Cams

[avus1]

found a pic of the chain tensioner its not that, its a gold unit with a large black vaccum pipe with a pita clip going in to it and a small grey pipe that you need to remove to get the cam cover off, any suggestions would be very welcome.......

[TopBear]

Could be the cam chain tensioner?

What's this about a 'cam chain tensioner'? The B5 has a cam-belt

the cam belt only drives the exhaust cam from that cam there is a chain to drive the inlet cam (in each head)

Well, you learn somthing new every day.
Cheers

[MilkybarKid]

slightly off the oringinal topic here, are there any aftermarket cams available for RS4? OR, is it worth getting a not too badly worn cam reground & re hardened? this kind of thing was available 30 years ago for tuned engines.

There were one or two that tried, dont think it went too well.
Ill be looking into whether wed be better having them hardened or not.
One of the problems I found when did a few basic tests on the cams/lifters I got up was that the lifters were stainless steel alloy and the cams are mild steel.
Other problem is that none appeared to be surface hardened. The surface hardness and the hardness of the "worn area" ie sub surface on the cams indicated that they were almost definately annealed and normalised. Basic stress relief, no surface hardening.
Audi arent forthcoming as to who manufacture(s/d) them, or the spec they are made to.

[rickoshea]

I'd have thought the cams would have been ' designed' by Cosworth rather than Audi ? Anyone have a route into Cosworth to ask them ?

[missmouse]

slightly off the oringinal topic here, are there any aftermarket cams available for RS4? OR, is it worth getting a not too badly worn cam reground & re hardened? this kind of thing was available 30 years ago for tuned engines.

There were one or two that tried, dont think it went too well.
Ill be looking into whether wed be better having them hardened or not.
One of the problems I found when did a few basic tests on the cams/lifters I got up was that the lifters were stainless steel alloy and the cams are mild steel.
Other problem is that none appeared to be surface hardened. The surface hardness and the hardness of the "worn area" ie sub surface on the cams indicated that they were almost definately annealed and normalised. Basic stress relief, no surface hardening.
Audi arent forthcoming as to who manufacture(s/d) them, or the spec they are made to.

thats incredible! mild steel?
The cams are the most highly stressed component of any enginge. You would think they would have been made of very high grade steel & then surface hardened by nitriding or similar depending on material!

[MilkybarKid]

Exhaust cam- Iron/Carbon steel: 98.59% iron.
Hardness on flat of damaged lobe: 205-212bhn, good areas: 207-223bhn.

Inlet cam- Iron/Carbon steel: 98.10% iron.
Hardness: 202-207bhn.

Exhaust lifter: 97.66% iron, 0.93% manganese, 0.91% chromium.

Inlet lifter: 97.56% iron, 1.05% manganese, 0.87% chromium.

Bear in mind that all %'s in all steels will vary even within the same batch of ingots etc.
I am not saying that they are definately not hardened, they do not appear to be though. From those reading I think the only surface hardening is work hardening.
Newman cams said that you shouldnt even be able to measure the hardness of these in bhn, should be well off the scale.

Also I only had a few cams to test, so although it should be, its possibly not representitive of every cam out there.

[EuroSag]

I had hoped to get some Schrick cams for the B5, but they don't do them unfortunately.

[missmouse]

so they SHOULD be hardened or is the material suposed to be hard enough?
im trying to work out what is going wrong here. Its hard to beleive that any car manufacturer nowadays, let alone audi or cosworth,would use an unsuitable material for somthing like a camshaft!

Arent the failures more likey to be caused by oil and or usage problems?

[drjones1]

Is it both cams that wear or just the exhaust cams?

[MilkybarKid]

There are a couple of theories floating about as to why its happening.
1a. Simply that the material just isnt hard enough. (But then why is everyone not having the same problem.)
1b. (My own theory) Material from certain batch or batches, or the surface hardening (if there was any) of batches of the cams wernt up to standard, or not done at all.
2. There is a conflict between the 2 materials used. (again raises the question of everyone thats not having problems, possibly even batches again)
3. In certain circumstances, possibly in high heat areas, there is the chance that the heat is causing any oil between the cam and lifter to be thinned to the extent that there is less protection, more friction.
3b. Doug said something about (dont quote me, my memory isnt great) this happening more in certain lobes than others, and there was some relevance to position in the head or in the engine which may cause them to be more exposed to this.
3c. Spen suggested that heat transferred through from sodium filled exhaust valves (as all are as standard i think) into lifters possibly causing the above + overheated lifters/cams = softer material.

Main questions are
why is it only happening to certain cars (some have had multiple failures)
why in cases of failures is it usually limited to a few of the lobes

[m888rsy]

hi
this week we changed a set of cams in the offside head and chain tensioners on both heads on a customers 60k rs4!the customers car hasnt done a lot of miles in the last few years and a lot of short journeys as he retired 2 years ago so i dont know if this contributed to it?i thought it would be a bigger job than it actually was and we caught it in time before it did any serious damage!we only investigated due to tensioner noise an the cams showed slight wear but nothing substantial and obviously a few owners have had cam wear issues so advised the customer to accordingly and he asked us to replace them while it was stripped down.

mike

[andream88]

3c. Spen suggested that heat transferred through from sodium filled exhaust valves (as all are as standard i think) into lifters possibly causing the above + overheated lifters/cams = softer material.

IIRC, Lucas@MRC destroyed a set of RS4 cams on his car with uprated valves/valves springs. So probably the sodium filled valves are not the cause of the cams' premature wearing.

cheers

[MilkybarKid]

3c. Spen suggested that heat transferred through from sodium filled exhaust valves (as all are as standard i think) into lifters possibly causing the above + overheated lifters/cams = softer material.

IIRC, Lucas@MRC destroyed a set of RS4 cams on his car with uprated valves/valves springs. So probably the sodium filled valves are not the cause of the cams' premature wearing.

cheers

Good shout, didnt know what valves he was using, not sure how well inconel or titanium valves (do they make titanium ex valves for these?) transfer heat, also to add to that, if i remember rightly, he managed to destroy them in less than 15k miles

[Gibbons]

I posted in the cam wear good news post, are the exhaust housings on the turbo in line with the lobes which wear out?

[Gibbons]

Cosworth had a similar problem with radiating heat on the early sierras, heat radiating from the exhaust housing of the turbocharger was causing premature failings of head gaskets on the drivers side rear of the head when the cars were used "in anger"

I can sort of understand the valves thing, but the contact patch on the valve verses the area of the follower/oil reservoir inside the follower wouldn't I think cause that much of a problem at the cam contact area in normal use?