4.6is straight pipe with x-pipe.
 

hey guys. as some of you may already know, i had the mufflers removed recently... and the RUMBLING sound is AWESOME! it's the sound that i expected before when i had the resonator removed, but didn't make any difference in the sound... but after the mufflers gone, it sounds great. unfortunately, i lost back pressure and it's running like a four banger, very low torque. i also lost 30% mileage means that i consume more gas since i floor the pedal to gain speed at freeway entrances and/or stop lights. it's terrible! i want to keep the rumble but i want my torque and mileage back. i still have the original muffs and the resonator. i heard about Eisenmann but it's just way out of my budget right now. are any alternatives to eisenmanns?

Got any ideas? thanx!

Let me make sure I understand.

Initially, you removed only the resonator and left the mufflers. And you didn't think there was a sound difference? Did you replace the resonator with an x-pipe or just used straight pipes to the mufflers and no x-pipe aht the time?

Now you removed the mufflers and the resonator too. Is the x-pipe location where the resonator was?

I'm thinking just put back the stock mufflers and be happy. Otherwise you'll have to experiment with different mufflers to see:

1) If you have enough back pressure.
2) Like the sound.

Sounds like a lot of work to me.

Now, I'm glad I didn't remove my mufflers. I like better sound but I don't want to lose too much performance.

Sorry I couldn' be of much help. Maybe someone with a setup similar to yours will chime in with a solution.

Something else is up. I was a performance motorcycle engine builder for many years. So I understand the theory of whats going on. The term "back pressure" is over used and misunderstood. The more "resistance" in a intake OR exhaust will result in less power (performance) So the opposite holds true as well. Decrease the resistance and you WILL gain efficiency (more power)

The problem with a free flowing motor results in all of the power in one spot...... way up top in the RPM range. (aka, drag racer..... they only need red line RPM's) This free flowing set up make a motor like a light switch. As the RPM's build, the power isnt avalible at lower RPM's. And at some point in the mid range of the RPM's, a surge of power and acceleration and suddenly you went from the engine poping and mis-firing to a screaming, white knuckel power. (light switch effect)

With out getting too technical...

Is the exhaust pipe the correct diameter for the amount of flow? A good example of this is a Honda civic. They put on a huge diameter exhaust to get a particular exhaust note. But because the pipe is too big, and the flow to small, the exhaust gasses start to slow down, and "tumble" in the pipe. Tumbleing exhaust is traveling a longer distance (because its not traveling in a strait line) thus slowing down the exit path.... which translates into more "back pressure". (exhaust is no longer "single file line")

^ see that? The larger diameter pipe, actully caused more "back pressure". Or better defined as more resistance.

So in your case......

Because you reduced the exhaust resistance by deleting all of the mufflers, the flow is too low for how large your exhaust pipe diameter. If you ran new exhaust pipe that was..... say...... 20% smaller diameter, your power would wake up!


But you discribed a symptom that did not show these results. I am guessing that the computor may be trying to compensating for change in flow and is making your performance less then desirable.

I vote you keep or get an X pipe. And install an aftermarket muffler that will still carry a happy medium between the flow and resistance.





^ sorry that was so long. I hope you can follow me..... I could have made this 10X easier to understand if we were talking, not typing.

B&B, aka Billy Boat, I have their exhaust on my C5 Corvette.

gentlemen! thank you for your input.

@Twinspoppa: Yes, first, i replaced the resonator with a Magnaflow X-pipe and kept my original mufflers. the x-pipe was installed where the resonator used to be. i was disappointed that the sound was the same. Months later, i removed the mufflers and the rumbling sound i've been looking for came out.

Since the gas prices are now ridiculously high, i am tempted on putting back the stock mufflers. at the same time, i'm hesitant on doing that because i already spent $225 on replacing the muffs plus additional fees on putting back the stock muffs. i'm thinking that maybe i should just find a similar Eisenmanns type mufflers for less. Anyways, definitely keep your mufflers on unless you're replacing them with performance specs.

@Jordo: that was some technical information, man. thanks though. you're right, less resistance, more power. not on this case though. i literally step more on the gas pedal just to gain decent speed... which made my gas gage needle go down drastically fast. you're maybe correct on the computer theory. i'm gonna have to talk to a BMW tech or something. i already have the x-pipe where the resonator used to be. i may have to find a performance type mufflers or maybe install the stock ones back on. Thanks, man.

Sorry to dig an old thread, but did you ever get this sorted out?

Hey Ducs... Thanks for the follow up. I just reinstalled my stock mufflers and kept the x-pipe. It still growls a little bit... but not the way I liked when it didn't have the muffs. Just saving up for the Eisens now.

Do some Magnaflow universal mufflers. I was lucky and scored an Eisenmann on the cheap, but if I had to re-do it and didn't have the cash, that's what I'd do.

So the power came right back, right? Just like it was before.

so what ever happened to the cats in this situation??

and generally you don't want more than 1.5psi of back pressure. generally.