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

[James & Son]

I have had another day to think about this. The center dot wear issue is exactly that. The center dot. Look at my #1 follower which has been in for about 55000 km (not much).
The center dot is tore rate out. The black and the metal below were tore rate out. A perfect dot. This is the center of rotation.

The trouble now is that I believe there is two places where this wear dot phenomenon is taking place. Where the injector fires and the follower takes the injector force instead of the bearings( this may happen at low speeds, oil viscosity may have an effect as well on bleed rate). This is what is shown above.

The other place is the point where the apex of the lobe and cam shaft center line, lines up, with the follower center line and you can see the center dot marking on the nose of the cam.

So unfortunately what i suggest above will supplement what I have already done and for me might not even be necessary since i believe i have stopped the follower loading by other means(which are beyond DIY). But the suggestion is valid and a .002-.003 inch taper from the edge where the galling is taking place to the cam face center in that area may relieve the high loading( idea is to remove the galled area only but with a very mild relief so the rotating side of the follower takes more of the load). But the more I think about it the more it could have disastrous results without control over how much cam bearing clearance and therefore how much up and down cam movement can take place.

I guess I have to back off on a low cost DIY.

In a nut shell this should improve follower life.
1) reduce valve spring pressure by 15% so that injection spring pressure is greater and prevents the #5 journal from lifting or orbiting around.
2) relieve the #3 bearing to eliminate the possibility of #3 bearing acting as a fulcrum causing a tilting action to take place depending on which injector is firing. In other words #3 must get pounded down as fast as necessary so that #4 bearing acts as the fulcrum instead of #3. This prevents the firing of #4 injector from lifting the cam belt and the journals of 1 and 2.

Now the bearings will take the injector firing loads instead of the followers.

Further to the above. If one does the above then you could relieve the galling as i have suggested to further supplement any possible injector loading being transferred to the followers.

The answer to the lobe wear dot point is what eddif, Franko, others(A5Inky and Jnitrofish to name a few) and myself have done, can't say what the long term is for that but I know this. Do not reduce the bearing area of #1 and #2.

CJ4 oils with an ounce of zddplus seem to be the simplest most effective for the first 30,000 to 50,000 km or use the standard no load break in method.

Edit: I forgot, one of the most important things that has a pronounced effect on the follower loading is the thermostat. The thermostat loses 2 degrees per year and my 6 year thermostat was making a 40 wt into a 50 wt. which would have a pronounced effect on follower leak down.

 

[James & Son]

I did chop one of my old lifters apart to see if there was any means by which Ina prevents total take up between the closed cam dwell and the follower. But it is a simple construction with no means of closing the check prior to total oil filling. If the cam moves up the follower moves with it as there is 2.5 lbs of spring pressure and 50 psi of oil pressure which works out to a force of 7 psi in addition to the spring takeup. The check valve ball spring is extremely light and the 2 mm ball will open I believe at a minumum of 28 psi( I think that is in the bently). 28 psi is .14 lbs of force against the light spring check and I am sure that is more than enough.

Basically the way I see the causes of follower wear(associated to the wear dot) is this.

1)As I said above, the center loading of various followers caused by the up and down movement forces over the cam lenght caused by a pair of valves / injection pump.

2)Just plane wear as the lobe crosses center.

3)Just plane wear generated by the 2.5 lb spring and additional 7 lbs of oil pressure force acting against the follower center and the cam closed dwell. This does not seem much but consider the forces when one realizes the contact is straight line .010 wide x .470(lobe width). This works out to 2000 lbs per sq. inch depending on the actual effective oil pressure( 50 psi), but lets face it, it has to be over 28 psi in the follower and even at that minimum it is still a loading of more than 1000 psi. I know this seems absurd but remember the contact area is extremely small and thus the high result when compared to one square inch.

Edit: I made a mistake on the area of the lifter ram affected by oil pressure. There is a countering area where the oil enters at the top that reduces the acting area of the ram by 2.25 lbs which then reduces the force to 1500 and 760 psi at 50 and 28 psi oil pressure respectively. This is an improvement that makes me happier.

