TDI Pumpe Duse PD Cam Bearing Oiling and Related Wear (eddif)

[James & Son]

I have a theory that has slowly been developing. I wonder if Toolslick has these theories as well since it is oil and follower related. Maybe eddif might wake up.

The more calcium dispersant you have in the oil the more Zddp can be added without running into to much issues. This is because calcium prevents to some degree the hard glass forming and allows a softer film to form at a lower temperature and pressure.
http://www.apmaths.uwo.ca/~mmuser/Papers/TL05.pdf

I do not like to much boron and less than 20% maganesium ralative to the amount of calcium dispersant for this reason.

I am guessing here but I think some of the problems with the black follower and break in issues can be solved by playing with the amount of zddp and calcium ratio in a break in oil.

Soft break in of black follower use 2700/3000 parts calcium with 1600 to 2100 parts Zddp and a 10w-40 synthetic or a 15w-40 group II oil.

Edit- After reading all the posts on the low operating and warm up temps. I think I should change my thermostat and look for a stock or 90 C stat. I have noticed the oil cooler warms the oil before the filter to room temp. in less than 3 minutes even in winter.

I will be pulling my cam shaft shortly to verify this very break-in theory.
Edit
Simply put, an effective AW film will cross-link at pressures below the pressure (bulk modulus) of the target substrate and remain softer than the substrate.

Effect of calcium…..a positive aspect of this behavior is that softening the film through the incorporation of cations, such as calcium, may reduce abrasion of softer sub-strates.

I want to add to the above quotes I pulled from the study.
[a] boron adds to the hardness of the glass forming of Zddp.
By minimizing the slippage on the lobe apex as it rolls over the follower center point one should have minimal wear on both the lobe apex and the center portion of the black follower. Therefore an oil with high shear ( strong molecular attraction to steel) and minimal anti friction compounds and zddp only as AW will have high traction if I can use the term in reference to the rotation of the black follower.

Update Edit:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=258013
Some interesting reading on calcium magnesium and sulphated ash.

 

[James & Son]

There are two things i am concerned with with the black follower.

[1]Here is what will be happening. When the aluminum head is at operating temperature the follower will have enough clearance to sit flat against the lobe( the tip of the lobs gradually wear a taper and enough follower to head clearance is necessary for the follower to sit flush to the slight taper). But when the aluminum head cools (contracts) the follower to head clearance is reduced at 3 x the rate of the steel follower reducing the clearance from .00175 to .00075.

This results in edge loading of the cam to follower interface during the warm up.

[2] The other follower problem is valve closed cam dwell pump up. This sounds unusual since it happens when the valve is closed.
The continuously loaded injector springs hold the cam downwards at the 4:30 (static) to 5:30 running position. When the injector fires it pushes the cam to the 7:30 position. This amounts to the centerline moving and generating a downwards displacement and loading the hydraulic follower in the closed dwell position. This wears the center black through and the rest of the follower looks perfect. This happened to me in 5000 miles.

Rather than discuss this further I want to see what my followers look like now compared to pics 10,000 miles ago and pics I have taken 5000 miles ago.

Now in 2 to 3 weeks I want to pull my cam shaft and have a look at the black followers and cam lobes. Since the 5000 mile pictures I have made some dramatic changes to head off the follower center wear.

[1] I reduced valve spring pressure by 15%
[2] I went from TDT(not good) to T6( not good) and then at 5000 mile pics changed to group II 10w-30 winter to 15w-40 today. Why because of a better coefficient of pressure/viscosity (and lots of calcium dispersant with no magnesium) in the warm up zone. In winter 50 percent of my driving is in the warm up zone. I do have a coolant heater for the early morning starts.

In a few weeks I will have results?

 

[eddif]

All of the weak design issues cause every small problem be exaggerated.

Overcoming the hammering on the underside of the follower is hard to overcome with some procwsses (oil selection), but a better oil film between the follower and lobe should help (better as in a jet of oil aimed at tbe area).
.

The James & Son followers sure show the wear pattern.

We have a lot of work to do still.

I do not think additives will overcome hammered metal. They might help but the center wear dot still needs attention.

eddif

 

[Henrick]

Can anyone show a picture with the place on cam lobe highlighted which does 'hammer' the follower?

 

[eddif]

Can anyone show a picture with the place on cam lobe highlighted which does 'hammer' the follower?

Is this what you are asking about?

