DIY Warm-Air Intake

[RH77]

A request was made to post up some pix of my warm-air intake. It isn't fancy, but it does the job...

First, I removed the cold air tube and resonator (year-round: weight reduction) and the exhaust manifold heat shield.

Pick up some flexible exhaust tubing at the auto parts store -- you can bend it to conform to your needs. I drilled a hole in the side of my airbox to allow the tube attachment. A zip-tie holds it in place.



The difference in many airboxes vs. the Integra setup is the tubular style of the filter and a clean seal at the air intake directly from the filter assembly. This allows "dirty" air to enter at any place in the box. The stock air entry (front-bottom of the box) was covered with duct tape -- this makes it easy to peel it away when summer comes around again.



The hole was drilled to allow a tight fit. Simply crimping the end ensures that it won't slide out -- the tight fit allows it to not slide into the filter causing damage.



The piping doubles as the summer, cold-air intake, so the it's' a bit rusty, but it works. In my experience (with some Honda engines), if you get the IATs into the 100-110F range, you'll notice an increase in FE + faster warmups.

If your airbox is a "clean" setup, such as a drop-in, find the intake source and setup a similar routing . It may take some additional plumbing and duct tape

Enjoy!

-Rick

[brucepick]

Thanks! Looks like a pretty easy mod.

I think that to make this work on my '97 HX I'll need to remove the cold air tube and fit the new intake where that one went. Because the Civic air box is set up slightly differently - very little surface area for a tube to be attached at the side of the box so I think the bottom is better.

[brucepick]

Well now that I've taken a wrench to my car, it's not exactly an easy mod.

The Civic filter is rectangular and right up against the side of air box leaving little room for a hose opening there. I'd rather duct to the existing location at bottom of air box and reroute that intake tubing to the exhaust area.

I wanted to get the air box + intake tube assembly out but there's a crazy fastener for both at lower front of air box. Rather than bust it I think I'll wait till I can deconstruct one at a self service 'automotive recycling facility'. Hopefully one of these days, right after I finish a daunting batch of happy homeowner cleanup and maintenance projects.

[tasdrouille]

My WAI was very easy to do:

Stock:


WAI:

[RH77]

Originally Posted by brucepick

Well now that I've taken a wrench to my car, it's not exactly an easy mod.

The Civic filter is rectangular and right up against the side of air box leaving little room for a hose opening there. I'd rather duct to the existing location at bottom of air box and reroute that intake tubing to the exhaust area.

I wanted to get the air box + intake tube assembly out but there's a crazy fastener for both at lower front of air box. Rather than bust it I think I'll wait till I can deconstruct one at a self service 'automotive recycling facility'.

I'm trying to think back to when I had my '97 DX. The filter was on top of the intake manifold and ran to a resonator box where your filter is. If I remember right, it was a pain to remove, so I left it. That was back in the CAI days, so I just cut the tube and re-routed it. Most cars have this "clean" design (which makes my filter tube an expensive part to replace).

I'm sure you have the same problem -- there's a lot going on near the box intake -- hoses, coolant overflow tank, A/C lines, and the ABS unit for me. I didn't have much room to make a 90-degree bend and use the existing inlet, so I made a new hole. It's actually a bigger challenge to find cool air -- the tube snakes its way down to an opening in front of the wheel.

Tas- Nice! It looks good and was easy to install.

-Rick

[Christ]

RH77 - Would you not get even warmer air if you placed the heatshield back on, and put the tube behind the header?

Looks like you could make a simple metal strap that would bolt onto the header where the heat shield goes, that way you could keep the tube stationary, and still have the heat shield on...

And the heat shield keeps the header warmer which = better exhaust flow, so you'd be getting two benefits: warmer air and better scavenging of exhaust due to faster exhaust flow.

[RH77]

Originally Posted by Christ

RH77 - Would you not get even warmer air if you placed the heatshield back on, and put the tube behind the header?

Version 1.0, 3-years ago, drew the air from between the heat shield and manifold. IATs were way too high -- 180F in the Winter! The faster warmups were nice, but detonation wasn't. v1.1 moved the tube to its current location, which is far enough away, but never broke 90F. Removing the shield allowed "v1.2" to reach 100-110F on cold days, 140F on 40F+ days (fall is a bit unpredictable). This is in combination with a rad-block and has worked well since.

I still have trouble getting the transmission up to temp with straight-cold starts (no access to an outlet for the EBH). The TC fails to engage for quite some time, despite full operating temps and nominal IATs. The situation is long-term airport parking, cold-soak, and immediate entry onto an Interstate highway. The only thing I haven't tried is an undertray to insulate the transmission housing from direct cold air flow (which doesn't make sense, according to the shop manual's flow chart of TC engagement).

I've always had a problem getting the TC engaged quickly from a cold start. The kickdown cable has been advanced to allow solid shifts and quick TC lockup when fully warm for a while. It's probably the fuzzy logic in the TCU preventing perceived cold lockup.

RH77

[Christ]

Yep.

So what I was thinking while asking about putting the thingy back behind the other thingy... (your V1.0...) was to also incorporate a cool-air tube with a variable valve on it, (techie term for a motorized flap), that would be controlled by the (modified) output of the IAT sensor... so you could basically keep your intake temp optimal, +/- 15*F (reaction time)

Plus, it wouldn't be too hard to route cooler air, since there was that nice resonator under the bumper that you took out... I'm thinking a nice little valve there, instead of tape.

See what I mean? Plus, by the time you're done, it could look mostly stock... if that's a concern. (For me, it usually is.)

[RH77]

Originally Posted by Christ

Yep.

So what I was thinking while asking about putting the thingy back behind the other thingy... (your V1.0...) was to also incorporate a cool-air tube with a variable valve on it, (techie term for a motorized flap), that would be controlled by the (modified) output of the IAT sensor... so you could basically keep your intake temp optimal, +/- 15*F (reaction time)

Plus, it wouldn't be too hard to route cooler air, since there was that nice resonator under the bumper that you took out... I'm thinking a nice little valve there, instead of tape.

See what I mean? Plus, by the time you're done, it could look mostly stock... if that's a concern. (For me, it usually is.)

I see what you mean now...

I've had plans for a temperature-dependent intake system for a while (everything from an elaborate plan to use servos with butterfly valves and 2 tubes to using a simple used part instead). I'm told that I could source used parts from some 90's Volvos, GM throttle-body injection intakes, or old carburetted setups. I just need to take the time. The current setup works pretty well...

So, how much efficiency can be gained by adding back the manifold shield? It was a rattle point, so it was removed. As for the resonator, it was pretty bulky, so I got rid of it. It never really sourced cooler air, just air restriction and full-throttle sound deadening + weight.

[Christ]

Originally Posted by RH77

So, how much efficiency can be gained by adding back the manifold shield?

It was kinda a joke, honestly... it's marginal, if anything.

The idea is the same as with header wrap... keep the heat in the exhaust as long as you can, but if you're using it effectively for something else, I'm sure your WAI is overtaking any benefit you'd get from putting it back on.

Stop it from rattling - copper crush washers (read: fuel filter/rail banjo fittings) under each bolt, properly torqued to crush them a bit, should cushion the rattle.

Put grease on the bolts before you put them in.. they'll smoke for a bit afterward, but you'll still be able to get them out the next time you need to.


When I noted about wanting to put the heatshield on my aftermarket header, I basically plan on brazing some nuts to it that will act as standoffs, and bolt the shield back on, after using header wrap on the whole thing.

My concern is that it looks more like stock than anything...