HOW TO SOLVE A PROBLEM LIKE … intake carbon buildup
Powerful, characterful, advanced, the 4.2-litre V8 in the Audi B7 RS4 and first-generation R8 is a joy. But its performance is diminished by carbon deposits clogging its inlet
Aud’ s 4.2 FSI V8 looks good on the outside, but highmileage motors don’ t look so glamorous inside
Deposits of oil vapour and blow-by gases accumulate within the intake ports and on the intake valves, causing carbon buildup in all direct-injection engines. Naturally aspirated, turbocharged, diesel and petrol. All of them. So it’ s a little unfair to use Audi’ s 4.2-litre naturally-aspirated FSI( Fuel Stratified Injection) V8, known as the BNS in the B7 RS4 and BYH in the R8, as an example.
However, the consequences of carbon buildup are more significant in highly tuned, high-tolerance, high-revving naturally aspirated exotic performance car engines. That this engine is otherwise so appealing is partly what makes it the perfect example. It’ s also an issue that Audi has addressed.‘ B7 RS4s are particularly prone to it,’ says Steven Brown, the Workshop Controller of Regal Autosport – a company that specialises in the maintenance, repair and upgrading of performance cars. Regal has cleaned many 4.2 FSI engines
52 The Engine Rebuilder Issue 04