There is a little size problem with the camera lense and distance, but it shows the offset of lobe to follower top.

The camshaft is probably twitching from injector forces at a particular place in the rotation cycle (other cylinders as well influence all cylinders).

The limited area of the hydraulic unit contact rings makes the forces exaggerated at the point of contact under the follower contact area. The cam becomes the anvil (someone said that). We can see, however, the effect clear through the thin follower top and see wear of the black coating happen eventually. Very complex, but the wear modifies the hydrodynamic oil film to the point of not having a good strong film across the whole lobe area.

Pretty complex. I am sure open to you describing each force at which degree of crank rotation.

eddif

 

[James & Son]

Can anyone show a picture with the place on cam lobe highlighted which does 'hammer' the follower?

Scoring of #1 Exh Lobe


Scoring of #2 Exh Lobe


Edit- Update on Pump Up.

3 years ago heat was the problem and not enough oil getting to the followers was deemed to be the problem. More viscosity seemed to be an easy solution although it does not necessarily help a heat related problem if it reduces flow to the hot spot.

The answer to pump up is quite simple. Use a reasonable viscosity and avoid high rpm. The hydraulic follower will have a built in amount of compliance before hydraulic lockup. Thick oils at low rpm equal thin oils at high rpm when you want to maintain this complience or necessary clearance before hydraulic lock up.

At high rpm and injector pressures you need more complience in a reduced amount of time with the exhaust valve stem expanding from the sudden increase in heat. So what you need here is a extremely thin oil to increase compliance and follower cooling. Anything over 2500 rpm you don't need much in the way of viscosity because over this rpm a full film develops in the elastohydrodynamic lubrication regime between the lobe and the follower.

But if all your driving is below 2500 rpm as most of us are then a suitable compromise is required.

The link will help make it clear why oil leakage around the hydraulic follower can affect complience.

http://books.google.ca/books?id=DoY...6AEwAQ#v=onepage&q=hydraulic follower&f=false

 

[James & Son]

Jun/10/2012 Brg&FollowerUpdate&ValveSealFix

http://pics.tdiclub.com/showgallery.php?cat=5591

Cam is broke in now but took 10,000 miles. It looks like I used 2/3 of the life of the black coating to do this.

It looks like another 5000 miles will determine if there is life left after breakin.

I have made one change to #1 bearing while I had everything a part.

I re-added the eddif oil hole to #1 bearing. I removed it about 5000 miles back to see its effect on cam position and how it effected the oil wedge.
I had made 3 changes and had to remove at least one to find out what was causing the cam to move. I now no what caused the cam to move( the oil hole location was not a factor here) so I put it back in to help reduce #1 bearing wear, especially on start up.

I have had the cam in and out 3 times in the last 10,000 miles and have had the valve springs apart twice. The first time to put in lighter inner springs and the second to replace a bad valve guide seal that I found which had been damaged from the factory as the frayed edges were well oxidized( pictures).

Eddif mentioned he would be interested in the forces as the cam rotates. So I took some measurements of a few of areas that effect this so I could do a proper overview. Eg. roller offset to vertical axis of cam and injector spring preload.

Jun/10/2012 Brg&FollowerUpdate&ValveSealFix- pictures show the cam lobes at 50,000 miles, the first set of followers are shown and were previously removed at 40,000 miles and the replacement followers now have 10,000 on them. The reduced force inner springs and new #1 bearing( without the oil hole) went in 5000 miles back.

I have learned many things but one critical thing is not to be moving cam shaft position and changing bearings while the cam is still breaking in.

Any questions you might think of that might be of interest, please go ahead and ask as I will be carefull to keep it short and accurrate as possible.

Some measurements I took. Injection spring preload, roller dia. and vertical axis offset. Friction forces to rotate cam against valve springs and injector springs. Exact torque figures to allow reuse of stock bolts and an exacting procedure to replace cam caps without the need to hammer and hope.

I tried a new method to remove valve spring retainers this time based on a posted method used by an owner of an ALH.

 

[James & Son]

I must say I am a little disappointed about my results so far.

What are the positive things.

One thing i am confident of is that changing the fully supported upper bearings to an hour glass configuration I have balanced some of the crush force on the bottom bearings and reduced distortion especially on #5 bearing. The top bearing shape allows the upper bearing to compress equally instead of putting all the compression forces into the unsupported bottom bearing.

