That x-pipe is gorgeous.
^first public picture of one as well
here’s my A6’s catback, similar setup
Nice you should cross post this to the A6 section. Whats done to your A6?
I love the RS4 System that is a big difference not just in size but even the kit layout. Very nice
JHM exhaust all the way. I cant believe people buy that miltek setup now seeing the pics. almost like the stock setup. And i would bet the stock flows just as good with the h pipe welded in there.
The only difference between the stock and miltek is that the OEM bends are not a true mandrle bend so the pipe is actually smaller in the bends. So both flow about the same but put an X on the stock and it will out flow the miltek!
I can’t see on the RS4 exhaust stock. is there still the manufacture section thats smashed down like on the S4 and A4’s?
that’s insane isn’t it?
so is the 2.75 JHM vs. Milltek pic. Wow.
This thread really is an eye opener. 2.75 vs. 2.5 doesn’t sound like a big deal because it’s just a 1/4", but it’s a massive difference when you really look at it.
2.50" diameter = 4.90 square inches cross-section
2.75" diameter = 5.94 square inches cross-section
That’s a 21% increase.
The S4 world is even funnier…the 2.25" guys who are always saying it’s no big deal to go 2.5" are nuts. 2.25 is a 3.97" cross section…and going 2.5" (4.90 sq in) is a 23% increase.
Of course if you don’t know what the engine can/will/must flow to make good power, you don’t know what exhaust diameter to start with. You just try something that the other guys tried and is selling. I find that incredible. There’s some really basic homework you need to do to determine the optimal exhaust diameter for a 7000 or 8250 rpm revving 4.2 litre V8 engine…and it appears that Milltek, APR and Stratmosphere just flat didn’t bother to do it. Is that possible?
If I remember correctly the Milltek RS4 exhaust isn’t even 2.5 inches. Its less then that. Just like the S4 4.2 the RS4 4.2 Milltek offering is just a shade over stock size. Not enough to justify the 2000$ price tag or even the thought of putting on a new exhaust
oh snap, you’re right.
Milltek RS4 catback is 2.36". Great. More restrictive than stock.
Milltek S5 ‘large bore’ (lol) downpipes are 2.36" as well. The catback? Also 2.36"
That’s not even trying.
Bumped because its so interesting. Also, a new member pm’d me asking some exhaust questions and this thread was particularly relevant.
I hadn’t seen this thread yet. Its always nice to start the day with a chuckle… 
It’s pretty eye opening.
http://www.millteksport.com/exhaust.products.cfm?variantid=194
Stock Rs4 downpipes = 2.50" necking down to 2.36" at the end to mate up with the stock catback. Precat upstream, main cat downstream.
Milltek RS4 downpipes = 2.50" necking down to 2.36" at the end to mate up with the stock/Milltek catback. One cat, downstream.
Basically Milltek eliminated the precat…and created piggies (with cats that are worse than stock main cats). Piggies are free with 3hrs of DIY work in your garage. Milltek catted downpipes are $2,500!.
Stock RS4 catback = 2.36". No crossover, decent bends, but a crimp right near the mufflers.
Milltek RS4 catback = 2.36" H-pipe crossover, worse bends than stock and eliminated the stock crimps at the mufflers.
Again, nearly a stock replica with the exception of the h-pipe. Stock is free on your car. Milltek is $1700.
This is why I get a laugh when people say things like ‘THAT CAR IS NOT STOCK…IT HAS A MILLTEK!’
From a sound point of view, Milltek is fantastic, but from a performance point of view? I don’t get it. I REALLY don’t get when people are tuned…then they get Milltek downpipes and catback, and get a ‘custom remap’ then gain boatloads of power. As you can see here, that’s really not possible. You can also see why saying you need a custom tune to take advantage of your Milltek is also bunk.
Stock downpipes
http://jhmotorsports.com/shop/catalog/images/JHM-VAST_B7_RS4_Piggies.jpg
[b]Milltek downpipes/b]
http://www.audizine.com/classifieds/data/24/photo_111.JPG
Stock catback
http://audirevolution.net/addons/albums/images/650780120.jpg
Milltek catback
http://audirevolution.net/addons/albums/images/668062472.jpg
And as technical assiantant pointed out. Those crimps are not necisarily a bad thing.
Contrary to a bad bend which affects airflow and dynamics, the crimp gives the same pipe diameter, just oval instead of round. And its 2 inches away from the muffler so any “turbulance” it might cause is irrelevant at that stage since its at the end of its path anyways.
the reshaping of the cross sectional area will cause some pressure loss, same with a bend. I wouldnt say one is worse than the other.
The key is to not think turbulence, think pressure loss
The stock cat back isn’t that horrible for performance as I did trap 113 on it. Horribly restrictive , I think not. I do have home-made dp’s an let me tell you when I start the car it shakes the everything In the garage!
It’s horribly restrictive relative to a well designed 2.75 setup
P.s. someone on rs246 doesn’t think it’s possible you ran 12.26 @112.98. Named Arthurpe… He did some math and has decided it’s not possible
Enjoy!
oh god, not this shit again
Hahaha, this happens over and over with every car I own…
Thanks for the lol , saki!!
Fwiw , I have a anoth video of my best run from the stands, I’ll check and see if the time is visible.
Still I’ve had a quite a few compliments on my exhaust note. But I will never put a full exhaust on the car as I don’t want to spend money twice, since boost is around the corner.
What A fucking mathematician…So much work to discredit someone. I don’t get why instead of being pumped most RS4 guys don’t congratulate each other. Prolly just another guy that loves CC threads and hates the drag strip.
I also enjoy his shade tree engineer comment talking about JHM on page 1…