Where I have Been / Cam Pulleys

[FRP]

Hi All.

Update on my condition!

Yes I am still alive and I know I am a grade 1 scum sucking jerk for being MIA for so long! As I stated when I made my initial posts I have never been a "forum guy", (partly attributable to being 61 years old) and mostly just because I lack the energy at the end of the day and lack time during the day. Been working 6 - 7 days a week for the past year. I am the primary builder for a local shop that does a great deal of Asian car tuner work so that is piled on top of my VW / Audi work and I am busier than I ever intended.

I was going to go back to Bonneville to raise my record there this year and had the car on the dyno in June with Brendan here to handle the tuning. I had added a big Borg Warner Air Werks turbo, an S400SX3 with an 80mm compressor and a 87mm turbine and 1.25 A/R hot side housing with the plan to free the engine up more between 9000 and 10,500 rpm where it must run to make the MPH target we had which was in the 260 mph average range. I had also added 160 pound per hour injectors from Mike Moran and have developed a new piston (which I will be selling) that raised the CR to 10.4 to one with my highly relieved combustion chambers which would help us utilize the slow burning "event fuel" at B Ville which is 118 octane leaded fuel.

Anyway, we were sneaking up on the tune with A/F at a still rich 11.8 and not all the timing in yet. The engine sounded awesome and was reving very freely to 10.5 k rpm. The torque and HP lines were flat from 8k to 10.5k with no drop off. HP was 1048 wheel and 675 wheel torque
at 33 pounds boost. Then it happened! Engine suddenly showed rich (WTF) and sounded a little ragged so we took out a little fuel and made another pull. At 10K rpm the crankcase pressure relief blew open and a big cloud of oil and water vapor blew out. I knew the engine was hosed but how? Long story short - we pulled off the charge piping and found that the ice water intercooler core had failed severleypumping mass quantities of chilled water through the motor - game over. Piston rings on 2,3 and 4 had annealed from the chilled water hitting them and sucked away from the cylinder walls - hence the blow by.

There was no damage to the crank, rods, pistons or bearings and it did not push the head gasket out though you could see where it tried to on those cylinders. It did warp some exhaust valve seats and valves. No hydo lock though. The pressures must have been stratospheric and it is a hell of a testimony to Pauter Machine con rods!

Anyway I was too spent and too backed up on customer work to put it back together. The plan was to get it ready for next year. Then Speed Week got rained out so I am glad I did not thrash it and myself trying to get it ready!

*** I do want to take a moment to comment on the problems we have had with Nick's motor. If you have not heard, we have had 2 failures of the cam pulley to camshaft mounting. The first one was attributable to me just not realizing that there were problems in the mating surfaces of the cam nose and the timing pulley as well as stacking height problems between the Tommi's Billet cam pulley and the billet style Cat Camshafts. The key way on these Cat billet cams is machined too narrow to accept the locator tab on the TB pulley. It requires carful draw filing of the locator tab so it can fit in the indexing key slot in the cam. Additionally, when doing the first repair I discovered that on this particular exhaust cam,that the mounting shoulder for the pulley was back cut slightly (concave) and was therefor presenting a greatly reduced surface area where it must mate with,and transfer motion and torque from the pulley.

So while I had addressed the key issue on the initial assembly of the engine,I did not notice the nearly indiscernible stack height problems and was totally unaware of minute back cut angle on the cam nose pulley mounting shoulder. SO it failed. I told Nick to send me the head and that I would fix everything at no charge and I did. Fixed the depth / stacking issue with the Tommi's pulley and thought I had sufficiently addressed the lack of contact area by raising the profile of the back of the pulley in the area where the back cutting of the cam nose had reduced the contact pressure. The head was mocked up here so I could re check cam degree install points and the pulley joint was coated with Locktite as were the bolt threads on the retaining bolt which was tightened to 50 ft. pounds. (Spec is 48)

As some of you know the engine made some big numbers and Nick was having fun with it when it failed again! This time the bolt broke off down in the mounting hole! I don't have the engine back yet but I suspect that the joint had micro motion in it and eventually failed the bolt through cyclic fatigue.

I have NEVER had any type of problems with cam pulley mounting on ANY engine before this so I began to research the issue . I have seen a multitude of people posting on failures in this area on a variety of engines. I have consulted with Hank, Marc and Pete at I.E. trying to get input on this issue to form a consensus. They were all very helpful and of course we all have an interest in solving this puzzle as none of us want customers to suffer any type of failure.