The negative here is #1,2 and 3 are taking all the load and #4 and #3 are sharing some load but #5 journal is floating. #5 upper shows some nice light even contact.

With the upper bearing(s) reducing some of the cantilever forces the obvious solution would be to replace #1 lower with a reversed stock bearing shell and hope the non supported portion will take more load.

But now that I have #5 bearing square in the bearing bore a more radical approach that would provide positive journal location would be to skim .001 inch off the parting surface of #5 cap. This would help true the cam axis in both the x and y axis at the #5 bearing end of the cam. Since the belt end is pretty stable this would seem to be
the best way to stabilize both the cam position and even out the bearing wear.

Probably the best compromise would be to skim .001 on #5 and replace #1, 2 and 3 lower with a stock bearing. The 10:00 o'clock oil port( uppers are reversed with oil ported to 10:00 along with hour glass modification) would remain in the upper and i would now have also the stock oil port position at 4:00 in the lower as well.

Of course this suits my situation. I need a true stable cam shaft position so that the black followers can remain flat against the cam lobe face. This is especially true in the warm up zone where follower clearances are reduced considerably due to the aluminum cylinder head. A .001 inch shim would have to be added to compensate under the injector shaft on that bearing cap. Use the link in above post and view all bearing pictures. Find the 2 bearing pictures that shows the 4 #1 bearings, One set shows the latest bearing with and without the oil hole. Next examine how the running position is now at almost 6:00 when a stock BRM runs at 4:30. Is this good or bad? It really doesn't matter if the number 5 modification works. i am running out of time. I have about another 5000 miles to determine if I it is necessary to put another set of followers in. If i do this i want the cam bearing worked out asap.

I was caught of guard 10,000 miles ago when i had to change followers. This time if necessary I will be ready so I need to decide now how to provide a stable black follower break in.

 

[James & Son]

http://pics.tdiclub.com/data/5591/HPIM1867.JPG
First #1 brg 38000 miles
second #1 brg-1500 miles after brg mods. #4 & 5 brg oil port position at 8:00 and 2:00, all other brg at 10:00 only
3rd #1 brg- 1500 miles on after change( from 2:00 ) to 10:00 oil port position and retained 8:00 oil, all other brg 10:00 only
4th #1 brg-5000 miles, as above but without oil hole.

http://pics.tdiclub.com/data/5591/HPIM1869.JPG
re added eddif axillary oil hole

http://pics.tdiclub.com/data/5591/HPIM1865.JPG
note how wear pattern moved to 5:45 position from 4:45 with change of oil port location on #5 bearing.

http://pics.tdiclub.com/data/5591/HPIM1877.JPG
http://pics.tdiclub.com/data/5591/HPIM1876.JPG

I complained in previous post that I was not getting the results I had hoped. I am not entirely sure about that after comparing a mathematical analysis of the forces now to my previous visual analysis. It is helpfull to always supplement a visual result with more information.

Edit: note in pic. 1877 that copper is showing on the upper bearing. I noticed 5000 miles back that #1 upper was rubbing, caused by injector bolt torque. I removed the high spot by removing as little coating as possible( as little as .001 inch as shown has been removed carefully)

 

[James & Son]

Please note this updated information

http://forums.tdiclub.com/showpost.p...7&postcount=18

note the above is boundary friction.

A white paper called Friction in Elasto Hydrodynamically Lubricated Contacts using a special variable pressure/slip ball on disc test machine for simulation states friction coefficient is .06 to .045 depending on speed and slippage.

This works out to 9.3 inch lbs per follower at a stock opening spring pressure of 147 lbs. and a stock cam lobe radius of 1.4 inches.

One could ask what is the advantage of reducing spring pressure. The friction reduction is proportional to spring force. Therefore heat generated by friction between the lobe and follower is reduced.

Edit: for those that might be thinking so what. I have reved to 3800 rpm at near full go pedal using 15w-40 oil and feel 4000 rpm is safe with a margin ( A5 inky has reved to 5000 plus with stock springs). The Same paper I mention above also says DLC coating does not dissipate heat as well compared to uncoated. Franko can attest to seized followers in stock cars. The exhaust followers wear. At 3700 rpm 15 % less heat would be generated or equal to a reduction of 555 rpm of friction input.

I believe for the majority of BRM a 15 % reduction in spring pressure is the maximum that is practical. I have searched but can not verify that 100 lb spring opening is practical which is what you get if you remove the inner spring entirely. It might be practical for a 10,000 mile break in of cam and followers. The slower the break in the better. I think 125 lbs is practical and still retains good heat transfer and sealing.