 

[James & Son]

The more I look at #1680 the more I do see some wear so some of the forces causing wear are still there.

In post 1684 above I layout the 3 wear modes for the follower.

Going through my dates I just realized this event( #1646) is what could have caused the wear dot damage to #1 and #3 follower.

I am now back to normal wear mode after replacing the damaged #3 and as long as I don,t rev above a certain rpm maybe wear mode #1 in post 1684 will not be a problem.

Let me review the problem. I believe #3 4 and 5 cam bearing are level. But #1 and somewhat #2 bearing have more wear or seating in due to the higher loads imposed on #1 bearing. The underlying copper conforms to the journal at higher than normal injection loads( every time you put your foot into it). When #1 is fully seated the lower bearing shell is pounded down .0015 to .002 inches. At operating temp.the aluminum head also expands outwards opening up the bearing bore another aprox..001 thousands. #3 bearing now will act as the fulcum for the up down tilting action that starts with #4 injection and finishes with #2 and #1 injection firing in that order. This initially tilts the cam up with the followers following and then after injection the cam is resting on the over extended followers, the bearings are now no longer supporting the cam but instead the followers are of #1 and #2 cylinder. #2 cylinder fires next and hammers the followers that are locked closed on the compression and fire stroke. Most people are aware of the injection forces. Some think it is 27000 psi all the time( not possible). At idle it is around 4000 psi., at 1800 to 2300 rpm it is about 10,000 psi plus. and it goes up exponentially until you hit 27000 psi at 4500 rpm plus and full throttle.

The injector on the BEW is 8.0 mm dia. and I believe it is 7.5 on the BRM. At 27000 psi this works out to 1848 lbs x 1.2 rocker ratio = 2200 lbs force.

What are the forces holding the valves closed under compression. A rough esstimate based on 500 psi and valve area comes to 700 psi per valve. This is a minimum since ignition will initiate in milliseconds. ( you can add the 60 lbs of closed spring pressure as well here).

So to me it now seems reasonable that the follower can be and is being stressed upwards of 700 plus pounds. This is beyond the 500 lbs spring load designed into a 1/4 mile dragster where the life expectancy of components is maybe 30 passes.

Now it makes sense why the metal is being pounded and torn by galling out of the follower to create the center dot.

Its wonder A5Inky got 100,000 miles out of his cam with his modifications. But before you say his followers didnot tear out, look again at the unusal wear on his bearings. It is possible that his cam was not tilting on #3. There are a number of reasons why this could have been the case.
http://forums.tdiclub.com/showthread.php?t=367003&page=2&highlight=A5INKY

 

[James & Son]

Wear Caused by Closed Dwell of Cam

I spent the last few weeks making sure there is a proper conclusion to be reached here. First of all I need to know for sure it is the closed dwell area of the cam as shown in 1681 above that is generating the circular wear as shown here


The cam lobe is 12 mm wide and is positioned 4 mm and 8mm to the center of the follower. If you have circular edge loading you will generate an 8mm circular wear spot or a 16 mm circular wear spot depending. Now if you look at my followers closely you will see both possible wear circles. The follower is 35mm dia. if you want to scale.
It is very noticable in the top row of followers which left to right correspond to #1[1-exh] #2[1-intake] and so forth.

Now if you look at the course grind on the closed dwell in my post 1681 above you realize the rough surface could not support an EHD ( elastrohydrodynamic lubrication region) but the lobe could. It is unlikely the lobe that swipes across center could generate such a distinct 16mm circle without some feathering of the edges since it is doing more sliding through than rotating. But on the other hand the closed dwell would only generate a rotation or if it did not it would scuff the surface which is also possible for both the closed dwell and the lobe. I have distinct circular wear marks from the loading in the closed dwell position( see 1684 for reasoning and 1685 for calculated load [edit]).

