Test Pipe vs. High Flow Cat

[b5a4erik]

Hey all,

I'm looking into getting either a Test Pipe or a High Flow Cat.

Here's what I think I know so far:

TEST PIPE:
-completely free flowing
-more low end torque, quicker spool, more horses (compared to both hfc and stock cat)
-pulls harder and quicker than a hfc would
-raspy tone
-bad for emissions
-smells like gas
-cheap

HIGH FLOW CAT:
-more free flowing than a stock cat, yet not completely free flowing
-quicker spool, more horses, yet not as much of a low end torque gain
-pulls smoother than a test pipe would, yet better than a stock cat
-more mellow tone
-can pass emmisions
-doesn't smell
-expensive



With all this information I have, I'm torn.

I want my car to be more fun to drive, yet I'm not so sure I wan't my car to smell.
I want to be nice to Mother Earth, but at the same time, I figure "go big or go home."
I like the idea of getting a high flow cat, I don't like the idea of dropping twice the amount of money of a test pipe.

amongst other things...

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Any information, personal experience, and/or opinions would be great.

Help me make up my mind!

[Hugh@EuropaParts]

I would personally go with a HFC, the gains with a test pipe are not worth the smell/sound. On top of that you see tons of test pipes in the classifieds but you hardly ever see a HFC.


We received a pallet from our friends at 034Motorsport filled with High Flow Cats and Test Pipes which means they are back in stock and ready to ship!

034Motorsport High Flow Catalytic Converter (1.8T)

034Motorsport High Flow Catalytic Converters (HFC) are designed to replace the restrictive OE catalytic converter, and allow for quicker spool while increasing horsepower and torque throughout the powerband. This HFC fits:

• 1997-2001 Audi A4 B5 1.8T (FWD & quattro)
• 2002-2005.5 Audi A4 B6 1.8T (FWD & quattro)
• 1998-2005 Volkswagen Passat B5 1.8T (FWD & 4Motion)
• Direct bolt-in for OEM cat-back exhaust, or aftermarket cat-back exhaust systems designed to fit with the OEM catalytic converter.

034Motorsport dyno showed gains of over 26WTQ and 15WHP on stock turbo tunes.

• Full 304 stainless steel tubing construction.
• 250-cell stainless steel matrix cat.
• TIG welded and backpurged.
• CNC machined flanges to prevent warping and expansion.
• Factory correct oxygen sensor and exhaust hanger placement.
• Full 3" tubing is used throughout.
• Direct bolt-in.
• Dyno proven horsepower and torque gains!
• Smog tested.
• Please Note: HFC installation kit and oxygen sensor spacer are highly recommended and available in the related products.

FREE SHIPPING (Continental USA)










034Motorsport Test Pipe (1.8T)

034Motorsport Test Pipes are designed to replace the restrictive OE catalytic converter, and allow for quicker turbo spool while increasing horsepower and torque throughout the powerband. They feature high flowing 3" stainless steel construction that fits in place of the stock catalytic converter with no modifications necessary. This test pipe fits:

• 1997-2001 Audi A4 B5 1.8T (FWD & quattro)
• 2002-2005.5 Audi A4 B6 1.8T (FWD & quattro)
• 1998-2005 Volkswagen Passat B5 1.8T (FWD & 4Motion)
• A direct bolt-in for OEM cat-back exhausts or aftermarket cat-back exhaust systems designed to fit with the OEM catalytic converter.

Typical horsepower gains are 10hp+ on stock turbo tunes, 15hp+ on K04 tunes, and 30-40hp when combined with a GT28RS or larger.

• Full 304 stainless steel tubing construction.
• TIG welded for maximum durability and flow.
• CNC machined flanges to prevent warping and expansion.
• Factory correct front and rear oxygen sensor bungs and exhaust hanger placement.
• Full 3" tubing is used throughout.
• Direct bolt-in.
• Dyno proven horsepower and torque gains!
• Note: For offroad use only! Test pipe installation kit and oxygen sensor spacer are highly recommended and available in the related products.

