Another day, another B7 RS4 Intake Valve Clean! What is Carbon Cleaning or Decoking?
Carbon cleaning is the process of cleaning carbon, specifically from the engines intake ports and valves. The B7 RS4’s engine is direct injection, which is where fuel is injected directly into the combustion chamber. This direct injection fuel system is a development onwards from indirect injection, in pursuit of better emissions and fuel efficiency. Indirect injection is where fuel has been injected into the intake ports, past the valves and into the cylinder. With indirect injection the fuel also serves a function of cleaning the intake valves of blow-by gasses and breathed gasses – whereas with direct injection this does not happen, so the intake valves gradually build up carbon deposits, building up over time to greatly restrict the intake port flow and reduce the engines knock threshold.
On a high-performance naturally aspirated engine such as the B7 RS4, port flow is critical to engine performance. With this port flow lost, there is a dramatic reduction in power.
With the RS4 on our ramps, we begin removing the intake manifold to allow us to inspect the condition of the intake valves. This customer had a “carbon clean” which was carried out without the intake manifold removal, its clear to see by the below image just how little that worked.
You can see just how bad the issue can be. With the carbon deposited the valve and valve stem, this decreases port flow and increases the valve train weight, dramatically reducing performance. As well as the carbon also being deposited within the port itself. 
With our well refined cleaning process you can now see the bare metal of the valves and port.
With a performance increase of almost 100 horsepower and 50lbfts, this RS4 truly has another lease of life. Restoring power from 340HP back to almost stock. It goes without saying, this RS4 was a night and day difference to drive in terms of power, torque, delivery and response!
