* Dyno And Facility:Dynojet, Courtesy Of K&N Filters
* Testing & Installation:James Yim, Nestor Cabrera, Luke Munnell
Pros
Prior to the RDX's launch in '06, if you were to ask any Honda tuner what their dream swap would be, they'd reply with something along the lines of what this modern day crossover offers straight from the assembly line: a factory turbocharged and intercooled Honda K-series engine. Marking their return to turbocharging technology after nearly 20 years since the discontinuation of the City Turbo in '87, Honda chose to boost a version of one of their most tunable engines, to a claimed 240 whp and 260 lb-ft of torque. Big power and torque, with factory reliability and potentially huge aftermarket support? What was there not to like?
Cons
In true Honda fashion, instead of boosting one of the most well-designed four cylinders of all time in the name of all-out power, and dropping it into a platform capable of challenging performance giants like the EVO, STI, and Mazdaspeed 3, the company opted instead for fuel efficiency, midrange torque and decreased emissions when designing the K23A1, and fitted it into a crossover SUV, to rival the likes of the Forrester, CX-9 and Santa Fe. Not that this completely negates the "cool factor" of a factory turbocharged Honda K-series, but... how completely badass would it have been to see the engine tweaked slightly and dropped into, say, the Mugen Civic Si?
Notes
At the rollers of K&N's all-wheel-drive Dynojet, regular 2NR contributing photographer Steve Demmitt's '08 RDX rolled out 66 whp less than its claimed flywheel hp number, indicating a driveline loss of almost 30 percent. If such a comparatively low number is a bit surprising, consider that the K23A1's power is transferred by an automatic transmission to all four wheels before our chassis dyno can measure it, and the 90+ degree ambient temperatures encountered throughout testing decreased power significantly, compared to conditions inside Honda's own climate-controlled engine dyno facilities.
Pros
Factory programming of the RDX ECU limits boost generated by its K23A1 to between 13 to 14 psi until 4,500 RPM, then decreases to 8 psi approaching the 6,500 rpm redline. Hondata's ECU reflash raises boost by 1-1.5 psi under 4,500 rpm, and 3.5-4 psi to an extended 7,500 rpm redline. Additionally, the reflash advances ignition timing, and leans out the RDX's conservative air/fuel ratio to within more ideal tolerances. The result is more power and torque across the board, with improved fuel economy to boot, provided you can refrain from driving with a lead foot. Finally, the entire reflash process is reversible, should users ever want to return their vehicles to the stock tune, or re-tune for additional modifications.
Cons
Because of Hondata's more aggressive boost, timing, and AFR adjustments, 91 octane or better gasoline must be run at all times, otherwise under instances of stress (high heat or engine load), the RDX's knock sensor will kick in and retard timing, robbing power until conditions improve.
Parts
Reflash of the factory ECU
Tools
10mm socket and ratchet, postal service
Installation Time
2-day turnaround, 5-minute removal and re-installation
Notes
Since the Hondata tune is designed to accommodate 91 octane gas, use of higher octane fuel may lead to improved power output and fuel economy. Also, the heightened redline only functions in the "Sportshift" mode; all other features are available in every mode.
Pros
Powder-coated, mandrel-bent, thin-walled aluminum tubing; a flow bench-tested and properly-sized re-usable filter; and a black powder-coated heat shield worked together to feed our K23A1 with the most efficient amount of smooth flowing, cool, clean air to improve output by more than 11 whp and 13 lb-ft of torque at points throughout its powerband - all in lightweight, aesthetically pleasing style, complete with a lifetime guarantee and CARB certification.