[B7A4WD]

Just go for the Testpipe, I had mine on for 3 Years now and the smell isnt even that bad... I guess it all depends on how picky you are with your car. If you want more fun, noise, and your all about the power go for test pipe, if your conservative and want both but dont like the smell or the rasp go for a HFC. If I were you like you said go big or go home and get a testpipe. When it comes to smog checks it can be a pain but if your good enough you can get it passed with magic. Yah everyone wants to be nice to mother earth but with China, Russia, and all these other countries polluting... isnt really going to help sadly =[ so just have fun while your life last.

[redline380]

On top of that you see tons of test pipes in the classifieds but you hardly ever see a HFC.

I would personally chalk this up to members runninga test pipe are more apt to upgrade their turbo system, requiring a different test pipe and freeing their stock fitment one for resale.

With that said, I'd stick with a HFC since you live in Cali. The mild gain of a test pipe over a HFC wouldn't be worth the work to replace it with a cat for inspections. Just me though

[MacFady]

I'd go HFC as well.

[BaseDrifter]

Another vote for HFC, love mine. I was able to pick it up used for $125.

[MetalMan]

HFC, definitely. I used a test pipe for short periods to help with diagnosing, and didn't like it at all. I didn't notice any improvement in power/torque vs. HFC but it was a little louder so the "butt dyno" may have registered more power.

[RallyeBourne]

I see that the 034 HFC is listed as "smog tested," but is it CARB approved? If not, you can fail smog if the smog tech notices it's aftermarket.

[b5a4erik]

I see that the 034 HFC is listed as "smog tested," but is it CARB approved? If not, you can fail smog if the smog tech notices it's aftermarket.

My father actually had the 034 hfc on his late b6 a4, and he had trouble getting it to pass smog, I believe because of that reason.

Another tempting reason making me lean towards the test pipe...

But so far the majority is saying hfc...

Keep em coming!

(anyone else with personal experience with both / butt dyno comparisons?)

[BaseDrifter]

034's cat is not CARB approved and should always fail visual inspection in CA. Tail pipe emissions with the HFC have been hit or miss on passing. Whether your car passes visual inspection is up to the discretion of the tech, some places are much more lenient than others..

[Mad Cow]

HFC hands down, the power loss over a test pipe is basically negligible but you have the benefit of being able to park in an indoor garage without everyone giving you the stink eye because your car stinks up the whole place after 30 seconds of running. I think all the people saying test pipes don't smell so bad have damaged noses or something, I can smell mine after not even 10 seconds of idling in one spot outdoors.

[b5a4erik]

HFC, definitely. I used a test pipe for short periods to help with diagnosing, and didn't like it at all. I didn't notice any improvement in power/torque vs. HFC but it was a little louder so the "butt dyno" may have registered more power.

So did your butt dyno register more power?

What didn't you like about the test pipe?

How was the sound of the test pipe different from hfc?

[b5a4erik]

HFC hands down, the power loss over a test pipe is basically negligible but you have the benefit of being able to park in an indoor garage without everyone giving you the stink eye because your car stinks up the whole place after 30 seconds of running. I think all the people saying test pipes don't smell so bad have damaged noses or something, I can smell mine after not even 10 seconds of idling in one spot outdoors.

Hehe.

The *stink* eye.

But in all seriousness, I appreciate the input.

[MetalMan]

So did your butt dyno register more power?

What didn't you like about the test pipe?

How was the sound of the test pipe different from hfc?

What I was referring to with the "butt dyno" is that since it sounded slightly louder/deeper/raspier it seemed as though it should have been mildly more powerful, but in reality it didn't actually feel any faster.
Just like in Mad Cow's situation, I found the smell with the test pipe to be aweful. I even get a bit of smell with my HFC, but I'm suspecting that may be related to issues I've been having with my FrankenTurbo (that nobody else seems to have).

[walky_talky20]

Not to mention that the "funky smell" is not only annoying - the very fact that you can smell it is indicating that you are breathing the toxic fumes into your body. They are very harmful, carcinogenic gasses and can actually make you physically ill in a short amount of time. The human detection and "stink-eye" reaction to this bad smell is a very real preservation instinct.

