DIY CAI alternatives on NA6?

[speed]

Just thinking outside the square on this one.

Ok so I'm aware of the mania CAI through the firewall but what other alternatives are there?

I would like to reduce the amount of plumbing and run it under the drivers side headlight, mount my AFM in there and have a pod filter in front of the radiator.
Obviously I would need to do some cutting (2 holes) and extend the AFM wiring.

The whole purpose of this is to not have a bunch of plumbing in the engine bay and to shorten the plumbing in the process.

I suspect that any cutting will have to be reinforced.

Anybody else done this before or do you have any info or suggestions that may help me?




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[chrisearl88]

FYI shorter is not necessarily better, you tend to loose low down torque with something like that. The mania is very well proven. Use the search function, a guy did some testing of the resistance of the various components in the intake system, results are quite interesting and will lead you in the right direction.

[chrisearl88]

http://www.autospeed.com/cms/article.html?&A=110680

[Apu]

Talk to NitroDann - he's got a few options

[speed]

Thanks Chris and Apu.
Certainly don't want to lose any torque.
Will message Dan when i can.
Thanks again!


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[mitch_f1]

IMG_7683 by modena photo, on Flickr

Aluminium flex pipe and PVC pipe sika'd into the airbox

[droo]

keep in mind, every sharp bend before the throttle on an NA engine, and every bend before the inlet of a turbo setup robs low and midrange torque.
Piping going past the radiator (engine bay side) will get heatsoak when stationary/traffic idling and will never fully recover (as in, getting back to it's previous lowest inlet temp) even if highway driving for 2 hours.


I've used half a dozen inlet intake configurations, ranging from the typical cowling style (noisy induction noise, only heard by vehicle occupants) an NA8 arc chamber (slight/noticable difference in very low end torque - ie, air con on, and accelerating from standstill 1500 to 2000rpm - slightly but noticeably less hesitation from the air con load) and a custom shorty style as well as two variations of a design i havent seen on anyone elses roadster.

First of my shorty designs was:



This allowed for quiet in cabin driving on full load (no loud resonant drone when driving under constant load of mountains/hills in high gears).
Improved fuel economy.
Improved throttle response over stock on highway driving. No change on city driving economy.
Reduced but not ideal inlet temps (not ideal for what i was chasing)
On idle in traffic, heatsoak eventually took place.
Had this setup for over 7 months.


Second version (not on video)
From the throttle, 4cm straight then bending nearly 45deg toward the driver side from via the AFM (na8) and then bending about 45 deg facing the front of the car pulling air from between the radiator and driver side headlight.
This was about 35cm long from filter to throttle.
Throttle response was outstanding, good midrange feel, 0-3 degree above ambient air temps (recorded at the throttle inlet), significant increase in km/L on highway driving and no annoying cabin induction noise. Heatsoak never exceeded 5 degrees above ambient in extended traffic in melb during the 40deg summer heat. Dropped rapidly to 1-2 deg above ambient when moving, and never deviated more then 1 degree above ambient (usually staying exactly ambient) at highway speeds.
No cabin drone from induction at all, but as above, easily heard reflecting off buildings/barriers etc back into the cabin.
Improved fuel economy over previous intake setup on highway cruising. No change on city driving economy.
Had this setup for 5 months, including over the summer.
Downsides were clear risk of water ingestion during rain due to the location of the intake, especially when the headlights were up while also using a thin sponge filter. Having a thicker filter also picked up hotter air as it wasnt flowing smoothly from outside, rather, picking up air from around the radiator and headlight and sucking in from behind (from the engine bay). Intake temps with a thicker sponge filter rose 4-8 degrees. (never being lower then 4deg higher after the car had warmed up, in any condition)

My current setup is an intake from below the (australian) driver side headlight. Overall length is 20cm longer then the version above. I've also made a large volume plenum underneath this headlight, ahead of the driver side wheel with a fibreglass shield blocking the wheel well, floored off with fibreglass in the form of an under tray and isolated from the radiator. I have a pod filter for easy replacement and draws air from the main front body kit air dam. Cornered off by the tapered edge of the body kit (driver side corner) the volume of this plenum is about 40 Litres.

Benefits of the filter being surrounded by fibreglass enclosure:
Nice induction note from outside the car. (described by bystanders as throaty during regular common sense driving)
Nice induction note from inside the car without drone. (both especially above 80% throttle)
Inlet air is 100% isolated from the engine bay, only pulling in external air.
Plenum volume helps to disperse heatsoaked air from extended idle in traffic.
Dramatic improved fuel economy (along side a simultaneously modified throttle, additional large frontal undertray and aftermarket body kit design)



Despite the sharp angle in the design, i've flared the piping diameter around this bend.


Internally, 50% of this pipe is straight through.

Draped in carbon fibre, i've dubbed this my "blue tongue" intake.

This pic shows the installed setup, with the driver side headlight removed.


As described in the video, the finished version of this clears now the headlight actuation.
The pod filter is now completely enclosed, isolated from wheel well dust, water, and the engine bay.

I wasn't initially keen on doing this design as i never wanted an NA setup having to lift air UP through piping.
There is a slight but noticeable decrease in midrange throttle response 3500-4500rpm compared to the previous setup but it utterly sings at WOT.
I've now travelled nearly 4000km on this setup both on highway cruises and mountainous roads. I will probably make alterations to the pipe design to try and smooth it out more, reducing the bend hopefully reclaiming some of that midrange throttle response and maybe a bit of extra economy at the same time.

Overall, this is my favourite setup, it neatens up the engine bay significantly, sounds good from the cabin and from the outside together and is the best setup i've done for fuel economy. I'm still to do some work with making (as best as i can develop) tuned length lipped piping from the front bar air dam to the filter plenum.

Sorry for the long post but i have looked long and hard for info before doing this last project. On finding nothing of benefit i needed to do it myself. Could have turned out sh*t but i typically couldnt get a straight answer (or any direct answer) from online forums on the setup i wanted to do.

[speed]

Wow Droo, thank you very much for your post. This is exactly what I was after. Being a NA6 my AFM is bigger than yours.
Do you have any pics showing what it looks like in front of the radiator or is your filter still in the section under the headlight?
Thanks again!!!


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[Snowmotion]

Great write up Droo.. Very inspirational.

[droo]

I don't know how the na6 MAF behaves if it's not level. If its facing down, i don't know if gravity will will load the flapper and cause issues with the electrical readings.

Also behind a stock front bar, the space is tight. I can't speak for being able to fit it there and the space and piping considerations, but give it a go. Feeding air from in front of the radiator would be great if you can manage to keep the pipe radii not too sharp or you'll loose out on the benefits.

[speed]

Thanks Droo. Have considered the MAF and will keep it as close to level as possible. Might not get to it until a couple of weeks though. This would all be easier if I went for a narrower radiator, as I wouldn't need to cut the holes and could get away with less bends but I'd imagine the core would have to be thicker. Hmmm lots to consider but worth it.


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[droo]

I hear you. The radiator and it's return pipe placement position is pretty dumb. I don't know why that placement took priority over the air inlet design, it does nothing but obstruct the piping. Especially so ok the na6 and also na8 design. If I had skills in welding and metal fab, I'd probably have chosen a narrower but thicker radiator, and have a nice straight thru inlet pipe to the throttle.