CAI Question.

[sketchman]

I want to run hard 2.5" pipe from TB to VAF. There is a 1/2" or so rubber hose right in front of the valve cover breather hose that I assumed to be just a fresh air inlet for some thing, but when I unplug it, the car won't idle. Does it actually use the little bit of vac that is created between the VAF and TB when idling to control the idle, or is it just a coincidence that I put all the stock junk back on and the car idles again.

If it just MUST have that hooked up, I'll work it out, but I want to be sure before I drill a hole in new piping.

[bhazard]

The whole thing isn't worth your effort on a stock engine man

[sketchman]

The stock pipe is old and cracking. A cheap eBay intake kit for a civic was $35 shipped to me. It will be worth it.

[blkfordsedan]

I want to run hard 2.5" pipe from TB to VAF. There is a 1/2" or so rubber hose right in front of the valve cover breather hose that I assumed to be just a fresh air inlet for some thing, but when I unplug it, the car won't idle. Does it actually use the little bit of vac that is created between the VAF and TB when idling to control the idle, or is it just a coincidence that I put all the stock junk back on and the car idles again.

If it just MUST have that hooked up, I'll work it out, but I want to be sure before I drill a hole in new piping.

Are you referring to the small hose with a 90 degree bend that goes from a nipple on the valve cover (by the oil filler cap) to the plastic intake tube, just in front of the throttle body? If so, you can't just unplug it or you'll have a vacuum leak and it will run lean. The PCV system pulls a vacuum on the valve cover. That's why your car idled rough when you unplugged it.

[sketchman]

Not that one. The bigger one right in front of it, but both were unplugged for the test fit. I didn't even think about the little one. I'm used to a MAP sensor where you can do whatever you please with intake plumbing before the throttle body and the engine doesn't care. I guess I'll be hooking them up then.

[Glow_Mouse]

yikes...both are important. You can use a Little breather on the head PCV cover. But the other vacuum hose runs back into your manifold. As far as the aspire goes thats pretty much how ive got mine set...

[Aaronbrook37]

The whole thing isn't worth your effort on a stock engine man

Can't say I agree. Intakes are a cheap and fun way to really liven up even the plain-janest of B3's. For under $50, you can't really go wrong. Gas mileage, great intake sounds, and a little performance bump make for a really worthwhile upgrade, even on the carby models. I'm much more of an intake sound guy than an exhaust sound guy, and intake whine is a very good synergetic for the Butt Dyno Placebo Effect.™

For those of us on an even tighter budget, you can find everything you need from a budget metal shop and a local Home Depot. For low/no boost, plastic plumbing couplers and clamps are more than sufficient. <Opinion>No need for 10000-ply silicone type-r ultra grade unobtainium-infused couplers that cost more than an oil change and a tire rotation.</Opinion> Grab yourself a couple feet of thin-wall piping, a straight/90/45 degree set of couplers, and go to town!

Short rams are even better for loud vacuum intake noise, but their preference is debatable. Some people prefer the hot air for testing with fuel economy or covertness in an engine bay, or weather protection. I'm more in the cold air camp myself, but whatever works.

The theory and physics of intake design and development is really quite an interesting research topic. The speed and continual flow of air is so rapid and dense that it exhibits a lot of liquid-like characteristics. Thus, quality and unrestricted designs are really important.

Sketchman, I'd love to see some pictures of what you're talking about, as well as the modifications to the kit in question. As well, some specifics on that kit would be super cool for archival purposes - I presume EF or EG Civic?

Likewise, I come from a Mitsubishi community that ran on MAP, so I feel your pain, brother. All we can do is make the most of it I guess... without paying up the wazoo for MS or a stand-alone fuel management system. The Australian Laser boys and girls are experimenting with GM MAF conversions by doctoring and tweaking signals to convert the famous DSM upgrade to a 3.0" low-restriction hot-wire MAF on BP's and B6's. It's an interesting process, but hardly worth the effort on a stock B3.

I've said it time and time again, but the factory air box and plastic piping are far more of a restriction than the factory filter, even when heat-wrapping and or box drilling/feeds are thrown into the picture. Australian testing has revealed that of the pressure drop in intake systems, filters (even the cheapest of them, yet alone K&N) are responsible for under 20% of restriction of the system.

Autospeed.com did some testing to try and minimize intake restriction to a point where air doesn't have to enter the charge, but will actually be forced into it. If anyone has read my write-up on aerodynamics and air flow, they'll know that you can muster up a couple tenths of a PSI of boost at speed from a quality-designed intake system with a ram-air feed.

Thus, short of serious anxiety about police attention (if you should live in such a region or country where modifications of any sort garner inspections and such), an intake can never really be a bad idea. The only thing I'd put before an intake would be a routine tune-up and some precautionary maintenance measures. Maybe a B6 swap too!

[sketchman]

I'll try to get pics tomorrow if I can remember.
I bought this and cut it up to get what I wanted from it.
http://cgi.ebay.com/ebaymotors/ws/eB...=350416435644&

[Safety Guy]

Sketch, is that kit a 3" diameter pipe size?

Karl

[sketchman]

2.5" I go by whether or not there is a reducer in the pics as none of the eBay guys actually know what they have or will offer to check for you. I've asked more than once.

I think I just realized why the car died with that hose unplugged. MAP thinking messed me up again. Pretty sure I can remove the whole ISC-BA(or whatever it's called) now and just use the IAC screw on the throttle body. It never worked right anyway. Threw the idle all over the place from WOT to near dead.

[sketchman]

Finally got it close to done. Still waiting for the filter, but piping is all hooked up, and successfully bypassed the stock idle control so I can just use the screw on the throttle body to set it and forget it. Yes, I know, my engine is nasty. That's next on the list. Function first.

[Aaronbrook37]

Nicely done... looks great! As I recall, you're the one who snagged an MDM header as well? That's really gonna open things up nicely for you! The sound improvement alone will be fantastic.

[sketchman]

Yeah, but the header is for the Aspire. Mom doesn't care for "changing things" when they "work well enough". Since the Festiva will be hers soon, I'll spend as little as possible, and tinker with the Aspire for myself. Now that the idle is stable and the intake is good, she'll be happy with it.