Quest. About CAI For 2006 4.7 [Archive] - Jeep Commander Forums: Jeep Commander Forum

: Quest. About CAI For 2006 4.7


crispepsi
10-05-2009, 03:00 AM
Wanted to know if any one thats installed the k & n CAI on a 4.7 V8, if you have to keep the intake plenum(the black thing that says 4.7 V8 under the hood) off, after you installed the CAI. I know its really a useless piece of plastic but i actually like it! Oh, im new to this site but really love it. Pics coming up next week!

jcoulter
10-05-2009, 06:08 AM
Yes in order to use the K&N you must remove that piece.

crispepsi
10-05-2009, 05:09 PM
Thanks J! Is it the same with all the CAI(AFE, AEM,Airaid)?

jcoulter
10-05-2009, 07:00 PM
I believe so. A quick check of their websites should confirm.

rwmorrisonjr
10-05-2009, 08:50 PM
K&N you remove the plenum, AFE uses the plenum since that's where the Mass Air Flow sensor is located. The K&N moves it to its tube.

Stormtrooper
10-08-2009, 01:41 PM
Removed the big plastic box on mine, and did not recall a mass air sensor. Don't think the 4.7l has one. If it did and it was removed, the vehicle wouldn't run correctly. Seems the purpose of that plenum box is to remove intake noise, hence, when an CAI is installed, sounds like "Darth Vader" at startup. I think what RWMorrison is referring to is the "air charge temp" sensor.

CanadianCommander
10-08-2009, 02:27 PM
i thought the AFE removed the plenum....:icon_confused:

down2far
10-08-2009, 05:07 PM
You didn't ask about AEM but I had to remove it on my AEM 4.7 install. I had to plug something back in about midway down the tube(see picture).

rwmorrisonjr
10-08-2009, 08:31 PM
The MAF sensor is located on the hose intake on the plenum, it has two wires running to it. All modern fuel injected engines have one to tell the computer how to enrich or lean out the mixture based on air temp & volume.

robby
10-08-2009, 09:31 PM
Actually that is a IAT sensor that is in the hose and was transfered to the new tube. Stands for Intake Air Temperature.
The MAF is located just prior to the throttle plate. It looks like a fine screen.
The Manifold Air Flow sensor is heated and the air flowing through it cools it.
The resistance of the heated screen changes with air flow (throttle position, and RPM)
The combination of IAT, MAF, and MAP, (Manifold absolute pressure) help the ECM determine air temp, air density, and current manifold vacuum in conjuntion with the TPS,
(Throttle Position Sensor) to make its fuel trim adjustments.
There is more, but....how much info before ones brain bleeds?
Anyways, the box is a Heimholtz Chamber.
It smooths the airflow but its primary function is noise reduction.
Think of it as a muffler for the intake pulses, and on some vehicles it does become restrictive towards the top of the RPM range.
As a result, some engines will show a slight increase in power in the last 1000 RPM or so prior to redline.

Rob

Kansas1230
10-08-2009, 10:45 PM
Anyways, the box is a Heimholtz Chamber.
It smooths the airflow but its primary function is noise reduction.
Think of it as a muffler for the intake pulses, and on some vehicles it does become restrictive towards the top of the RPM range.
Rob

I was looking inside this Hemiholitzerish box the other night and had a thought; if instead of the slotted tube structure it was hollowed out to create an large, open, but particulate free cavity, would it allow for better throttle response by acting as a low-pressure chamber with air readily available upon demand? Like having your throttle body open to the big blue sky, but without all the bugs and dust! I also imagined it would act as some sort of resonator box, enhancing all sorts of scary growling and sucking noises, which I like.

robby
10-09-2009, 08:37 AM
Well, the chamber was developed on a flow bench.
The channels are positioned to quiet intake roar but more importantly, the chambers must be configured so as to not create REVERSION.
This is when entering air rams into an area and compresses and tries to bounce backwards towards the entry source. (Reverse direction-Reversion....get it?)
All the gobblygook aside, I don't recommend reconfiguring it unless you have a flow bench and a thorough understanding of fluid dynamics.

I have a Hennesy C.A.I. on one of my Impala's.
The Hennesy design uses the air smoothing effects of the cars chamber (we call it home plate) in conjunction with their system for best air flow characteristics.
The intake roar is just as loud, in my opinion, as the K&N version for the same car and theirs does not use the chamber.
Evidently K&N determined that their inlet tube design would smooth the air as effectively as the Hiemholtz Chamber.
I rather like the chamber on the Impala....gave me something to paint and pretty up a bit.
I think it's more important, from a performance standpoint, to use a design that uses a plastic inlet over a metal one.
The metal ones pick up underhood temperature and as it turns out, kindof negates the potental power increase by heating the incoming air.....which of course is what we were trying to avoid.
So, it becomes what do you want to see when you open the hood.....a tube directly to the throttle body or a tube to the chamber.
Likely, the results will be about about the same.
There is no definitive answer to whats better.....you must decide what looks good to you.

Good luck,
Rob

Kansas1230
10-09-2009, 10:07 AM
Rob, if I ever wind up on a million dollar game show and have to phone a friend, I'm phoning you.

robby
10-09-2009, 12:05 PM
Rob, if I ever wind up on a million dollar game show and have to phone a friend, I'm phoning you.

OK, your on.....if you share ha ha.

Rob