piston back and forth along the shaft splines, with a gap at all times.

I think that makes sense...

End of part 3.

Regards,
John.

 

[johnlear]

Part 4:
So how does all this inhibit variator rattle?

When the spring force causes the disc and piston to begin moving closer to each other the splines begin to misalign. The causes the spline flanks to move into contact with the flanks of the helical splines inside the cylinder, and the faces of the contacting flanks become significantly loaded against each other. This occurs in one rotational direction for the disc splines but in the opposite rotational direction for the piston spines, i.e. the disc and piston splines both become equally loaded against the cylinder splines, but in opposing rotational directions.

Because the rotations are opposite, the piston splines press against the cylinder splines in one direction, while the disc splines press against the cylinder splines in the opposite direction. This causes the clearance between all helical splines to effectively become zero, in the opposing rotational directions (vectors) of the different spline loadings. This prevents rotational disc movement relative to the piston (beyond the initial very slight rotation that brings the spline flanks into contact), and so inhibits rattling that may arise as a consequence of fluctuating torque passing between the splines.

I’ll reiterate that this only occurs when the disc is being pushed against the thrust washer at full retard, and as soon as oil pressure enters the variator the piston moves rearward, pulls the disc away from the thrust washer, and the anti rattle effect ceases. At full advance (and there is only full advance, full retard, and a rapid transition between them) there seems to be no deliberate anti rattle effect, I assume because it isn’t required due to, other factors...

The force which drives the anti rattle effect comes from the spring. The stronger the spring the stronger the anti-rattle effect will be. Conversely, the weaker the spring the weaker and less effective it will be.

I strongly suspect that the spring, as supplied in a new variator, may be only just strong enough to perform its’ function. If so, then it may not require much of a reduction in the force exerted by the spring to cause the variator to begin to rattle. Loss of pre-load, as a consequence of reduced free length, will occur if the spring ‘sags’ over time. So if the spring ‘takes a set’ and gradually becomes shorter it will push with less force against the piston and disc, therefore the anti- rattle effect will reduce, or even cease...

From reports it seems that these variator springs do in fact lose some free length over time, old springs becoming shorter than new springs...

The plastic thrust washer:

As far as I can see, the washer doesn’t appear to do all that much. It isn’t a proper seal by any means, too many leakage points where it abuts the forward end of the shaft splines (effectively a small hole at each spline for oil to leak through).

The washer lives between the forward face of the disc and the inner face of the cylinder, and so may act to reduce impact noise when the oil pressure is cut and the spring suddenly forces the piston, and so the disc, to the front end of the variator. If not for the washer this would be a metal on metal contact, possibly with enough force to make an audible noise. The softer (than steel...) washer might therefore be another noise reduction measure, an impact of metal on plastic most probably being significantly quieter than metal on metal...

I’ve seen two of these plastic thrust washers. Part of the washer bears against the forward end of the straight splines on the shaft, which fit into a rebate in the washer where it is thinner than the thickest part (see washer F diagram in Figure 4). The thickest part of the washer is 2.5mm (both that I’ve measured). The rebated sections of the two washers were different thicknesses, one being 2mm, the other only 1mm (obviously worn). Of course in my ‘rebuild’ I used the least worn of the two washers I had on hand.

Other than perhaps being for noise reduction, I’m failing to deduce what else the washer might actually do. It is odd that it seems to wear where it bears lightly against the forward end of the shaft splines, but not to wear where the spring forces the disc against the end face of the washer with some force.

Belleville washers:

Two are stacked and placed at the front of the shaft. They act in effect as very short stroke springs that prevent axial shaft free play, thus reducing or eliminating a source of rattle (I think, probably). If the washers did not exist then the shaft could easily rattle back and forth.

I’ve experimented with manually rotating the shaft inside cylinder, both with Belleville washers installed and not installed. Without the washers it is very easy to rotate the shaft in the cylinder with almost no resistance. With the washers it takes a lot more effort.

The force exerted by the washers (pushing against both the shaft and the cylinder) is strong enough that it may well act as a rotational damper, acting to inhibit rotational vibration between the shaft, the piston / disc, and the cylinder. This could occur because the clearances between the straight splines (piston/ disc to shaft clearances) are otherwise rotationally un-damped.