I am running custom inner springs, that reduce my initial and open spring forces by 15%, for the last 5000 miles. Initially I broke my cam and followers in with stock springs( the lighter custom inner springs were not ready in time unfortunately). Using T6 oil( no zddp added) and stock springs everything was quiet by 5000 miles. The T6 worked and got things broke in initially but the followers were already starting to wear through in the center( I don't think I should have blamed the oil for this).

I then added the new #1 bearing as previously discussed and the lighter springs and changed the oil to a calcium detergent based 0w40 for the winter and then 10w30 and then 15w40 this spring. When I made the oil change and the spring change and the bearing change things got louder but quieted down nicely after another 5000 miles and still using the 10w30.

I think I probably should have left the T6 in when making the spring change as now I have added another variable. My guess is that there was still break in left and T6 was doing a good job. The added noise from the changes indicated this( break in left). The different oil and springs continued on from where T6 left off but the new oil amplified where as T6 suppessed. The 15w40 is doing a good job, in the couple of days of this summer heat, but will return to T6 this fall. We got the same heat Kansas and NY got for 3 days(33/35C).

I want to note again that I put new INA stock black followers in on a OEM cam( edit, it was a warrantee replacement done in sept. 2009) with 38000 miles. My pictures show the cam is in good shape( a few tenths(.000x) wear at the most) but the center black is worn, still smooth and still not quit through after a 10,000 mile break in ( I think the followers could have benefited from 1.5 ounces of zddplus( I have a couple of bottles but did not use?).

 

[James & Son]

Cam loads and forces

The firing order is 1,3,4,2

The closed injector spring force is 62 lbs

#1 cam bearing is the problem bearing.

If #1 cylinder is firing #1 cam bearing gets half this load and #2,3 4,5 cam bearings gets the other half of the load caused by the injector pressure.
If you look at the full completion of the firing of all 4 cylinders each bearing will receive the same load generated by the 4 injector springs and 4 injector pressures so this is not a problem.

What throws an imbalance in this is at the time of injection pressure load, one exhaust and one intake are open and are both on the closing ramp. We will take a look at this imbalance and its influence.

Example, If #1 cylinder injector fires #2 cylinder exhaust valve is closing and #4 cylinder intake is closing and #3 cylinder is on compression. If one memorizes the firing order you can envision all this because it is the previous cylinder(#2) that must be on exhaust(just fired previously) and the previous to this(#4) is on intake and the one next to fire(#3) is on compression. You then can compare these forces for any cylinder.

Injector lobe forces and valve lobe forces act radially to the cam centerline but because of cam bearing clearance the cam journal can move about in the bearing depending upon the angle of the lobe. Eg. if the valve lobe is opening the cam lobe is generating horizontal and vertical forces on the journal in the 12:00 to 2:00 oclock region of the bearing. Maximum horizontal load is at partial to mid valve opening maximum vertical is at full valve opening. When it closes the lobe generates forces moving the journal in the 4:00 to 6:00 region.

As I said when one exhaust and one intake is closing the injector fires. This is spread across the distance of 3 particular cylinders as per the firing order.

So what is the combined direction of forces when the injector fires? The middle 3 bearings have the lobe forces pretty well balanced. And the resultant force is evenly loading these bearings. It is #1 and #5 that have the worst loading and the belt loading will need to be incorporated when we talk about them. The injector closed spring loads in conjunction with the particular valves that are partially open also effect #5 the most which then influences the wear pattern on #1. More later.

 

[James & Son]

I have worked out the following information.
injector spring preload on cam roller and therefore pushing down on cam is rocker ratio x 62 pounds or approx. 1.2 x 62 = 75 lbs. Since the rollers are almost always on the closing ramp of the injector lobe, I am going to use an average load per spring of 85 lbs x 1.2 = 100 lbs approx. x 4 = 400 lbs. pushing down on cam.

Except for top dead center we always have two valves open and the force of the two valves( full open) at mid-stroke of crank is 147 x 2 = 300 lbs approx. At the point of injector firing the valves are partially closed for an average load of about 150 lbs between the two.

I am estimating when I say the belt pull is about 275 lbs.

