My take on a modified stock intake . . .

[Ryan T]

Intakes must be the most-debated topic here on 8thGen, and it’s probably like that with most cars. Having an R18, your options are pretty slim, and DIY Customs can lead to scary results. I really don’t want a CAI, because I live in south Florida, and I have to run through pretty deep puddles when it rains where I live and where I work.

And it’s raining while I type this!

An SRI doesn’t have enough gains to justify the cost, and the downsides of compromising the factory intake are just too great.

So I’d consigned myself to the K&N drop-in filter. But I didn’t want to just disconnect the hose on the front of the airbox and suck in all that hot air, but at the same time, the resonator makes that whistling/vacuum cleaner song.

So I got some 4” flexible duct from Pep Boys, and a 3-4” silicone 90 degree elbow.

I had to remove the battery to get at the bolts for the first pipe going to the resonator. The second pipe coming from the resonator is attached to the fusebox but it just pops off.

Then I had to remove the bumper to pull the resonator out. It’s held on with two bolts.

The problem I then faced was that the stock airbox hole is only 2.5” (I measured it with the hose installed, duh). So I crammed a bunch of the flexible rubber hose into the elbow and it was tight, airtight, and still flexible.


I wanted to run the 4” duct along the same path as the stock intake, so I had to get it through that tiny slot. What I did was cut the duct in half, and pushed a couple inches through from the engine bay toward the outside. I had to push one side and then the other. Then I used the spiral of the duct to connect the two halves back together a couple turns (it was very tight), and then for insurance, I put the supplied rubber coupler over the joint.

I secured the pipe to one of the bolts from the resonator with a zip tie, not that it was going anywhere. I ran the end of the tube up by the opening to the quarter panel.





It’s a little tight-fitting on the engine side. The elbow allllmost touches the lower radiator hose, but I understand that that’s the cool coolant going into the engine, so it shouldn’t melt the silicone. In fact, after driving about 30 minutes, I stopped, and felt both pipes. Both were warm but nowhere near uncomfortably hot to the touch.

I was able to get the battery back on just fine. The coolant reservoir, on the other hand, no longer fit on it’s little stand on the battery cage, so I fashioned a zip-strip harness for it and attached it to the front sheet metal. Everything is nice and tied-down, with nothing rubbing or rattling around.

Now as far as performance, I did this in conjunction with a K&N filter so there is a noticeable gain in throttle response (what I was really after), and it feels a bit faster.

To improve it more, I’m planning on drilling vents into the wheel well liner, so that cooler air comes into the quarter panel, behind the headlight, which is where the intake is sucking from.

The sound is MUCH improved with this intake. It has a lot more balls, but it also has a more articulated tone than I experienced with just removing the hose from the airbox. It's less droning. Also, that annoying whistling sound I get when accelerating normally is gone.

Total cost for the mod:
Elbow: $25 www.siliconeintakes.com, Duct, $30 Pep Boys, Filter, $48 Advance.

PS-while I had the bumper off, I swapped the horn. I cannot recommend this enough.
I HIGHLY recommend FIAMM’s Freeway Blaster (Low Tone). It sounds SO much better in person than on the website’s clip. Very piercing and authoritative. At only $15 at Advance, it’s a no-brainer.

[CDRoot]

so what did u do exactly? Just change how the air goes into the airbox? Did you remove the resonator in the end or just modify it?

[Ryan T]

Yes, I removed the resonator. The resonator is a big plastic box that restricts your airflow for the purpose of quieting the engine. You can see it on the right side of this picture:


Also, I changed the intake from the box forward from 2.5" or smaller piping to 4" piping.

Here's one of the wimpy stock pipes. It flattens and narrows out at the end there. Very small.
Here's the diameter of the duct I put in.


When I put a high-flow filter in the car, I wanted to make sure it wasn't breathing through a straw. Yes, it still steps down to 2.5" at the inlet at the box, but there's nothing I can think of to remedy that at this point.

And it's still better than breathing through this:

[aki]

A major performance sapper is turbulence--and the issue I see with your intake is that pepboys flex pipe. All those ridges leads to more turbulent airflow, meaning less air can pass through than a smooth pipe.

[Ryan T]

Originally Posted by aki

A major performance sapper is turbulence--and the issue I see with your intake is that pepboys flex pipe. All those ridges leads to more turbulent airflow, meaning less air can pass through than a smooth pipe.

Okay, yes, I agree that the duct I used wasn't the optimum duct for a 4" but it's GOT to be better than the 2.5" smooth duct that was there.

