Valves- carboning up

[2manytoys]

This is an interesting topic.

I've been chasing a problem with my car, and thinking it maybe carbon buildup? It's pinging bad now, and has gotten progressively worse over the last 4-5 months. Below is the Dyno. It's in the dealer now while they track the problem down.

In Australia the RS4 is rare, so I've never been able to see another dyno graph. How does this compare (not the peak power, more the shape of the curve) with others?



Mal.

[EuroSag]

Does anyone know if the fuel makes any difference?

I seem to recall a few years ago a magazine did a test on about 4 different cars with dirty valves, they ran them all on Shell Optimax (now V-Power) for 1,500miles and the differences were remarkable.

They took photo's before and afterwards, and I must admit, I've always used Shell V-Power ever since - and it's nothing to do with the supposedly better performance.

[pippyrips]

Not really, as the engine is direct injection so the fuel is going straight into the head.

V-Power does have good cleaning properties but it can only clean where it goes and it doesn't go in the inlet manifold which is the problem. My brother recently rebuilt his impreza engine after 70k - it was clean as a whistle inside.

I also think there is more to the problem than just oil getting in via the inlet - when mine was opened after after running a VTA breather system for 2,000 miles the valves were still starting to get covered in muck..

[sonny]

Not really, as the engine is direct injection so the fuel is going straight into the head.

V-Power does have good cleaning properties but it can only clean where it goes and it doesn't go in the inlet manifold which is the problem. My brother recently rebuilt his impreza engine after 70k - it was clean as a whistle inside.

I also think there is more to the problem than just oil getting in via the inlet - when mine was opened after after running a VTA breather system for 2,000 miles the valves were still starting to get covered in muck..

..and hows that looking now mate, have you changed to a different breather system?

[ArthurPE]

I would look at the intake inlet flaps...it looks normal below ~6000

the dyno might not have been set right, the ramp up appears to be too long, this determines the load the engine must supply, it looks like it may have satisified it at ~260 HP or so

the HP is dead flat from ~6300 to redline (`8200)
since P ~ engine speed it must increase (P = T x w, w =2 x Pi x rev/sec)
something is limiting it:
the dyno
engine controls, traction/stability, airflow/fuel/timing

valves with 2-3 mm of deposits may not even cause measurable loss, at most a few HP, you are down ~60 at 7500 or so...

the limiting restriction (or pressure loss which causes volume loss during filling, which in turn is the mechanism for power (loss)) of airflow is not the annulus/torus formed by the valve opening, it is the circlular valve seat opening...deposits have almost no impact, and even less in a DI engine since they do not absorb fuel...

[karl]

Not really, as the engine is direct injection so the fuel is going straight into the head.

V-Power does have good cleaning properties but it can only clean where it goes and it doesn't go in the inlet manifold which is the problem. My brother recently rebuilt his impreza engine after 70k - it was clean as a whistle inside.

I also think there is more to the problem than just oil getting in via the inlet - when mine was opened after after running a VTA breather system for 2,000 miles the valves were still starting to get covered in muck..

..and hows that looking now mate, have you changed to a different breather system?

No Sonny, he's sold the car! And I think that was one of the contributing factors.

[MarkD]

This topic has been around in some of the North American boards for more than a year.

One poster, who at the time went by the name RI_RS4, seems to have done a lot of work to try and minimize/eliminate the carbon build-up issues with the FSI style engines.

To sum up what I believe to be the point of RI_RS4's posts;
The FSI engine destroys the Audi "approved" oils by fuel dilution. The fuel breaks down the oil, allowing components of the oil past the PVC system and onto the back of the valves where it adheres and bakes into carbon deposits.
To alleviate the problem, RI_RS4 paid someone to formulate an oil that wouldn't suffer from this dilution. It's called RLI Biosyn. The link to that company is below.
Lastly, to help with the dilution problem, run Shell V-Power because it doesn't contain ethanol. Ethanol seems to assist in the decomposition of "approved" oils.

Below are two links to RI_RS4's later posts on the subject;
http://www.bobistheoilguy.com/forums/ub ... 591&page=1
http://forums.audiworld.com/showthread. ... 981&page=1
You can read them at your leisure.

This is a link to the company that made the oil for him;
http://www.renewablelube.com/motoroilsHP.htm
The oil you are interested in has the name RI_RS4 under it.

This is a North American company, and don't know it it's possible to get this oil in Europe.
My only experience with this oil is that a distributor is located in the town I used to live in. I had a 45 minute conversation with him regarding this product, and learned that the Municipality's road maintenance vehicles had all switched over to using this oil after a trial period, and was planning on switching over all the vehicles due to the results of the trial.
Given the above, and the information in the links above, I'm going to switch to it when my car goes back on the road.

