Quote:
Originally Posted by Bicycle Bob
"The air pump can't tell the difference between manifold restrictions and throttle butterfly. At part throttle, their relative percentages are irrelevant. Real ecomodding is a lot cheaper than performance work in some areas. What's the length of a tuned exhaust at maximum mileage? Can pulses get through the close-coupled cat, anyway?
If warm air can carry enough oxygen in for the power required, it will flow easier, and vaporize the gasoline better. Presumably, except in open-loop, near wide open throttle, the injectors will keep the mix lean, just enough for good ignition. See the "warm air intake" threads. (WAI)
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What "air pump?" You mean the intake system? My Sentra's intake has two sensors: a Mass Airflow (MAF) and an Intake Air Temperature (IAT) Sensor. Both have very relevant significance as to how the car will run. If the MAF craps out, my car will go into "limp mode" as a precaution and won't go past 2K- 3K RPM and the IAT regulates idle at start-up. And if you mean to tell me that reducing pumping losses yields "relatively irrelevant percentages" then the same could be said about keeping a restrictive airbox, so as to keep the air-to-fuel ratios leaner. Guess my $45 cone filter replacement isn't a bargain. You asked what the perfect length would be for a fuel-economy oriented. Please note that a stock cat won't contribute enough backpressure (Barely +/- 0.5 PSI) to warrant a replacement, unless you want a high-flow type, (To make way for a monster turbo setup) but those aren't as effecient at controlling emissions than the former. The ideal setup would be as I just said: a larger diameter pipe, not too big, to allow for more exhaust scavenging, reducing pumping loses and maintaining a constant stream in both the open and close cycles of the exhaust valves. Personally, I don't want to attract too much attention, so when I put one on mine, you better believe I'm investing in a resonator. (If it's not included)
There seems to be a rebellious spirit against the establishment of aftermarket performance parts amongst some of the members here. While those companies may jack up their claims to get a stronger base, their products are results of research and development, as well as actual customer usage in various places, (Street, track, top MPG tourneys, etc.) for the most part. (EFI throttle body spacers not included in my ex.) Maybe it's not even them that rubs dudes like you the wrong way. Could be the stereotypical rice-doucher image that plagues your head. (Thanks, makers of "Fast & the Furious.") Either way, the same proven aftermarket replacements of intakes, exhausts, headers, etc. could definitely be used to achieve more MPG's, aside from HP. Most tuners I know love boasting their highest miles-per-tank. It's very common in Sentra, Fit and Civic forums, which I frequent. It's not all about power.
I'm gonna see this WAI thread that you speak of. You can't seriously be putting in one of those for a leaner A/F ratio. I wouldn't feel too comfortable with my car running leaner than it already does from the factory. (14.7 or so) In the event that you do need to run in open-loop, acceleration will surley suffer. How hot do you want your engine to operate, anyhow?