[CDRoot]

hey thanks a lot for the picture...now I finally know what a resonator looks like! But following this thread
DIY Quick Intake Mod

I removed the rubber tube that enters the stock airbox. By doing this, it bypasses the resonator completely then right?

[Ryan T]

Originally Posted by CDRoot

I removed the rubber tube that enters the stock airbox. By doing this, it bypasses the resonator completely then right?

Yes I did that. This seems to have more giddyup than that did though, cause that sucks hot air coming off the engine and radiator.

[CDRoot]

thanks so much ryan.

[xtant21]

Not trying to critique because it sounds like you did some good work here. My only question is to the increase in the tubing size...well more so where the change took place.

Air flows faster when going from bigger to smaller...it speeds up through the smaller passage...so...I would want the 4" inlet at the intake of the intake and the 2.5" at the TB. This would help speed the flow of air into the TB and help get cooler air there faster which is what you want.

Not sure if that is in essence what you have or if it is opposite...just trying to clarify. If you do have it going big to small...sweet. If not, I'm wondering if it really is helping you or not.

Nice work nonetheless.

[Ryan T]

Originally Posted by xtant21

Not trying to critique because it sounds like you did some good work here. My only question is to the increase in the tubing size...well more so where the change took place.

Air flows faster when going from bigger to smaller...it speeds up through the smaller passage...so...I would want the 4" inlet at the intake of the intake and the 2.5" at the TB. This would help speed the flow of air into the TB and help get cooler air there faster which is what you want.

Nice work nonetheless.

I'm definately with you there.

I was thinking about the Bernoulli effect when i did this too. the way I have it set up for now, the bernoulli principle speeds the air up when going from 4-2.5" at the airbox, making the air come at my filter faster. Then the filter slows it down (and should smooth a lot of the turbulence caused by my non-smooth pipe), and kills some of the positive effects of this, I know.

What I was trying to accomplish with this was to get more air TO my filter, since I was going from paper to K&N. I think I was pretty successful at that.

Thanks for your comments, they actually gave me an idea. I'd love to cut out the current inlet to the stock air box and attach something like this:

That way I don't get the bernoulli effect until after the filter, when the speed will help a lot more.

[Phalanx]

VERY interesting. Once you get a lot of the quirks worked out, I may consider going back to a modified stock intake instead of my K&N SRI. I already have the K&N filter as I had that before I got my SRI.

I must Say Ryan, youve been here a very short time and I can tell you'll be a valuable asset to this site. Nice work!.

Not that theres going to be a huge difference in power, but do you plan on doing a dyno to see what kind of #s you get with your modified intake?

[Driversound]

I know they sell the plastic pipes at Home Depot and with the right amount of heat, you can actually shape it. I was thinking about doing a CAI with it with a modified maf. Lately, I just haven't found the time.

[Ryan T]

@ Phalanx, thanks a lot. I really appreciate the kind words. This site is awesome, it's given me a ton of ideas and know-how, and I'd just like to give back wherever I can. Though, with the intake, were you referring to it as it sits now or the idea with the PVC Bushing?

Either way, I don't think I'll dyno it. First of all, I don't have a baseline bone stock dyno, though I guess putting a paper filter back in there would make it stock enough.

My mantra has always been that I'm not looking for a ton of gains, just better throttle response. For those purposes, the butt dyno is plenty enough for me.

Originally Posted by Driversound

I know they sell the plastic pipes at Home Depot and with the right amount of heat, you can actually shape it. I was thinking about doing a CAI with it with a modified maf. Lately, I just haven't found the time.

I looked at my Home D and couldn't find anything of the sort. Lowes had 4" Aluminum semi-rigid dryer ducts but there would've been 2 problems there. First, they don't spring back when you cram them in between the wheel well liner and the frame. Second, I would've needed a big coupler to join it to the silicone elbow I did. This, along with the high-heat black spray paint I was going to coat it with, brought the cost back up to about the cost of the duct from Pep Boys.

[Driversound]

PVC pipes. They sell them next to the rubber couplers. The only thing I'm afraid of is that they will melt.

[Ryan T]

If they were in direct contact with some metal part of the engine I would worry. To be safe, you could always coat them with some of that Rustoleum High Heat paint.

[ryker]

Why not route the air intake to the foglight area? Could get the ramair effect and cooler air.

I've got a air temp gauge in my car (SGII) and the air temps are stunningly HIGH!

[4ADAM12]

read the first post and you find out why he didn't route it to the fog light area. As far as high heat paint, I don't think it will keep whatevers painted with it cooler, it just means the paint can withstand high temps without burning off. The PVC under the paint will still heat up the same.

[deestylez]

Sounds interesting.

You should get some Dyno results and post it up after your finished. =)

[maximus20895]

^word