I have now closely studied the factory parts and well as the aftermarket parts. ONE issue sticks out. That is the frictional coefficient of the parts as it compares to the load and cyclic / dynamic conditions. We know that the key in this system only serves to index the pulley to the camshaft. We know the torque has to be transferred,from the pulley to the cams,through a joint with very limited contact area,with only the friction between the back of the cam pulley and the little shoulder on the nose of the cam to carry the load. We know further that quick lobe opening rates and increased valve spring pressure, along with an elevated rpm range increase the load on this joint.

It is now my opinion that the surface treatments of the mounting surfaces is critical. When you study the factory cam and pulley you see that they have relatively soft "dusty" surfaces with Parkerizing on the stock cam pulley mounting face and the raw machined back surface of the stock pulley providing a relatively hi traction surface.

When you look at the cast version of the Cat camshafts you see that the mounting surface is a non directional finely ground surface with a pattern like that on a new brake rotor.

However. When you inspect the billet version of Cat camshafts you find and extremely smooth, slick case hardened surface. It is "glossy" when compared to the surface of even the cast version Cat cam, but especially so when compared to the stock cam.

Now we have the pulley! The aftermarket pulley has an extremely slick anodized surface and the alloy is quite hard to avoid galling and deformation. I am certain that a load carrying test conducted without a key, would demonstrate that the friction within joint and hence the torque transfer ability, would be far greater with the factory parts than with the hard slick surfaces od the aftermarket parts.

In the case of Nick's parts with their machining deficit - never had a chance. (I will be repairing Nick's motor with no labor cost to him)
I wanted to provide a fix that did not require him buying a new exhaust cam but it did not, obviously, work out. We will be using a new style pulley as well.

In case you are wondering; The race car has the cast version Cat cams in it and the old style Tommi's Billet pulley which was immune to the stack depth problems as it was a different design. This combination, you could say, is well proven!

We are working on a solution involving a thin aggregate coated traction washer. Integrated Engineering already has this in use on 1.8 T applications and Pete tell me it works well when combined with an ARP retaining bolt. The washer or wafer goes between the back of the pulley and the mounting shoulder to provide grip between the parts. I have some bolts ordered from ARP as well which should allow a higher torque than the factory bolt.

Those of you using the Tommi's Billet pulley on non factory cams should probably check the torque / tightness of your pulley retaining bolt periodically. I know of no problems with the Tommi's pulleys when mounted to the factory cams for which they were modeled.

Lastly, I promise to finish the engine building article I started last century - sorry about that again.

Nick or Matt. If you want to post the photos I sent you of the various parts and surfaces I have been describing feel free to do so.

[scubagli]

Great post, good info I hope this solution works as I really want to see Nick's car at the track! Matt's too for that matter.

[loxxrider]

Thanks for this post Jeff. This is EXACTLY what I suspected was going on. I have always hated that friction interface, and the same thing applies to the crankshaft pulley/cog.

I look forward to having you finish up my long block, especially with this new knowledge and that which you are gaining from your 10,500 RPM motor. I am especially interested in how the timing belt is acting at high RPM! We'll have to discuss more later.

[chaloux]

Good work Jeff. I thought I remember reading about special diamond or other washer surfaces for friction, but I can't really remember where now. Makes a lotta sense. Tommis/cat gonna give you anything for the free r&d?

[loxxrider]

Matt, the diamond washer is stock on the aan crank damper /pulley.

[chaloux]

Ahhhh yes. Makes sense

[ringbearer]

Great post Jeff.

People like you make the Audi community what it is

[elaw]

Matt, the diamond washer is stock on the aan crank damper /pulley.

*Some* AAN pulleys!

If I remember correctly the earlier ones didn't have it and the later ones had a slightly shorter "snout" and the washer would make up the difference. In my notes from way back when, I have that damper 054 105 251J uses the washer and 054 105 251H does not.

Reading the writeup above, I wonder if Audi realized there sometimes wasn't enough friction between the pulley and the end of the crank (possibly causing all those sheared cam sprocket keys you read about) and the washer was the solution?

[loxxrider]

Hmm interesting information there. I'd bet that is exactly why they changed it. Those with high power 3b engines with high power beware!

[EDIGREG]

Hmm interesting information there. I'd bet that is exactly why they changed it. Those with high power 3b engines with high power beware!

high power 3b engines with high power? Holy shit that's a lot of high power!

[loxxrider]

haha I really hate using this forum on my phone! The cursor jumps around randomly sometimes, its weird!

[pilihp2]

Hmm interesting information there. I'd bet that is exactly why they changed it. Those with high power 3b engines with high power beware!

high power 3b engines with high power? Holy shit that's a lot of high power!