The anti-rattle effect associated with the spring and helical spline alignment / misalignment doesn’t affect the straight splines (between shaft and piston / disc), which have a somewhat larger clearance than do the helical splines. Any spline clearance risks rattle unless eliminated or damped in some manner, so maybe the Belleville washers serve this function by creating a relatively strong longitudinal force pushing oppositely against the shaft and cylinder. This will create a frictional damping effects at both the Bellville washer / shaft interface and the large circlip at the other end of the shaft (the shaft flange abuts the circlip). This effect must exist in some degree (significant or insignificant...), and could conceivably be what prevents rattle between the straight spline clearances...

End part 4.

Regards,
John.

 

[johnlear]

Part 5:
More words:

I’ve read comments related to installation of ‘variator kits’ that the old spring was found to be significantly shorter than the new spring from the kit. I found that the used springs from both variators that I’ve dismantled were 53mm and 55mm in free length.

I don’t know the exact length of a new spring, but have estimated that it is probably near to 60mm, or a touch longer (or thereabout). I didn’t have a new spring to measure, but did the best I could to estimate it by copy and pasting several photos of new springs into CorelDraw, resizing the photo so the springs’ on screen diameter matched actual spring diameter, then measuring the apparent spring free length on screen (as best I could, considering parallax issues with the photos). Not the best way, but better than a total guess...

Anyway, if the only problem (causing a variator to rattle) is that the spring has become too short, I wondered whether simply stretching it back to new length (or thereabouts) might not fix the rattle problem. So, I manually stretched the longest of the used springs I had (55mm) back out to 62mm, re-assembled the variator, and re-installed it. I also used what seemed to be the least worn of my two thrust washers (but have no idea whether that made any difference...).

Since stretching the spring back to near more or less original length a few weeks ago, the variator hasn’t made any noise whatsoever, it is completely silent. The engine now feels like a different engine, a smoother, more powerful, torquier one. I’m very pleased but a bit surprised at the difference. The engine is now very happy pulling higher gears in places where previously it really wanted to shift to a lower gear. Once where it would begin to falter and struggle, it now feels far more effortless.

This begs the question;

Could it be that a weak variator spring could possibly cause a loss of power elsewhere in the rev range, not just at very low rpm? Speculation and thought experiment suggests, maybe, perhaps...

Oil pressure forces the piston to the rear of the variator, so advancing valve timing. When oil pressure disappears the timing should immediately go to full retard, and the piston must rely opon the strength of the spring to push it fully back to the front of the cylinder. This may require a certain minimum degree of force, which may or may not adequately exist if the spring has weakened. ..?

With significant rotational load acting on the various splines (all of them, both straight and helical) as a consequence of driving the camshaft, there will be some degree of axial friction between all the splines (most likely to be greater at higher rpm due to friction between cam lobes and tappet faces). This friction could conceivably be strong enough to inhibit or maybe even prevent a weak spring from returning the piston / disc from the rear to the front of the variator (i.e. prevent it returning from full advance at higher rpm to full retard at lower rpm), at least perhaps until rpm decrease significantly and friction decreases, when it might ‘pop’ back.

If so, then this would mean that the timing may fail to retard as and when required, which would affect power lower in the rev range, where most engines spend most of their time (and may also affect fuel economy...?).

Such an effect, if it occurred, could easily be erratic, timing would in effect be ‘stuck’ at the wrong setting, at least some and possibly much of the time. It might ‘unstick’ at any moment, it might ‘stick’ and ‘unstick’ more or less constantly, or only sometimes in certain conditions....

Might this explain why my engine seems so improved since stretching the variator spring? I can’t answer this definitively, but it does seem possible...

End document dump...

Regards,
John.

 

[johnlear]

Sorry, forgot this, might be helpful:

Regards,
John.

 

[armoore]

Superb post. Many thanks. Consider posting this in the engines section on AO and in all the models that use the TS engine. With the price of new variators I would think many will consider the refurbishment of their existing one a viable option.
Incidentally stacks of large Belleville washers were used in the main undercarriage legs of the Junkers 88 as springs and were self damping. Not many people know that! Also in artillery pieces to control recoil.

 

[bazzbazz]

Love the diagrams, what program do you use?

 

[johnlear]

I hate the diagrams, (edit, diagrams now fixed) they should be far clearer and in fact are when I actually draw them in the original program. They are made using an old version of 'CorelDraw', and display clearly in that program. However, CorelDraw (at least the iteration I have) doesn't generate formats which are compatible with posting onto this site. I work around this problem by pasting the CorelDraw drawings into 'Paint.net', and then saving them as a file format that will paste onto this forum (which Paint.net will do).

