All about Audi Engines

The all new B9 generation of the Audi S4/S5 is going to hit the market very soon. Compared to the last generation (B8), besides enhancements to the platform/body structure, one major change is decommission of the firm’s aging supercharged V6, which is replaced by a brand new turbocharged V6.






This new V6 is fundamentally different than its predecessor (the supercharged V6). Audi has not reveal too much detail about this new engine, however we are able to extract some useful technical information from a recent officially published video. Below are some brief analysis.
Major Changes and Highlights


Reverse flow header (which makes using twin-scroll turbocharger possible)
Integrated exhaust manifold into the header
Cast-in iron cylinder liner (not Alusil in the old supercharged V6)
Direct injection system changed to spray-guided type (Audi has been using air-guided type previously)
Single turbocharger with twin-scroll design
Introduced Miller cycle (a.k.a Atkinson cycle) in its operation
Air-to-air intercooler
Modified version to be used in 2017 Porsche Panamera V6 trim


Cylinder Block

The below image indicates the new turbo V6 is still using the closed-deck design, same as the previous supercharged V6:




The turbocharged V6’s cylinder block

One major change is the cylinder sleeve. On the new V6, Audi is using cast iron cylinder sleeve, totally different than the old supercharged V6, which is using the Alusil layer. The indication here is: if you have experienced excessive engine oil consumption on the B8 S4/S5, you probably should not worry this on the all-new B9 S4/S5.

Due to the lightweight design principle, the new V6 only weights at 172 kg, a significant decrease from the predecessor’s 189 kg.

Due to the V6’s 90-degree bank angle, it will naturally require uneven firing, Audi uses offset split crank pins to correct this. The 90-degree geometry also brings in unbalanced vibrations, so that is the reason why you can see in Audi’s design, an extra balance shaft is added on top of the crankshaft, as shown in the below illustration.

Crankshaft and also the balance shaft
Reverse Flow Header

This can be considered the biggest innovation in this V6 engine, and it is also the first (and only) modern turbo V6 that uses the reverse flow design.

Here Reverse Flow means the exhaust manifold is on top, and the intake is on the side. The reason that Audi chooses such scheme is in order to adopt the twin-scroll turbocharger for the V6 engine, without complex pipping and routing.

The single turbocharger sits between the V-bank



Such design also minimizes the path length that exhaust gases need to travel to reach the turbocharger, which means better throttle response and less lag.



Specifications
Bore pitch/spacing: 93 mm
Displacement: 2,995 cc
354 hp, 369 lb-ft (500 Nm) @ 1,300-4,500 RPM

Pic Courtesy : Swati