It is unlikely that others have this rough a grind and I am the only one experiencing this dramatic wear so quickly, but the forces are there even if I am the only one experiencing the 16 mm wear. The 8 mm circle wear does exist.

If you look at A5INKY http://forums.tdiclub.com/showthread...ghlight=A5INKY he only has the 8mm circular wear.

Because he had a regrind cam the cam wore out before the followers did. You can also notice some gray on the black tops where the black is nearly worn through(#4 and others). You will notice how the scoring bites into these areas and skips over the thicker black spots.

So there is a difference between coated and uncoated. Also a reasonable fine finish grind should help promote an EHD lubrication regime on the closed dwell surface before the black wears through.( see 1684 for cause)

 

[James & Son]

So there is a difference between coated and uncoated. Also a reasonable fine finish grind should help promote an EHD lubrication regime on the closed dwell surface before the black wears through.

I want explain this as this is needed to understand the cam wear and wear dot together and possible answer why some cams only lasted low mileage

http://www.zddplus.com/TechBrief11 - Internal Combustion Engine Lubrication.pdf

View the graph of cam velocity, acceleration and lubrication thickness( pg 9 of tech brief #11). Now look at the pickup on my cam and the approximate location on the closed dwell( what I am about to explain the exact location is unimportant since the valve is closed during the injection event). I am guessing it is about opposite of the apex of the lobe as seen in above 1681 post. The pickup covers a range of 35-40 degrees on the cam dwell. I have to make an assumption here that this is a major injection event at higher rpms and load and travel or duration would be using up a good deal of the ramp.

Now in post 1685 I point out the injection load at high rpms can be about 4x plus what the cam lobe max. spring pressure is. I should inject here for interest sake that forces on the cam lobe are actually valve train inertia forces plus cam spring pressure(147 lb is stock tdi) which is talked about in the link as well( tech brief #11). So cam ramp inertial forces( the first 45 degees) and spring force at this initial lift could be assumed to be 147 lbs approx at 5000 rpm plus and 125 lbs at 4500 rpm plus ( again educated guesses).

Now we know the pickup is on the exhaust valve dwell so the injection event is in advance of the lobe opening 180 degrees.( not so much a guess after all).

ok, the graph shows a thick oil film for the closed dwell area due to the loads are low even though this is a line contact which means a thick hydrodynamic oil film in the wedge and line contact.

Now because we have a force that puts the dwell line contact into loads well into Elastohydrodynamic (EHD) lub. regime you need to modify the graph for 40 degrees and show an oil film 1 micrometer thick (.000039 inches) (generic EHD thickness). How this happens is partially explained post #1685.

Now if the surface is rough it is possible this EHD squeeze will not form and the cam and follower make contact and the course grind lines on my cam actually shear the black coating until eventual break through. This could easily explain the early cam failures back in 2006-2009. Now if you were lucky enough to get a reasonable smooth cam that would develop a EHD film then the cam would last X miles based on the other 10 or more factors that might influence a normal life expectancy. My stock warranty cam has broke in well enough after 2 sets of followers but the rough cam dwell still exists that I can do nothing about with any precision.

But being proactive I have shimmed #5 bearing and reduced valve spring forces so that the injector springs load the cam more holding it in place and reducing the chance of follower loading in the closed dwell.

But as I explained above, inertia forces as well as the cam springs are pushing the cam up allowing the followers to follow. So I figure I can only rev my motor to 2700 rpm before inertia and spring forces push the cam up.

I am learning how to take advantage of the stock turbo charger in the 1400 to 2700 rpm range. I have advanced my torsion to .5 degrees and the motor accelerates nice and smooth from 1200 to 2700 rpm. Now I only have to deal with wear #2 and 3 which one ounce of Zddplus should take care of. I am satisfied for now. We will see what the future brings.

