Oregon, USA based Radium Engineering have released a new product they claim will release up to 21.5 extra peak horsepower over the OEM intake system for the naturally aspirated Evora along with a significant increase in torque throughout the range. We’ve not tested the system directly but a few TLF members have fitted the kits and are so far very impressed with the ‘seat of the pants’ dyno results and induction sound improvements. The Radium CAI (Cold Air Intake) kit includes everything you need to replace the stock system and they say it takes less than an hour to install, including removing the old air intake. Those who have fitted the kit warn to be careful of dropping any bolts or the like as they’ll end up on top of the engine undertray which leads to a lot of work to retrieve the dropped item. Images are courtesy of Radium but here’s the OEM system followed by an image of their system.

The company also have an oil catch tank which can be used in conjunction with this system, very handy if you do a lot of track days they say. Here’s the information from their blog about the intake system:

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 sound. 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 1 hour.

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 separately. 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.

All Evora’s are currently within warranty and we recommend all owners to discuss fitting an aftermarket induction kit with their supplying dealer or the Lotus Cars Warranty Team. In theory the warranty will remain valid however you could find yourself on sticky ground if this item were to cause any problems after fitting with the induction/combustion or any other related parts. Obviously, the rest of the warranty for parts unrelated to the intake system would still be valid. It’s also worth noting that Radium fitted a Larini exhaust to their Evora so it wasn’t entirely stock to begin with so with what may be a more free flowing exhaust, the benefits of the intake could be exaggerated. Also, one of the side effects of removing the stock system and replacing it in an increase in the induction noise. For many Evora owners this will be a positive as they noise of an engine intake under load is lovely to behold however for others this could be a negative and the noise too much, taking away the effortless elegance of the car at speed. Your personal preference is the only guide here. The kit costs $399 in the USA (currently on sale!) which is around £250/€290 plus shipping and import duty to the UK/EU.

We’ve heard from a couple of people who have fitted the kit and feedback to date is:

All I can say is wow.. this is a different machine. Where full throttle pressed me a little back in my seat before.. now it it is ‘HANG ON’… no kidding. I was able to chirp my tires in 2nd gear. In the past, if you were doing 70-80 in 6th gear (I have the sports ratio transmission), you had to downshift to get any acceleration… well no more… and when you do downshift… hang on.

The exhaust not is brutal when get get on it… sounds better than my V8 R8… and I would put it on par with some of the italian cars out there. One side note, the car now sounds like it has a turbo… when you step on the gas, you hear a swish sound… very interesting…. My MPG is up for a given MPH, one side effect I have noticed is the car is running a little warmer (nothing to worry about.. it is still very hot down here in Florida)… which makes sense… more air… more power… more heat…

Simply amazing!!

FalconFlyer, Florida, USA

I have the Radium CAI now in the car = fantastic. The car drives easier on throttle, fine till 3000 and then it gets loud. What a difference. I can recommend it to everybody=save a lot of money against buying the “s”. This is a real performance part powering up the normal Evora to a really fine sportscar.

Ritchie, Switzerland

Sound much improved over standard. Subdued at idle and in low power standard driving, but with a “cleaner” note. (Sports silencer.) At mid-power range, louder, deeper and more purposeful tone, appropriate for serious sports car but acceptable for general use. At high power and peak revs: loud – not for those of a nervous disposition; thought marvellous, but on the road only for appropriate circumstances and duration or could attract undesirable attention. Think Sports motor bike.

Mel Davies, Hampshire, UK

Those are the personal and non-professional opinions of those not connected to the company bar being customers and having just purchased or tested the product. You can join in the discussion on this system with owners on the forum here.

More video (thanks Kris Myers!) of the noise once fitted.




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