S6/S7/RS7 Catless DP Question

[CR8LUCK]

For those running Catless Downpipes, does the smell ever go away so you can't smell in the cabin?

Would you recommend adding high flow's?

Any idea on gains that you've experienced with these?

Has anyone gone through emissions testing with the catless DP's and did you pass?

Thank you!


Sent from my iPhone using Tapatalk

[GameBreaker]

I can't say to the C7 platform, but in general it's all the same. I had a catless setup on my Mustang, and ran catless for a number of years on my old S4.

Sadly, the smell will never go away but you most likely will never notice it when your windows are up. However, you will notice it anytime you get out of the car, and whenever you have to roll your window down you will get the teary eye and the longer you sit the worse it will get.

I plan on shilling out the extra money for downpipes with high flow cats. You might be able to pickup a used catless setup and add HJS cats. I may be losing a little performance, but I've dealt with the smell for years and I'll pass on it.

The gains will always be better than stock, but as far as how much it's hard to tell as there haven't been a lot of reviews with just them. It also depends on cell count and their position in relation to the engine. Normally it is preferred to have them near the rear of the downpipe, but with the turbo placement on our cars it's not really known whether this is a factor anymore. Catless will always net the biggest gains, but you will have to give some concessions.

Yes, and yes. If you have a tune, odds are you will pass. The way the OBD setup is, as long as you don't have any CELs all that happens is they plug you in, and two minutes later you are on your way.

[S4Per]

To add on to GameBreaker: I had catless on my RS4 for a year. The smell never goes away, and my conscience also caught up with me. You lose a little bit of low-end torque switching to hi-flow cats.
Emissions in WA are OBD-II based. As long as there aren't any meaningful codes, you'll pass, i.e. they never measure anything coming out of the tailpipe. I passed in that way while the car was stinking up the place without cats in place.

Net/net: get some hi-flow cats. It's the right thing to do all around.

[DrBeerMD]

Yes they smell. Windows up it's not as bad. They don't always smell.
The sound and increased performance is worth the smell. I'm constantly being complimented on how men it sounds.
In CO here I would fail an emission test
I won't post dyno numbers as it will start a pissing match, but I did see better 1/4mile times after adding the full exhaust.
If you are asking me I strongly advocate the catless DP's

[hubris]

To OP - I have heard that the performance difference between catless and high flow cats is in the range of 1-5 hp.... Negligible. Certainly not worth walking around smelling like a gas can. This is an Audi, not a 70s muscle car. But to each their own. The high flow cats will wake the car up a tad bit and make it sound very mean. It is worth the expense. Do it right.

Here is a neat article about HFC vs catless although I encourage you to do your own research: http://store.uucmotorwerks.com/articles/catless.htm

And Milltek's info about the construction of their HFCs versus OEM cats: http://www.millteksport.com/hiflow.sports.cats.cfm

[Bkitch89]

Its a very strong smell when running no cats. But I kind of like the smell (to an extent). No idea to the exact amount of gains or if it will pass emissions. I wanted the car loud, so the cats had to go.

[S4Per]

Fwiw, you don't need to get rid of cats for the car to be loud.


Sent from my iPhone using Tapatalk

[ATL_]

Fwiw, you don't need to get rid of cats for the car to be loud.


Sent from my iPhone using Tapatalk

But is louder if you do.

I would go the HFC route unless running exclusively e85. Castles really does smell like shit and at power levels lower than a balls out turbo swap, the gains are negligible. On a turbo car, less back pressure will always produce more power with no sacrifice anywhere in the power band - in this case it is probably too minimal to be worth the smell.

[hubris]

But is louder if you do.

I would go the HFC route unless running exclusively e85. Castles really does smell like shit and at power levels lower than a balls out turbo swap, the gains are negligible. On a turbo car, less back pressure will always produce more power with no sacrifice anywhere in the power band - in this case it is probably too minimal to be worth the smell.

My understanding is that on our turbo cars, all of the backpressure generated by the presence of the turbos itself negates most of the 'gains' seen from switching to a better flowing exhaust. Can anyone else chime in?

[Delurker]

My understanding is that on our turbo cars, all of the backpressure generated by the presence of the turbos itself negates most of the 'gains' seen from switching to a better flowing exhaust. Can anyone else chime in?

Non-turbo cars benefit from back pressure at low rpm because the air pushed back into the cylinders slightly raises compression. In a turbo car, the additional air pressure (and way more of it) is generated by the turbo(s) forcing the air in from the front end through the intake tract. You don't lose bottom end (or top end) on a turbo car by increasing exhaust flow (or reducing exhaust restriction); quite the opposite, because a less restrictive exhaust helps the turbo(s) spool faster, adding torque sooner.

[MagnaFlow]

For those running Catless Downpipes, does the smell ever go away so you can't smell in the cabin?

Would you recommend adding high flow's?

Any idea on gains that you've experienced with these?

Has anyone gone through emissions testing with the catless DP's and did you pass?

Thank you!


