Traum

Since my first summer with the beater Civic, I've been noticing how serious her already minimal power levels suffer from high ambient temperatures. Every time when the weather gets hot, the car feels like it has less than 1/2 the power it does during the winter months. With the factory air intake snorkel sitting right at the front passenger corner of the engine bay, this is hardly surprising news -- the intake is just drawing in hot air from the engine bay, and hot air is less dense than cold air, which means it also carries less oxygen for the engine to burn and create power. Measurements from my Scan Gauge readily confirms this -- on a typical summer day, the intake air temperature can range from anywhere between the low 40's (degree Celsius) to mid 50's. In the winter, it is usually in the mid teens.

I've been toying with the idea of a DIY ram air / CAI intake for quite a while. From research on various forums, I am well aware that the D17 engine respond rather poorly to the typical IHE mods in that power gains are often minimal. For my purposes, however, I am not really interested in additional power gains per se. Rather, I only want to look for a simple and effective solution to address the intake air heat soak issue that brings about a severely reduced power output. I don't mind the solution looking ugly or ghetto, but being the cheapa$$ that I am, it has to be cheap. With only a narrow but tall strip of space between the radiator and the front engine bay structure, there isn't a lot of room for the air duct to pass through from the grill to the intake snorkel. It is obvious that larger diameter air duct isn't going to work (and I want more air coming in to feed the intake, dammit!)

When I came across a set of the following vinyl tubing at Home Depot recently, however, I started getting ideas:


Instead of using a single larger diameter but squishable hose, could a similar air duct not be built using multiple smaller diameter hoses? And with that new idea, I fitted 3 sections of the vinyl tubing into the lower grill like this:


As you can see, the vinyl tubing is only held in place by some trusty zip ties. I fully admit that it looks ugly and ghetto as heck. But it looks like it will draw in some cold, fresh air once the car is in motion. It will draw in some cold, fresh air once the car is in motion, right? Right? RIGHT?

I didn't take any pics during the fitting / installation procedure. But essentially, the battery came out to give me some fitting room while I was fitting the tubes around. This is what the finished product looks like:


Here is a close-up of how the tubing came up from the grill. I wrapped some aluminum foil tape around the portion of the vinyl tubing that sits close to the radiator and engine coolant reservoir. We'll see how well that holds up.

On the intake snorkel side, there is only enough room for 2 vinyl tubes between the headlight and the battery. So unfortunately, one tube ended up getting routed to the middle, right above and behind the upper front grill, and not really doing anything useful.


Notice in the above pic how the vinyl tubing doesn't actually bend into the intake snorkel to feed air into it. When I was test fitting the vinyle tubes, I found that this particular type of tubing can very easily kink up if you try to bend it too much in any particular direction. With a kink, the interior of the tubing essentially gets blocked off, so it can't flow any air at all. With very little room between the intake snorkel and the engine bay wall, I couldn't get the vinyl tubes to bend into the snorkel without kinking, so I had to give up and just feed the vinyl tubes into the open area immediately before the factory intake snorkel.

With everything zip tied up, it was time for some testing.

Results

At the time of installation, overnight temperatures has been hovering around the high teens -- ~16 - 18C, and mid day temperatures are hovering around the mid to high 20's. Before the GDIYRA CAI is installed, the intake air temperature from my 13km morning commute would typically climb up to the mid to high 30's some time before the half way mark, and more or less stay there at a fixed temperature. With the GDIYRA CAI, however, the intake air temperatures climbs up more slowly and doesn't get as hot -- it only reaches the low 30's some time after the half way mark of my commute. Furthermore, one time when I am caught by 2 consecutive red lights that are quite close to each other (< 400m aparts according to Google Maps), the intake air temperature climbs up to 34C. But soon after the car is moving again, the intake air temperature drops down a notch and back to the 31 - 32C range.

For a less controlled test, it is fairly common for the intake temperature to read over 50C after parking the car with a warm engine, and letting the car sit under the blazing sun. Typically, once the car gets going again, the intake temperature would slowly drop back down to the low 40's (or high 30's at most), and stay at that range for the rest of the drive. With the GDIYRA CAI, however, I noticed that the intake air temperature is both dropping more quickly, and stabilizing at a lower temperature in the mid 30's range.

As two final bits of anecdotal results, I would also say the GDIYRA CAI seems to work better at higher speeds. This is hardly surprising news as we can all see how more air will get channeled to the stock intake snorkel as speeds pick up. Additionally, the GDIYRA CAI also seems to work better (with intake air temperatures dropping faster and by larger amounts) when engine speeds are higher. Again, this is hardly surprising since higher engine revs mean more of the cooler air passes through the intake.

With the lower intake temperatures, the beater Civic is definitely feeling livelier than before. I wouldn't say the GDIYRA CAI has given me any extra power; rather, I think it is more appropriate to say that the GDIYRA CAI has prevented me from losing power due to high ambient and intake temperatures. For a mere $10, I say it is money well spent!

lowlife9

is this real life ???

Traum

Huh? Not sure what you mean here, bro. I rigged up the ghetto mod and got all the temperature measurements myself via the OBD II connection with my Scan Gauge.

EM2abe

i see the method to your madness but jesus christ. thats downright hideous. lol. i would have found an old vacuum hose and fit it where the fog light goes, at least. then maybe somehow found a way to get it near the intake. i dont know. sheesh... lol i honestly laughed at this, but hey. if it serves a purpose, why not?

toyomatt84

iTrader: (1)

An easier way to pull colder air towards the factory snorkel, would be to temporarily remove the air box and fabricate a mount for some dryer hose leading up from in between the front of the transmission (right behind the radiator) and having it exit just under the factory intake snorkel. That way, when you put the air box back on, it covers up the dryer hose.

This will net you similar results at speed, if you angle the dryer hose a little bit or make a funnel for it to draw air from under the front of the car.

Traum

LOL~

I agree that it looks down right hideous. In coming up with the ghetto design, I wanted something that is as reversible as possible, so I decided against drilling through the fog lights opening cover.

And Matt, I'd say you are over-estimating how handy I am when it comes to working on cars.

speedjunkie_g35

Sorry but those tubes are so small and restrictive, that they are serving no purpose!

I did what matt is speaking of to my 94 civic. I used 4" dryer vent with a 6" velocity stack(speaker port) coming out of my bumper. I have noticed a difference after several passes down the track when the heat soak gets bad under the hood. Prior to installing this I would lose a couple tenths of a second after several back to back runs. I am running more consistent times now.

OGxruiner

so 3 small hoses > 1 larger hose > 1 really big hose? amirite?

James89DX

Nailed it

Traum

Undoubtedly, a bigger diametered hose would work better than my narrow vinyl tubes, up to the point where the custom intake hose is as large as factory intake snorkel. However, I would have to disagree with you saying that the hoses serve no real functional purposes. The OBD II-measured numbers speak for themselves -- it wasn't a huge drop in the intake temperatures, but it was a noticeable and objective measure. My anecdotal observations are also consistent with those measured numbers as well.

I am not knowledgeable enough in fluid dynamics to give an intelligent answer on this. However, conventional wisdom and common sense would suggest that the amount of (cold) air flowing through would depend on:

1) the intake hose's diameter, and
2) the intake air's velocity

I totally agree that my ghetto vinyl tubes are quite small, and I doubt they would be more effective than a single larger hose. But hey, 2 small hoses are still better than none, right?

speedjunkie_g35

The outer diameter may be the same but the ID is maybe half of what the OD is. You would do better with some 2-2.5" PVC pipe so you have larger ID allowing air to better travel to the opening.