Picked up my new car this weekend........955hp V10 Audi RS6! (HP figure updated 08/10/22)

[ianh]

Sigma - The only "decent" upgrade is over £4k for 50hp-ish (new Intercoolers) or £3k for a head port/polish etc and around 30hp.

Now if money was no object, well I'd be hitting 1k HP by now

 

[sigma]

Well if it's all apart, it makes sense to do it

 

[ianh]

If you'll give me £7k as a Christmas present then it'll be done!

 

[ianh]

So got the spring out yesterday

and got my 16mm spark plug socket today and whipped the plug out (extremely surprised to see an OEM plug too!). It looks OK with no damage, it's just coated in oil stopping it firing -

And the boroscope, despite being producing an absolutely awful pic, doesn't show any obvious signs of damage, just more oil burning, so the oil doesn't look to be coming past the rings so it must be coming coming down through the heads which makes me think Valve Stem Oil Seal but the boroscope pics aren't clear enough to be absolutely sure -

 

[Gibbo]

Hard to tell from those photos, but is that not bore scoring on the walls?

Have you pulled the other plugs to check their condition, I know I know you got 10 of them so its more work.

 

[Dis86]

I'm with Gibbo on that one. Looks like bore scoring. Very similar looking to the issues the old Porsche 2.9's used to have.

 

[ianh]

Although it's difficult to tell without removing the heads those vertical lines up-close look like more fine scratches filled with burnt oil, where as bore scoring is much deeper (can feel it with your nail) and leaves metal swarf in the cylinder (hence the 360' photos, no swarf).

However the pics aren't clear enough to be absolutely certain. I'll be pulling a few more plugs tomorrow for a comparison but, with 108k miles, I'd be surprised if they didn't all show something like this but my big fear of a missing plug tip or a hole in the piston etc has been put to one side now.

 

[Dis86]

There was no visible swarf on the last cayman I had my mits on. I really hope it isn't the case but it does look very very similar.

 

[ianh]

I looked up "Bore Scoring" on Google before and 90% of the results were Porsches, are they made of cheese?

Worst case now is that it is scored and it gets honed or I swap in a spare block (one is available) but that tiny amount of scoring doesn't explain the huge amount of oil "suddenly" appearing in the cylinder, enough to drown the plug so much it can't fire. Thats got to be something than a simple bore score.

 

[Dis86]

Lol, yeah it's a pretty big issue with them. Again it's generally a question of not if, but when. Scoring would still explain oil loss...may be worth investigating your other cylinders.

 

[Rainagul]

Compression check will tell you quickly dude. How do you have a borescope but not a compression test kit

 

[Gibbo]

Lol, yeah it's a pretty big issue with them. Again it's generally a question of not if, but when. Scoring would still explain oil loss...may be worth investigating your other cylinders.

I loved my 911 but it was a major fear of ownership as they all eventually go.

Back to IanH cars, it looks like scoring and the reason there could be so much oil is maybe the bore has gone slightly oval due to the huge power being pushed will naturally create a lot more heat in the cylinders which could oval the hottest one, then score which will allow a lot of oil to pass. Hope this is not the case but could be an explanation for the oil.

Ideal but not best situation is the gasket has broken between cylinders due to age, this should reveal itself if the case the the plug directly next to it should also be full of oil, if not the case then its not a gasket failure.

 

[ianh]

So I took the plugs out of the other 3 easily accessible cylinders and checked both the plugs and the bores.

The plugs all looked fine (all the same as this)

I did a quick boroscope of the 3 cylinders and found a "little" amount of shallow scoring on all but nowhere near as much as on the No 1 Cylinder and I also found that all the pistons had that same "missing" section in the piston crown so thats the design of the piston and not an issue in the No1. Here's a few random pics of the other cylinders showing the same "missing bit in the No2 an No4 and showing some of the bore marks and the No 2-3-4 cylinders.

So I cleaned up fouled plug, rebuilt the engine putting the No1 cylinder plug/coilpack into cylinder 3 to see if they were fine and put the working No3 plug/coil into cylinder 1. Started the engine and there is still a misfire on Cylinder 1 (No3 runs fine so plug/coil OK) and, now I've got bore pics from 4 cylinders to compare, it's pretty obvious that the No1 has 1 if not 2 deep scores about 180' apart so I'm fairly sure it's lost compression

It gets taken up to Unit20 next week so I'll let Grizz take it apart and see how bad the damage is, cry a little and then prepare my anus for the bank manager/Audi!

 

[Dis86]

*bro hugs*

Hope you don't get shafted too badly.

 

[Hedge]

Ah that's bad news. How many miles have you put on this beast?

 

[hominid]

Are you sure it's not detonating and slowly eating the piston(s)?

Just because it's the same on the others doesn't mean it's ok, it may mean the same is happening just to a lesser extent. It could happen in the same place because of the geometry of the injector angle/piston crown shape etc..

Trying not to give more bad news but the rims of the pistons doesn't look right, although I don't know what the rims of the RS6 pistons normally look like either..

 

[CaptainRAVE]

Ouch, that can't be cheap.

 

[kindai]

Ouch, that can't be cheap.

Could be worse, could be a v12

 

[ianh]

Ah that's bad news. How many miles have you put on this beast?

Bought it at 84K in Aug '15 at 580hp, got it to 740hp within a few days, got it to 907hp at 96k miles and done 108k now so 24k miles with it running more power.

At 900+ problems are expected, it's just the timing sucks

Are you sure it's not detonating and slowly eating the piston(s)?

Just because it's the same on the others doesn't mean it's ok, it may mean the same is happening just to a lesser extent. It could happen in the same place because of the geometry of the injector angle/piston crown shape etc..

I'd say 4 identical looking pistons makes it more likely to be a piston design but until the heads get taken off I can't be 100% sure of anything.

 

[Simon]

Comparing this to many engines I've seen I'd say pistons got a bit hotter than designed and have picked up on the bores. I assume the engine has clearances to allow this but 920hp is a lot of heat.

Not really related but what oil are you using out of interest ?