Sent from my iPhone using Tapatalk

As others have said, the smell will never go away. Running cats, particularly on modern cars and especially on modern performance, isn't detrimental to power production. Modern three-way monolithic catalysts flow really well. If there is any performance gain to be had from removing the catalysts, it's negligible and certainly nothing you'd feel while driving. Also, when you throw in the possible ramifications of being caught without them and the associated fines, it definitely becomes a lot less attractive of an option.

[Roccorace]

I agree with magnaflow. Whoa that is a first ;)

I have catless Milltek to non-res exhaust and it is loud and smelly as hell. To be fair once I updated my APR software it only is smelly in the garage (which is mildly annoying). I would prefer to do the high flow cats.

[mwmaroney1]

I agree with magnaflow. Whoa that is a first ;)

I have catless Milltek to non-res exhaust and it is loud and smelly as hell. To be fair once I updated my APR software it only is smelly in the garage (which is mildly annoying). I would prefer to do the high flow cats.

Just curious what flash APR gave you to use with catless downpipes? I know they are planning on releasing something with their upcoming downpipe but do they already have a file meant to be used with a full catless exhaust system?

[S4Per]

As others have said, the smell will never go away. Running cats, particularly on modern cars and especially on modern performance, isn't detrimental to power production. Modern three-way monolithic catalysts flow really well. If there is any performance gain to be had from removing the catalysts, it's negligible and certainly nothing you'd feel while driving. Also, when you throw in the possible ramifications of being caught without them and the associated fines, it definitely becomes a lot less attractive of an option.

I agree with everything minus the not being able to feel a difference, based on my experience in my RS4. I could feel some low end torque missing - not a ton, but it was noticeable to me - after a year with straight 3" pipes front to back (plus - hey, wouldn't you know - some Magnaflow mufflers :) ).

[markreed]

This is interesting to me. MagnaFlow seems pretty sure cats are not very restrictive (and they would seem to be a good reference point...)

All I can do is relate to my experience which is completely based of other platforms. On my last car, I gained 35 horsepower just with a set of test pipes. (Same dyno, same day, before and after...with an extra degree of timing I couldn't run before). If we are simply saying removal of the cat isn't worth much then I would agree, but on other platforms there are large gains if the tune is adjusted to compliment the removal. Moreso, folks were blowing cats apart at the 650 whp mark. (Stock, MagnaFlow hfc, you name it...)

Is this car somehow different?

Sent from my SAMSUNG-SM-N910A using Tapatalk

[Roccorace]

Just curious what flash APR gave you to use with catless downpipes? I know they are planning on releasing something with their upcoming downpipe but do they already have a file meant to be used with a full catless exhaust system?

They have a specific file for dp that is for the value range coming out the back o2 sensor.

Sent from my SM-N920V using Tapatalk

[markreed]

Does the back o2 sensor impact the tune?

Sent from my SAMSUNG-SM-N910A using Tapatalk

[hubris]

Does the back o2 sensor impact the tune?

Sent from my SAMSUNG-SM-N910A using Tapatalk

The only thing that the publicly available stage 2 "test pipe" file from APR currently does is eliminates the check engine light/code. It does not utilize the additional capability from the downpipes in any way. APR's real stage II file remains "under development", however I have it on good authority that they are expecting release soon.

[markreed]

Thanks! That was my understanding. A previous comment made it sound like something had been altered to allow for less smell. I just wanted some clarification.
An actual improvement of the tune would make me much more likely to modify the exhaust.

Sent from my SAMSUNG-SM-N910A using Tapatalk

[mwmaroney1]

The only thing that the publicly available stage 2 "test pipe" file from APR currently does is eliminates the check engine light/code. It does not utilize the additional capability from the downpipes in any way. APR's real stage II file remains "under development", however I have it on good authority that they are expecting release soon.

I was originally told by APR sometime in November for release with downpipes. It was then changed to first week of January (right about now) from my last update. Have they told you anything different?

[hubris]

I was originally told by APR sometime in November for release with downpipes. It was then changed to first week of January (right about now) from my last update. Have they told you anything different?

Nope. Last I heard directly from APR is that they are "nearing completion" of their downpipes and stage II file, and they will be available "early this year". I thought I was told January, too, but in reading my emails, the vague direct quotes were all I found. I'm not holding my breath but it seems they are certainly set on actually getting the product out there, and they stand behind their word very well from what I have seen.

[hubris]

Talked to APR today:

As for the Stage 2 software, we are in the final stages of calibration. It should be available VERY soon.

[mwmaroney1]

Heh, they just told me "a couple of weeks" so maybe that's very soon.

[hubris]

Heh, they just told me "a couple of weeks" so maybe that's very soon.

Either way, it's enough to keep me on the hook and waiting not-so-patiently.

[Ensoniq]

Either way, it's enough to keep me on the hook and waiting not-so-patiently.

They told me they were very close 14 months ago at H20 international 2014

[CR8LUCK]

I'm working with GIAC right now to see about getting a file created. Anyone else on here using GIAC? If not, why not?

[Delurker]

I'm working with GIAC right now to see about getting a file created. Anyone else on here using GIAC? If not, why not?

GIAC tune here.