The problem is that the drawings lose a great deal of fidelity in the process, and are very unclear compared to the original drawings. I don't know enough about graphics software to obtain a better result, I'm probably doing something wrong...

Regards,
John.

 

[johnlear]

Superb post. Many thanks.

The variator is simple but also complex, it's very difficult to describe concisely (at least for me...).

I re-read some of it just now, lots of clumsy grammar, repetitive explanations and typos I just didn't see earlier, too close to the forest to see the trees...

Consider posting this in the engines section on AO and in all the models that use the TS engine.

I posted it here because this sub forum seems far more active than the 'engines' sub forum...

With the price of new variators I would think many will consider the refurbishment of their existing one a viable option.

New variators are very spendy, I think I could probably purchase a complete second hand engine in good condition for not dissimilar $. I certainly couldn't justify new variator cost to my spouse if the engine was actually still running...

The kits are within justifiable reach, but still pretty expensive for a little ring of plastic and a spring. The trick is to put the variator back together properly, i.e. with a gap between disc and piston...

Incidentally stacks of large Belleville washers were used in the main undercarriage legs of the Junkers 88 as springs and were self damping. Not many people know that! Also in artillery pieces to control recoil.

I would assume Belleville washers would have some degree of inherent slight self damping because when the washers move against each other there is some friction where the washers abut and rub each other, not dissimilar to that which occurs with 'multi leaf' leaf springs, due to the contact between each leaf.

Regards,
John.

 

[armoore]

I bought a new spare sometime ago (still in my spares store - the loft) for under £100, I’ve seen them for three times that. I did have a used one off my daughter’s 147 that was clacking which I kept n case I ever wanted to investigate the innards. I’ve used a repair kit (£15) on that to keep as a refurbished part. Your post prompted me to take it apart earlier to check, more by luck I presume, but I had done it correctly, I’d used the ‘witness marks’ left by the 2.5 mm holes on the main slider, phew!

 

[Jetronic77]

I had an engine with noisy variator that became silent again after a few oil changes in short succesion. In my case it couldn't have been the spring lossing too much tension, or wear. But maybe dirty oil made the variator sicky and not seating fully without oil pressure?

 

[johnlear]

My variator too was notably quieter with thicker and / or newer oil, getting noisier as the kilometres racked up. Old oil thins out, I think especially in engines which run fairly rich, i.e. unburnt petrol gradually gets past the rings and slowly dilutes the oil and so reduces oil viscosity. This would might be in addition to any viscosity loss caused by long chain polymer additives being shredded into shorter chains in use.

With no data to prove it, I do suspect TS engines are set up to run quite rich, probably to reduce nitrogen oxides in the exhaust. TS engines also tend to have marginal piston rings, so more fuel may well wash past them, particularly with engines that also leak oil past the rings in the other direction...?

Why quieter with thicker oil? I'd guess that residual oil remaining inside the variator, before any more oil is pumped in, acts to 'buffer' or 'cushion' between metal components, preventing / minimising metal to metal contact. Thicker oil will buffer better, probably. Thicker oil will drain more slowly, so there may be more residual oil to act as a buffer on start up.

Regards,
John.

 

[johnlear]

I had an engine with noisy variator that became silent again after a few oil changes in short succesion. In my case it couldn't have been the spring lossing too much tension, or wear. But maybe dirty oil made the variator sicky and not seating fully without oil pressure?

I don't know the answer. Variator malfunction as a consequence of inadequate oil pressure is not something I have yet given much any thought to.

Oil pressure pushes the piston to the rear of the variator and holds it there, until the solenoid shuts the valve and pressure drops to zero. Normally, the force of the pressure acting against the piston is probably considerable, I'd expect the splines would have to be pretty gunked up to prevent the piston moving.

I suspect it might perhaps and possibly be more likely for the valve (operated by the solenoid) to become stuck with deposits, or an oil gallery to become constricted with gunk? New oil over time, X several times, might be enough to clean a sticky valve and / or dissolve said gunk? This might increase pressure and restore variator function...

The variator is not a very 'oil tight' device. There are no positive oil seals in it. There is a metal 'seal' at the rear of the piston (like a 'piston ring' as found in any piston engine) which will slow the rate at which oil escapes past the piston, but it doesn't prevent oil from getting past.