Injector spray load is 11,000 psi at around 2300 rpm. If i remember correctly the plunger is around 7 mm dia. and this is 656 lbs. x 1.2 rocker ratio or 787 lbs.

stock bearing contact area load is about 30 degrees of the rotation after 5000 miles which works out to 1300 psi bearing load at 2300 rpm. Oilhammer has stated that after 60,000 miles the bearings stop wearing. On high mileage cars or highway cars this is very likely. The copper underlay is gradually pounded into conformity with the journal diameter and it is possible at 60,000 miles the loads at 2300 rpm are as low as 650 psi.(60 degrees of contact) from injector force.

If any one wants to comment go ahead. I never actually put this down completely on paper before. This has always been a work in progress because I never had taken the measurements until recently to be accurate enough to come to a reasonable conclusion. Visually I know what I see but will the mechanics verify or show different reasons for what is happening. Anybody else want to work out the results and post there conclusions?

Edit - bearing ID is 29 mm x 25 mm wide.

 

[dieselfuel]

Doesn't Franko6 have a fix for this problem...? Seems to me he has a cam, bearings, and lifters to fix the problem with the BEW & BRM camshaft issue(s).


df

 

[Jnitrofish]

Doesn't Franko6 have a fix for this problem...? Seems to me he has a cam, bearings, and lifters to fix the problem with the BEW & BRM camshaft issue(s).

Different methods. Different limitations. Different philosophy. Similar goal.

If we absolutely agreed that Frank's stuff was perfect and an absolute solution for all VW PD TDI engines, I don't think any one of us would have volunteered our time and funds to continue researching and experimenting with our cars, we would all just go buy Frank's stuff and keep on rolling.

Don't you think so?

Before you pass judgment, remember that some of us have had first hand experience with Frank's designs. I personally find his camshaft to be wonderful as a performance item, but haven't shared similar enthusiasm for the bearings.

 

[dieselfuel]

I guess time will tell.

 

[Jnitrofish]

As it has been...

 

[turbocharged798]

If someone would come out with a PD roller lifter upgrade kit, all problems would be solved. There's gotta be a way without re-engineering the head. Take a lifter, put a roller on it and a hydro lash adjuster. Only tricky thing is that it needs to be keyed into the lifer bore so the roller stays straight and does not spin. A simple hole drilled in the head with a pin coming out of the roller lifter should do the trick.

I see no reason why this cannot be done.

 

[James & Son]

Different methods. Different limitations. Different philosophy. Similar goal.

If we absolutely agreed that Frank's stuff was perfect and an absolute solution for all VW PD TDI engines, I don't think any one of us would have volunteered our time and funds to continue researching and experimenting with our cars, we would all just go buy Frank's stuff and keep on rolling.

Don't you think so?

Before you pass judgment, remember that some of us have had first hand experience with Frank's designs. I personally find his camshaft to be wonderful as a performance item, but haven't shared similar enthusiasm for the bearings.

Analyzing the loads and visually looking at the bearings one sees the same result. #1 bearing is receiving more load and is compounded by #5 cam journal moving in an orbital path about the center line of #5 bearing.

This leads to edge loading of #1 bearing at the 4:30/5:00 position.

http://forums.tdiclub.com/showthread.php?t=241279&page=99

Look at eddifs BEW #1 bearing post 1476 and look at your BRM #1 bearing post 1484. No matter what the modification including mine as well #1 bearing edge loads at 4:30.

The cause of this is that #4 cylinder (#5 bearing journal) when its injector is loaded moves the journal to 7:30 position and then the next cylinder to fire is #2 and then #1 during which the exhaust and intake valve are lifting on 4 & 3 and 2 & 4 respectively. There is enough valve spring force to lift that end of the cam even against the injector spring preload. In other words the loads on #5 journal is causing the edge loading on #1 cam bearing over 3 different cylinders while #3 cylinder has little effect.

I think there might be a solution. Make a one piece bearing that replaces the split bearings on #5 journal and bore the centerline .001/.0015 offset of the centerline so that it compensates for half of the .003 diametrical clearance in that bearing. This would maintain the cam shaft on the center line. If positioned correctly it would compensate for half of the edge loading on #1 bearing. Since the coating is only .0003 thick( note we are talking tenths of a thousands here) this might allow the bearing to fully break in ( it actually pounds into conformity) and have enough area to reduce wear to a point that hydrodynamic oil film is maintained.

