jediknight7

im trying to decide what hi flow cat to get and im torn between a drop in cat, or a supposedly higher flowing Mmetallic substrate. the mettalic is a little more expensive but doesn't have an air tube and would require some custom welding to make it fit(wich isn't a problem), whereas the drop in is well, drop in, and its cheaper. what i really want to know is what does the air tube do? it used to open my six ports but i did the air pump mod instead and im sure it also provides exhaust to the egr. is there anything else it does? thanks for any help

unek87

from what i know all it does is supply air to the cat thats it if you get the drop in what brand is it i need one. aqlso what about that other cat you whats the info on that one

jediknight7

i thought the air pump supplied air to the cats? but that doesn't matter anymore cuz my headers block the air tube into the exhaust. here are the links;

hi-flow drop in:
http://store.summitracing.com/partde...=KeywordSearch

'higher flowing' mettalic substrate one:
http://www.rpmoutlet.com/powercat.htm

MrFuzzy

iTrader: (1)

is the summit one bolt on?

jediknight7

yes it is bolt on, my friend has one

jgrts20

i have one, i just remove my superflow cat w/ airpipe.

Icemark

No, it does more than supply air to the main cat, it also provides the pressure for the aux ports to open on a S3 and S4.

jgrts20

anywho, just replace the cat with a straight pipe. I disconnected the air sensor thingy(next to the lean/rich adjustor). I use the air hose going into the air sensor to open my 5th and 6th ports. Guess what disconnecting the air hose from the sensor and using the hose for the ports, got rid of my aux hesitation problem. Also my car starts right up on cold start AND idles fine!! try it, I bet you will be surprised.

Icemark

The hose going to the "air sensor"???

If you are talking about the hose from the air pump to the air filter, then it would not open your aux ports at all

Funkspectrum

iTrader: (5)

I think he's talking about the vaccum hose comin out of the pressure sensor....

Icemark

Well, that would not do a thing either... that line is never pressurized unless there is a Turbo or supercharger on the car.

jgrts20

umm............actually, it is the vacuum hose from the air sensor and you know what it does work. The hose has suction, and Ive watched the actuators open as you give it gas. Not to say your wrong Icemark, but maybe you should check it yourself. My car runs alot better w/o the hose connected to the air sensor AND IT DOES WORK for the actuators(Iam using it now)!!

Icemark

Ah, I think you are missing something... The aux ports need around 2.1 PSI to start opening on a S4. They do not open under vac (or as you say "suction").

There is not a vac line on a non turbo S4 that gets pressurized.

The line you mention never ever gets even over .10 PSI, so if you are using that line, there is no way in hell your aux ports are opening on a non turbo S4. You are imagining things or are communicating the wrong line.

So, If you are using the vac line from the intake manifold that goes to the pressure sensor and the aux ports are even moving... well I am not calling you a crack head (as someone here complained that I did recently to them), but I am sure am thinking that you are.

jgrts20

um.....welp whatever for some reason my actuators are opening at precisly 4000 rpm under suction. Ive double checked it and sure enough they open fine, I dont even have an cat w/airpipe anymore(replace with straight pipe 3"). I took pics of what im talking about so i will post them!! You know what Icemark its funny, you probly do know alot but i am not seeing things and im not a crack head. So watch what you say.

Icemark

They don't work by suction. I suppose they could be moving out slighty at idle/and lift throttle and moving to the closed postion when you have low vac (but I have never tried that to see if they would).

But they are not opening. Are the rods in the actuators moving back (into the actuator), or forwards (out from the actuator) when they are moving at 4000 RPM???

You know the sad thing, is that if I am right (which I would bet money on that I am) is that you are probably down 15 peak HP with it set up as you have it.

jgrts20

no, the rods actually go down like they would with the airpipe. But hey whatever theyre working so i dont care weather you want to believe me or not. I have pic of the setup, I will post them as soon as i find my cable for the dig camera.