High flow cat vs test pipe

[SoFarGon]

What do you guys run? Why did you choose what you chose? What are the benefits of each? What do you recommend?

[eastcoastjettin]

not to be the dick, but this topic has been covered over and over. search is your friend.

[makav3li]

test pipe=illegal but if your state doesn't do emmissions, who cares
cheap
HFC= Legal and expensive

[SoFarGon]

test pipe=illegal but if your state doesn't do emmissions, who cares
cheap
HFC= Legal and expensive

Performance wise?

[makav3li]

both about the same i'd say, test pipe i'd assume gives a little more performance because there is no restriction whatsoever, but nothing you'll really notice just driving the car.

[b4a41point8t]

hfc is arguably legal and i can attest to that...

[wildbill]

search button
nearly identical, all turbos need some backpressure, test pipe is very small to create, hfc is obvious why it creats backpressure
depends on state if its passable, some do not use sniff test
no real need for either unless running more than a chipped car

[9Hooker]

not to mention the AWFUL raspy sound associated with just a test pipe. no one has mentioned it (surprise). it's noticeable, and from outside the car even more so. i laugh at cars i see drive by (4cyl) with no cat.

[JRMSLINEA4]

not to mention the AWFUL raspy sound associated with just a test pipe. no one has mentioned it (surprise). it's noticeable, and from outside the car even more so. i laugh at cars i see drive by (4cyl) with no cat.

+1

[SoFarGon]

So you guys recommend the hi flo cat over the test pipe? My options r 034 hi flo cat/test pipe... But I'm leaning toward the hi flo cat. I also don't wanna drive an Audi and have it smell

[Charles]

not to mention the AWFUL raspy sound associated with just a test pipe. no one has mentioned it (surprise). it's noticeable, and from outside the car even more so. i laugh at cars i see drive by (4cyl) with no cat.

Perhaps it's cause I have a full exhaust, but mine's not raspy at all. 3" tp all the way back to the split, then 2.5" into Magnaflow muffs.

I hardly ever notice any smell from mine.

And yes, there are tons of threads on this. Search and read up on what others have said.

[crazytex21]

test pipe=illegal but if your state doesn't do emmissions, who cares
cheap
HFC= Legal and expensive

actually, federal law says that any modification to your Catalytic Converter is illegal, no matter what your state laws say. but when is the last time you got pulled over by a fed... haha. i run a VMR test pipe. i love i. i don't have emmissions testing in my county, so i can get away with it.

[b4a41point8t]

I have just a TP and it isn't raspy AT ALL. In fact, it's not loud at all. Almost identical to the cat being on. I was actually surprised. If anything, the spool is SO loud that it muffles the engine noise out. I'm guessing all this raspy talk might be with a full turboback and loud mufflers.

Test pipe+stock mufflers=no noise at all (raspy or otherwise).

[b4a41point8t]

^ and yes it does smell a bit, but i know 100% i have an exhaust leak at the turbo->test pipe gasket. I can feel it, but i have just put this "Thermaweld" putty on it designed to repair cracks and holes so we'll see how it holds up. Temp rating up to 2400F

[Stewy]

I have an APR test pipe and I love it. It does make for a louder exhaust note through my Neuspeed exhaust, but its not raspy at all.

[Baruch]

I have a test pipe.... smell it when you get out, noise doesn't sound raspy at all either... i like it!

Smell is around for like 3 seconds and its not bad what so ever

[Quattro]

very quick breakdown:

testpipe - cheap, more hp gain...louder and smell gas.
hfc - more expensive, not as much hp gain as tp (5hp less maybe?), a bit louder, no gas smell..

[baldy]

I have an APR test pipe and I love it. It does make for a louder exhaust note through my Neuspeed exhaust, but its not raspy at all.

I dunno... I have Neuspeed exhaust on mine too and it's definately raspier than it was with the cat.. Plus my exhaust drones even more (avant)...

Anyone local or in Seattle that wants to trade exhaust? My Neuspeed for your APR or anything quieter..

