DIY Intake
 

So at first when i thought of this idea I was excited to try a DIY intake but couldnt seem to find a real good way to do it without a Frankenstein coupler nightmare. I currently have the K&N typhoon pop chargers which, as you can see below has the maf tub and then the filters attached to a heat shield. I was thinking i could use the exsiting tube as my starting point and run something past the firewall but i didnt know what....

http://www.knfilters.com/images/l/69-7078TS.jpg

so a few weeks ago I was walking through a local performance superstore here in Sacramento (Tognotties) and saw some exhaust flex pipe ($21.95 for 6 feet). it was 2.5 internal diameter and fairly smooth even when bent.

http://www.the370z.com/members/cbtec...ke-install.jpg

So that got me thinking...I can use my existing MAF tube, couple on the flex tube, and run the pipe Stillen style since it was flexible. My buddy Dave (FYD) was laughing at me because he thought that it was another "dryer hose" mock up idea that I had but I thought that this could really work!

so here's what we needed:

• K&N Typhoon or any other MAF tube that is compatible
• 6 Feet of 2.5" exhaust Flex Pipe
• 2.75 - 2.75 silicone couplers
• K&N cone filter or similar (smaller tube filter works too)
• High Heat Spray paint
• **Optional heat reflective Tape

First take your bumper off and remove all necessary airboxes etc you need to cut out your firewall hole just the same as you would with the stillen G3 install. We marked our spot based on the diameter of the flex tube:

http://www.the370z.com/members/cbtec...ke-install.jpg

We used a dremmel to widen the hole and test fitted our piping to make sure that it would make it through.

http://www.the370z.com/members/cbtec...ke-install.jpg

After making our test fit we cut the pipe down to 2' 6" on the right and 2' 8" on the left (measure again to make sure)

once we made our cuts we put the filters on the ends and clamped them down. This tubing is very durable and wont crush easily. We pressed the filters with the pipe connected to where we wanted and installed the upper bracket. The filters that came with the Typhoon set up fit perfectly and were actually held in by the upper bracket quite nicely.

http://www.the370z.com/members/cbtec...ke-install.jpg

http://www.the370z.com/members/cbtec...ke-install.jpg

We took everything apart and moved onto the next step.

***FIRST OFF*** you must cover your AC lines to prevent them from being damaged by the tubing rubbing against them.

I used some fuel line hose and zip tied them on the lines to prevent this:

http://www.the370z.com/members/cbtec...diy-intake.jpg

Next since the flex tube is not galvanized it can rust. the way that you can prevent that is by spraying it with a high heat Rustoleum spray paint.

http://www.the370z.com/members/cbtec...diy-intake.jpg

http://www.the370z.com/members/cbtec...diy-intake.jpg

The way you cover the interior of the flex pipe is by "fogging" the inside. You hold the can of paint about 6 inches from the opening and spray directly into it. I did 2 coats to make sure everything was covered.

http://www.the370z.com/members/cbtec...diy-intake.jpg

After the paint dried i wrapped the pipe that was exposed to the engine compartment with a heat reflective fiberglass tape i got on Amazon for $15. it stuck well and had no issues with covering 1/3rd of the pipe.

After the wrapping was done I put everything back together the same as the original mock up with the 2.75 - 2.75 coupler and tightened it all down.

Final product:

http://www.the370z.com/members/cbtec...diy-intake.jpg

http://www.the370z.com/members/cbtec...diy-intake.jpg

http://www.the370z.com/members/cbtec...diy-intake.jpg

All in all the whole DIY cost me around $50 and there is a noticeable difference in performance. Before doing this my average temps were around 20-25 above ambient temperatures based on freeway driving.

http://www.the370z.com/members/cbtec...orque-copy.jpg
http://www.the370z.com/members/cbtec...84257-temp.jpg

With this new piping the average freeway temps are between 5-6 Degrees above ambient temperature. to me this is well worth the additional $50. For some, they may argue, "well why not just spend the extra $100-$200 and get a G3?" For me, a nice well done DIY that saves me that $100-$200 and does the exact same job as the higher priced competitors is more of a feeling of satisfaction.

Not worried about the rattlecan flaking off eventually and potentially hurting the vroom-vroom or sensors? I say this when one of my cars has no filter or room for air filter at all.

Interesting to see how this compares in temperatures and laminar flow to other intakes. It seems ducting in cooler air using flexpipes to the shorter intakes might have the best of both worlds, but Kudos for a DIY.

Not bad. I'm sure it will perform better than oem but those ripples in the tubes are not going to help with flow. What i did with my typhoon intake was flipped it around and run 3" piping to the front.

http://i1380.photobucket.com/albums/...psdlum3cmi.jpg

I thought about this but stayed away because the inside on the tubes are not smooth, Turbulence = :/.. I how ever keep the stock air boxes and added a air intake mount plate to each one of the rad support ram air ducts, used silicone elbows and air ducts at the ends to make my own cold air intake. See my mod stock air box thread.