 

[carl_b]

I have a 2006 Jetta Tdi that was manufactured 11/2005. I have 103k on the car.
I have been using Valvoline synpower.. In the winter I use 1 qt 20-50 and the rest 5-40.. In the summer I use 2 qts 20-50 and the rest 5-40.. Both oils are vw 505.01..
I have been worried about the dreaded cam problem, so just sent in an oil sample to Blackstone and got a fantastic report back..5000 mi interval.. 10 ppm iron, 0 chrome, 1 lead..
It looks like this has worked real well for me... Just thought I would pass this on..
The only thing I have had to do on this car has been to put in new brake pads..It has never been
in the shop for anything else...

 

[James & Son]

I have a 2006 Jetta Tdi that was manufactured 11/2005. I have 103k on the car.
I have been using Valvoline synpower.. In the winter I use 1 qt 20-50 and the rest 5-40.. In the summer I use 2 qts 20-50 and the rest 5-40.. Both oils are vw 505.01..
I have been worried about the dreaded cam problem, so just sent in an oil sample to Blackstone and got a fantastic report back..5000 mi interval.. 10 ppm iron, 0 chrome, 1 lead..
It looks like this has worked real well for me... Just thought I would pass this on..
The only thing I have had to do on this car has been to put in new brake pads..It has never been
in the shop for anything else...

I would be interested in seeing the report in its entirety. Log in to or start your album and you can upload a pdf to it. This may help some with that.
http://forums.tdiclub.com/showthread.php?t=207484&highlight=picture

 

[carl_b]

It looks like a pain to upload the report... What else would you like to know??

 

[James & Son]

What was your viscosity at 100 C in cst. I can't convert soybolt as its a pain too. What was the oil used for the first 50,000 miles.

 

[carl_b]

Oil vis

I have always used Valvoline syn power as stated in the original post.
cst at 100c was 14.6

 

[eddif]

When the mileage piles on and the hammering on the bottom of the lifter top finally breaks off the coating (hard carbon?) the wear just starts. The follower (lifter) I cut apart still tells the story.
http://pics.tdiclub.com/data/500/Copy_3_of_DSC00097.JPG
The Porsche method of dedicated oiling for the follower lobe interface point will help.
I need to get back and post new information on bearings. The information is interesting, but may not solve all the TDI problems.
eddif

 

[eddif]

The oil conversation returned again.
IMHO. ZDDP importance is for the first (early) TDI engines. The early engines did not have the coated followers. ZDDP bonds to both surfaces of steel on steel contact (follower and lobe). I am not convinced steel on coating contact has the same process going on. I am convinced that the hammering of the hydraulic follower / lifter unit causes coating separation.
Of course thickness of oil film is important. Narrowed TDI cam lobes are more stressed per area than older wider lobes on previous VW engines. The previous VW engines used thicker oil, but the later hydraulic followers probably have less internal plunger clearance to deal with thinner (lower viscosity oil). So you have a battle. Thicker oil will help the interface between the cam lobe and follower top, but at the same time the followers have less bleed off causing the potential for higher contact pressure during the non lift portion of the valve event (especially at high RPMs & greater potential for valve float).
A weak design just depends on never having the least chance of overheating, over speed, wrong oil (too thin included for tropical areas), etc. This is why the discussion of maintenance is often mentioned. A robust design will be more forgiving. A weak design is just on the verge of disaster at all times. My 4000 rpm shift yesterday (traffic need) does not help a wearing cam (neither does a wreck help the whole car).
LOL. Interesting.
eddif

 

[hotrodfeguy]

I replaced my cam with the chrome plated Stage II Have not had a bit of issue, in fact gained 2-4 MPG. As the grinder/MGF said it has Stage II intake/Exhaust lobes but the same Injector pattern as stock. As far as the bearing issues you guys seam to have when replacing, my cam my bearing wear did not look like yours at the flywheel. I wonder if the head cores had some casting/machine variance as per bore alignment when the engine heat and head bolt TQ gets to them.

