View Full Version : HFC or Test Pipe

09-22-2009, 07:08 PM
So I have been looking on classifieds and I have been trying to narrow it down to a HFC and testpipe. What is the real power difference and which one will give me the most bang for my buck for the best gains?
All opinions are wanted!

09-22-2009, 07:25 PM
Test Pipe is better, but will also be louder and leave an odor (as many say). I have a HFC mainly because I like it quieter and my state emission laws require one (I must pass a visual inspection of a catalyctic converter to pass inspection). You should look into your state laws for emissions and see what it states about a catalyctic converter. If it states you need one, I would just do a HFC.

09-22-2009, 07:29 PM
In Texas you have to have one, it was such a pain in the ass to find someone to get me a sticker. Now I have stock cat on so no worries. I did love my test pipe though, it did make my car drone a bit though even with two resonators.

09-22-2009, 07:30 PM
i know HFC has a short life span and starts to throw codes after two years or so

09-22-2009, 07:33 PM
Well I live in ky, so no emissions, but I want all the gains but not to loud. What do you think?

09-22-2009, 07:35 PM
This is what I want, but want opinions.

09-22-2009, 07:37 PM
A test pipe wil be loud. You can get a HFC with maybe a 200cell count if you want it quieter with a more free flow. You would need to add a spacer onto the secondary 02 sensor bung to avoid the P0420 fault code.

09-22-2009, 07:43 PM
200 cell count?

09-22-2009, 07:46 PM
Cells per square inch. The less cells, the larger they are, which means more room for air flow. Mine is 300 or 400 cell.

09-22-2009, 07:47 PM
So what would I need to do?

09-22-2009, 07:48 PM
If you plan on getting a HFC LeBree or 034 have good ones, but if you plan on having a wideband air fuel ratio gauge, then a test pipe because there is a error percentile is the readings with the HFC but not a great difference.

09-22-2009, 07:51 PM
I have a Labree.

And not to thread jack, but would back pressure from a HFC cause that much of an error of percentage on a wideband even if the HFC is maybe 200cell? I ask this because I want to go BAT and would have a 200cell count HFC welded into the dp. I would need this to pass inspection.

09-22-2009, 07:54 PM
HFC is less shady, test pipe flows more in theory.

If I did it again, I'd go HFC. I was broke at the time, so I went TP.

09-22-2009, 07:54 PM
But you don't think what I posted was a good HFC?

09-22-2009, 08:02 PM
Without mileage known? No. For the price? Yes. But it was priced fairly well, so.........

D's Avant
09-22-2009, 08:02 PM
Go with a HFC and you'll have the same or close to the same gains as with a test pipe and save the planet a little bit too. I run a 034 HFC and I'm pretty happy, little extra gain and a pretty sporty sound too, you def can hear the turbo whine better.

09-22-2009, 08:38 PM
I'm going to get it!

09-22-2009, 08:52 PM
i have a labree and couldnt be happier, but have never ran a test pipe for comparison

i went with the hfc as i didnt want the smell others had talked about nor the drone in the cabin and the labree has met both those marks for me very well

there is a local nissan guy who runs a pretty popular tuning shop who works with tons of drift cars and rb26dett swaps and he is trying to start a movement to keep cats on drift and high performance cars, not as a mandated law or anything just encouraging others to do it for environmental benefits and to aid in keeping noises down (to help keep track hour restrictions based on neighbor complaints down), and he has done back to back dyno runs with a test pipe and with a cat on a 500whp drift car and has gotten near identical power results with each while just compensating something in the timing/fueling tuning for each setup (dont quote me on what was changed but i am 99.999% sure the boost level was kept the same). His results may be biased since he really is a pro-cat guy but its interesting none the less.

Its not exactly comparing apples to apples, but interesting in the fact that in a sport where top power is key hes able to get those numbers with a cat still in place and several others are as well, so cats may not be all bad, or the gains of ditching one might not be significant over a hfc except in price

09-22-2009, 09:06 PM
Did you look at the pic I posted. Does it look like a labree?

09-22-2009, 11:21 PM
The one you plan on purchasing looks no way like the labree unit. Plus the one you want to purchase is a 250cell, while Labree is 400 or 300cell. I can not recall which one. Link (http://labreemotorsports.com/products_vw.html).

09-23-2009, 05:16 AM
I guess I don't understand the 250cell and so on. The guy thinks it's the same as stock size. Will you explain the cell?

D's Avant
09-23-2009, 05:46 AM
Stock has a higher cell count say 1200(???) and less flow due to the cell density and a HFC has a 200-400 cell count on average, thus better flow.

09-23-2009, 06:11 AM
So the one I'm wanting flows more then the labree? Thanks for all the info

09-23-2009, 06:29 AM
A test pipe alone won't make your car loud. It all depends on what you do with the rest of your exhaust. I have 2.5 inch piping(turbo back) and its not loud at idle or WOT. Of course what's is considered loud is subjective but no one I've meet thinks its loud.

09-23-2009, 07:06 AM
Well my downpipe is 2.36 and the rest of the piping is 2.75, so I think it will be loud

09-23-2009, 08:44 AM
Noise of an exhaust system will have to do highly with the quality of the metal. The thicker the metal, the less drone and less loud it wil be. Then you factor in your resonator and muffler. My exhaust setup is quieter than my stock exhaust was. Labree HFC to Milltek Exhaust.

But yes, having a HFC with fewer cell count will permit more air flow. I tried to explain it in a previous post. You have cells per square inch. If you look inside of a catalyctic converter, you will see what looks like a honeycomb. With the lesser amount of cells, the more room you create for exhaust flow to exit. For example, a room filled with 20 people will be alot more congested that a room filled with 5. When you remove people from the room, the space increases dramatically. Thus, permitting more room. In this case, more room for the burnt exhaust gasses to flow.

09-23-2009, 08:50 AM
Thank you for the great explanations!

09-23-2009, 05:15 PM
Well my downpipe is 2.36 and the rest of the piping is 2.75, so I think it will be loud
i have a testpipe with 2.75 exhaustand the test pipe made the tone deeper not louder... And my exhaust isnt loud by any stretch of your imagination unless your a female... (my wife says its loud because the stock she wouldn't know the car was on and with the exhaust she hers the rumble....)

09-23-2009, 06:57 PM
that cat looks familar
http://getcoolparts.com/ShopByVehicle.epc?q=1998-AUDI-A4--Quattro--/--L4--1781cc--1.8l--Gas--Fi--Turbo--aeb-Exhaust--Fuel--Tank&yearid=1998%40%401998&makeid=AUDI%40%40AUDI%40%40X&engineid=1313453%40%40A4+QUATTRO++%2F+L4%2D1781cc+ 1%2E8L+GAS+FI++Turbo+%28AEB%29%40%40A4+QUATTRO&catid=Exhaust+%26+Fuel+Tank%40%40Exhaust+%26+Fuel+ Tank&subcatid=Catalytic+Converter@@Catalytic+Converter&mode=PA
piece of sheit, dont want to get into how I know. But no emissions= no doubt testpipe. I like it.