 

[A5INKY]

If someone would come out with a PD roller lifter upgrade kit, all problems would be solved. There's gotta be a way without re-engineering the head. Take a lifter, put a roller on it and a hydro lash adjuster. Only tricky thing is that it needs to be keyed into the lifer bore so the roller stays straight and does not spin. A simple hole drilled in the head with a pin coming out of the roller lifter should do the trick.

I see no reason why this cannot be done.

Take a PD head apart and you will see why this can't reasonably be done. There is simply no room.

 

[James & Son]

http://pics.tdiclub.com/data/5591/HPIM1865.JPG
First #1 brg 38000 miles
second #1 brg-1500 miles after brg mods. #4 & 5 brg oil port position at 8:00 and 2:00, all other brg at 10:00 only
3rd #1 brg- 1500 miles on after change( from 2:00 ) to 10:00 oil port position and retained 8:00 oil, all other brg 10:00 only
4th #1 brg-5000 miles, as above but without oil hole.

http://pics.tdiclub.com/data/5591/HPIM1867.JPG

http://pics.tdiclub.com/data/5591/HPIM1869.JPG
re added eddif axillary oil hole

When the cam is higher up the bearing shell it seems to slide down more and the surface contact is more glazed or polished like #2 or the stock bearings.

When i changed the oil location to 8:00 and 10:00 on #5 or completely to the opposite side of stock the cam stayed down low and is comforming( underlay of copper is conforming) in one location only although there are some moderate slide marks to 7:00 position( brg #3 and 4).

At first this does not visually look good compared to #2 polish. But if you note in #3 actual single contact is very small maybe .25 wide compared to #2. Both #2 and #3 have 1500 miles.

In theory I think #2 will have less load carrying ability in the long run as it never really conforms to the bearing (its sliding rather than sitting in one spot).

Now look at #4 which has 5000 miles on it and the bearing is still in the same spot but has a greater surface due to the continued loading of the substrate in one spot. When the area of conformity becomes great enough and the loads do not exceed the yield strength of the substrate the conformity will stop.

Will straightening of the cam and thus the single location conformity out live the stock location and its polishing or sliding. I now believe #4 with the eddif oil hole readded may provide more support before wear through.

Going back to my previous post where I said #5 journals oribital motion is causing a problem with edge loading of #1 bearing. Unfortunately this is still true and may still affect the ability of #1 bearing to fully conform but always be very slightly be oversize and continuously wearing caused by the non stable motion.

What is to much edge loading. Take the distance between #5 bearing and #1 bearing and divide it into the difference in centerline location of the journal of each bearing. In this case .003/15= .0002 inches per inch. At light to moderate loads the oil film is .0002 to .0001 thick but when the injector fires it drops to .00005 to .00008 thick. So when i said I could cut the edge loading in half with a new single piece bearing for #5 if it was not for single location conformity it would be of little benefit by itself.

The conformity must widen to about .5 inches ( about .312 wide now at 5000 miles) I would think, somewhere around 30,000 to 60,000 miles and the loads will be low enough to stop wear. This is my estimate for my driving (2300 to 2500 highway)

 

[Henrick]

If someone would come out with a PD roller lifter upgrade kit, all problems would be solved. There's gotta be a way without re-engineering the head. Take a lifter, put a roller on it and a hydro lash adjuster. Only tricky thing is that it needs to be keyed into the lifer bore so the roller stays straight and does not spin. A simple hole drilled in the head with a pin coming out of the roller lifter should do the trick.

I see no reason why this cannot be done.

Yep, I thought about this some time ago.

Why making a roller and having a pain about how to keep it straight? Why not making a plate consisting of two rollers in pair, per cylinder? E.g. you mount a 6x4 cm plate consisting of two rollers straight onto the place where the followers live. Rollers go inside the follower bores, the edges of the plate touch the edges of the cam towers. Then simply you could secure all this with one bolt (like the PD injectors are secured with only one bolt). Problem solved, or no? Well, this would be what I'd actually call a 're-engineering'.

 

[James & Son]

Yep, I thought about this some time ago.

Why making a roller and having a pain about how to keep it straight? Why not making a plate consisting of two rollers in pair, per cylinder? E.g. you mount a 6x4 cm plate consisting of two rollers straight onto the place where the followers live. Rollers go inside the follower bores, the edges of the plate touch the edges of the cam towers. Then simply you could secure all this with one bolt (like the PD injectors are secured with only one bolt). Problem solved, or no? Well, this would be what I'd actually call a 're-engineering'.

