I want to build a new exhaust. What size do I "really" need?

I am planning on coming out of the headers with most likely 2.5" pipe, then Y them together, and if I can fit it, run a single sidepipe/glasspack down the passenger side, exiting in front of the rear tire.

Can I stay 2.5" all the way through, even after the Y, or should I start smaller and end in 2.5, or 2.5 into 3?

Engine has 360 hp, with a potential 150 shot of nitrous in the future.

I am looking for good torque, not just noise and big pipe.

 

3 Inch, my motto go big or go home!

 

My truck has similar horsepower on a 5.7 hemi, and only runs siamesed 2.75"

Also, not convinced of the glasspack, yet. If the answers are in favor of 2.5 all the way, I may keep one of my flowmasters and ditch the second one. It is already hung...

 

Never been a fan of glass packs, Flowmaster 40 series is the best sounding/performing muffler in my opinion glasspack just sound terrible, not to mention choking off the the exaust. like trying to breathe while being choked. lol

 

Since you are wanting torque Id try 2.25 siamesed into 2.5 and through a single muffler. I think this would help get rid of alot of noise and drone. and if you are going to Y it togethor in the trans tunnel you wont have much room or it will get too low.

 

Since your set on a single exhaust

2.5 in 3"

Flowmasters suck for performance fwiw

 

How about this...

I can use my existing exhaust setup, taking off one flowmaster and just routing my 2.5 driver side pipe into a Y on my passenger side pipe, into a single 2.5 into a Flowmaster super44 2.5 in/2.5 out, and just let it dump at the axle. This would be the cheapest and quickest way for me, since all I need to buy are the L and the Y and cut it all to fit.

Otherwise, I have to start from scratch from the collectors on back.

I wouldn't mind a side pipe, but I have subframe connectors in the way in the middle and Caltracs in the way at the back. The only way I could do it is if I immediately L off the two collectors and bring the pipe to the side at the passenger side where the e-brake cable is. That is the highest point on my frame. Then I could do a pipe along the side with some sort of glasspack or similar shaped muffler, and exit out the side before the rear tire.

Of course, you all know me. I will do the cheap and easy route now, and the better setup later when I have more money...

 

Do as you suggested and instead of dumping it have a pipe made to run out the back. This will reduce interior noise and resonance from bouncing off the ground. Should still be pretty cheap compared to starting from scratch and wont be loud inside.

 

I don't like glasspacks myself, but like Russ mentioned Flowmasters don't flow well at all. They do sound awesome I've run 40s myself.

You have to remember this is for a street car that he has had resonance issues with before. I don't think he wants pure volume.

Bigger diameter pipe will also have a deeper sound while a smaller one will be louder. So 3" would be deeper than 2.5 and 2.5 would be louder than 3". Just look at all those import guys with their 1.75" single pipe, ever wonder why they're loud as hell?

Best recommendation would be to run a Turbo muffler, they're one of the best mufflers you can run. Quite while cruising then they sound mean as hell at WOT.

You can pick them up cheap, I got a Cherrybomb Turbo II for $20 at auto zone.

If you want high performance then the dynomax Super Turbo wins hands down, you can look up the independent tests done on them. They flow more than glass packs and magnaflow even with the handicap of not being a straight trough design. And they free up more power with the added flow, the greatest benefit is that it actually works to quiet down the exhaust.

Dual 2.5 to a single 3" will be fine for 360 flywheel HP. For that nitrous it's gonna want to breathe more though, but you can always uncap it at the track.

 

Id rather see you change the mufflers to a dynomax super turbo's and run tailpipes and be happy rather then killing off your power.

(If you were closer i got a set of 2.5" tailpipes id give you)

 

Then drive on down and make yourself closer!

I have pretty good money invested in these super44s and I LOVE the sound. The drone is annoying, but that is part of why I am swapping this setup around.

Even if I do go with a different muffler and/or setup, I still want to run the super44 (single) on a Siamese setup dumping at the axle, just as an experiment to fully determine if the drone is due to the muffler or due to having two of them, or due to the dumping under the car.

 

Its the muffler making the drone, My truck droned REAL bad (2.5 y'd into 3" through single super 44) until I adjusted the length of the pipe after the muffler. I originaly had it running out behind the rear tire, then tried dumped then I finally ran it out before the rear tire and the drone is gone.

 

Really, even on a truck?

I have a 40 or 50 on my truck, siamesed, dumping. It is loud, but no drone.

I have a dodge with 20" rims, so it sits pretty high. Might make a lot of difference.

 

Huh lots of Flowmaster bashing based on Dyno testing.I guess my Dads Duster never really picked up 1/2 a tenth by putting Flowmasters on.Maybee should have dyno raced it to find the truth.

 

I have heard yea and nea about flowmasters. There is no foam or restrictions in them, so they seem to logically be free-flowing, or close to it.

I picked up a couple of mpgs in my truck swapping from the stock muffler to the flowmaster, and got an awesome deep guttural tone, and a great WOT roar from it. But it puts me to sleep when I put the cruise control on.

I really like the sound of glasspacks, and I see no reason why they should restrict flow. They are just a straight pipe. You can look into the inlet and see straight out the other end. No restrictions whatsoever. Just a few holes in the side to catch the noise, and filter them through fiberglass threads. I had 61" sidepipes for a while and by far, the best sounding exhaust I ever had. But that was on the stock 302, not this roller engine. So I cannot compare.

So I have no issues with either muffler.

My concern now is getting rid of the drone, and cleaning up the underside real estate.