UK-POLOS.NET - THE VW Polo Forum

Reading about direct injection engines one of the problems seems to be carbon build up behind the valves.
This is not a problem on MPI engines as the port injection cleans the valves on entry whereas in direct injection the injectors go directly into the cylinder.

Is this a big problem that can shorten the life of the engine ?
Problem has been around for some time, have VW got to grips with it ?
Has anyone got a TSI that has done a high mileage and hasn't had the engine apart ?

It is indeed a problem on some of the TSI engines, since there is some exhaust gas recirculation happening, bringing in some soot and other stuff from the exhaust gases. This, in combination with the oil from the PCV system, can lead to some carbon build up in the inlet manifold.
There are companies that specialise in the cleaning of the inlet tract of TSI engines.

I'm not very familiar with the impact of the problem such as narrowing of the inlet ports and improper sealing of the valves.

While it will be an issue, it is said to be an issue more for naturally aspirated GDI engines - the TSI GDI take longer to show up any issues due to the effort from turbo to stuff air into the engine.

The current solution, but only for newly designed engines, I think, is to add another fuel injector into the inlet tract before or at the inlet manifold area, now being clever and honest people, VW Group claim that this extra injector is to improve emissions etc under certain running/loading conditions!

I'd guess that the new 1.0TSI, 1.5TSI etc ranges of petrol engines will have an extra inlet tract fuel injector.

I know they did a fix on the 1.8TSI in my gti.

they have installed an extra set of injectors in the inlet manifold.

not sure if they made this move on all TSI engines but it might be an idea to have a look if you have the extra injectors.

Would it be a good idea to use premium petrol (V power etc) ?
I know this has more detergents/additives to help keep the engine clean and although it does not reach the valves and seats it might keep the injectors/plugs working more efficiently............or is it a waste on money.

i'd say it would only be worth using if you have the extra injectors.