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brucepick 03-07-2009 06:56 PM

Quick HAI/WAI for '97 Civic HX
I finally decided I REALLY need HAI or at least WAI as intake temps below about 35-40 degrees F seem to prevent the car from going into lean burn mode.

Well I did it today. Easy to do, once I realized how. Cut openings in bottom and driver's side of air filter box, to let it pull air that's passed through the radiator. Success! Normally the intake air temp (IAT) has been 10-15 degrees above ambient, once the car warms up. With the new openings cut and the original tube blocked, temperatures were fully 30 degrees above ambient for highway cruising. Those intake temps were very stable too, in spite of hills and all the needed throttle changes. In town with stop and go traffic and errand stops, temps went about 40-50 above ambient.

This should be warm enough to get me lean burn even when outside temperatures go down to about 10-20 deg F. I'm not sure about wet weather though. Wet weather seems to also snafu the chances of running in lean burn mode; I'll just have to see how that goes.

The usual HAI / WAI method is to run a tube to the exhaust manifold. However that path is crowded on this car, especially if you want to pull air into the original open end of the intake system (I gave up on using the original opening though).

Easy method on this car: Cut openings in the bottom and driver's side of the airbox. In first photo below, yellow oval shows location of original intake port. Green arrows show where I cut openings in filter box. I used a Dremel type grinder (Black and Decker, actually) with a small cutoff wheel.

Openings at green arrows pull in air preheated by the radiator (photo above).

This photo below shows the locator tabs at front of air box widened by grinder. Pry tab jaws apart with a flat blade and cut away some plastic to be able to get the thing out of the car. Then widen and clean up the cuts a bit once it's free.

Here's a closeup of the cuts I made. I also blocked off the original intake port near fender with duct tape. You can add/remove tape where needed to adjust the amounts of hot/cold air.

Here's one more: Looking down into the air box. Top of pic is the forward/front end of air box.

PaleMelanesian 03-09-2009 11:32 AM

Nice work! Clean and easy. If you need cold air again, you can just tape / untape holes to suit.

*Looks over at my civic. It cowers in fear...

brucepick 03-09-2009 09:08 PM

Thanks, PaleM!

Today I verified - outdoor temps were about 35-40 degrees. Very cold rain and occasionally snow. Intake air temp went up to 69-72 degrees, and I was able to stay in lean burn mode with the exception of some steep upgrades that needed heavy throttle.

In the past, rain or snow at those temperatures would have made lean burn nearly impossible.

The next verification will be when I fill up.

I have to say, cutting open the air box makes for a noisy intake. Not as loud as fat exhaust pipes and oversize muffler, but some would find it objectionable. If there were a way to route heated air to the stock intake location that would take care of the noise. It sounds like a loud moaning. Heavier foot = louder sound, especially at lower rpms. It's better at higher rpms.

RH77 03-10-2009 12:27 AM

I have a similar stock setup, with the airbox intake at the bottom. I blocked that off, cut a hole in the side, and inserted a flex-tube routed to the exhaust manifold. This results in ~100F in the Winter.

My non-lean-burn engine likes 100-110F for optimal FE. Have you tested the range of limits vs. FE and lean burn?

Best FE...


justjohn 04-27-2011 12:26 AM

Any chance of getting these pictures back up? I am interested in forming some sort of WAI for my '96 HX and would like to see how you did this.

eg6_bliss 12-08-2011 05:36 PM

Please put back the pics thanks.

brucepick 12-08-2011 10:09 PM

Restored, with one more pic added.

Thanks Darin for unlocking it right away!
Now if we could only get some of the folks where I work to respond to fixit requests that promptly.... Oh I forget, that's MY specialty there!!

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