I seem to disagree with some of you respecting cold air intakes and K&Ns. I am a geezer who grew up innovating hot rods, etc. This is my third Genesis. I have developed my own simple/cheap cold air intake using a K&N model #1040 cone filter attached to the OEM intake for each Genesis. I use as much of the OEM intake as possible including the ductwork leading to the OEM air filter. I have done some simple heat shielding around the exhaust manifold. The 2009 and 2011 have a BMW-style secondary filter, which I removed. I also removed the screen on the mass air flow sensor on the 2009 and 2011. There is no mass air flow sensor on the RSpec.
I am concerned about intake air temperature. The OEM system keeps the differential temp between ambient and intake to about 13-15 degrees more or less, depending on the day temp. and how long the car is driven on the highway. A car sitting in traffic will raise easily double this differential.
There is a mild power increase, and, of course, intake noise increase at full throttle. At low throttle acceleration and cruise there is no noise increase.
Gas mileage seems a bit better, which is to be expected with less pumping loss. On my 2009 and 2011 I often saw temp differences of less than ten degrees, which was a bit less than OEM. My RSpec differential is more like 13 degrees, and this may be due to a different temp probe placement on the RSpec.
My installation is easily reversible to OEM, which was an objective.
This spring I did a baseline dyno with OEM airbox and K&N filter. HP was at 352. At wide open throttle this motor, and all current motors, changes the fuel delivery system from a closed loop to an open loop system. A closed loop is designed for emissions and keeps the air fuel ratio steady at about 14.5:1, which is optimum for emissions. For mileage one might go a bit leaner. For power you want something around 13:1. When one engages wide open throttle the ECU cuts over to an open loop system and essentially dumps about as much fuel as the injectors will handle. This creates an over-rich mixture, which OEM manufactures desire as it is probably better for engine life on wide open throttle to be rich as opposed to lean. On the dyno my RSpec had a fuel mixture of about 10.5:1, which is pig rich. If one could lean open loop fuel mixture to optimum my guess is that you would gain 20-30 horsepower without any loss of economy or durability.
ECU tuners typically leave the closed loop alone, with maybe minor adjustments to lower idle on some cars. Their work is fixed on leaning open loop. Unfortunately, no one to date has broken the source code for the Hyundai ECU to allow this kind of tuning. That's the bad news. The good news is that the system is so rich on wide open throttle that there is no danger of running lean with any intake or exhaust
mods. The system will also nicely adjust on closed loop for any intake and exhaust
mods. I measured fuel mixtures before and after intake/exhaust
mods on my 2011. There was no change to closed loop; and only minor leanness on open loop.
