Noob exhaust question

[NickZag]

So... I think I'm going to upgrade to Stage II with either a down pipe or HFC. Part of me thinks I should just with a down pipe seeing as Stage II won't past smog anyway, but I don't want any drone or have the horrid smell that some down pipe systems have. Do any of you experience that with your down pipe setups? From the research I've done, you get around 10hp and 20ft0lb torque at lower RPM from going with the down pipe, and it's cheaper so I can see the benefits here. I HATE annoying drone and I don't want my car smelling like unburnt fuel and having a cloud of smoke everywhere I go. I had a Jetta a long time ago with a down pipe and the noise and smell was enough to go back to the stock cat for me.

My current set up is dual Remus exhaust with the 2nd resonator removed so you can see my concern that I have for drone. I have a 6MT so I'm thinking it shouldn't be crazy, but I just wanted to pick your guys brains before I do this. My down pipe or HFC will either be from Eurocode or 034. There is no way I'm spending $800+ on APR for something so basic.

[Hugh@EuropaParts]

If you don't want to smell burned gas... stick with a HFC. It's as simple as that.
The down pipe area of your exhaust is hands down the most restrictive, with biggest power gains coming from replacing a stock cat.


034Motorsport High Flow Catalytic Converter


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[AofC_RR]

The downpipe is actually separate from the cat except for the APR set up. See AWE's website for reference. I think you're really referring to a Test pipe vs a HFC. Personally I'd go Eurocode HFC. And I believe APR has a Stage 2 file with o2 readiness codes on.

[AK47]

Personally I'd go Eurocode HFC. And I believe APR has a Stage 2 file with o2 readiness codes on.

I have this exact setup - couldn't be happier!

[KremlinGremlin]

Just to clarify that I am understanding correctly - Eurocode HFC is fully compatible with APR Stage 2 software (whose sole purpose is to allow you to pass emissions control)?

[Hugh@EuropaParts]

Just to clarify that I am understanding correctly - Eurocode HFC is fully compatible with APR Stage 2 software (whose sole purpose is to allow you to pass emissions control)?

APR stage 2 software eliminates the CEL caused by either HFC/Test Pipe.

[Highlander1010]

APR stage 2 software eliminates the CEL caused by either HFC/Test Pipe.

I can confirm that as I went Stage II with APR without changing my exhaust first and it was fine. Loved the increased torque and HP with little added noise at all. Now I'm APR Stage II Turbo Back'd and really happy with minimal increase in drone and a great sound. Plus I gained again in HP & Torque (albeit smaller).

[jordancl]

Just to clarify that I am understanding correctly - Eurocode HFC is fully compatible with APR Stage 2 software (whose sole purpose is to allow you to pass emissions control)?

The purpose of stage 2 software is more power which is not possible or safe until your engine can exhaust gases easier. Therefore a HFC or TP is needed for stage 2. These options usually cause CELs, so APR stage 2 can write out the second O2 sensor. This will remove the CEL, but will cause the second sensor to show as "not ready" on OBDII scans. In some states, you can not have items showing "not ready" (some states allow 1, others 2, others more). If you are in a state that requires readiness the solution is either no stage 2, or stage 2 w/o the sensor write out and a spacer.

[KremlinGremlin]

The purpose of stage 2 software is more power which is not possible or safe until your engine can exhaust gases easier. Therefore a HFC or TP is needed for stage 2. These options usually cause CELs, so APR stage 2 can write out the second O2 sensor. This will remove the CEL, but will cause the second sensor to show as "not ready" on OBDII scans. In some states, you can not have items showing "not ready" (some states allow 1, others 2, others more). If you are in a state that requires readiness the solution is either no stage 2, or stage 2 w/o the sensor write out and a spacer.

That makes sense, thank you for the insightful answer.

[rippin'av]

I was just at 034 yesterday to get my 034 HFC removed. I asked them to also flash me back from Stage II to Stage I since I have to get ready and pass smog since I'm planning on selling my car. They didn't want to flash me back because they said it would be a waste of money and that I should be fine. They told me it will pass smog even with the Stage II software. It was my understanding that it disables the sensor. It should pass with no problem with the sniff test and maybe with some persuasion could also pass the visual inspection but they told me not to worry about it because the Stage II file that I have is the same as Stage I...it just codes out the 02 sensor. On the computer they showed me and the file I have said "APR Stage I/II w/ testpipe". I guess I didn't get the fancy new Stage II file that I wanted that increases power once you have the HFC. They said that my file doesn't make the secondary 02 sensor "not ready" but in fact all the time it reads as "ready" even with a HFC or testpipe. It essentially just ignores the sensor completely and tells the system all is "ready" and nothing to see here. Not sure the validity to that claim because I haven't tried to get smog tested yet but they seemed convinced.

Any first hand experience in CALIFORNIA?

[jordancl]

I remember Arin specifically saying that their stage 2 software writes out the sensor and it will show as not ready. He said "forced readiness" is illegal and they would not do that.

[NickZag]

I've seen a few posts from people saying stage II didn't pass smog.

[luca10]

Im putting a test pipe from RAI in my a5 because i personally don't mind the smell and I love the sound, but if you looking to get power without more noise and smell, you should defiantly get the 034 motorsports hfc.

[NickZag]

In all seriousness, smog isn't too much of an issue for me. The smell and noise is. Think I'm gonna go test pipe and see how it goes from there. Thanks for the feedback.

[Wah]

Nick, if you're worried about smell, I would lean towards getting a HFC rather than a TP.

[NickZag]

Nick, if you're worried about smell, I would lean towards getting a HFC rather than a TP.

I bought a used TP from another user, so if I don't like it I'll switch and buy a HFC. The TP was a good deal so I have nothing to lose. I figure it can't be worse than the fumes my massively over carbureted and over cammed 1969 SS Camaro and used to pump out lol

[jordancl]

Might be a good deal but the install is a painnnnnnnnnn

I am not looking forward to taking out my hfc if i need to

[Speycaster]

I have had the ARP turbo back quad exhaust on my car for two months now, and have not ever had any smell/ fume issues. It is pretty quiet at low RPM, but belts it out when you put your foot in it. Also, there is no drone at any speed or RPM. I do know what drone is like, as my allroad had Magnaflow and the drone at low RPM was horrific.

[NickZag]

I have had the ARP turbo back quad exhaust on my car for two months now, and have not ever had any smell/ fume issues. It is pretty quiet at low RPM, but belts it out when you put your foot in it. Also, there is no drone at any speed or RPM. I do know what drone is like, as my allroad had Magnaflow and the drone at low RPM was horrific.

Solid info, thanks! That's the set up I used to have on my Jetta years ago. I had a custom made TP with Magnaflow mufflers. The drone and fumes drove me crazy after just a day.

[ultra]

Nick, I have the EuroCode test pipe and recommend it + it passes smog .

[KremlinGremlin]

Is Eurocode HFC compatible with APR Catback exhaust (are the diameters of the two ends the same)? Tried researching on my own to no avail.