As on many race engines, the exhaust port is more oval due to the exhaust ports of each of the two valves per cylinder. So the first part of the exhaust manifolds runner transitions from oval to round.
Packaging is tight within the chassis of the Indycar and Chevy decided to package the turbos differently than Honda which we looked at earlier in the year. The wastegate actuator has two ports for improved control.
Check out the billet and adjustable bracket used to help support the weight of the turbo. To improve the life of the exhaust manifold, it’s a good idea to find an alternative way to support the weight of the turbo so the manifold doesn’t have to. I have to say, the design of the support bracket is pretty slick. The fat base part which bolts to the bottom of the valve cover supports most of the vertical load for the weight of the turbo. The arm which extends out of view to the top left counters the moment force the turbo creates around the pivot point at the fat base mounting location. Lastly, the adjustable end link with heim joints attached to the turbo allows for slight part-to-part variation along with thermal expansion and contraction.
While you can’t buy the Chevy twin turbo V6 Indycar engine unless you own a race team, you CAN buy this Nissan GT-R twin turbo V6 VR38 engine setup from Greddy. This setup makes more power than the Indycar engine anyways! This engine has Greddy’s cast intake manifolds, big throttle bodies, ported cylinder head, metal head gaskets, IC kit, turbo kit, and the hidden but high importance 4.0L stroker it.
The turbo kit is based around Garrett by Honeywell’s GTX3076R turbos using their V-band turbine housings. Thank goodness for the V-bands because trying to get a wrench on four nuts of a T3 flange setup in the tight confines would be a royal pain in the ass. The merge of the exhaust manifold looks really well done. Also the placement of the wastegate giving it flow priority is ideal allowing for the most precise wastegate flow control.