Look into the engine bay of most V engines and the layout is the same. The air comes in through the middle, in the valley between the two banks of cylinders. The exhaust leaves on the outside, and if there are turbochargers, they hang off the sides of the engine at the end of long pipes.
The Audi RS 4 of 2017 does it the other way round.
Inside out
Its 2.9-liter V6 has the exhaust side of both cylinder heads facing inward, into the 90-degree V. The two turbochargers, one per bank, sit right there in the valley, on top of the engine. The intake is on the outside.
The point is distance. Exhaust gas leaves the cylinder and reaches the turbine almost immediately, with very little pipe in between to cool it or slow it down. The turbos spin up faster, and the engine answers the throttle more like one without turbos at all. Audi's figure is 600 Nm of torque available from 1,900 rpm and held all the way to 5,000.
The layout is also compact. The whole engine weighs 182 kg, 31 kg less than the naturally aspirated V8 in the RS 4 before it, and it makes more power: 450 PS, enough for 0–100 km/h in around four seconds in a family estate car.
The price of it
There is a cost. All the heat of the exhaust is gathered in one place, on top of the engine, and the turbochargers sit in a tight space that is difficult to reach. Anything that has to be done to them takes longer than on a conventional engine. Audi accepted that in exchange for response, and every RS 4 of this generation carries the result under its hood.
The models
COBI makes the B9 RS 4 Avant at 1:35 in several versions. The Audi RS4 Polizei, set 24672, is built from 153 blocks and comes with a police officer figure, a street lamp, solar panels and a brick-built speed radar. The Audi RS4 Red, set 24670, and the Audi RS4 Green, set 24669, are the road car in two colors, each built from 100 blocks. Set 24671 is the cycling team car.
All three are available to pre-order. The expected shipping month is shown on each product page, and you can cancel any time before it ships.
See the COBI Audi RS4 Polizei, set 24672
See the COBI Audi RS4 Red, set 24670
See the COBI Audi RS4 Green, set 24669
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