Fuel adatives....

[chrissyr32]

Has any one ever tried any so called "fuel adatives" to improve performance, clean valves etc etc? If they have any difference in performance? any problems?

YES OR NO???

[P_G]

No more than using decent fuel, i.e 98/99RON rather than 95. I tried Millers Octane Booster and STP and both didn't make any difference, if anything made them worse and the engine occasionally suffered from pinking.

If you want a quick fix on a one off basis fill up with BP 102RON!

[caldy]

This is a view of an inlet and you can see how 'gummed-up' the valves are. This is after only 3500 miles of Shell Optimax and Castrol Edge, God knows what a 20k+ miler will look like! Guess we need something to 'clean up' the breather output into the manifold.

http://i271.photobucket.com/albums/jj12 ... G_2200.jpg

[P_G]

What are you doing to your car to have a picture like that?

[PetrolDave]

Over the last 15 years (ever since I got my first fuel injected car in 1994) I've used something like RedEx injector cleaner whenever I've felt the engine is running rough or feeling hesitant. It's made a big difference on every car I've owned, except the RS4 where it has no effect and a "drive it like you stole it" run gets it running as normal.

Wonder if the different injectors (beacuse it's FSI direct injection and not indirect injection) is behind the difference?

[Andyuk911]

Caldy,

Before the Shell, and I assume you mean V-Power, what petrol had you been using ?

To clarify ... are you saying your car's TOTAL mileage is 3,500 OR that you have only just started on Shell Super unleaded? - Thanks

[silverRS4]

Hmmm. That looks familiar. Thats about half as bad as mine were at 8000 miles. All I use is either BP or Shell Ultimate. Andy - I'm pretty sure Caldy means 3500 miles total. Also in a related post, I didn't mean to imply that ALL RS4's were suffering from power loss, hesitations, poor cold starts, etc. What I meant was that if a RS4 was displaying those problems, more than likely this kind of buildup is the root cause. I think some amount of buildup, varying from slight to moderate (caldy's pic) to excessive would be expected on any 4.2FSI. I think good fuel or supplimentary additives will certainly help with combustion chamber deposits, but buildup on the valves would have to be removed the hard way. I am using a good additive now. I was planning on putting 4000 miles on the engine, then removing the manifold to inspect.

[Andyuk911]

Yes I noticed your valve ... how about the vanes.. Caldy's will be very carboned.

It would be interesting to know what the liquid on the valve is .. petrol or oil

Ps

I can't believe that 3.5k miles would show this sort of build up .. if it is that is staggering ...

[caldy]

As you can probably guess, I was seduced by silverRS4 and Anto's work on the inlet manifold and so that set me off! I will post the full story once the job is complete.
However, the history is that since I bought the car in Oct '07 with less than 1200 miles up, I have advanced to 3700 miles and have run exclusively Shell Optimax and V-Power type fuels. The oil was changed at 2500 miles to the recommended Castrol Edge.
So yes, that build-up has occurred over 3700 miles total. As silverRS4 said to me in one of his replies- ' The heavy oil volatization of the 4.2FSI is a fact of life. The engine is already equipped with a 3-stage venturi system (catch can) that drains into the crankcase.' It is the whole of the inlet tracts that are covered, although not quite as badly, not just the valves. The fuel is injected after the manifold so any fuel additive will not stop the manifold from gumming up.
I'm going to have to clean them in-situ as best I can and hope that upon start up, the residue will be blown out of the exhaust.
Unless anyone has a better idea......?

[pippyrips]

It seems this is very common in the RS engine.

I am about to have mine cleaned so will get some before/after pictures, the car has done 18,500 so it will be interesting to see their condition!

[Marcus-RS4]

Who are you getting to clean them pippyrips? (out of interest)

[caldy]

The deposits are not a dry carbon type, they are quite 'sticky' and soften even further after having been soaked in Redex. That is the way I am trying to clean them, activating the deposits with a stiff brush and a wooden spatula and then soaking up the residue with tissue. Let's hope it works.
I'm expecting a lot of white smoke on start-up!

[Andyuk911]

Well I just had a little chat with SilverRS4 and I think we will all be stuffed ... If the engine makes oil vapour and it goes through the inlet ...

Here is a nice pix of the inlet track ... but a 2.0TFSI ... I can't see a way of stopping this ...

[silverRS4]

The oil vapor in the intake charge is not unusual. Its present in all internal combustion engines to various degrees. The problem with FSI is that the cleaning ability of fuel additives has little effect in cleaning the valves since the injectors are spraying into the combustion chamber rather than into the inlet port.

[PetrolDave]

Mitsubishi had GDI long before Audi has FSI - is there any evidence of this sort of problem on their engines? If not, why not - what's different about their configuration?