What would happen if I put straight pipes on a 4.2 v8?? Would I be making less/more/same power compared to a non-resonated cat back system?

 

less torque more bhp.. freer flowing on the top end.. nominal loss of low end grunt..

 

but would it be still more torque than stock?? i mean when you said more hp less tq, did you compare it to a non resonated cat back or stock??

 

It all depends on the size of the pipes. With properly sized diameter piping you would get a bump in hp and torque, but with piping that is too large you would lose exhaust gas velocity and torque would suffer. Too small and you would choke the motor at higher RPMs (where more gas is being pushed out of the motor) and hp would suffer. It would be VERY loud, but these motors sound very nice when uncorked though.

There is a youtube of a V8 S4 (don't recall if it was a B6 or B7) with straight pipes, and it sounds mean - not sure if it is something I would like for a daily driver.

The thing is, there are mufflers available that are able to reduce the loudness of the exhaust and produce very little, if any, restriction. If you are considering straight pipes, then you are obviously contemplating building a custom exhaust. It should be possible to incorporate a couple of these low restriction mufflers to keep the noise level down in the acceptable range and still get about the same bump in hp.

That being said, I doubt the increase in power is going to be significantly more than anything you could get from one of the existing exhaust providers (Fast Intentions, Motorklasse, AWE, Milltek, etc.). Two factors constrain how much hp can be gotten from these motors: 1. they are pretty darn efficient from the factory, and 2. once the exhaust from the cat back is opened up a little bit it becomes the manifold and downpipes that limit flow more so than the exhaust.

IMHO, FWIW...

 

^^here's the video you're talking about^^

http://www.youtube.com/watch?v=maygdvKBV9s

personally I think it sounds like a lifted truck with a "Famous" sticker in the back windshield. I'd prefer a more refined tone for sure.


also here's a really good read about exhaust systems:

http://www.audizine.com/forum/showthread.php?t=250634

 

Good for the track, terrible for a daily driver. Not to mention every cop in the county would pull your *** over for noise pollution. I would eliminate the stock resonators, and at the very least put in a couple of glass packs to quiet it down a bit. Two glass packs will still have the same tone as an uncorked exhaust, but you won't lose your hearing.

 

you could also throw on some Magnaflow 14851. They change the sound a little bit (for the better), fill out you exhaust cutouts (4" tips!) and don't cost too much. A pair can be had for around $250.

check it:

 

I daily drive my car in Turkey and there is a lot of traffic here. I wanted to do straight pipes with just one muffler on each side since it looks like i will get the most hp with that setup but I think it'll be too loud. so here is what i've decided to do:

stright pipe no resonator from the header, glasspacks in the middle and QTP Cut outs right after that then the stock exhaust will continue till the end.

basically, when i turn the switch on for the cutout, it'll be straight pipe no resonator with just one glasspack on each side.
when the switch is off, it'll be no resonator, then glasspack, then the stock rear mufflers which i hope will be a lot quieter

 

please make some comments on my exhaust setup since I still am a newbie and not sure if this will provide any gains when the cutouts are on

btw, never heard of this glasspack. are they good? or should i get something like borla or magnaflow?

 

I just put straights on mine...Love it sounds sick...i drive it everyday the trick is just release the gas when you driving by cops...