Aftermarket Intake or original Black air box.,
 

greetings to everyone.
I have a Civic HX 98. It came with aftermarket air intake. I already bought the black air box but i dont know what part is better for fuel efficency.

thank you

The stock airtube and box a few reasons. The stock tube is likely smaller giving better low engine speed velocity and it should draw air from the best location.

If you can bend or maneuver that aftermarket air tube so that it draws air from directly above the catalytic converter you will have a "warm air intake." Many of us have had success with those. The warm air is less dense, and therefore less oxygen get to engine. The engine will reduce fuel to maintain the 14.7:1 air/fuel ratio needed to burn the gasoline. But you'll have to push the gas pedal further to produce the same power. Doing that opens the throttle plate further. Opening the plate further reduces the energy lost as the engine tries to pump air to mix with fuel. Reduced "pumping losses" seems often to mean improved fuel economy.

I hope that helps.

James

The oem airbox is usually more restrictive than an aftermarket intake. On my 07 fit i noticed a 20 mile per tank increase in fe .18 mpg however on my 89 crx dx, a -1.5mpg. Both with a warm air intake of about 30-40 degrees avove ambient air temp. Unless someone has done a proper aba test on that motor it falls to you to find out my good sir

Air intake velocity in the airbox/CAI makes ZERO difference as the part that matters for air intake velocity and amount is the intake manifold after the TB and warm air intake will just hurt the overall power of an engine for no reason other than making you the driver push the petal further for the same result, much better just to maximize the engine's output and drive to a target rpm and speed

I'm sorry, but I'm going to have to disagree with everything you just posted Striker2237. :D

Intake pipe diameter and length definitely do play a role in the torque curve of the engine. Here is an article that shows some testing:

AutoSpeed - Pipe Dreams


Also, its widely known that warm air reduces pumping losses and increases flame speed in the combustion chamber. Both of these things increase engine efficiency. Not all engines react well to warm air though due to a number of factors, but it mainly boils down to ignition timing. You get too hot and the ecu pulls timing and you loose some of the efficiency you gained from reducing the pumping losses. Each engine handles the warm air differently.

Pretty much echoes my own testing. Longer piping, up to a point, helps make more power... which helps explain why CAIs are effective in making power. I ended up with a long stainless tube attached to my intake, putting the filter as far away from the engine as possible, but still inside the engine bay, up and away from possible water ingestion.

My tube made 5 hp more with the K&N filter than a standard legth tube with the same filter, and up to 10 hp more with extra fuel and ignition tuning. Certainly bang for the buck.

Unfortunately, finding the proper length and diameter for your car is an expensive endeavor, unless someone else has already done the legwork for you.

The theory goes that long, narrow tubes pack air in more efficiently at low flow rates. Meaning low RPM especially. The air in the pipe picks up a lot of momentum being pulled through it, so it keeps moving into the chamber even when there isn't much suction pulling it in.

Conversely, short and wide tubes are better at high flow rates. A higher volume of air can get through the tube in the same amount of time, and that more than overcomes the extra air that gets packed in with that momentum effect above.

So it stands to reason that for any given flow rate (meaning engine size, throttle setting, and engine speed) there is one optimum set of tube width/length that will get the most air into the engine.

When driving for fuel economy, we are almost always running at low RPM. So generally, the long skinny tube approach is better than the short wide tube for our needs.

In practice, there are even more factors that go into intake design. Smoothness will promote flow, and bumps will promote turbulence. Flow is good for getting more air in with less pumping losses, while turbulence is generally good for mixture quality. (And that also gets changed drastically by the throttle position.) And where the air is drawn from, as alluded to above, has a noticeable effect. And on and on.

-soD

After Market Filters
 

Unless you need to shave a few 10ths of a second off your 1/4 mile time you need to consider the function of the air filter.

If you go for the "Aftermarket" air intake, you lose A LOT of filtering capability, so you really risk getting your engine crudded up shortening its life.

Don't take my word for it, many others have looked into this and came to this conclusion. Here is another forums great web read on this. NICOclub.com Air Filter Thing

Bottom Line. (See Below)

=----> NOT Recommended. <----=

The Civic VX intake tube (original equipment) was a smaller diameter than all of the rest of the same year civics (except maybe the cx). They did that for a reason.

regards
mech