 

[Rod Bearing]

The most important things affecting these cams and lifters IMO, are

Valve spring pressure variations

Camshaft lobe profile and finish

Installed height of all valves

Camshaft bearing bore alignment

Head bolt torquing sequence

It is essential to do a top notch cyl head rebuild when a cam galls and fails. I installed a dripper tube under the valve cover to add some oil to the lobes. It is externally fed from a bypass oil filter.

My particular BRM since doing these things has 185,000 miles on it using Delvac 1300 Super. Original valve spring pressures were all over the place, the cyls with galled lobes having way too much spring pressure.

 

[turbocharged798]

That's interesting find on the valve spring pressures. That could explain why the PD cam wear issue is hit and miss.

 

[bl00tdi]

And would also explain why some chamfer is missing on my #1 exhaust lobe while the others are virtually flawless.

 

[James & Son]

And would also explain why some chamfer is missing on my #1 exhaust lobe while the others are virtually flawless.

Read ediffs first post in this thread and you will understand why #1 exhaust lobe is wearing. You can improve your issue by replacing the lower bearing halves of #1 and #2 cam bearings.

 

[James & Son]

The most important things affecting these cams and lifters IMO, are

Valve spring pressure variations

Camshaft lobe profile and finish

Installed height of all valves

Camshaft bearing bore alignment

Head bolt torquing sequence

It is essential to do a top notch cyl head rebuild when a cam galls and fails. I installed a dripper tube under the valve cover to add some oil to the lobes. It is externally fed from a bypass oil filter.

My particular BRM since doing these things has 185,000 miles on it using Delvac 1300 Super. Original valve spring pressures were all over the place, the cyls with galled lobes having way too much spring pressure.

Rod Bearing,

You forgot to mention you were the first to post about using the proper no load break in procedure.

Just so you all don't jump to conclusions, nobody except Rod bearing checks their spring tension when they replace their cam and I have not heard of anybody on their third cam yet.

Anybody want to admit they are on their third cam???

 

[A5INKY]

Technically on my 4th cam, first two don't actually count though. Dealership FUBAR.

 

[pruzink]

I have a 2004 BEW Jetta with 177,000 miles. I just installed my second timing belt and also installed a new camshaft/lifters/bearings. I didn't think the a BEW camshaft would make it to the 3rd timing belt but now that I have the old camshaft and lifters out they look like pretty much new. I will post some pictures when I am done. I would recommend for anyone doing a camshaft inspection on the BEW or BRM engines that they remove the rocker arms (fuel injector arms) as they block a good view of seeing camshaft lobes & lifters. Frank 06 sells the reusable rocker arm bolts (I'm not sure if the other vendors sell them also) but its just 8 bolts to get these out of the way & then you can see what is going on with the cam & lifters much better. I installed the frank06 chromed camshaft with the modified bearings. The original lifters were the shiny silver ones, the new ones are the darker ones. I am kind of kicking myself for doing this job right now, everything that I replaced (cam, lifters, bearings) looked perfect.

 

[bl00tdi]

Read ediffs first post in this thread and you will understand why #1 exhaust lobe is wearing. You can improve your issue by replacing the lower bearing halves of #1 and #2 cam bearings.

Already done. Replaced all the bearings in fact.

The interesting thing is that none of the oil slots on the lower halves were covered up. Can you quickly reference where he discussed the #1EX lobe specifically? Thanks.

Sent from my LG-d801 using Tapatalk

 

[James & Son]

Already done. Replaced all the bearings in fact.

The interesting thing is that none of the oil slots on the lower halves were covered up. Can you quickly reference where he discussed the #1EX lobe specifically? Thanks.

Sent from my LG-d801 using Tapatalk

Eddif corrected his initial bearing problem and then went on to dig up every possible problem he could conceive of but never was able to determine if increasing oil supply and moving the oil inlet alone would solve the wear problem. it seems the operating environment affects each car differently.

Jnitrofish and myself proved it was not a good idea to use cut bearings on #1 or 2 bearing specifically on our brms. His cut bearings seem to do fine on his bew but until he puts some miles on them he can not be sure.