[makav3li]

^ and yes it does smell a bit, but i know 100% i have an exhaust leak at the turbo->test pipe gasket. I can feel it, but i have just put this "Thermaweld" putty on it designed to repair cracks and holes so we'll see how it holds up. Temp rating up to 2400F

i think i got a leak at the cat as well, the new exhaust didn't sit right and i can smell it pretty bad in the cabin till i get off my lazy ass and fix it.

[a4dc89]

I have a HFC and the only difference I see if that when you aren't really getting on the throttle it smells and sounds like a stock car. When you get on the throttle it smells like gas and sounds pretty fucking good

My understanding is the TP smells all the time and sounds raspy when not really getting on it

[vdubjetta02]

They brought emissions back to my city, sooooo HFC

[Matt@EuropaParts]

I prefer the HFC just because it keeps the car a bit more civilized. I have 034 test pipes in stock, but I think I just ran out of the HFC's (http://www.europaparts.com/a4/b7/2-0t/exhaust.html)

[JRMSLINEA4]

very quick breakdown:

testpipe - cheap, more hp gain...louder and smell gas.
hfc - more expensive, not as much hp gain as tp (5hp less maybe?), a bit louder, no gas smell..

Well written. +1

[SoFarGon]

I prefer the HFC just because it keeps the car a bit more civilized. I have 034 test pipes in stock, but I think I just ran out of the HFC's (http://www.europaparts.com/a4/b7/2-0t/exhaust.html)

Yea I was gonna go see u guys on mon or tues... Damn

[06B7]

034 hfc says that they seen gains of over 27WTQ and 33WHP on our dyno on stock turbo tunes.

[SoFarGon]

034 hfc says that they seen gains of over 27WTQ and 33WHP on our dyno on stock turbo tunes.

Prolly with stage 2 programming

[06B7]

When i had it, it felt like i had chipped again but i took it out because there was oil coming out from transmission idk why. When i put the stock fc it was not leaking.

[Sprode]

search button
nearly identical, all turbos need some backpressure, test pipe is very small to create, hfc is obvious why it creats backpressure
depends on state if its passable, some do not use sniff test
no real need for either unless running more than a chipped car

Turbos do not need backpressure. That is all.

[9Hooker]

Turbos do not need backpressure. That is all.

agree. turbos need the LEAST backpressure possible, meaning they need the largest pressure differential across the turbine. 0 is the lowest we could concievably go (without negative pressure, or a vacuum downstream from the turbine... impossible) and the largest pressure that can be attained is limited by the motor (the thing creating the pressure in the first place).

ideally you'd have the exhaust of the turbine vent to atmosphere. that's obnoxious and not really feasable.

actually you'd look for some type of venturi that would create a slight negative pressure downstream from the turbine. again, not feasable.

[Charles]

When a turbo builds boost, then you want as open as possible. It's the curve under the boost that requires some back pressure. This is more evident with turbos that have lots of lag. If you're exhaust is too large, your car will have terrible response until the boost comes in. Ideally, there'd be a variable sized exhaust.

[Sprode]

When a turbo builds boost, then you want as open as possible. It's the curve under the boost that requires some back pressure. This is more evident with turbos that have lots of lag. If you're exhaust is too large, your car will have terrible response until the boost comes in. Ideally, there'd be a variable sized exhaust.

Sorry. N/A engines like some backpressure down low, but that is a function of the cam design and overlap. On a properly setup turbo car, the turbine itself provides all the backpressure an engine will need. The performance of the turbine is directly related to the outlet pressure.

On top of that, our engines have got to have the least lag of any turbo engine I've seen, probably past the point of detriment as it runs out of breath so quickly.

[b4a41point8t]

^ this. Backpressure for turbo= no need. As for our cars having no turbo lag, I agree and support this with empirical evidence. The k03 is SO small, that it spools by 2krpm. I have buddies with turbos that ask, where is it? When I point it out they laugh. It really is a tiny bastard. But then again, they don't see boost till 4k (evo) so it's really just a trade-off. Would you like a big slower turbo with incredible high end power (but u have to strangle your engine to see power) or a small snail that hits hard but falls on it's face after 4-5krpm. And believe me, the 4g63(evo) has DISGUSTING turbo lag. I mean... Disgusting! Feels NA 2.0L till late 3krpm.