Most new Audi, VW, Seat and Skoda cars now use FSI Technology (Fuel stratified injection) for emissions and fuel economy but this system also has a down side. Since fuel is not sprayed down the inlet manifold and over the intake valves, carbon deposits from the crankcase breather system, which is plumbed into the inlet, get baked onto inlet valves under normal driving conditions. After approx 40,000 miles you’re intake valves will look like this.
There is no easy solution to clean the intake valves but to remove the inlet manifold and put in some hard labour to clean them.
This is what the valves should like like. This is after a full carbon clean on a 2008 RS4 with 60,000 miles on the clock.
This is the amount of carbon which was removed from one Audi RS4.
Another big issue we are also seeing which is a direct relation to the carbon build up is leaking injectors or blocked injectors. Cars which are not cleaned at around 40,000 miles, generally have slight misfires or ‘running too lean’ faults. This will require the injectors to either be replaced or refurbished.
What will this do to performance?
This RS4 was timed using Racelogic performance meter and timed from 30 – 50 and 50 – 70 mph. The results are clear to see.
Before carbon clean
30 – 50 mph 3.0 secs
50 – 70 mph 3.2 secs
After carbon clean
30 – 50 mph 2.8 secs
50 – 70 mph 2.8 secs