6th gen Civic Question

[thoraldshib]

Building my car I had planned to use my existing K&N tyhoon short intake tube, but how that I have converted to a manual steering rack and VTEC-E engine, im unsure if this will be best for optimal MPG, the engine's EX,HX,SI style intake box would require sawing a hole in the body, but it would allow engine to get cold air from under bumper.

Thanks for reading

Car is a 2000 LX Sedan
Engine is a D15B - D15Z7 3 Stage Vtec
Transmission is a 1996 CX
ECU is 37820-P2J-003

[California98Civic]

Don't cut holes in good stock equipment without total necessity and commitment. There is debate about CAI and WAI intakes. The CAI is for power (opposite of FE most of the time). The WAI usually is thought of as power *reduction* with a fuel economy increase. The increase theoretically comes from reduced pumping losses. I run a WAI that I tested and am reasonably confident works to increase FE, but my Civic has the DX/CX/LX style intake that went with the D16y7. With a VTEC-E (D16y5?) you probably do not want a WAI, unless you plan to do a lot of P&G instead of cruising in lean burn.

EDIT: I SHOULD HVE READ MORE CAREFULLY... i SEE YOU NAMED THE ENGINE YOU HAVE ... 3 STAGE IS COOL. yOU HAVE A BUILD THREAD SOMEWHERE?

[Ecky]

I have a short ram intake in my car, and have been hand-tuning the fuel maps. One issue I ran into, took me a while to figure out, is that my fuel maps would be a few percent lean in the morning and 6-10% rich in the afternoon. I finally figured out why - intake air temperature was much higher in the afternoon, resulting in lower air density (at the same pressure), which threw the maps off. Having warmer, less dense air gives (in theory) better combustion but more importantly it allows the throttle plate to be open a bit more, which cuts down on some parasitic losses and gives better fuel economy.

It's not true for every vehicle, but broadly speaking colder air = more power, worse economy, and warmer air = less power, better economy.