2.5" would be better :thumb:

I have an eco, and this isn't my place to make a comment but I'm gunna get a flowmaster 50 delta. I don't know of anyone having one or mentioning the sound. Cat back is going to have to wait 2-3 months cuz of ASS09.

i thought most flowermasters didnt sound to good on 4 cyc?

i had a flowmaster it sounded like sh*t so i took it off

he can get it for his. I spent the money on mine I'm not turning back now

You don't want any backpressure in an exhaust system.!!!!!!!!!!!! haha lie!!! u need back pressure unless ur wanting to buy a new motor dont even touch ur resnatior u have a 4 cylinder point less!

This deserves one or more of those face palm pics...

That whole back pressure myth was only slightly true with old cars with primitive (badly adjusted?) fuel systems.

The whole back pressure thing is debatable people will tell you need some others will tell you that you don't need any me I personally don't care it's not that big of an issue to me.

my personal experience: you need at least a little back pressure (not a lot though) for NA/SC, and more for Turbo (just to get spooled)

Sorry, you don't want any backpressure at all in your exhaust system. Backpressure = a restriction somewhere. Think about it.....backpressure is exhaust trying to push back to where it came from. That is bad. You want the exhaust to get out of the engine and out of the exhaust pipes as quick as possible.

On a naturally aspirated engine you want to choose the right pipe size to maintain fast exhaust velocity to help with scavenging. With a header and the right sized exhaust, the velocity helps pull the exhaust out of the cylinder, and during valve overlap, actually helps pull the intake air into the cylinder. You also want to get rid of the retrictions with free flowing, straight through mufflers.

On a supercharged or turbo engine, the air is being forced in, and there isn't much of the scavenging effect that there is on the NA engine. With boost, there's also a bigger volume of exhaust gas to get out of the engine, so you can go with larger piping than NA.

If you have backpressure on a turbo engine, the pressure pushes back on the turbine wheel. That slows down spool, it doesn't help it. The turbo is the restriction, and you want to get all the restriction off the turbo, so the larger the piping the better. The lower the backpressure in the exhaust system, the faster the turbo can spool, and the more power it can make.

Your whole post was pretty well thought out and informative. And I agree, 4 cylinders are pointless, and can't possibly be very powerful...

/sarcasm

This deserves another

that was a lovely explanation, thanks.

I agree 4 cyc = waste of time/money no power at all...ha

Actually, you do want some back pressure. Since there is typically overlap between the time the exhaust valves close fully and the intake valves opening, if the flow out the exhaust is too fast you will pull the intake air and fuel out the exhaust side. That hurts performance, since the whole goal is to have as much stuff blow up in the cylinder as possible.

On turbos the turbine provides the back pressure so everything after that can be as free as a bird, without hurting performance. You also want to have it flowing as fast as possible from there to keep the temp down.

I've got charts somewhere at home (from when I cared) showing the difference from stock to header->larger piping->high-flow cat->performance muff. And there is a reduction in TQ.

I second the DynoMax, I have a video of how it sounds with stock piping, if it’ll help, its the MySpace link, lol. But I love that muffler, it is baffled and has a little bit of fiberglass, its pretty quiet @ idol and sounds pretty sweet @ high RPMs ^_^

Sorry Eddie, that's incorrect.

With backpressure in the exhaust, the piston has to work harder to push the exhaust out of the cylinder. The harder the piston has to work, the less efficient it is and the less power the engine makes. With no backpressure, the exhaust is easy to push out of the cylinder.

High exhaust velocity helps the scavenging effect, and any amount of backpressure slows down the exhaust. The exhaust exiting the cylinder at a high velocity helps pull all the exhaust out of the cylinder, and when the valves overlap, helps pull fresh air into the cylinder, letting the piston work less and therefore more efficiently to draw in fresh air.

You say air can escape through the exhaust if the velocity is "too fast". There's not a set amount of air that's going to enter the cylinder. Even if air escapes into the exhaust stream during overlap, there's still air being drawn in by the piston after the exhaust valve closes.

Even on a turbo car you want to reduce backpressure before the turbo, since the turbine itself is a big restriction. You'll want a free flowing manifold and turbine housing with a low backpressure wheel, as well as large, free flowing piping after the turbo. High velocity and equal pulses before the turbo, and low restriction after the turbo help it spool faster and make more power.

Hey guys,
What if I was to replace the stock catalytic converter with a magnaflow HI-FLOW cat. and leave the stock resonator would this kind of be redundant? I am also thinking of replacing the cat and deleting the stock resonator and running 2.5 pipes to the muffler. I DO understand that the car would be louder by doing this, however my question is would it sound like a honda with a fart can?
Thank you to the guys that have already tried answering this for me...Alerosaint, Heineck, Sburke.

I am interested in getting in contact with Chris (C2) to find out what his car sounds like with the muffler in place of the resonator.
Any info would be appreciated.
Thanks,
-Smurf-

When I bought ion's old rims and tires, I got to hear his exhaust in person, along with the S/C whine ^_^ It sounds realy good, a little louder than I thought, but still sounds great. I think he has a magna flow "race" muffler as a resonator, high flow cat and DynoMax muffler W/ dual exits.

Im gonna geuss that deleting the resonator wouldnt make it sound terrable, or too much louder with a DynoMax, but then ageain i dont know for sure, I have stock pipeing, lol

Like I said, I've got dyno pulls that show a reduction in low end torque with a higher flowing exhaust, but, your still right :banghead:

Sounds great. Post 'em up, along with the specs on the engine and exhaust.

I know I'm right :dance1:

I know your theory does not apply to all motors and every setup out there.

So unless you have built every motor known to man and every setup possible and dyno tested all of them, your roosteryness is only that.

I'm siding w/ spilner on this one.