straight pipe? exhaust question

[nissamax]

So i have a 04 wrx stock turbo upipe dp tune

but i want a straight pipe me and my dad are gonna custom make an axle back and cut the resonator out and weld a straight pipe in there as well

my question is am i going to loose power from this? since its a turbo car do i need back pressure? especially since it will be basically full 3 inch back

Any info is helpfull thank you

[renn]

on my sti i made more power with a cobb cbe than with a straight pipe. proven on precision tunings dyno.

the straight pipe was also ear splittingly loud, i wouldn't do it..

[Subie_sleeper]

DON'T DO IT !!!!!

The Baja is destroying my hearing ONE commute to work & back at a time. :lmao:

AT LEAST keep a resonator......

[nissamax]

Sound is not the problem ive been running my car open midpipe for months now im completely used to the sound so it doesnt bother me.

renn was it like a huge difference power loss or just a tiny bit?

[DaBombDiggidy]

turbo cars are not about back pressure N/A is. turbos are more effecient if they can push out exhaust faster so bigger/less restrictive piping is always better you are simply sacrificing drivablility because itll sound retarted with no kind of muffler/resonator.

edit: your on stock turbo (guessing) IMO no reason to go with straight pipes you can max out the effeciency of that turbo without being uber loud.

[nissamax]

The point of doing this is actuay to be uber loud lol. I've heard my buddies n1 race with no muffler and that has no resonator and it really wasn't that loud. I just love the sound and rumble even thou that sounds retarded

[renn]

i made like 15 whp less. we thought it might have been so loud that it was setting off the knock sensor.

if you're set on doing it, do it. its just ricey on a street car... no one will want to ride with you either

[jpalamar]

I'm running staight pipes on my Mustang after the cats. It actually isn't much louder the most aftermarket catbacks. Not all engines sound good this way but if you like it go for it(my GTO sounded like ass without mufflers). There shouldn't be any noticable power loss or gain from it. Just a few shaved lbs at the end of the day.

[nissamax]

Yea I'm going to be running basically a straight pipe from the turbo back. No cats no resonator. And ive been running open downpipe which is basically. A straight pipe with a resonator and it's loud. And people actually like the sound yes it gets loud at times on the highway.

[renn]

http://www.youtube.com/watch?v=AtD5QUWNYv8

it did sound bad ass, don't get me wrong.

but driving this and driving with an open dp are two different things.. both are loud but the straight pipe resonates so much more and there was so much drone cruising you couldn't even try to have a conversation.

[nissamax]

My bad I meant I've been driving open midpipe. Idk why I said downpipe I feel it's so loud now because it's bouncing off the bottom of the car and the ground and when the straight pipe is made it will exit behind the car which will still be loud as **** but not as bad

[DPancoast]

Just try and make it an efficient setup. If the piping is too big you'll def lose power.

[Honest_Bob]

3" straight pipe with a litte resonator in the mid pipe.

http://www.youtube.com/watch?v=orFdlFE15TE

I cant say if I lost or gained any hp, but I will say the motor was less restricted compared to my Greddy SP2. Holy **** was it loud that is until the waste gate opened up and drowned it out.

[renn]

you couldn't hear when the ewg opened on my sti, that's how loud it was. tial 44mm

[nissamax]

I plan on eventually going vf39 with external wastegate.

[nissamax]

So my cars going to be loud as ****.

[STi<LGT>EVO]

Originally Posted by nissamax

My bad I meant I've been driving open midpipe. Idk why I said downpipe I feel it's so loud now because it's bouncing off the bottom of the car and the ground and when the straight pipe is made it will exit behind the car which will still be loud as fvck but not as bad

this is true, but get used to sounding like an srt-4 when you let off the gas. the backfiring will get on your nerves

[DPancoast]

Meh. My teg has a cat and a muffler and it pops and backfires. It's not so bad

[Merp]

Originally Posted by DPancoast

Just try and make it an efficient setup. If the piping is too big you'll def lose power.

No, not on a turbo motor. No ifs ands or buts about it. The less post turbine pressure, the more pressure gradient across the turbine.

You guys that lost power going to a straight pipe definitely had some issue with the tune. Changing the backpressure will have a big effect on the BCS which likely put you into new load cells on your maps.

If it's a big enough change, to have a significant effect on pre-turbo EGBP, you'll start changing with the motor's VE, really throwing the tune off.

[renn]

Originally Posted by Merp

No, not on a turbo motor. No ifs ands or buts about it. The less post turbine pressure, the more pressure gradient across the turbine.

You guys that lost power going to a straight pipe definitely had some issue with the tune. Changing the backpressure will have a big effect on the BCS which likely put you into new load cells on your maps.

If it's a big enough change, to have a significant effect on pre-turbo EGBP, you'll start changing with the motor's VE, really throwing the tune off.

not specifically saying it was lost backpressure but when my STi had a straight pipe -- completely straight 3" tubing from the turbo back, and headers and an external wastegate, i made something like 15-20whp more changing to a cobb catback. the gap in power at redline was even more - something like 35 or 40whp.

i was dyno tuned for the straight pipe, and then with no other mods dyno tuned again on the cobb catback.

like i said before the sheer loudness and resonance of the exhaust could have been tricking the knock sensor to go off. but no matter how hard we tried on the dyno, we couldn't get the car to safely break 300whp. and then with the cobb cbe we made 317 after one or two pulls worth of tuning. the only thing the straight did for me was spool the turbo BARELY earlier. like 100 rpm earlier (on the dyno.)

i'm going to look for both of the dyno graphs and try and post them. it's pretty suprising considering the tuning conditions were identical and the only change was the exhaust.