Every high power ever powered, ever.

[my2000apb]

well ya instead of
((power) + (power)) = fast

its (power)^ 2nd(power) = waaaaay faster

[amd is the best]

Stock cams:


Cast CatCams:


Billet Steel CatCams:

[gtn116]

The billet picture has a nasty shadow.

[Marc]

turns out the bolt/cam gear wasn't the most likely cause of failure anyway. I'll let Jeff / Nick fill in the details.

[amd is the best]

So that's the end of that :(

[scubagli]

Ouch.

Sent from my KFSOWI using Tapatalk

[chaloux]

Oooohfuk

[speeding-g60]

Ekagrip shim.

so, that looks broken..... what failed do we know??

[amd is the best]

Ekagrip shim.

so, that looks broken..... what failed do we know??

The lifter bucket failed. Not 100% certain as to why however several of the lifter faces have stress cracks on them. This one just let go before the others and when the face came off it got lodged in the intake cam locking everything up. Then snapping the cam pulley off. That's what we believe has happened anyway.

Now the question of why. Are these Lightweight INA hydro lifters at fault? Did they get outsourced and cut the quality down? Are my cams a bit to aggressive? Is the overall cylinder pressure too much for these hydro buckets? These are questions we are coming up with as of right now.

The head is almost certainly toast. Repairing that section where the bucket rides may not be possible.

Jeff plans to speak to several people about this failure and see what we can come up with.

It sucks big time for me though. I now question a few more things... should I drop to a more modest power? Maybe downsize on cams and turbo? I don't know... The car has been far less reliable/enjoyable since the "big" build. I am 100% not pointing any fingers here. Jeff, Hank, Marc and everyone else who have had a hand in something along that way have been excellent and helpful but overall it's been a tough battle. I've got the winter to think about it.

[speeding-g60]

oh trust me, i know first hand where you are coming from and where you are at.

such as my own thought this year. remove 10 psi from the tune (47+ is redic), dial it back and make it last (supposedly) LOL.

this, is what people (such as us) who push the envelope and find new places to travel, are faced with on the regular.

it sucks, but like you said, take some time to mull it over. its almost winter and thats plenty of time to think about things.

and one thing catches my eye about what you said: "The car has been far less reliable/enjoyable since the "big" build." being a driver for you these are more of an issue, and more pf a point in decision making. the ENJOY FACTOR probably weighs heavy on this decision.

[amd is the best]

Exactly. I agree 100%.

Don't get me wrong, it was very very enjoyable when it was running. The thing was an animal and surpassed all expectations! It's the unreliable part that made the overall picture less enjoyable. If that makes any sense.. I also expect there to be hiccups along the way as always. Hell even at 400hp there are unforeseen obstacles.

How could you not enjoy breaking loose in 2nd:



That all being said, I really didn't want to have to be spending more money on the engine. Now I need a new exhaust cam, a new head, 30 hours worth of Jeff's porting/machining/prep work, lifters (solid or OEM), etc. At the same time, I am this far invested. It's like damned if I do and damned if I don't...

I don't know if this is the right place for all of this, lol. I sound mopey right now haha. Winter is long, the excitement will come back and things will change I'm sure.

[loxxrider]

I feel your pain Nick. When you're pushing the limits with unproven parts, you have to call this sort of thing R&D. There are plenty of people who have been successful at this level of power with these engines, so maybe we need to figure out what they're doing differently... Maybe the answer is simply solid lifters? One thing's for sure, if those buckets were cracking, they were either over-stressed or inadequately made. I'd be interested in exploring some reasons for potential over-stress which it sounds like you guys are exploring.

Have you thought of the potential that the buckets aren't being filled up sufficiently quickly after the lobe depresses them? Then a gap would open up between the lifter and the cam and the next time the cam lobe comes around it would smack the top of the lifter resulting in a much higher impulse of stress than the buckets were designed to see.

Whatever comes out of this, I don't think you should be too discouraged. Look at Jeff's engine and the reliability he has been able to get out of it. I think you can keep this car at a healthy and reliable 700 whp with the right combination of parts. If not, then I'm doomed.

[chaloux]

Or this damage could have been from the cam breaking and valves hitting pistons. I know a lot of the time in the TDI world if you toss a timing belt you need to look at the lifters for stress cracks (which are lightweight lifters BTW, exact same dia and weight as the lightweight ones sold for AAN). Most of the time people just replace everything in the head because they don't want to drop a valve or lifter later and do it all again.