I would vote in favor of a high flow cat. Very much yes.

[jmcwayne808]

My grandmother drove cars that had no cat and she lived to be over a 100 , lets get real cars pollite regardless of if you can smell it or not, meaning inhale exhaust from a car with or without a cat and its bad for you, that being said go with what u can get smogged, if you want a little more performance and can live with your exhaust being a little loud I say go test pipe

[b5a4erik]

Interesting about the harmful gasses, I actually watched an episode of "Cosmos" recently where they talked about them... The scientist who researched them, who, at the time, no one believed when he was saying exhaust from cars are harmful. hmm...

Anyways,

Can someone confirm for me that the black/moss lines on the graph is the turbo working?

In which case would mean that the test pipe spools much quicker than the hfc?

[biketsai]

I didnt notice a crazy difference for spool with my turbo setup when I went from TP to HFC. I ran my testpipe for 5 years and put on a HFC last year. Honestly I wish I went with a HFC a LONG time ago. The exhaust smell isn't nice and the HFC setup is much much quieter.

[DeathKing]

I didnt notice a crazy difference for spool with my turbo setup when I went from TP to HFC. I ran my testpipe for 5 years and put on a HFC last year. Honestly I wish I went with a HFC a LONG time ago. The exhaust smell isn't nice and the HFC setup is much much quieter.

Same experience here

[b5a4erik]

Same experience here

Ight then, It's decided.

High Flow Cat it is!

Reasoning:
-Smell of test pipe / harmful gases.
-Only Slight difference in effectiveness between the 2.
-Everyone preferring the HFC seemed passionate with their preference, after experience with both even.

I'm hoping that once smogging time comes around, everything is a-okay.

The HFC also has a more well rounded power-band, making it preferable to me.

Thanks everybody for your input!

[MetalMan]

Good decision. Just to add more fuel to the fire: I've heard of mobile sniffers in CA, where they sniff for high emissions by cars on the road and pull over cars detected to release high emissions. Can't say I've ever see one but if this is true then it's another reason in favor of the HFC!

[RallyeBourne]

Good decision. Just to add more fuel to the fire: I've heard of mobile sniffers in CA, where they sniff for high emissions by cars on the road and pull over cars detected to release high emissions. Can't say I've ever see one but if this is true then it's another reason in favor of the HFC!

Truth. Riverside county and LA county seem to have them a lot. I don't know much about them, but it seems that the cities that are patrolled by the Sheriffs department have them. Temecula is policed by the sheriffs dept, and they have them all the damn time.

[Sickws6]

Funny that most guys for the HFC are in CAL where not legal to run without a cat. I got a TP for my set-up and have not finished my build yet so I cant say either way yet. I have a cam/heads trans am with long tubes and no cats with E-cutouts. When I run the cutouts open I hate the smell it even sticks on my cloths and smell like gases for the rest of the day. Yet the cut-outs are under the drivers and pass seats so the fumes travel up while sitting still. If the audi with the TP is comparable to this I will not even install the TP and go with a HFC or modify the TP installing cat.

[jmcwayne808]

Dude its no where near that unless u got an exhaust leak, I just insralled my 71r elim with the test pipe and 2.5 inch cat back system and honestly cant real tell the difference from when a cat in and now besides it sounds louder without the cat

[redline380]

Funny that most guys for the HFC are in CAL where not legal to run without a cat.

You do realize that it is illegal to run without a cat in all 50 states right? You can thank federal legislation for that. I forgot the exact year, I think it is around 1990, but all cars after that require a cat.










Sent from my windows phone on Tapatalk since iPhone blows

[Sickws6]

Well yes, I should have stated rather than illegal it's impossible to run in Cali without a catalytic converter. Thanks for correcting me.