I suggest that you also need to heal your lobe and follower by running zddplus, which is a very active anti-wear additive. An addition of one or two ounces will start the smoothing of the follower if it is not worn to much.

The stock springs only have a spring force of 147 lbs. open. I removed my springs and measured their free length and they were all within .8mm of each other and these were the springs my first cam went out at 80000 kilometers or just inside the warrantee (50,000 miles).

Just for reference 1 mm equals 10 lbs of spring force. So the accuracy of my springs was +/- 4 lbs of the mean. In other words next thing to perfect.

 

[James & Son]

Well it has been 11 months since I posted 1681 pg 113.

When I saw thread 2006.5 tdi Cam Wear? I new the first day above 0 C I would pull the cam shaft to look at the followers.

It has been 125,000 kilometers on the cam shaft since replacement in the fall of 2009. I will call this cam replacement mileage(although in kilometers) or CRM

i had wear dot tear out on #1 and #2 exhaust follower at 48000 kilometers CRM of the cam replacement. I made a decision because of the low mileage to replace all my followers with oem black followers(INA) from the dealer just as the replacement cam and followers were( done at dealer in 2009) Lobes good and still breaking in fact.

If you read my posts 1681 to 1683 on pg113 you will see that I have made the 3 modifications( post 1683) necessary before doing what I proposed in 1681 which would be to relieve the cam dwell. I feel they may or may not be necessary before doing the relief proposed in 1681. These posts were at about 84000 kilometers CRM.

I was hoping 1683 mods would avoid 1681 mod. But no luck and it was 3:00 in the afternoon with the car half in the garage and freezing rain forecast overnight.

Anyways its all back together with new followers on #1 exhaust and #3 exhaust because they had wear dot center scoring that was leading to the same pickup on the closed dwell area only more so as the followers were at 125000 CRM with 77000 kilometers on them since replacement of all the followers at 48000 CRM

I measured all lobes and they are flat with 1 2 and 3 cylinder lobes measuring 2.429 inch. and both lobes on #4 cylinder at 2.430. I believe a new stock cam is in the 2.432/2.430 inch range according to franko. I am pretty confident that the cam new was ground at 2.430 or 2.4305 inch as I also measured it at 48000 and it measured pretty much the same( talking tenths difference).

I did the proposed modification 1681 on all 4 exhaust lobes after running out to get the replacement followers at the dealer. I have pictures that I will post but have to figure out how to get them on the site as my album is full but I do not want to delete.

So this summer sometime I will have another look.

This is still a shot in the dark as far as my modifications although I am following the picture evidence. I have not had success so far but the relief modification may be the necessary final step...?

I think the real problem( 80% worth) is just a rough grind on the closed base circle. But it does make sense to at least monitor your followers between 50,000 to 75000 kilometers when if you do have these loads you will have scoring of the center of the follower. Replacing the damaged follower is so far only buying me time to see if the relief is going to be the solution.

I will post the pictures hopefully soon.

Edit: Pro's and con's

Pro's of clearing.
-oil gets to center of follower in advance of initial opening of exhaust valve.
-movement of cam in bearings is taken by intake followers and/or cam bearings instead of exhaust followers when loaded by injection forces.

Con's
-risk. Well if it don't work I will still have made it to 100,000 miles, since replacing followers was only buying me time I really need to take the gamble.

 

[James & Son]

This is #2 cyl. exhaust lobe. When the black wears thru on the follower it picks up as shown. This is the reaction to the injection forces early on. I have been correcting this by replacing the black INA followers.

As I said I went ahead and cleared this area up to half the width of the lobe in the above contact area of each exhaust lobe. I am now counting on the intake followers and the bearings to take the injection downward load.

It is now pretty clear to me that it is the closed dwell base circle that is taking loads as well as the bearings when the injector fires.

I have added some pros and cons in my post above to clearing the high friction area caused by injection downward force.

