Can someone please explain these to me a little bit better? I just got a new exhaust with a high flow, but looks more like a resonated TP to me...i'm just a little confused so if someone could give me some insight it would be appreciated....pictures help too

When I think of a HFC I think of something that looks like the AMS one...I do realize there could be multiple types and heat shield coverings.


For instance this is the "Perrin HFC" which looks most like mine and is sold as a HFC:


And this is the "AMS HFC":


and this is the "AMS resonated TP":


and this is my new "High Flow catted test pipe"

 

the test pipe is empty. the cat as you can see is not. now the resonated testpipe have something like this, but its quieter then a test pipe but louder then the hfc.


and mine looks like this


resoneted test pipe will give you more whp and when its heats up, doesn't restrict the flow more .Unlike the HFC. So the WHP and tq numbers are stay as when its cold.

 

I know a TP is empty, I guess I was just more curious about the inside of a resonated TP...that clears things up, thanks.

 

 

hey lithium who makes that "high flow catted test pipe" Never seen that before. "inside" the test pipe is some type of muffling material I'm assuming.

 

it's part of the new cobb exhaust

 

oohh so thats what the cobb hfc's look like. Some type of steel wool or glass fiber inside of resonated test pipes maybe?

 

IIRC that's what cats look like inside...I was just a little thrown off from the appearance when I opened the box today, because I thought I saw a picture of their HFC previously that looked a lot more like the AMS one above.

 

Oh my bad. Shouldn't have put those 2 sentences together. I meant thats what they pack resonated test pipes with I think (some type of resonating material like steel wool or glass fiber, etc.) if thats what you're originaly trying to ask.

yours is a metallic substrate and is considered a hfc, won't flow as well as a testpipe or resonated test pipe but it'll keep the environment clean

From the pics you posted, the ams resonated test pipe is the only one that is straight through on the inside just like the picture robevo posted. All the others have some type of catalytic converter

 

You're correct, that's the cat section you see in the pic. My Wrx had the same thing in the stock up pipe, and it was one of it's many cats that magically fell off one day.

 

get a test pipe cut it out and put these in. Perfect! Racing High flow cat.. not that dense like you have, but woks just fine.

 

The one I have looks really good actually, that pic above makes it look more restrictive than it really is...here is another that is a little bit better (somewhat).



I've read all of the HFC and TP arguments and supposedly this one is supposed to flow very well and perform very close to their TP.

 

the problem is when its heats up. its getting more restrictive ,because of that very fine structure. So when its heats up,because of the heat, it will be more busyer inside vs the not that fine design.
But i'm sure its a great hfc. as long as its works fine /pass inspection / and don't robbing more power then others ,who cares ,right?

you see the light dot in the middle,how much bigger in the other hfc althought your is a closer picture.

 

The AMS piece is amazingly big for a test pipe. Will be part of my next purchase!