There seems to be a notion 'out there' that a reason for variators to become noisy is because "the seal" starts to leak and the so the variator won't retain oil after the engine has been shut down, and so on start up the variator rattles until it again becomes filled with oil. I don't think this is at all correct. For a start there is no actual oil seal to start leaking.

The variator is by its' nature a very 'leaky' device, with no positive seals to prevent oil from escaping after shut down. No matter the condition of a variator, once the engine has stopped running the oil will drain out, past and through the straight shaft / piston splines, into the cavity behind the piston (where the soring is) and then through the two drain holes and past the edge of the piston flange, into the crankcase.

There is nothinbg that would prevent this. The piston ring style 'seal' at the edge of the shaft flange will prevent oil spraying copiously out into the cambox, but it won't stop it slowly draining. What it does is retain enough pressure that the constant supply of pressurised oil can compress the spring and then continue to hold the piston against the circlip (full advance), until the oil supply is cut off (full retard, assuming the spring has all the strength to push the piston to the front of the variator).

What might help is thicker oil, which would take longer to escape through the labrynth of leakage points.

Regards,
John.

 

[MO8IUS]

I hate the diagrams, they should be far clearer and in fact are when I actually draw them in the original program. They are made using an old version of 'CorelDraw', and display clearly in that program. However, CorelDraw (at least the iteration I have) doesn't generate formats which are compatible with posting onto this site. I work around this problem by pasting the CorelDraw drawings into 'Paint.net', and then saving them as a file format that will paste onto this forum (which Paint.net will do).

The problem is that the drawings lose a great deal of fidelity in the process, and are very unclear compared to the original drawings. I don't know enough about graphics software to obtain a better result, I'm probably doing something wrong...

Regards,
John.

If they look better on your screen than they do after saving you could do a screenshot, paste into MS Paint, then crop out the bits you want and save. Or just use the snipping tool that comes with Windows.

No doubt this post will help many others well into the future.

 

[Fruity]

TS engines run similar mixture to virtually all other petrol/gasoline/benzene engines (excepting Subaru turbo lumps). The reason is similar narrowband O2 sensors and catalytic converters.

Nice investigation but I'm disappointed there is not a modification to keep them quiet forever. Seems I have let my expectations of John's work run away somewhat.

 

[johnlear]

OK, thanks MO8IUS,
I've changed all the diagrams to screen shots, the resulting clarity is far superior to previous efforts (the drawings look almost as clear as they do in CorelDraw).

I've not ventured into 'screenshotting' before, didn't realise it was so easy, and too lazy to find out...

Regards,
John.

 

[johnlear]

TS engines run similar mixture to virtually all other petrol/gasoline/benzene engines (excepting Subaru turbo lumps). The reason is similar narrowband O2 sensors and catalytic converters.

Then that would be quite rich then, as seems most common in the modern world. It's a long time since I've seen an exhaust tip with a light grey colour inside it, a sign of a leaner mixture. This used to be pretty common once upon a time, it's mostly black and sooty pipe ends these days...

My understanding is that rich mixtures burn cooler, and a cooler burn creates less nitrogen oxide, this may be an incorrect or simplistic understanding...? And, I have read somewhere or other that if the mixture is very rich it can be made to continue burning as it passes into the exhaust, assisting to bring the cat' up to temperture faster and also helping to keep it there if it starts to get too cold for whateve reason...

Seems I have let my expectations of John's work run away somewhat.

Whatever you mean by that...

Regards,
John.

 

[jonb.gt]

I've not ventured into 'screenshotting' before, didn't realise it was so easy, and too lazy to find out...

Another surprisingly easy "hack" you may have been too lazy to discover is that you can copy (ctrl-C) numerous items at one time; then when you want to paste if you use Windows key-V, instead of ctrl-V you get a pop-up list of all the clipboard contents that you can select from to paste. A real time saver if you're dealing with multiple images eg.

Thanks for sharing the wonderful piece of work you've done here.

 

[Fruity]

#18 reply.

Interesting. I agree that what is considered stoichiometric is actually quite rich. Yes, it keeps NOX emissions low.

The other bit... You only found the fault and cause but no permanent fix. Hence my comment of great expectations.
You have to stop getting people to explain light hearted humour though. Yet again there is no criticism or conflict but only an acknowledgement of your attention to detail.