Having gained so much experience with the B5 RS4 it was only logical that we cast our tuning eyes over the new B7 RS4. The biggest complaint from customers was the lack of claimed power so we set about looking at way to increase it. We invested in a development engine to dismantle and analyse.
This was set on a stock ECU file with the latest software version (0090). The car has 19K miles and a Milltek cat back exhaust.
Efficiency in the engines intake tract was the area we wanted to focus on first so the intake manifold came off and went to our flow shop to be flow tested, ported and polished.
Removal of the intake manifold reveiled further possibilities at increasing flow. The valve stems were coated in a carbon layer and gummed up with an oily residue further restricting air flow. This is a common appearance in FSI cars due to the lack of fuel passing through the intake manifold and cleaning any deposits that build up over time, something that we will be monitoring and looking to solve in the future.
Another concern was the amount of oil sitting in the intake manifold. While there is a small OEM swirl pot designed oil catch can it is clear this is not sufficent for seperating the oil the engine is breathing.
Worryingly for owners of B7 RS4s this was on a car with less than 20K miles.
The valves and intake ports were cleaned in situ.
The intake manifold was refitted after being returned from our flow shop modifed, ported and polished with proven results from the flow bench.
After various modifications the intake manifold was optimised for peak flow at 8000rpm with good gains from low valve lift.
We went back to the same independent dyno to prove any gains. The dyno graph overlays our results at three different stages.
We dyno'd the car first with the same stock map but this time with the MRC modified intake manifold. (Red line)
We then remapped the ECU to further increase gains. (Blue line)
Baseline run done 4 days before (blue line)
After proving that cleaning and modifying the inlet track made a significant increase to the power of the engine it was now time to work on the exhaust system.
Some free flow downpipes were fitted and the cars ECU was remapped again to take full advantage of the exhaust airflow.
After all the work we have done on this engine the power went from
390bhp up to
430bhp and
340ft-lbs and gains of up to
50bhp and
50ftlbs in the rev range.
