Valves- carboning up

[byrnie]

Read about this, but do all our cars suffer from this, and at what mileage.
What are the symptoms? Thanks a lot.

[BlingBling]

No. Varies. Poor performance

[P_G]

Apparenrtly suffer from it from the firts few yards you drive all through their life.

It is a side effect of FSI technology, how detrimental to the performance of the car has been logged by some as up to 5%, how much it is actually detrimental to the longevity of the engine is unknown.

Drive it as much as you can and enjoy it, long motorway runs or long runs in general will keep it in tip top shape, they are not really designed for 5-10 mile per day stop start commuting although theu will of course do this.

[BlingBling]

It is a side effect of FSI technology, how detrimental to the performance of the car has been logged by some as up to 5%

The half empty statement.

[P_G]

How so?

[don]

...It is a side effect of FSI technology, how detrimental to the performance of the car has been logged by some as up to 5%, how much it is actually detrimental to the longevity of the engine is unknown...

This is a very interesting statement and makes a lot of sense.

I would hypothesis that the FSI/direct injection of the fuel into the cylinder head (rather than the inlet manifold) would eleminate the cleaning effects of the atomized and high velocity fuel particles which would normally help to clean the valve, stem and seat.

The direct injection must eliminate the cleaning effect leading to a build up in carbon. I would assume over time this may affect the seating of the valve which would be responsible for the loss in power notwithstanding the disruption in air flow but I would think this would be minimal.

It is ironic that the very technology that is meant to make the cars more economical may well end up being less economical and more costly in maintenance. I guess since FSI is relatively new only time will tell.

Going by other posts though it does seem to be a problem in the long term if one wants to maintain the max performance of the vehicle.

[JackS4]

At 20-odd thousand miles the valves on my car where sufficiently coked up that 3 of the valves where not seating properly. Symptoms are as mentioned a lack of power esp higher up and in my case a very lumpy idle. No issues now since I have had the valves cleaned up.

J

[P_G]

You say that though JackS4 yet I have a 58,000 mile RS4 with at this time no such issues, running normal drag times and nigh on 400bhp on a rolling road with a fault at the time. That's why as much as blingbling suggests what I originally said is a 'half empty' statement, there is no concrete proof at this time that it causes significant deterioration in longevity or performance and I would go as far as to say that it doesn't.

[Nib]

I've now done 22k miles and mine feels significantly quicker than it did when it was just run-in. Don't know / care what bhp it's putting out.

Several of the other "high performance" engines that I've run over the years have also disliked being run in town too much. The RS4's unit seems better then most but it also needs a good thrash every so often to clear it out.

Enjoy!

[SR71]

In my line of work, if I trusted my senses, I'd kill XXX people a day...along with myself.

My own opinion is that the body's ability to detect and/or differentiate between small accelerations is nigh on useless. Vestibular illusions including those of the somatogravic/somatogyral nature or something like that?

Thats why I've got a few hundred grands worth of laser-ring gyro's keeping me "right side up".

You only need to hook up VAGCOM to your car pre and post cleaning to see that clean valves are worth a few % on your mass flow rate which will translate into more power, although granted, it'll likely be of a magnitude you won't notice it.

How longevity is affected, no-one knows...none of us are knocking up against the design life of the car yet...

Looking at a typical set of RS4 valves below, I'd prefer it if mine were clean, for all kinds of reasons...

Your choices are:

1) Avoid FSI and get a E90/E92 M3 for arguments sake
2) Ignore it
3) Clean it yourself on a regular basis - my option; it'll be the first time @ ~30K
4) Get someone to clean it for you i.e., MRC
5) Devise some kind of workaround like methanol injection a la the 2.0 TFSI boys...

I'm sure there are others...

My $0.02

[don]

Hate to be a dooms day but I have just been reading up on this problem on other sites and it seems a lot more serious than some may think:

http://forums.vwvortex.com/zerothread?c ... id=4397707

http://blogs.edmunds.com/greencaradvisor/2009/03/...

What is worse is that it seems manufacturers have known about the problem and released the technology without a viable solution. Direct Injection, a great sales marketing campaign but if only people really knew.

See this 2005 Patent, particularly p. 14 looking at solutions but not yet implemented.

[SR71]

http://www.rs246.com/index.php?name=PNp ... ght=patent

http://www.rs246.com/index.php?name=PNp ... h+manifold

[JackS4]

You say that though JackS4 yet I have a 58,000 mile RS4 with at this time no such issues, running normal drag times and nigh on 400bhp on a rolling road with a fault at the time. That's why as much as blingbling suggests what I originally said is a 'half empty' statement, there is no concrete proof at this time that it causes significant deterioration in longevity or performance and I would go as far as to say that it doesn't.

Up until the end of the summer I reallly only used my car at weekends and then a change of job had me using it daily for 5 miles each way which is when the problems I notced became progressively worse. MRC did mention that my inlet valves where one of the worst they had seen.

I can't see how valves not seating (as it was in my case) wouldn't cause a loss of power. One of photos I have of my engine shows where detonation from the cylinder was escaping into the inlet and actually burning off some of the gunk (although not enough to have the valve seating properly). Happy to share the photo if someone can show me how.

J

[BlingBling]

How so?

There have been cars with this problem that have/are seeing greater than 5% reduction in performance but your statement paints a differnt picture. Actually I should have said half full.

Do you serioulsly believe that carbon build up over time will not adversely impact performance or longevity. Think again. Carboned build up can lead to valves not seating properly or in some cases not closing at all. If that is not evidence enough of a problem then I do not know what is.

It is OK to defend something, especially if you have a vested interest, but deny any larger drops in performance and no longevity problems is fool hardy.

Also because your car is OK does not make everything hunk dory.

[P_G]

Fair enough however as was said in another recent thread, we are talking about a handful of cars compared to the 3000 sent to the UK and as yet none bar that handful have generated issue to the ooijt that they needed cleaning. So it is fairer to say that there could be an issue but as yet is undefined and very much a consequence on how these cars are driven.

If occassional / weekend / approx. 5 miles per day use then there would appear to be evidence to suggest that this minimal running does accelerate the build up of carbon. As for power loss, 5% is effectively 20.7 bhp, 10% 41.4bhp; so on a rolling road that would mean assuming all other factors are ideal that our cars should be doing between 372.6 bhp and 394 bhp. So perhaps the results that have produced have been accurate after all? But then like you say I had 396 bhp with a vacuum pipe issue so I can say this does not affect my car that much if at all.

I am not and have never advocated there is not an issue, merely suggested at this point there is too much conjecture and not enough hard facts. I too will probably have the inlet manifold taken off and cleaned if necessary next year but in the meantime I'm not going to lose sleep over it and would suggests potential owners do the same.