Great idea and excellent execution, even if the extra turbulence turns out to rob a little power. Rep'd.

It would be interesting to see some data on whether or not the cooler air offsets the added turbulence.

It might be worthwhile to get someone to bend some tubing for you. A good custom muffler shop should be able to do it.

Thank you sir! I did look into some muffler shops locally to see about doing some pipe bending for me but most shops around town did not do mandrel bending. And in order to get the tubing that I wanted, done it would have been cost prohibitive unless I had a large lot of pipes to bend. From what I understand a little bit of turbulence isn't bad, but I could be wrong. But the interior of these pipes are quite smooth with only a few ridges to create the turbulence. They're not like large dryer vent hose that is quite ridged and can definitely cause a lot of turbulence.

Another issue that I didn't bring up was with having the typhoon sitting in the engine bay; while at a stoplight, the maf temperatures would increase anywhere between 30 to 50 degrees hotter in the summer time while waiting for the light to change. Which would in turn cause the motor to bog down when launching off the line.

True, I thought I had shared my story with Ruben about the dryer hose intake on my Honda Civic 12 years ago in hopes to prevent him from doing it, not to encourage it.

However, these supplies impressed even me. The flex pipe is very smooth on the inside and difficult to bend (had to wrap around my knee and pull with both hands). The filters attach to the piping very securely. This particular pipe was very rigid and not as bumpy on the inside as you might expect.


Hi temp engine enamel, no, this is not a concern. It's main purpose was to prevent rust, as this was bare metal.

True, there is some turbulence caused by the non-smooth inside of the pipe, however not as much as you would think. Additionally, some turbulence in the intake is a good thing. I was genuinely impressed and excited by the pipe Ruben had found. I'm sure the benefits outweigh the cons with this particular piping.

Overall if we were to do another, I might bump it up to 3" piping which would get reduced to 2.75" at the MAF and K&N tubing, which would definitely factor out any turbulence due to the flex pipe.

Pics and "most of the work" credit goes to me, FYR. Just kidding, I don't want my name associated anywhere near this thing ;)

Also, good work with the write up Ruben, nice detail and pics.

you can always buy cheap mandrel bent tubing here

Nice job!

We thought about piecing together pre-bent pipes or even maf tubes, as you can get those in different sizes with different bends as well. Only problem was we didn't know the exact path and dimensions we needed. We do now, and when we do my car, that's what I'll use! FYR ;)

do you have any more pix of the coupler and pipe going through the firewall?

yeah but the Jew will end up spending a lot more for his set up than me :P

FYD give me my heat shields back bish!!

thank you... and Nice find...i didnt think about looking up mandrel bent piping on ebay. My only concern was it not being specifically bent for this application or fitment issues.

How long is each pipe?
Nvm I over looked it lol

Well done Scott! i might have you beat on cost though :P

Had i seen your DIY i probably would have done what you did

I could see some young kid driving a civic doing something like this but come on guys don't do this to a 370z... Not to mention that the tubing isn't even smooth inside and is going to cause turbulence. If you can't afford an intake just leave it stock.

Thanks for the bump, it's not that we couldn't afford a brand name intake, it's that some people get a bigger feeling of accomplishment and sense of pride making something themselves, equivalent to something brand name, for a fraction of the cost. You never built a dog house from old pallets?

I'm sorry, I've got to comment again. That so many people are under the misunderstanding that any intake pipe which is not smooth must create air turbulence, which must be bad for your engine...


Without getting into aerodynamics, venturi effect, and optimal velocity equations, is a golf ball perfectly smooth? Are an airplane's wings perfectly straight? Do the factory rippled intake tubes on billions of cars create turbulence which would reduce the efficiency of said car? Is some / any air turbulence always bad? Think about why...

http://shop.achtuning.com/productima...ke_Surface.jpg

Sorry can't agree. Surface drag has many factors including the air temperature (i.e., density), velocity, compressibility etc. Hence, given the relatively low velocity of the air in an CAI, and the many turns of an engines CAI system, I'd still say that smooth is better.

Correct, and if it's reduced surface drag and a smoother air flow you are trying to accomplish then congratulations. However, if it's horsepower you are trying to accomplish (as with an intake), then you want more air as opposed to smooth air, as well as some turbulence (see: volumetric efficiency) to aid in mixing with fuel, which is heavier than air.

What do you think a turbo does? Makes the air really smooth going into the engine, or crams a crap ton of air into it without worrying about how "turbulent" it is.

This is where most people go wrong. Yes, usually when trying to reduce drag, smoother = better. But you're not trying to reduce drag here, you're trying to increase volume. More air = more power, smoother air !=(necessarily) more power.

Why is intercooler piping smooth then? So your saying it would be better if it was ribbed? Your logic is way off. You don't want turbulence.

The problem is the overly sensitive MAF's on this car -- they are VERY sensitive to turbulence.