If you want to search the internet for all of RI_RS4's posts, try RI_RS4 or RI_A6, as I believe he has since sold his RS and now drives an A6 and has changed his screen name.

If all this information is prior knowledge to those on this board, I apologize for taking up space with this post.

[sonny]

No Sonny, he's sold the car! And I think that was one of the contributing factors.

Of course he did, totally forgot

Interesting post MarkD, it has been covered on this forum for some time now regarding valve build up. be nice to know if it was as simple as changing to a different grade/type of oil.

[SR71]

RI_RS4 was/is a member of the board and, like you say, the issue originally surfaced in 2007.

His tribologist is Terry Dyson and I use his services here in the UK to analyse my oil every time it comes out of the car.

You can source the Biosyn oil from the US yourselves but it turns out to be super expensive.

I tried to get Opie Oils to stock it on our behalf here in the UK but ran into a brick wall. Just isn't the demand for the product at that price point.

Silkolene is the next best thing.

Terry also has a "secret" fuel additive that will assist in reducing build-up available if you consult with him.

Bar avoiding DI/FSI though, nothing will eliminate the problem.

[ArthurPE]

to the OP, try this:

do some timed runs in 3rd gear, 3000 to 8000 rpm...rough estimate with a stop watch is fine...
with your numbers you should be running 15+ sec, stock is ~8.5...this will tell you if the numbers are valid...

your rate of acceleration should decrease dramatically >6000 rpm with those numbers, in a properly operating car it should be increasing slightly or steady...F = ma or a = F/m, F in this case is torque, which from the graph is decreasing quickly >6500, and since m (mass) is constant, the acceleration should be decreasing...

this is NOT deposits, something else is going on here, oil won't fix it...

[2manytoys]

Guys, I just got the car back from Audi. I can confirm it was carbon build up. A VERY bad case of it too. What a disaster.

Arthur is 100% right with his acceleration test. I'd say if you use second gear (so you're going a little slower on a public road) you should feel significantly better acceleration above 6000 rpm. If you don't have a noticable kick, and the revs don't increase quicker, you have a problem. It's as simple as that.

This is going to be a real pain, and something that is probably needed every 6-9 months. At least I now know what the problem was.

Thanks for everyone's help.

Mal.

[aidanjaye]

Guys, I just got the car back from Audi. I can confirm it was carbon build up. A VERY bad case of it too. What a disaster.

Arthur is 100% right with his acceleration test. I'd say if you use second gear (so you're going a little slower on a public road) you should feel significantly better acceleration above 6000 rpm. If you don't have a noticable kick, and the revs don't increase quicker, you have a problem. It's as simple as that.

This is going to be a real pain, and something that is probably needed every 6-9 months. At least I now know what the problem was.

Thanks for everyone's help.

Mal.

So what was Audi's views on the problem??

[2manytoys]

They said that it's poor fuel. When I said I've owned it since Jan and only ever used V-Power they said it was the previous owner. I'm not sure I agree with this.

Anyway, I said I'll remove the manifold in 6 months and check again. I'll actually remove it in a few days to check their work and take some more pictures.

Audi Australia also said it's the first in Australia to suffer from this and are sending the pictures etc off to Audi Germany. I'm sure if Germany know how to read stuff on the internet they'll know all about this problem.

I really hope Germany come out with a fix, as pulling the manifold off every 6-9 months is going to be a pain.

[sonny]

Poor fuel, who are they trying to kid, as for taking the pictures, I think that will be a good call. would be interesting to see what they have actually done, did they get rid of the carbon build up by hand or did they replaced the the head/engine/valves?

[ArthurPE]

Guys, I just got the car back from Audi. I can confirm it was carbon build up. A VERY bad case of it too. What a disaster.

Arthur is 100% right with his acceleration test. I'd say if you use second gear (so you're going a little slower on a public road) you should feel significantly better acceleration above 6000 rpm. If you don't have a noticable kick, and the revs don't increase quicker, you have a problem. It's as simple as that.

This is going to be a real pain, and something that is probably needed every 6-9 months. At least I now know what the problem was.

Thanks for everyone's help.

Mal.

how many miles on your car?
honestly, I'm not buying that the 60+ HP drop was due to deposits...I think they are BS'ing you...
the engine was obviously limiting power >6000
do you have your service reciept? or did they show you the engine when it was opened up? my guess would have been coils...

mine has ~25 k miles and will go 3000-8000 in 3rd in ~8 sec...
timed it on Saturday, 3 runs, certified chronograph and surveying quality GPS