OT: Cold Air Intakes... Questions, Length of tube Options

[Qarl]

Not 914 related....

Does anybody know anything about cold air intakes?

I have seen some different CAI for various cars. Usually some sort of filter, a mandrel bent pipe, then a mass air flow sensor adapter and some Samco silicone connectors and straps.

How does the length of the pipe between the filter and the MAF Sensor affect performance?

Is there an upside/downside to longer pipes, straight vs. curved pipes, pipe diameter, etc.?

I don't know nothing 'bout no cold air intakes?

Thanks.

[meares]

don't know but i'm interested also!

[bd1308]

it's the overall curvature to the system that affects performance, the BIGGEST hit on performance is when the filter resides in a box, like the 914 stock system. I take it off and i get much better performance, esp in the 4k rpm range (well i used to....)

[bd1308]

the CAI system is DESIGNED not only to lengthen and create turbulence in the air going through the system, but also is specially designed to pull in the COLDEST air in the car, usually near the front fender or in the fender......as far as i know, the MAF sensor is unaffected bc it measures air volume and not air flow......

[meares]

does that mean the throttle body is exposed?

[bd1308]

QUOTE (meares @ Jun 7 2005, 02:22 PM)

does that mean the throttle body is exposed?

no the CAI system is complete from the throttle body connection to the point where the filter is....nothing is left exposed....in my case yes i was being stupid, but CAI systems are designed to be a better option than the stock system. In my case i was testing only.

[Jakester]

I don't know a lot about them, but from my understanding, the idea behind the CAI is twofold. One: the filter upgrade allows the engine to "breathe" easier. The reason you improve flow through the exhaust system is the same - to improve the in and out flow to the motor. Two: To direct the coldest air possible into the engine. This is not for cooling the engine heat, but because cold air is more dense than hot air and therefore affords more energy to the combustion process (the same is true of fuel temps to some degree). Every car by design has a "CAI" in that there is always some mechanism by which the combustion air is collected from the outside air (usually through the grill area) because it is well-known that hot engine air into the intake is bad (from a performance point of view).

The creativity has to happen when you upgrade the filter from a restrictive box to a free-flowing cone (typically) and then you are faced with "now where do I get cold air from?"

I am unfamiliar with any theories about bends or turbulence within a throttle body, but, in general, turbulence is an inhibitor to efficient flow. Turbulence is good in terms of mixing, that is not relevant with respect to port injection systems (except within the combustion chamber but that is WOT).

The biggest gain is in the change from the restrictive boxes and long runs of tubing that usually accompany stock intake systems to the shorter, more free-flowing runs that a well-engineered CAI has. When you have a column of slow-moving air, the longer the column, the longer it takes (and more energy) to get that air moving fast. Thus, shorter throttle bodies are better from a throttle response point of view.

There is some sacrifice made for low end torque that I've heard about, but I do not understand the mechanism for that.

Here is a pic of the CAI setup on my Passat. I noticed a significant improvement in throttle response with this upgrade and it sounds COOL! (IMG:http://www.914world.com/bbs2/html/emoticons/cool_shades.gif)

[Qarl]

Thanks... I am looking at CAI for the Elise.

There are three designs out there right now. All three are distinctly different in design and price.

CAI # 1 - Designed by ITG that makes a lot of F1 air intakes - $699.00

The ITG filter has a carbon fiber housing around the filter, that ends up pointing in the vicinity of the air inlet on the rear fender. Supposedly the filter housing is designed for optimum flow around the filter. Note, however, that there is no heat shield separating the inlet from the rest of the engine behind the wheel well. The installation of the ITG filter necessitates the removal of the wheel well liner. So theoretically, some warm air from the engine can recirculate back towards the inlet. But supposedly, the carbon fiber also acts as a heat shield from the engine since the CF and resin aren't good heat conducters.

(IMG:http://img239.echo.cx/img239/5622/97zn.jpg)




Next candidate... ForcedFed Cold Air Intake. Forcedfed is well-respect turbo outfitter - Cost = $425.00

Forcedfed, has a relatively straight MAF adapter tube, that attaches to the intake via some silicone SAMCO fittings.

(IMG:http://www.cpdserver.com/elisetalk/pic/tech/ff-cai/ffcai17.jpg)

They also designed a heat shield that separates the engine compartment from the filter. So only the air coming from the fender inlet and wheel well gets to the filter.

(IMG:http://www.cpdserver.com/elisetalk/pic/tech/ff-cai/ffcai20.jpg)




Finally, the Pipercross CAI- About $575.00

This system is a new for the Elise and comes from Pipercross in England. The intake is much, much longer, but puts the filter literally right at the fender inlet.

(IMG:http://www.914world.com/bbs2/uploads/blog-1118196986.jpg)

[Aaron Cox]

option 2 - has a heat shield. nice bonus..

option 3 - directly into cold air flow land.... (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

[Qarl]

Speaking of CAI... here is a filter change for the 914 on ebay (being sold by 9xAuto, cough, cough!)

http://cgi.ebay.com/ebaymotors/ws/eBayISAP...&category=38634

(IMG:http://www.9xauto.com/images/914filt.jpg)

(IMG:http://www.9xauto.com/images/914int1.jpg)

Not sure how "cold" the air is in the engine compartment.

[TimT]

Usually the filter element is questionable.. The oil required for the filter can play havoc with some MAF sensors..

This is of course what I have picked up from other thread on other sites

nuther tid bit, when I picked up my F250 Diesel, they dealer mentioned they knew all about Cold Air Intakes, chips etc.. and they may void the warranty

[Qarl]

From what I have read, manufacturer cannot void a warranty for modifications such as cold-air-intakes unless the manufacturer can prove that the addition of the modification directly caused the problem being addressed by the warranty.

[JmuRiz]

QUOTE (Qarl @ Jun 7 2005, 06:59 PM)

From what I have read, manufacturer cannot void a warranty for modifications such as cold-air-intakes unless the manufacturer can prove that the addition of the modification directly caused the problem being addressed by the warranty.

But they can refuse to work on the car (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) If you take it in for service, I'd put the stock system back on, just to be safe.
Having said that, I'd go with option #2. The #3 option is cool (har har) but if you are in the rain at all you might get some water into the engine and mess up the MAF and all that stuff. The #2 option is nice with the hoses, heatsheild etc...plus if they are turbo guys I'm sure they think more about the heat/intake temp relationship. Good luck!
BTW I'm in the process of doing an MAF, velocity stack and intake mod on my A4 using the stock airbox, good stuff.

[Rough_Rider]

Like the VR6 shield & kit. I used to have a Corrado which we built the original kits using aluminium sheet. It makes me laugh the prices manufactures charge for this stuff.

Anyway too cold air kits.

Basically you want to aim for the coldest air possible directed into straight into the engine. Without contracting heat soak or pre-warmed air from engine bay. Watch out for the sucking water problem.

The carbon box has 1 cool trick. With the neck expanding into a chamber it effectively slows the velocity of the air coming in. This can create a mild increase in air pressure, maybe 0.01 bar. The F1 & Champ boys use this trick.

If you've the time experiment with tubing lengths & inlet position. Simple plastic drain pipes & bends from your local DIY store will suffice for test, then make some metal items once finished.

Note on airfliters, a clean stock filter should flow within 1% of a nifty cotton or foam filter. Plus it filters better. The choice is yours, but i'd stick with the oem stuff. Just change / clean it more often.