ethan_in_seattle

Hi, I've been trying to find factual data to compare different types of air filters and CAIs but I've been largely unsuccessful. Has anyone posted a performance comparison between different makes of CAIs using the stock air filter as a baseline? I was considering replacing the OEM paper style filter with a K&N. I don't see the value in a CAI, other than possibly a slightly more throaty sounding engine, and so I was curious if anyone had actually seen a dyno comparison between different intakes that might justify the added expense. It seems all manufacturers of CAIs claim that their product will grant more power and better economy, but I've yet to see any numbers to support these claims. My suspicion is that a K&N replacement filter will do just the same, and perhaps better than most CAI systems on the market. My reasoning is this: manufacturers dedicate a great deal of effort towards optimizing an engine to achieve the best balance of power, economy, noise, cost, and emissions. The weakest link in the system appears to be the filter itself. I believe manufacturers continue to use paper style filters because they're cheaper and ensure reoccurring revenue. On the other hand, the stock air boxes are made of thermally insulative plastic that significantly reduces heat transfer to the incoming air and are designed to draw the air from directly ahead of the engine bay where the air is coolest. I've heard the argument that CAIs are designed to encourage laminar flow and that this increases the amount of air the engine can aspirate, but most intake tubes are large enough that the effects of turbulence near the boundary layer will have little impact upon the pressure drop through the pipe, particularly through such a short distance. Furthermore, turbulent air is a good thing in the intake because it helps to mix the air with the fuel more efficiently. The pressure drop across the filter greatly outweighs the frictional losses is the pipe so it makes sense that simply replacing the filter element with a less restrictive style of filter would provide the greatest overall value. As I own a IS350, squeezing out another 1-2hp is not my primary goal; rather, I would first and foremost like to improve my fuel economy without sacrificing performance. I'm aware that there exists a plethora of anecdotal evidence to suggest that one or another CAI works well, but I want facts, not hearsay.

Hi, I just bought a set of winter tires and wheels including new TPMS sensors. My plans was to have a set of wheels for winter and a set for summer that I can simply swap at home, without fuss. Unfortunately, things didn't go as planned. The TMPS warning system kicked in and from what I can determine from reading previous posts and browsing through the manual, the new sensors need to be programmed into the ECU. The manuals says that this must be done at the dealership. Does anyone know how to program in the sensors codes without going to the dealership? I do not want to use the old sensors because I would have to deflate the other set of tires to remove the sensors and then take my car to a tire store to have the old sensors installed, which defeats the purpose of having a second set of wheels in the first place. I've already tried initializing the TPMS system using the satellite switch and that didn't work. Also, the computer is set us to store two sets of sensors for this very purpose. Any help would be greatly appreciated. Thanks,

Agreed. I don't mean to undermine the significance of driving behavior. This is undoubtedly one of the greatest factors in determining gas mileage. I've ridden with many people who seem incapable of modulating throttle response smoothly. These very same people seem to be rather vocal about their car's poor gas mileage. Coincidence?

"Ethan - don't forget topography as well (think San Francisco vs Topeka). But you've listed some good variables that aren't always obvious to some." As I originally stated, "there are many factors that affect the mileage of a vehicle, 'including but not limited to'...". There are of course more factors than what I mentioned, such as topology, type of fuel used (formulations varies by region and throughout the year), and maintenance (air filter, oil, etc.). The importance of what I was trying to say is that people need to consider the many factors that influence gas mileage when considering the numbers and not compare directly with other people's numbers when all factors are certainly not equal. Your observation about topology deserves further attention. Consider that work is defined as force times distance, and that when a car does work it consumes gas. The more work is does, the more gas it consumes. When you're driving on a flat surface, the amount of work your car does is basically equal to the sum of forces (drag, frictional losses in the drive train, tire resistance) required to propel the car at a constant speed multiplied by the distance that the car has traveled. When driving on irregular topology, the car must change elevation too. The amount of work done when climbing elevation is equal to the weight of the car multiplied by the change in elevation. Of course, roads don't go straight up or down, so the real work done by a car while traveling on hilly roads is equal to the work required to move it forward plus the work required to gain elevation. It should be obvious then that even a small change in elevation requires significantly more work, and thus consumes more gas, than driving on a flat road. Also, you don't get back the work done while climbing a hill when you go back down, though gravity does help reduce the amount of effort required to keep the car moving forward at a constant speed. In conclusion, the heavier the car or the hillier the terrain, the more gas a car is going to consume, regardless of the type of car. Our cars are relatively heavy, and so anyone who drives in a hilly area needs to understand that they will get significantly worse gas mileage than someone else who doesn't drive many hills, all other variables being equal.

[Well, thanks Scott, however, the discrepancy can not be that wide unless one car got to be tuned. No matter what bad driving habbit one have it should not be that big difference. I myself never got any higher than 18; when I fill in my tank with Shell(10%Ethanol) I get 14 mpg.] The apparent discrepancy in gas mileage is likely not a function of the quality of the car, as some have suggested. There are many factors that affect the mileage of a vehicle, including but not limited to altitude, barometric pressure, type of tires installed on the vehicle (a big factor), tire pressure, condition of car, driving style, weight of vehicle (this includes the weight of the driver and passengers). Most, if not all, cars vary at least as much as has been suggested by people posting on this forum. I used to own a Nissan 350Z, and that car, even when driven conservatively, got only about 18mpg. When I would park that car in my garage I would have to leave the garage door open for about 10 minutes to let the smell of exhaust clear. By contrast, my IS350 is odorless. This demonstrates its efficiency (exhaust odor is due to unburnt hydrocarbons which causes poor fuel economy). The IS's engine is truly an incredible machine; it meets federal ultra-low emission standards, gets 307hp (18 more than my Z), and gets an average of around 20mpg, combined driving (I do not have a light foot). Anyone who questions this car's quality or efficiency simply doesn't have enough experience with cars. As far as internal combustion engines go, this one is top-notch.