Truth or BS? - Decomposing V8 engine blocks.

[tiktok_78]

I've been having a conversation recently with someone about high mileage 4.2V8 engines (such as you get in the B7 S4).

The other person is telling me that 'they have been told by an Audi tuning specialist' that the aluminium engine blocks used in the V8 are specially treated to 'withstand the stresses of being an engine block'. OK I think.

Apparently this treatment starts to 'break down' at 100k miles and causes issues in the block and cylinder.

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I have never heard of this phenomenon, so thought I would throw it to the wisdom of the internet (rofl) and see what opinions came back.

I'm familiar with cam tensioner face issues on this model, but not much else on the V8.

 

[sportquattro]

Having just bought a B7 S4 4.2 V8 I did a LOT of research prior to buying, I've not heard the story you refer to before. However I have read about the V8 engines can have a drink problem, usually down to scored bores and a borescope before buying is recommended to see if the engine in question is affected. The bore is coated from new and once the coating is damaged it's FUBAR'd Mine has now got 89,000 miles, I bought it in November with 82600 miles and did an oil change right away, since then I've added less than 2 litres of oil so I'm happy that mine is not an oil drinker.

Hope this helps. If you're looking at buying a S4 and find a good one you will love it!!

Nige

 

[tiktok_78]

Hi Nige, I've owned an S4 since December 2014 and put 12000 miles on it with no issues at all.

I guess the cylinder(?) bore coating is what was being referred to in my OP.

I guess keeping the moral is - keep the oil changes regular and the level topped up!

 

[sportquattro]

Hi Nige, I've owned an S4 since December 2014 and put 12000 miles on it with no issues at all.

I guess the cylinder(?) bore coating is what was being referred to in my OP.

I guess keeping the moral is - keep the oil changes regular and the level topped up!

Nice one, and your right the key is good quality oil and regular oil changes will
make a world of difference to longevity.

 

[desertstorm]

As above comes down to regular oil changes with the right oil and a bit of luck.
https://en.wikipedia.org/wiki/Alusil
http://forum.a8parts.co.uk/showthread.php?t=2290

 

[ricostuart]

Mines at 120k miles and still doesn't drink oil. Good engines in my opinion.

 

[desertstorm]

Problem is you don't know where you are with this kind of issue. It could be all sweetness and light one day and down hill the next. Hopefully your car has been looked after and has many more miles in it.

 

[bennyball]

Definitely BS. A lot of modern cars use heat treated aluminium alloy engine blocks, with a steel cylinder liner as the steel is harder wearing than the aluminium alloy.

The engine block will over time deteriorate due to the stresses incurred from engine forces and heat expansion etc, but so will any engine made from any material. You certainly could never say 'at X mileage', as there are so many factors.

 

[desertstorm]

These engines don't have a steel liner. The block is cast with Alusil which is aluminium with a high percentage of silicon.The bores are machined to size and the etched to remove a very small amount of aluminium. The Silicon is very hard and forms the surrface for the rings to run on and a load bearing surface. It's great for several reasons as the engine is lighter, heat transfer from the cylinder to the block is much better.
It seems though that this surface is not as durable as a traditional engine liner and owners find oil consumption problems which when the engine is stripped down are quite often caused by the bores being marked.

 

[bennyball]

Apologies, I hadn't realised that hypereutetic alloys were used for blocks as well as pistons, thanks for correcting me.

 

[kanecullen89]

These engines don't have a steel liner. The block is cast with Alusil which is aluminium with a high percentage of silicon.The bores are machined to size and the etched to remove a very small amount of aluminium. The Silicon is very hard and forms the surrface for the rings to run on and a load bearing surface. It's great for several reasons as the engine is lighter, heat transfer from the cylinder to the block is much better.
It seems though that this surface is not as durable as a traditional engine liner and owners find oil consumption problems which when the engine is stripped down are quite often caused by the bores being marked.

Is this the same with the 3.0 tdi block desertstorm?

 

[desertstorm]

No not at all. The 3.0 TDI engine block is a cast iron block. Although they use a particular kind of compacted vermicular graphite iron which means you can make castings with thinner walls. Diesel engines have to stand upto a lot more stress than petrols.
http://www.autoblog.com/2010/05/05/audi-introduces-lighter-more-efficient-3-0l-v6-turbodiesel/