Stock downpipes with the cats gutted.
how is that any different from JHM down pipes, other than the size of the piping. The cat is still not there. If it doesn’t smell gutted then i dont see how it would smell with DP’s.
There is still a larger collection area where the cat used to be. Stock piping is smaller and witht the collection area is a more turbulanced flow. Straight 2.5 pipes are going to be the smoothest, fastest way for the exhuast to escape out of the car. Hence why they will be more beneficial than the piggies.
My assumption is that the “gas” smell will be trapped or mixed around in the piggie kind of trapping the smell in there, instead of just being shot out the car where you can smell the sweet smell of horsepower and unburnt race fuel ;D
I’m no tech and I can still fuck up an oil change, but hey, I’m learning. Thats my .02
That makes perfect sense, I think that info is worth more than 2 cents Zingo
So a fairly newb question for you guys, but does the magnaflow 16601 cat-back system work with the 3.0 without any modification? Like is it a direct fit?
Performancepeddler.com has it for $580 and Im really debating on that or just mufflers.
Please help 
see I’ve never bought that the open cat chamber will cause huge turbulence throughout the powerband… maybe down low when flow is limited, but at higher rpm I think you’d see a stagnant buffer region in the cat chamber edges with the middle flowing air through it… of course there is some drag along flow out of the boundary areas but how much, I think its limited at WOT… my S4 made very good numbers despite having an open cat chamber.
as far as smell its unburnt fuel. With no cats it simply comes out, with a cat it is drawn to the precious metals on the cat matrix where it is then oxidized (same reaction as burning fuel just different kinetics due to the catalyst)… this results in no unburnt fuel and no gassy smell
Yea, sorry when I posted about piggies not smelling, I was thinking about the S4 which has pre and main cat (thus people only gut the precat). Most of the 3.0’s have just 1 large cat chamber correct? There was one version that had two correct? If you’re catless, it’s going to smell, if 1 of the two cats per dp is still there, it won’t.
I wonder how close a B6/7 dp would come to bolting up, it’d be interesting, but I’m sure far from close.
Thank you for clarifying this. I understand now. My car does have 2 cats each side. But my question now, I will be taking a B6 S4 exhaust and connecting that to my JHM DP’s, will I still have 2 cats on each side?
Unfortunately not, your cats are attached to your either end of your stock DP’s
http://audirevolution.net/addons/albums/images/361609541.jpg
The JHM dp’s end up replacing that entire piece. your could probable get an exhaust shop to chop off the secondary cat and make it so you can take it on and off between your DP’s and exhaust if you desire to catless every now and then
I’m talking about the rear cats, does an S4 exhaust have a cat in the rear on each side? cuz thats what i thought maddog was saying that it has a precat and a main cat but didn’t say how many.
^Yes, each down pipe on a S4 has the Pre-Cat (which is removed in a normal “piggie pipe mod”) and then a larger main cat.
The picture Lout posted roughly resembles the S4 DP variance that has the pre & post cat. However, my understanding was that some 3.0 A4’s have just one main cat in what would normally be considered the precat location.
If you have 2 cats on each dp, the one can be removed closest to the motor to help fight heat, aid in performance, still pass emissions (even a sniffer test), and not smell like a catless cat (but a tune or O2 spacers will be required to prevent cel). If you only have one cat per dp, all that is out the window as when you remove that it’s a catless pipe just like any other setup.
It would be my GUESS that JHM is just going to make a 2.5" catless setup. I would be surprised if they sold a catted version of that dp as the additional cost just isn’t worth it for most people (one off production aside obviously).
I have a question that kind of relates to this exhaust topic…in a round about way…
Before getting my LWFW from JHM which is like driving a new car! i had CEL 421 and 431 (I think) for the Cats not heating up properly or whatever, and was told to get new cats, blah blah blah. I replaced the flywheel and clutch only, and CEL went away. I figured i would see it pop back up after a few days because the battery being disconnected. 500 miles later (2 weeks or so), it finally pops up again while hydroplaning through slush ::). I just figured it was the cats coming back to say “hey!”. two days later…CEL is gone again and hasn’t been back up after about 300 miles…whats the deal?
Im not sure what is going on with your car,
I am just throwing an idea here but it could be your o2’s on the way out
This is what I would look to first as well. Since it comes and goes, I would think it’s a flaky sensor.
not necessarily. piggies are stock B5/6/7 S4/RS4 downpipes with the pre-catalytic converters, or precats gutted.
The B5/6/7 S4/RS4 downpipes (one downpipe for each engine bank, so 2) all had a precat right up by the motor, and a main cat downstream just before the downpipes mate up with the exhaust. The main cat flows really well and is highly effective while allowing the car to perform reasonably well. The precat on the other hand is a disaster that chokes the engine by keeping heat jammed in, right at the exhaust manifold.
The precat is there to heat things up quickly on a cold start, in order to reduce cold start emissions. Unfortunately after a minute of the car warming up or so, it’s not necessary…but it’s still in the way blocking/choking/corking the engine’s hot exhaust gases. Gut the pre-cat material and you open up a bunch of flow, and thus performance.
The concept was apparently an idea of Mike from VAST performance back before they turned psycho and started hating their customers and supporters. His nickname is PIG, thus the product name ‘piggies’.
Not sure if all the 3.0 guys have this 2 catalytic converter per downpipe setup…but in this pic posted by lout, the big rectangular shaped bump is the main cat (good) and the cylindrical bump that looks like a rabbit inside a python is the pre-cat (bad). At least that’s the setup on the B6/7 S4/RS4. Remove the downpipes, gut that pre-cat material out = free horsepower.
http://audirevolution.net/addons/albums/images/361609541.jpg
Some 3.0 have DP’s that look like mine, but it is more common to have a DP’s that will look like snake trying to swallow 2 rabbits at the same time.
http://i1108.photobucket.com/albums/h411/halo549b/923562d6.jpg
Labree CATS.
Only problem is the flex pipe is too low and hits my trans support.
Slightly larger then stock but not 2.5.
Ummm. … “only problem” is a bit of a stretch. (size, cat location, flex joint, material?)
Just like Milltek catted dp’s on the S4 (until recent redesign), the cat should be down stream rather than up by the motor where the precats were.
Also, how the heck does that cat work. it looks like a catless version with that secondary O2 sensor being right in the middle of where the cat material should be.
It’s very difficult to find a worthwhile aftermaket catted dp on the audi’s. Like I’ve said, catless or piggies’, it’s tough to justify anything else. Usually b/c the catted versions offer virtually no benefit (due to design etc) or they’re well made and cost so much the performance is minimal compared to piggies (if you have the dual cat per dp for oem dp’s).
yeah, not really ideal there.
Labree used to have a guy named Danny as part of the team, and they made great stuff. Now Danny has his own shop, Fast Intentions. Although the FI catted downpipes had a screwy set up too didn’t they?
Had the same thing happen to me, cel would pop up and go away then come up again. i was hoping it was a sensor but unfortunately not. my Bank 1 cat was melted on the inside and so it started to make my Bank 2 cat go bad as well. so i just gutted them for $200