[AudiB5owner]

Most of my Audi friends locally in California run test pipes actually. They just have ways of getting around the law. The HFC isn't as easy as easy to sniff out as a DP. I know someone who avoids all California CARB smog laws by registering his cars in counties that don't require smog with vehicle registration... WIN

[RallyeBourne]

Most of my Audi friends locally in California run test pipes actually. They just have ways of getting around the law. The HFC isn't as easy as easy to sniff out as a DP. I know someone who avoids all California CARB smog laws by registering his cars in counties that don't require smog with vehicle registration... WIN

Uhh, what counties? As I recall, it's a State law, superseding any city or county laws. I know people used to get PO boxes in AZ or NV to avoid smog, but you can't even do that anymore.

[BaseDrifter]

Uhh, what counties? As I recall, it's a State law, superseding any city or county laws. I know people used to get PO boxes in AZ or NV to avoid smog, but you can't even do that anymore.

El Dorado, Placer, Riverside, San Bernardino, San Diego, and Sonoma.

[RallyeBourne]

El Dorado, Placer, Riverside, San Bernardino, San Diego, and Sonoma.

I know for a fact SD requires smog, that's where I live. I bought my b5 from San Berdoo county, they require it. Riverside county sheriffs department does the random smog checkpoints, so I'd imagine they require it.

[BaseDrifter]

I know for a fact SD requires smog, that's where I live. I bought my b5 from San Berdoo county, they require it. Riverside county sheriffs department does the random smog checkpoints, so I'd imagine they require it.

It varies by zip code. Some counties only require a smog when the vehicle is changing ownership. You can find all of this out and more at the DMV's website.

https://www.dmv.ca.gov/vr/smogfaq.htm

There are six counties that require smog certifications within certain Zip Codes only. These counties are:

El Dorado, Placer, Riverside, San Bernardino, San Diego, and Sonoma.

Follow this link to determine which Zip Codes are included.

[RallyeBourne]

It varies by zip code. Some counties only require a smog when the vehicle is changing ownership. You can find all of this out and more at the DMV's website.

https://www.dmv.ca.gov/vr/smogfaq.htm

You're my hero. Now to find a zip that doesn't require smog...

[AudiB5owner]

Just note that if a certain area zip code doesn't require enhanced smog checks for biannual registration renewal doesn't mean it is legal to run a DP. I am not sure if living in a smog check-less zip code means your car doesn't have to be CARB exempt. But then again, that freedom would be nice

[BaseDrifter]

Yes, all Federal and State emissions laws regarding emissions components and functionality still apply, even if you live in one of the areas that doesn't require biennial smog checks. (Biannual would be twice a year, biennial is every other year.)

[nynoah]

I use a HFC and its a great. No nauseating smell and the car does not sound like ricer ass. Even if I was running and EFR, I would still have a HFC in the exhaust system.

[BaronB5]

This is so awesome! I was about to pass on a hfc. But now that I live in Humboldt County I dont have to smog every two years! Thanks for the info everyone

[b5a4erik]

Before this thread gets put to rest:

I have a 2.5" catback exhaust.

Would it be better for me to get the 3" 034HFC or the 2.75-2.5" Techtonics HFC?

I figure it would be best to keep everything as similar in diameter as possible, but if I'm mistaken, I'd be happy to know why.

[Mario_Schizo]

I'm pretty sure selling a used cat is illegal... I remember seeing signs up everywhere at junkyards saying that it was, lol
Also, I'm pretty sure not running a cat is illegal everywhere, regardless of if your state does emissions or not... All of this is just from my very hazy 12:32AM memory though, too tired to look it up and confirm. But 85% sure it's valid. 100% sure I'm hungry.

Anyway, I'm getting ready to fab up a 3in SS Mandrel bent test pipe within the next two weeks, my state has emissions but they only do OBD scanning for codes and readiness, nothing a good tune can't handle
My vote is on the test pipe! MORE POWER.

[iLovPieNCake]

From what I read, cars have been required to have cats from before the 90s.

[b5a4erik]

Before this thread gets put to rest:

I have a 2.5" catback exhaust.

Would it be better for me to get the 3" 034HFC or the 2.75-2.5" Techtonics HFC?

I figure it would be best to keep everything as similar in diameter as possible, but if I'm mistaken, I'd be happy to know why.

Any input?