Okay, let's have an educate me session about downpipes
 

So for the not-so-mechanically inclined, what do downpipes do? I can figure out that they pretty much increase the efficiency of a given volume of the exhaust leaving the engine.

But is that it? Why are they so expensive. I mean, they are *just* pipes, right? What's so special about them?

And, if you do something like, oh, a turbo upgrade, is it necessary to add these downpipes? What are the downsides to them and who are the available vendors.

Thanks.

i don't know much either.. but have not people on the board get custom made one on muffler shop for
 

like $200 or so?

time to start audi DOWN PIPE group like the Brake system?

better volumetric efficency,
 

expensive because they sometimes include $$ MM catalysts

IMO
cermaic cat, downpipes should be less than they currently are


and the potential market, is small and specific

(market means how many peopole will actually buy YOUR brand of DP..not just the number of cars sold)

a RX-7 or Supra or WRX downpipe is cheaper

beacause the potential market is MUCH MUCH bigger

and the only need One......LOL

300zx DP's are a simlar example...but a larger customer base...who usually bought the car used for $10-20K

downpipes will help high RPM power...neccessary is another issue...

But, for and extra $2K on top of bigger turbo's?

why the hell not?

If you do a turbo upgrade I would say they are a must....here is why....
 

Example: Essentially you are trying to cram 200lbs. of fat into a size 6 dress. Granted some women can do it, but form and function are lost. Spandex does not apply to our cars :)

Exhaust gas temps are hot, well, damn hot. The quicker you are moving them out of the exhaust the better. More efficiency means more power. You might only get 15 hp from the DP and high flow cats with a chip, but if you want to hit high hp levels, i.e.400hp/400+tq, then they are in order.

The effiency level is way down on the engine with the current exhaust setup. A perfect example is when you put a cat back exhaust on your car. You now have more power on the high end (~6300rpm or so instead of 5500) With the DPs and cats you have a strong power band pull all the way to 7000-7200 rpm.

I would say that the cats are the main factor in the factory system. You have a precat bolted right to the back of the turbos. And then there is a secondary cat on both pipes right before it meets the straight exhaust piping. DPs take out the first cat and they incorporate a high flow cat in the place of the 2ndary ones. The flow efficiency goes way up.

For 340 hp applications, DPs are necesary, but above that you are just trying to push to much through a restrictive hole.

I agree the price is high. The bulk of the cost in my EVO system is with the renKATT race cats. When your cats cost $550 a piece and you need 2 plus the 321 Stainless and labor you can easily see a price tag of $1800-$2K emerging. If a company made a set with out cats I would think that it should sell for under $1K. But you'll have engine codes out the azz.

My wrists hurt so I think that is all I can type for now :P Hope that it helps.

Won't work, the exhaust temps are so high that you need a high grade ss pipe that will cost way over
 

$200 or so. When it is near900-1000`F then you need to watch what you put in its path.

Actually the removal of pre-cats (even the location of them)
 

effects the output of the motor. This is even true for N/A motors.

I think the tuners exagerate the numbers related to the downpipe kits a bit since they are so expensive. I bet on the S4, the whole turbo back exhaust gives around 30HP and the downpipes & cats alone no more than 20HP.

well,
 

why does the RS4 have different downpipes?

-ok-

so why don't you have the RS4 ones on you car yet? :-P

Downpipe info & dynos
 

<center><img src="http://pictureposter.audiworld.com/12322/merged-runs.1.jpg"></center><p>
Read my other post, but this sums it up quickly...

Greg
2000 Pearl S4<ul><li><a href="https://forums.audiworld.com/s4/msgs/465384.phtml">Downpipes...</a></li></ul>

well, how much do the RS4 pipes cost?

thanks for the post....
 

i am putting the apr down pipes on soon...cant wait for the 100 octane w/ the race chip