The cam journal is 29 mm aprox and the base circle of the lobe is 52.3 aprox. and the lobe lift is about 9.4. If you made a custom cam you might have room for those who would like to sketch this up. the bearing caps are 88 mm apart. The followers are 35 mm dia.

The follower does not change and you need to mount the roller to it. So it is obvious you need to modify the cam. If you need anymore information to work out if you can re-engineer, ask I might know what it is.

 

[Henrick]

Okay, let it be a different cam too in addition to what I've said. Then either (1) this is not that widespread and serious problem (cam/follower/bearing premature wear) or (2) most people are just too lazy to do anything [in aspects of an aftermarket redesign] to save PD engines.

 

[James & Son]

4500 Rpm Spring Test

Not only did I freak myself out, after realizing the significance of the situation I should be kicking myself around the block. I had to get around a slow moving vehicle before it started up a blind hill. I was probably a 100 yards behind it starting to accelerate from low revs in second gear. I have know idea what rpm i shifted at in second gear, as i was accessing the situation but as I shifted from 3rd to 4th just as I committed to go around I glanced at the revs. My God I was at 4500 rpm.

As you might or might not know I am using a custom lighter inner valve springs to my specs but based on the length and inner dia. of the stock inner spring. This reduces the open force from 147 lbs to 125 lbs and I estimated that I would be good to 4600 rpm since A5Inky had revved 5000 plus with stock springs. I had gone to 3800 rpm but planned to go no higher because of the unknown. Like what about resonance and someone mentioned boost pressure when I first decided to do this.

Well I now know my motor will rev to 4500 rpm with 125 lb springs. Passing at the bottom of a blind hill was not the place to find this out for sure.

 

[turbocharged798]

The cam journal is 29 mm aprox and the base circle of the lobe is 52.3 aprox. and the lobe lift is about 9.4. If you made a custom cam you might have room for those who would like to sketch this up. the bearing caps are 88 mm apart. The followers are 35 mm dia.

The follower does not change and you need to mount the roller to it. So it is obvious you need to modify the cam. If you need anymore information to work out if you can re-engineer, ask I might know what it is.

I am sure colt can grind us a custom cam. That's really not an issue. The main issue is making a lifter that has a roller on it and fits in the stock lifter bore.

 

[James & Son]

I am sure colt can grind us a custom cam. That's really not an issue. The main issue is making a lifter that has a roller on it and fits in the stock lifter bore.

I just provided all the information for anyone with basic drafting skills and a piece of graph paper a pencil and a rubber to determine if this is phyically possible. To proceed further you need a bright engineering graduate that is willing to work out possible engineering problems that will become obvious from your sketch( strength). You will also need to address the increased inertia and side thrust loads from the extra weight and higher location of the roller.

I think it would be easier to find a way to increase the PD cam lobe width from 13mm back to the 15mm width( approx.) of the ALH which seems to be reliable enough cam wise. I think 2mm per lobe is actually easily doable and wonder why VW didn't try a little harder here.

 

[jhs]

I think it would be easier to find a way to increase the PD cam lobe width from 13mm back to the 15mm width( approx.)

Hmm... is there enough space for that?

I think 2mm per lobe is actually easily doable and wonder why VW didn't try a little harder here.

Well... probably as usually happens things from paper and pure math don't replicate well in reality especially without a large magic reserve constant used in the fraction's nominators

Plus the narrow bearing support... and after all the cam is playing in a funny way with the oil introduction position and the added freaking forces from injector's rockers.

It's a puzzle without a magic one shot solution. That's probably why VW abandoned the design so quickly.

...then run into the hpfp issue (which seems less wide spread though).

Not being a mechanic or a specialist, just participating in the conversation as a proud owner of a BRM.

Just popped in my mind: What would IDparts and BoraParts (any other vendors too please) provide as a statistical data of the number of PD cam shafts sold over pre-PD ones. Nowadays and during the early months of PD especially BRMs.

Of course the user induced damage factor should not be neglected - oil used especially of the early days when dealerships used to pour in oil not designed for PD or that 5w30 instead oil for diesels 5w40.
Similarly the "sky is falling" regarding the hpfp - apparently many of the failures are due to misfueling or other contaminants. If it was all so bad with so many VWs in Toronto I should have seein at least one CR failed road side.

