Civic EG

I was told that 3" piping- the most common size that I've seen sold commercially- is too big for the average 4 cyl engine. Ironically, I read about guys who put "Elephant Dicks" on their Honda engines. Because I wouldn't want to run lean, what size would be the best fit for a small displacement engine like a D15B7? (I was also told that these engines typically don't run on much air to begin with)

Another question I have is in regards to the stock intake system. Does a throttle position sensor regulate the air-to-fuel ratio on a D15?

Thanks in advance.

A n/a engine isn't going to suck in more air than it can handle. The ecu will compensate extra fuel if needed to keep from running lean.
The o2 sensor regulates the AF ratio.

3" vs 2.5" intakes...
You can go with either size. Dyno results are the only way to tell for sure if 3" is better than 2.5". I've used both and couldn't feel a difference. But 3" would seem like the one that will offer more air. Even with a 3" intake, you still have a bottle neck when the air reaches the stock throttle body. A good filter will help too, stay away from generic ones.

Length is just as important as diameter as far as tuning an intake pipe. Talking about diameter alone is absolutely pointless. A longer pipe shifts the power increase lower in the RPM band. A larger pipe shifts the power higher in the RPM band. Too long or too short, too big or too small, or a bad combination of both, and you lose power over the stock intake.

A larger pipe means slower air velocity. If the engine isn't high compression with an aggressive cam profile, you'll lose power. Bigger is not better.

And besides that, intake tuning isn't as simple as air moving one way into the engine. There are actually pressure pulses bouncing up and down the intake pipe and reflecting off the back of the intake valves as they open and close. A properly designed intake system will time the pressure pulse to arrive at the intake valve just as it opens (and this is only possible at a particular RPM). A deeper understanding of pipe tuning is the reason why AEM's V2 intakes make the most power with the best overall power band.

3 inches is a bigger diameter than I've seen on any aftermarket intake that claims to have done R&D. I'd stick to a smaller diameter unless you have a Type R engine.

http://www.team-integra.net/sections/ar ... icleID=466

^^^^ very good info