I have done some research on early failures and besides.
2006.5 tdi Cam Wear?
another good post with pictures is
http://forums.tdiclub.com/showthread.php?t=252590

Why these and my cam problem happening very early.
The above cam problem is with my wifes 2006 BRM.( second cam car now at 208000 kilometers.

You may or may not know I now only resently own GoFasters magic car as Bob S calls it.
It has 432000 kilometers or 276,000 miles on the original cam. Since MetalmanParts and ID Parts have reduced prices on stock cams I thought I should have a look.

Perfect is the word to discribe the cam. Except for #4 intake and exhaust closed dwell base circle of the cam which has a haze of a fine smooth even wear or pickup( feels smooth enough though), every other lobe and base circle are perfect. Their has been absolutely no contact to show any polishing or wear-in except for the nose of each lobe, not even the take-up ramp until you enter the actual .37 inches of lift area. NO CONTACT completely contact free except as I say for #4 base circle and nose of lobes. The lobes are scratch free and have no oval circular marking that corresponds to contact with the follower.
There is no sign of copper release from worn bearings.
This is the original cam that came with the motor the day it left the assembly line. This is only the second time the valve cover has ever been removed and Gofaster did the first early on in its life.

I hope the pictures turned out.

 

[GoFaster]

^ Good to hear!

 

[A5INKY]

Gofaster's (former) head should be studied IMO. I would be curious as to installed heights of valves, valve spring rate and cam bearing bore concentricity especially.

I have a feeling that installed heights creating too much follower preload coupled with poor cooling of exhaust followers is a big part of typical PD wear. If that is so, tuning and aggressive driving would contribute negatively to the typical wear pattern.

Maybe that is why I'm on my 4th cam

 

[James & Son]

Heres the pictures of go fasters cam.



I think it is still early enough LOL( 432,000 kilometers) to help #4 cylinder closed dwell beginning stages of pickup.

 

[James & Son]

I have now enough information to predict what my cam will do in the future. First review this.
http://www.stle.org/resources/lubelearn/lubrication/#elasto
Now I do talk about this situation as it applies to the closed dwell or base circle of the cam in post #1684

Now I am providing another link. It is only necessary to read the abstact on page 2.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19750015918.pdf


Preferred Surface Finish of a Cam Lobe( based on nasa paper and gofasters cam).

The middle of the range for surface roughness of a ground surface is .4 micrometers, i am perfably looking for the next step down in roughness at .2 micrometers ( this is equal to 16 and 8 microinches in old measure respectively). When you get this measure the surface seems nondirectional and has a refined texture.

Now going the other way the next increase up in grind roughness from a middle range of .4 is .8 micrometers. Well the Nasa cut off point in the test was at .56 which is not much more than the mid-range. So I am definitely looking for a highly refined surface texture of about .2 maximum. The lower the better for non-contact lubrication of non-conformable surfaces(cam and follower).

This has nothing to do with breakin. The lobe nose will breakin but the closed dwell base circle will not and that is how you get the center wear dot forming if the surface is to rough to allow for elastohydrodynamic lubrication to form to prevent contact in the closed dwell.

Now look at above post 1706 and you can count the ridges on this cam that is how course the grind is... probably in the range of 6.3 to 1.6 micrometers, smaller is a better finish and the nasa paper used .56 micrometers as the cut of for max. roughness. I assume they knew any higher was a waste of time.

Just for the heck of it I counted 11 ridges in the first 4mm and the cam width is 12 mm so we have a total of 33. Each ridge and valley is .36 mm or .014 in. Now how is this possible. It seems the wheel was dressed to form these ridges!!!!

How much surface area is available for support. The width of a hair is .006 so lets use that x 33 for .198 in. or 5 mm. This is less than half the width of the lobe. Now using a line contact width as I used in post 1684 of .010in. we have an area of .0019 sq in. Using 8 lb load on base circle from same post we would have a load of 8/.0019= 4232 lbs per sq in.

Now you know why you have to review link
http://www.stle.org/resources/lubelearn/lubrication/#elasto
because you wouldn't believe me otherwise.