If the home made intakes are sufficiently secured, should work okay (heat soak being the only issue if unshielded). If they are moving around, i can pretty much guarantee you you will see evidence of losses on a dyno due to random misreads of air flow...

EDIT: I wouldn't have painted the inside... that is almost definitely going to flake off and make its way into your engine...

A for effort! But... this car is an icon, not a Honda Civic you had in high school. Ghetto air intakes like this should not be on any Z car, including a CRZ!

I showed this to a friend who worked at K&N for a long time, and he cringed.

He said he's never seen a flowbench or anything other instrument in testing produce better flow results from corrugation vs. smooth internal piping. Which is probably why almost every single intake kit every produced has smooth piping. :confused::confused::confused:

He also said there may actually be a small increase in power due to increased velocity due to the tube length (which is the benefit to longer tubes, not temperature) but an ebay short ram would likely net the same power gains.

Both pipes are secured with the MAF tube as well as at the bend and the filter by the bumper brace, there is no movement. Also heatsoak would be an issue for a G3 as its chrome pipe and completely unprotected

As far as spraying inside, the paint is enamel not typical wicker basket rattle can spray so there is not going to be any kind of flaking unless there is something scraping it off on the inside which also would need to be pretty sharp to do so.


the piping is not "corrugated" which stays corrugated even when bent. Example below:

http://images.orgill.com/200x200/6353395.jpg

The piping is "flex pipe" which has a the same smoothness shown below internally when bent. there is minimal undulations in the piping

http://upload4.smarteast.com/%7B0A3B...2816471605.jpg

I would be on the same page as all of haters if it was truly corrugated piping as that would not be conducive to fairly smooth air flow.

I never owned a Honda so i wouldnt know. Again as Dave said, this is for the love of DIY and not the person that wants to spend the most money over others. By looking at the finished product you would never, ever suspect that it was a DIY unless i pointed it out to you. Most look at it and ask me if its the Stillen G3 set up. I have done several DIY's on this car that work very well and are less than 1/3 the cost of your high priced retail MODS.

This DIY modded Z will keep up/beat any other similar high priced modded Z.

Doesn't Nate have G3's, a tune, FI exhaust, all that suspension work, etc...? Wasn't he the fastest of all of us for a while, until you figured out that map 1 vs map 2... Who's the fastest now? Yea... That's all I need to know.

...Yeah, but I'd still rather have a CRX (like a high school kid) than a CRZ.....

It's a damn air intake. You guys are all arguing over 1hp.

Also, if this car was carbbed or not warmed up, turbulent air could help atomize the fuel.

This reminds me of when my buddy tried using PVC as intercooler piping on his Eclipse GSX :rofl2:

That all sounds reasonable to me :tup:

I for one have nothing against DIY bang-for-buck projects. There's plenty of commercial products where you pay for crap or overpay for something that could be assembled/obtained for far less. If you've put thought into it and it works, you are set.

Bought or home made, tho', you might think about swapping back in stock airboxes, getting a baseline dyno, and then dyno testing yours to ensure it is working as desired.

If you do, and can get hold of some K&N filters, you could have a three way shoot out.

It depends on where and how much tho'. Many OEM MAF's have airflow sraighteners to reduce tumble effects and thus take more stable readings as air passes over the hotwire. Ours doesn't and is thus very sensitive to misreads when pre-MAF turbulence is introduced.

Also, we're talking air ingestion into a system ("suck") not the mixing and compression of air and fuel ("squish"). At that point, turbulence is not really an issue again until we get to its expulsion ("blow") to facilitate optimally timed post combustion (bang) events to re-create vacuum inside the cylinders (ready to "suck" again). However, internal turbulence can work against effective mixing, its just less of an issue as the aim is compression at a fixed point (timed spark event).

VE is another issue entirely -- effective cylinder filling, usage of the mixture, and ultimate emptying of post-combustion gasses. With a turbo, some of that is re-routed, to be used to spin the turbine, but, yes, restrictions or poor flow characteristics matter there too.

On the intake side of things, its a balance between smooth flow and speed vs. volume (faster in a narrower tube, slower in a wider tube, all things being equal), provided the engine can optimally accommodate the volume of air being drawn in.

As to the flex-tubing on the Z, that's strictly convenience (and maybe a bit of extra outer cooling) for Nissan -- "smooth tubes" definitely make a bit more power than the OEM ones as verified on several before and after dynos -- same diameter, smoother transitions, less flex, less internal turbulence, more airspeed, improved flow, better power.

Straitened vs greater turbulence is also a factor even in filtering incoming air. Straightened air simply flows faster, all else being held equal.

On a somewhat related note, you will have greater filling with hot over cold air, as the gasses expand, but you have less oxygen (reduced efficiency) taking up the same volume, thus, less power to be made during combustion events... same is true at higher altitudes as well.

BTW, compressors work by functionally improving VE by cramming more oxygen into the same space (available volume of each cylinder), not by simply creating a greater volume of gas. It's the number of oxygen molecules (and, well, a concordant volume of fuel) that matters.