ymeski56

My perusal opinion, 3" to 2.5"...as far as retaining your low end out of the hole, the party's already over by the time the 3" to 2'5 reduction occurs. All 3" to 2.5" will do by that time, is effect it's sound. AKA = More bark than bite out of the hole.

When I refer to "party", the party is manifold to the Y, regarding maintaining your low end torque. After that, your just talking sound effects as to what you want to do. Effectively, an increase in size after the Y, would be more advantageous as far as performance. But more theoretical than noticeable. So that's where you play w/ sound, if sound is important to you.

jameslleary

You would be doing yourself a huge favor by steering clear of flowmaster and cherrybomb extreme(logsplitter mufflers) and spintech....all gimmiks.
The best thing you can do, id retain your stock pipe, and add a muffler of straight through or super turbo design, and then jazz it up with a nice tip.
backpressure is not needed, its exhaust velocity you want. Keep in mind, if your truck is an 09, you already have a straight through muffler.

otto457

What they are trying to explain is the shift in powerband, not backpressure. The size of the tubing will shift the powerband to where there is optimal scavenging. Smaller pipe will optimize scavenging sooner. At lower rpms there are less pulses going through the pipe, the smaller pipe gives each pulse less room to expand and keeps lower rpm pulse velocities. It reaches a point though if the pipe is too small that it restricts the pulses flow in the higher rpms.
True duals verses SI/DO isn't really one over the other. Both systems done correctly will produce similar results. A single midpipe has a slight edge in lower rpm scavenging. There is no backpressure and none is ever needed.

I think the goal here is a little misguided looking for exhaust to fix the tires. Gears are a much more effective way to adjust to tires. I understand the tires aren't that big, so you should be looking for power gains and keeping a good range for the powerband along with that. If you want all the better low end and still want the duals look, go 2.5" SI/ 2.5" DO, if you want good all around driving 3" SI/ 2.5" DO with a straight through muffler either way.

papa tiger

Some of the exhaust plans go back to the butterfly in the manifold to divert gases for engine warm up thru the intake manifold and the heat riser for the automatic choke. 2 polished stainless 8" stacks going up behind the cab are beautiful works of art.

Robatt

Otto, What set up do you think you will run whenever you get around to putting an aftermarket exhaust on your 07 f150 if you havent already?

otto457

With this truck I'm not going all out like the old one. I'm doing my own catback system. I'm cheap, but also wanted to make it my way. I wanted mandrel bent for the tailpipe, so I talked with Gibson and got just a 3" stainless piece ($75). Then I have a 2.5"-3" adapter to go from the stock Y and a section of straight stainless pipe to go to the muffler ($80). I'm still debating which muffler to go with, as I like a fairly quiet system on my daily drivers, but I'm leaning towards a long body Dynomax or Magnaflow (looking about $120). So for $275, I'll have a 3" stainless cat back system that's right for me.
Is this a sign I'm getting old and boring that I'm not going with full headers? Oh well.

scastlet

Would it be bad for the truck for te excuse to end at the resonator?

jameslleary

Otto, if you have the space, Magnaflow has a 30" long round case muffler that is real mellow. On my truck, i dont have room, so i have a 14" about 2.5" ahead of where the tailpipe would bend up to go over the axle, and then replaced th UP part of the tailpipe with a 16" long Magnaflow. Very quiet.

jameslleary

Huh?

scastlet

Dam auto correct. Sorry. Would it be bad to take off the muffler and leave just the resonator?