You can see how this cam is junk the day it came off the grinder. The engine head is fine, the oil is fine. The nose of the lobe did eventually break-in. But the base circle will never break in enough to allow EHD lubrication and all the while it is grinding away it is forming the wear dot never allowing the nose of the lobe to fully conform and develope its own EHDL.

Putting the relief in the cam dwell was a waste of time but it will be interesting to see if there is an improvement. The nasa paper says a course longitudinal circumferential surface lay destroys the EHDL.

Basically, I think, I established a new surface at the central contact of the lobe and follower,

which is polished from my stoning of the relief edges,

to form a surface that may actually form a EHDL ( or not??)

 

[James & Son]

The most important things affecting these cams and lifters IMO, are

Valve spring pressure variations

Camshaft lobe profile and finish

Installed height of all valves

Camshaft bearing bore alignment

Head bolt torquing sequence

It is essential to do a top notch cyl head rebuild when a cam galls and fails. I installed a dripper tube under the valve cover to add some oil to the lobes. It is externally fed from a bypass oil filter.

My particular BRM since doing these things has 185,000 miles on it using Delvac 1300 Super. Original valve spring pressures were all over the place, the cyls with galled lobes having way too much spring pressure.

If you have followed my issues and you read this link below. You can easily determine the main issue( cause) that i believe is having an effect on all cam wear. The complete effect mechanism is might still quite complicated if you are trying to take all cam wear into account but I think this link clearly explains the cause. Now how did what Rod bearing do solve this issue.

I wonder if Rod Bearing manganese phosphate coated his cam? How would this have an effect. I need to know if Rod Bearing Manganese Phosphate coated his cam.

I think the surface finish of the closed dwell works hand in hand with the black manganese phosphate coating to allow this coating to help change the grind lay characteristics to allow EHD lubrication.

Without this initial surface grind lay characteristic change on the closed dwell base circle of the cam and because this surface never breaks in due to being nitride I believe it initiates the cause of all cam wear.

http://www.transportation.anl.gov/pdfs/MM/889.PDF

 

[James & Son]

Did i kill the Rabbit

Well, from knotching the cam dwell one would think i attempted to do so.
I pulled the cam on the weekend and all is well.

Ok, but I am getting fed up. I think I am close to some answers but am fed up with the slow progress.

What answers, doesn't Rod bearing, franko6 and Geoff have the answers. Maybe and maybe not. How come Kerma has removed the 5 year warranty. How about Franks warranty. Has there been failures. Why is TDT and Rotella T6 on Frank's banned list.

At this moment I see one primary causes that can prevent you from making it to 100,000 miles.

1) It is absolutely vidal that break in take place as fast as possible. EHD lubrication must take place on all line contact loads of the cam before you can switch from the break in joe gibbs oil. to the recommended service oils.


1a) My cam would never break in , in the life expectancy of joe gibbs oil which is 500 miles. Why? The closed dwell is still showing contact at 80,000 miles although it has improved considerably. Now if it had had a parkerized coating which is about .0002 thick and does break in, I am pretty certain that could solve that issue.

1b) My cam because of the rough closed dwell which is now becoming pretty smooth after 80,000 miles and 20 followers later might be ready for the last hurtle. It has to break through the black coating without galling. I am testing what i consider to be the ultimate antiwear oil to help it do this.
This post explains.
#50

Edit: Kema still has the 5 year warranty, my mistake. But i would like to hear from any body that had issues with there cam within a 150,000 window and how it was to deal with. Both Kerma and Frank have warranties. I can't believe nobody has had an issue with either one.
We have heard from everyone that the design is flawed the lobes are to narrow etc. etc. All of a sudden a flawed design and nobody is having anymore problems.

Would it not be interesting to find out the flawed design was corrected by parkerizing the cam. In fact now I believe I do remember Rod Bearing did parkerize his cam. I will find his post on cam breakin.

http://forums.tdiclub.com/showthread.php?t=257391
see post 8

Edit2; #192
#222 #224