I know it's more of speculation than help but that's what I think.
Soon (in 3000 miles) I will be due for TB and then we'll see how is the cam doing after roughly 45k miles being fed with Lubromoly Diesel High Tech 5w40. The mileage is so because the cam was replaced by dealership at the day of purchase.

 

[James & Son]

I know it's more of speculation than help but that's what I think.
Soon (in 3000 miles) I will be due for TB and then we'll see how is the cam doing after roughly 45k miles being fed with Lubromoly Diesel High Tech 5w40. The mileage is so because the cam was replaced by dealership at the day of purchase.

I use a 500 watt halogen light to be able to see the surface condition. Daylight or 100 watts doesn't show the fine scratches from debris or surface contouring caused by irregular circular center wear of the follower and finally what I call the oval smoke rings which I believe is the carbon wearing from the follower as the lobe rotates over the center of the follower. So as far as I am concerned when you are accessing the condition of your cam lobe tip you are actually looking at the condition of your follower.

By the way you may have noticed the new formulations of CJ4 oil use a detergent combination of calcium and magnesium. Once the zddp dropped below 1400 parts the old calcium formulas stop being as effective although boron and calcium and magnesium seem to have made up for it. I bring this up as what ever oil you use to break in with I would make sure the zddplus content is an extra 1-1/2 to 2 ounces depending on the oil. Again this protects the follower which in turn protects the lobe surface finish. The ideal lobe finish is in the mid-nano range so any visual minute roughness is not good. But in general extra Zddplus and a good CJ4 such as T6 or equal will start the healing process if caught in time.

 

[James & Son]

Edge Loading Conclusion

From 1640 I talk about edge loading( please reread) and then in 1642 talk about the running position of #1 bearing. After determining the moment loads( inch lbs of force) about #1 cam bearing location. This includes belt pull, midstroke valve force and injection force and ralative distance and direction of these forces about the #1 cam bearing. Using the firing order one can find the resulting force and direction for each of the 4 cylinders and find if the belt pull and valve spring force over comes the downward loading of the injection springs.

The cause of this is that #4 cylinder (#5 bearing journal) when its injector is loaded moves the journal to 7:30 position on #5 cam bearing and results in edge load on #1 bearing (which includes belt tension)at 4:30 or in my case 5:00 and then the next cylinder to fire is #2 and then #1 during which the exhaust and intake valve are lifting on 4 & 3 and 2 & 4 respectively. There is enough valve spring force to lift that end of the cam even against the injector spring preload. In other words the resultant loads on #5 journal are at 12:00 and at 6:00 on #1 cam bearing causing the unwanted edge loading on the overworked #1 bearing.

Note, that the edge loading is only during a short period of time considering the lobe open valve effective force duration of about 30 degrees of cam rotation. The injection force lasts about 30/40 degrees

http://forums.tdiclub.com/showpost.php?p=3629853&postcount=1484
Jnitrofishes #1 bearings shows the combined result of the 4:30 and 6:00 edge loading. The cuts in the bearing had no effect to cause this other than to improve the flatness of the supported portion of the bearing. This in conjuction with the Molydisulfide should have resulted in reasonable bearing wear. It is obvious in this case anti-friction does not equal anti-wear.

I think what happened the bearing coating wore through before the copper underlay reached a point it could support the edge loading. Also note the 12:00 and 7:30 bearing load of upper #5 bearing half.

Now if I compare my 125 lb valve springs to the above 147 lb stock springs only #2 cylinder causes #1 edge loading at 6:00 along with the inevidable #4 cylinder injection. This should result in less #1 bearing wear.

Eddif developed his bearing theory in this thread in page #1. He spent the rest of this thread trying to eliminate edge loading. Only the bearings he is running now really will tell us if he succeeded.

 

[eddif]

I have not gone far enough away to have dropped off the face of the earth. I do still have a long return back before I start posting on the PDs. Bandmill design. and other things have taken my time.

Thank goodness I did not post some of the information I was about to post. By waiting I have seen some things way beyond what I would have gotten into at the time. I am amazed at what can come into your head by Grace.

I also have seen why some of our confusion discussing #5 bearing came about. I gave a lot of information in text that needs some more drawings to finish helping everyone else understand what I wrote. The information is there, but it sure needs more help to be understood.

I have not ceased to have the problems in mind, but I have not spent the computer time to post them. We are using another car and the pressure was relieved on getting the PD problems resolved (traiter I suppose... lol).

Hopefully I have some more information on oiling the follower tops in the works too.


eddif