We took delivery of a Lotus Evora last month and we have been developing a few parts to enhance overall performance. Several concerns, including a tendency for the engine to burn oil after hot lapping, gave a direction for the areas of development that would be initially tackled. The oil burning issue was solved with a Radium Install Kit for the Evora using our billet aluminum catch cans (more info on this later).
Another idea was to improve the air flow to the Evora's engine, allowing it to breath more freely. This would improve the performance and create a more audible sports car engine sonud. This lead us to design a cold air intake system. Drawing from former experience as engineers at Advanced Engine Management Inc., we assessed the factory intake system, developed a test plan, began fabricating test pipes and designing parts.
The factory intake system is not only restrictive, it is heavy and HUGE! This monstrosity occupies most of the engine bay and it is exceedingly complicated. Without a doubt, Lotus went through many steps to suppress the acoustics; unfortunately, as a side effect, performance was sacrificed.
This particular Evora was equipped with a Larini Exhaust and a K&N drop-in panel filter. These factors may have resulted in a slightly higher power output than a 100% stock Evora. However, since this exhaust was in place for all of our testing, it was not going to affect our run to run comparisons. The graph below shows the peak numbers of one of the stock air box dyno runs, 242.18rwhp and 229.73ft-lbs.
Along with raising the rev limiter, the SPORT button activates a vacuum operated solenoid that opens a flapper valve in the intake system allowing a more direct air flow to the engine. The power output is not notably effected by the SPORT button.
Since the 2GR-FE engine in the Evora uses a MAF sensor to meter the incoming air, we needed to ensure that this ECU input functioned flawlessly with our new intake system. The inside diameter of the pipe effects how accurate the MAF sensor reads and can throw off the calibration if not dealt with properly. As expected, we saw large variances in the air fuel ratio when fabricating an intake pipe that created turbulent flow through the mass air meter. Some other issues that occur due to inadequate calibration include a stumbling idle, high fuel trims, and poor gas mileage. To replicate the diameter of the stock MAF sensor tube, we were constrained to source a non-standard aluminum tube size. Special tubing is more expensive than standard off-the-shelf sizes, but a properly sized pipe guarantees that the MAF sensor relays the appropriate signal to the ECU. Using the specific tube size, we constructed an intake system for testing using our own billet MAF sensor mounting flange.
On the dyno, we were able to experiment with different pre-MAF tube diameters and overall system lengths.
We found that the engine did not like many of the tubing configurations tested.
Some vehicles we worked with at AEM required long intake pipes (i.e. Honda S2000 = 42") to make the most power gains throughout the RPM band. The extra long tubing configurations (shown above) lost major power throughout the revs. We also realized that short intakes, like the factory Lotus 9" intake pipe, were way too short. After hours on the dyno testing multiple lengths and diameters, we found the perfect combination that made astonishing power.
Next, we constructed a prototype pipe that physically fit into the engine bay and located the filter to an area that would receive the coolest intake air charge. This pipe had the appropriate inside diameter and tuned length that made the best power on the dynamometer. We made a point to use minimal bends in order to reduce turbulent flow that can cause trouble for MAF sensor readings.
The graph above shows the peak numbers of our prototype Radium CAI dyno runs, 269.2rwhp and 239.71ft-lbs.
The graph above shows the average of the stock air box dyno runs (blue line) and the average of the prototype Radium cold air intake dyno runs (red line). On average, our prototype cold air intake picked up 21.5 peak hp (265.96WHP vs 244.46WHP) along with significant power gains throughout the entire RPM range.
The graph above shows the the torque difference between these two averages.
Our Evora CAI kit will include everything needed to install the system, including: K&N Cone Air Filter, Powder Coated Piping Weldment, Custom Made Silicone Coupler, Heat Shield, PCV Tubing, Hose Clamps, etc. The installation is very easy and quick and can be done with standard tools in less than 1hour.
Because of the extra room created by eliminating the Lotus air box, it allowed us to expand our Evora product line with a Radium Fuel Surge Tank, sold seperately. By simply unscrewing our heat shield's block off plate, the FST slips right into the location and mounts to the heat shield for a clean installation.
The FST installation kit will include its own heat shield in order to block engine heat and receive cool air flow from the driver side air vent. The FST installation kit will be available late 2011.
This intake system not only unleashes noticeable horsepower gains, it also provides an engine note that matches the performance of the car. Other benefits are: weight savings, added engine bay space, increased air filter surface area, and easier serviceability.
This video contains audio clips that compare the cold air intake sounds to the stock Evora air box.
The Evora intake system is now in production and we expect to have them ready to ship in 4 to 5 weeks. See our product page for pricing and details.