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Old 07-19-2009, 01:04 PM   #1
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I think I've found out why people have FE gains with their CAIs...

If you think about it, a lot of people's CAI kits are really WAI...

http://www.camaro5.com/forums/showthread.php?t=33172
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Let's all sit back and take a deep breath of fresh air (cool air). Now, crawl under the hood of your vehicle, lay across the engine, close the hood over you and take a deep breath of all that hot air from the radiator fan (160?-200?), engine (160?-220?) and headers (up to 1000?). Who the hell would do that, you say? Well, when companies sell you a "cool air" kit with an exposed underhood filter that sucks in the same hot 200? air from that heat soaked engine compartment, how do you think your engine likes all that hot power robbing air vs. theOEMfactory set up that inhales isolated ambient 70? fenderwell air? Then there's all that hot air the fan blows around. Remember the fan. It sucks hot air in off the hot radiator. Why do you think that for the last 25 years every vehicle manufacturer on the planet avoids hot underhood air and fan wash like the plague and instead draws cool dense air from the fenderwell, cowl or hood scoops?
...and here's what he was talking about:
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Old 07-19-2009, 01:11 PM   #2
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Wow- excellent point. I never thought of it that way.

So there are three types of intakes:
1. Stock- outside air (true cold air)
2. Underhood air (passively heated)
3. Warm air intake (actively heated by exhaust or radiator)
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Old 07-19-2009, 01:18 PM   #3
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Well, there are aftermarket CAIs that actually get cold air from outside (usually they use terms like "cowl induction", "ram air", etc)...but look at a lot of them and they're getting warm air.

I'd guess that too many people never measure their IAT before and after installing their "CAI".
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Old 07-19-2009, 02:24 PM   #4
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measure the idle consumption of 4, 6 and 8 cylinder engines. Then measure the same engines at no load and 2000 RPM.

My Insight will go 40 MPH on less fuel than a V8 uses idling.

My Echo idles on .19 gallons per hour. Average V6 is .4 to .5. Average V8 is about .7. Those amounts double at 2000 RPM with no load applied to the engine to move the vehicle.

Reciprocating mass is a major factor in the differences in consumption, beyond friction and pumping losses.

regards
gary
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Old 07-19-2009, 07:08 PM   #5
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Quote:
Originally Posted by theholycow View Post
Well, there are aftermarket CAIs that actually get cold air from outside (usually they use terms like "cowl induction", "ram air", etc)...but look at a lot of them and they're getting warm air.

I'd guess that too many people never measure their IAT before and after installing their "CAI".
Precisely. K&N is the only manufacturer I have seen that offers a tried and 'true' cold air filter kit in their FIPK. Essentially it's like any other underhood cone filter with a cold air box around it fed from you guessed it, the fender well. Many people could get similar performance out of an upgraded flat panel filter, eliminating the snorkel inside the fender, and enlarging the hole from the fender.

I actually data logged my intake temps when I built a custom kit of that sort for my race car. With intercooling and one very large turbo, I never saw more than a 4 degree difference from ambient temperature and my intake temperature at the manifold while crusing at 65. So even with a best case intercooling scenario of 80% efficiency, my intake air was otherwise never more than about 5 degrees over ambient with that setup.
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Old 07-21-2009, 05:08 AM   #6
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oh definately you need to block the heat properly to get a cai
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Old 07-21-2009, 06:05 AM   #7
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CAI used to mean CAI, but in the last 5 years, people have been calling short ram intakes or any cone filter CAIs, so it's due to the dumbing down of the term that some "CAI"s might now seem to be WAIs.

However, a well developed CAI kit should reduce pumping loss over a stock airbox, so economy should improve a little if you can keep your foot out of it. Also should make a more economical WAI vs a stock airbox converted to WAI.
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Old 07-21-2009, 06:13 AM   #8
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Quote:
Originally Posted by Snax View Post
Many people could get similar performance out of an upgraded flat panel filter, eliminating the snorkel inside the fender, and enlarging the hole from the fender.
I got a bit of a boost in Wile-E from an Airhog panel filter. The thing to remember about replacement panels from K&N is that unless it's a popular performance application, it may not flow more than stock, due to them making something that fits rather than developing it much. Escort folks say the K&N panel is useless, so I went for an airhog figuring that fram knew what their paper panel filters flowed and would make the airhog flow more. I am quite happy with it, and annoyed that all the stores round here seem to have stopped carrying airhogs, because I want one for Marvin. Whether you like fram or not, their paper flows at the higher end of the range of paper filters, so I figure any application airhog is going to flow more than any paper. With K&N it depends heavily on application, and whether the owners clubs bugged them about it if it was lackluster, and I guess what paper they compared it to. Some factory paper is horrible and you'll probably notice a diff with fram paper even.
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Old 07-21-2009, 09:30 AM   #9
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I have a hard time believing that a well developed CAI kit could increase FE for anyone who is driving for FE; though I guess the savings of pumping losses could conceivably help someone who drives anti-FE, if the cold air doesn't bring it down too much (which is possible since factory intakes often get decently cold air anyway).

As for factory paper filters vs. aftermarket, they have every reason and ability to put in one that won't reduce FE. There's plenty of monetary reasons why they should and few why they shouldn't. It's truly hard for me to believe that a manufacturer would be so negligent of their own bottom line for so little reason on a detail that is so popularly scrutinized.

And again, even if it doesn't flow well, it shouldn't affect FE for drivers who care about FE at all.

Don't forget the EPA's own testing on the matter, which showed that even a terribly clogged filter would have little effect on fuel economy:
http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf
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Old 07-21-2009, 11:31 AM   #10
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That report there says Buicks OEM filter was more restrictive than the aftermarket replacement.

However, the test methods were the EPA test cycles, they've got so many speed changes in them that nothing that affects steady state FE is going to show up in them. There's quite a number of technologies that auto companies have tested that give fairly amazing highway mpg, but they never implemented them, because they didn't show up on the EPA gas-brakes-gas-brakes test schedule. Ford had a DOD tech running in the early 80s, got 20 or 30% out of it at steady cruise, but it cut in for seconds only on the EPA schedule, so didn't make a damn bit of difference to their numbers, ergo, it wasn't produced.
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