Lotus Introduces Coanda Exhausts

Lotus had announced earlier this week that they would be finally introducing their own version of the Coanda Exhaust as pioneered pre-season by McLaren Sauber, Red Bull and Ferrari. The new exhaust system uses the Coanda Effect to aim the exhaust plume next to the rear brake ducts where the plume meets a series of vortex generators that aerodynamically seal the diffuser by reducing the air leakage from the gap between the diffuser and the track, as well as energizing the flow inside the diffuser to produce more downforce. 

The exhaust layout is very similar to Sauber’s 2nd iteration of the coanda exhaust as the bulge is not very big.  It is a very tidy solution from Lotus. The area around the exhaust unlike other teams is not carbon fibre coated with a heat resistant material but it is a metal, most likely inconel, the same material the exhaust itself is made from. 

Lotus have added a new winglet (highlighted) on the brake ducts to help direct the exhaust plume towards the diffuser and extract more downforce from it.

Lotus only used the new exhaust on Raikkonen’s car after testing it on Friday. Below is a direct comparison between the two exhaust solutions.

NEW

OLD

The coanda exhaust seems to have paid off as Raikkonen was faster than Grosjean by 3 tenths of a second while he was on average one tenth of a second slower when both drivers managed to get in Q3. That is a difference of 0.4 s and maybe an indication as to how much performance the coanda exhaust can bring, much lower than last year’s blown diffuser which was said they brought about 1.2 s or more of performance. 
Lotus haven’t yet managed to set up the car to suit the new exhaust as Raikkonen was complaining about understeer which is logical as the new exhaust shifts the CoP (Center of Pressure) backwards. As soon as they go out in Q1 the car’s are under Parc Ferme rules which allow them to change the front wing angle so the increased the AoA (Angle of Attack) to balance the aerodynamic grip.
Lotus is expected to improve further in the next few races as it took Mercedes 2 races to learn how to setup the car correctly and had a big improvement this weekend in Korea on the 3rd race  after they introduced their coanda exhausts. 
We can expect Lotus to bring a slightly modified version of their front wing in India to increase the front downforce as well in order to balance the car.

Finally Lotus’ technical director James Alison said “We are at the beginning of a relatively long road with them, [coanda exhausts] it's not straightforward to make them work from the start, but the numbers we got are good so we are quite pleased.”