Don’t know about gasket.
I’m still debating on putting cats in, which would be easy to do with the setup.
I’ve considered going 2.75" all the way back, but I might be too in love with the current sound to change it for that amount of gain. Sound is civilized when I want it to be (it’s a daily driver) and loud enough when I want it to be that.
@Jspazz - sorry, that pic was taken while finalizing fit and finish and therefore shows a temporary clamp which you can reuse between fittings. Clamp on car now is standard v-band clamp.
That 2.36 neckdown should be a bit of a killer on efficiency. Why bother with the downpipes if you’re going to move that massive restriction just 2 feet down?
It’d be nice to A/B setups to get definitive on the gains I’d get, and that might convince me to move.
As you can see by the graph, there were pretty good gains across the board with just the DP’s.
Indeed it was a nice bump but it would seem you’re still about 30whp or so short of a properly running stock RS4 (assuming the dyno wasn’t done at altitude). I know this is an old dyno but still…I would have been worried had I been in your shoes. My S4 dyno’d 270whp stock which is only 12whp less than your RS4 stock) and 292whp with catless DPs which is only 8whp short of your RS4 with DPs.
(And regardless of my own numbers, that’s like a 33% loss which is massive, especially a manual).
At the very least, I would have gone to another dyno to get a second opinion from another machine just to compare.
This post has nothing to do with the sc or anything. I’m only referring to your pre-sc RS4 and the concerns I would have had, had it been mine.
No offense but those gains are basically 0% related to the diameter of the downpipes and 100% related to the elimination of your catalytic converters. Your downpipes could be 2 feet wide (joking, but making an extreme point) and it won’t matter if your catback is 2.36". Which it is.
You could have just gutted your catalytic converters in the stock 2.50" downpipes, which neck down to 2.36" right at the end.
@Axel. I was concerned, too, and I guess going to another dyno now post-SC install still informs me directionally of differences between this dyno and others. I could’ve gone there right away, yes, but felt good about info I gathered regarding this dyno’s usual output re other stock RS4’s. Having been to another one now and seeing about 20-25whp difference as discussed earlier in this thread, confirms that well enough for me.
@Saki - I could’ve just gutted, sure. Honestly, I don’t think there’s a lot of magic in one DP vs another, and do believe that removal of cats is by far the largest contributing factor to improved performance across any and all DP’s, width being a distant second. Do I hear you saying the same thing?
(still wishing someone would enable editing of my own posts…lol)
And to be clear: my original response to you was regarding your question of benefits of DP & catback vs benefits of just DP’s (i.e. why do just DP’s and only move the restriction down 2 feet). I think we took a little turn there as you started discussing the ‘why’ of the DP benefits I saw…which is fine, but wanted to make sure we had closure on the first question.
Saki is saying a bottle neck is a bottle neck. 3" cat less DPs necked to the stock catback is going to provide the same result as gutting he stock DPs with stock CB…so your AMD DPs are more or less pointless. Don’t take offense to that, but it’s basically the truth.
wow…looks like although I can’t edit, the forum is making up words for me “beinefficientits”…really, I’d spell it like that twice? That is seriously…odd… O.O
@euro - my reply back was, is the belief shared that the vast majority of benefits seen with DP’s is really about the removal of the cats? i.e. width and design specifics don’t actually add that much comparatively, regardless of vendor? (keeping catback out of this point…purely DP benefits discussion).
lol…
someone else please type ‘benefits’
b e n e f i t s
benefits
b e n e f i t
benefit
awesome 
there’s magic in the downpipes if you have a good catback. Can’t think of them as seperate. It’s a system.
headers - downpipes - cats - catback - mufflers
if any of them are crap/restrictive, the whole thing is crap/restrictive
We tend to compartmentalize, but we shouldn’t. If you upgrade downpipes, you should make a commensurate upgrade to your catback and ensure that it’s well designed (straight as possible, straight through mufflers, good diameter overall to ensure you’re not hurting the intake side). Or you can just save your money on the downpipes. Same goes for a catback…there’s not much of a performance gain to a 2.75" catback with a 2.36" neckdown in the stock downpipes.
It’s an autocorrect feature following an argument about tuning and a site that begins with N E F and ends with M O T O. Try typing out this word that begins with N E F and end with A R I O U S for teh lulz
Agreed with your general point (it’s a lot less effective to upgrade just one part only to leave a big restriction somewhere else down the line.
Just to be specific though, head losses in pipe flow are cumulative and indeed very easily compartmentalized (by definition, the losses in the system are just the sum of the losses of the separate parts.) To take the hyperbole of 2ft wide DP’s only to terminate to a stock size catback to the other extreme, imagine a 2 ft wide entire exhaust that went all the way to 5" from the exhaust exit, and went down to stock diameter. Would that flow better than stock? Yes, because the losses are cumulative. Though, like you say, gains from that compared to something very significant like removing cats, are very small in comparison.
So I agree on the whole, just commenting on the specifics.
I thought fancy RS4 owners from quattroworld were all spelling bee champions?
No what I was saying was that the benefits of your big downpipes won’t truly be felt without a catback that keeps the flow moving. Not just size based, but all of the things I mentioned. Restrictions are killers.
if you leave a restrictive 2.36" catback in place, then put in some 2.75" or 3.0" downpipes, you still have that restriction in the catback. So although you are seeing some gains, the grand majority of those gains are the elimination of the catalytic converters…and people often see those (or similar) gains on stock downpipes with the cats gutted, when still running stock catback.
To truly realise the beinefficientinefficientinefficientinefficientinefficientinefficientinefficientit of a larger diameter downpipe, you need to ensure that the rest of the exhaust isn’t restricting flow.
Also, that spelling thing you’re having trouble with was deliberately implemented by the site owner to thwart references to a site where people take tunes and post them up for people to steal them. EPL should be well familiar with it…I believe they’ve had their files posted there a few times, and the popular theory was that a new tuner in the B5 world used those files as the basis for his new ‘tuning business’.
So i guess your phone is broken? Call Tony.
Back to Per, who may or may not be Swedish.
LOL I think you guys are past the exhaust system talk, but…I don’t want to say that people are wrong…ill just say:
hey! here’s an article that explains more than i could say about exhaust system sizing. Good read. It even uses that line that one member here always repeats…"… cars are leaving horsepower on the table" LOL.
http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/viewall.html
It’s a Norwegian name, but I’m born/raised and citizen of Germany…go figure 
To boil it down, opinion is: (1) I wasted money on DP’s if I won’t ever go with catback of similar diameter, and (2) full gains aren’t realized unless you address all points of restriction.
I agree with the above. I have the door open if/when I find the catback with matching characteristics to DP for performance and sound that I like. With that option in mind, it’s cheaper in the long run to do the DP’s now vs first gut then get DP’s down the road.
Game on.
Looks like a good article, I’ll have to check it out in more depth later. Tuning naturally aspirated exhaust for pressure waves, Helmholtz resonance, heat/velocity etc is definitely more involved than on a forced induction car, and that article covers some good bases!