Oh yea by the way avfrog love the sound of yours.

 

Thank you sir!

 

You going to hate it if you off all of them, I'll tell you that right now. UNLESS, you tune right after. The stock program won't be able to compensate. Just install high flows, it's free anyway after you sell your old cats. Or learn the hard-way, like I did lol.

You'll have flow, but NO velocity. You need velocity to clear gases in the pipes to make room for more.

Turn a garden hose on and you get flow right...? Put your finger over the end and you get velocity. You need this velocity for usable torque and hp and a high flow cat is your finger to the hose.

An exhaust that's all flow and no velocity throws the power-band up top, -you need all that rpm just to push the spent gases thru. As is, the 4six is hurting down low, so yea, you'll make that worse.

Do some research, it will save you time.

___________________________________

I pull a care hauler usually, or an enclosed trailer. The car hauler gets really close to 10,000 lbs at times, so I have to keep that as low as I can. I haven't software tuned, trans is tuned thru hardware, -thanks to Mike (Troyer).

First, I ran this set up -



This work great, until I decided to gut the those ^^^ two cats. Truck fell flat on it's face and felt like a heavy slug that could barley pull it's own weight.

So I went with this set up (below) LT's and High Flows. I got my torque back +++. That was 3 years ago, still going strong, same set up.



Good Luck

 

He is making that sound way worse than what it really is. I have a 2.5" set up with no cats at all, and I'm telling you, I have no complaints with torque issue. If you are concerned, then go with 2.25" and no cats, but it doesn't sound like your concerned

 

Yea, I have a name. -You don't know what your talking about, -passing bad info isn't cool. Your tuned, he is not. You have a 5four, longer stroke and a 3 valve to boot, he's far from that . Big Difference. - What your directing the OP to do is not only illegal, but it will run like a garbage truck.

I hope he tries your sugestions, then posts back the outcome lol.

 

Yea that makes alot of sense. Especially since I have 177,000 on the engine and no tune. It isnt too much for the high flow cats from magnaflow.

 

Ah... Sorry there. You have a point! I was basing on my personnel experience, not looking at the facts pertaining to his vehicle.
:o

 

I vote for high flows for cleaner air and staying legal (cats are required in all 50 states) and also for performance.

 

I'm not saying your wrong but I've never understood this.

Sure with your finger over the nozzle you get more velocity at and past your finger, but before your finger(in the hose) you have less velocity. You slow the water down before it.

The velocity at your finger doesn't scavenge more water behind it, it slows it down and it builds pressure.

Wouldn't the same apply with air(exhaust)? you may get more velocity in the exhaust after a CAT but that's just because the pressure is built up between the engine and the cat. i.e. the exhaust gas slows down.

So how can slowing down exhaust gases out of a motor give more HP??

I would think that a piston pushing exhaust out of a cylinder with back pressure would just cause the motor to loose HP.

Like I said Jbrew I'm no engine guy. I'm just a logical thinker.

 

Oh and sorry for the thread jack.

I'd go with high flows!

 

You are right about HP. The more flow is better for high end HP, but not low end torque. It is kind of a balance beam between the two. As far as the velocity goes... I Don't know the exact physics of it, but the smaller pipes have a higher velocity to help "pull" the hot gases out. I'm not sure about the CATs and velocity though.

 

The same goes for heads. If you put larger valves in you will make your HP curve higher, but you will also loose your low torque curve.

 

No problem, I've done allot worse; - Good post tho ~ yea I've done that one before as well, it easy to do.

 

Scavenging effects are directly influenced by pipe diameter and length right ? Thermal properties as well, I better mention that. There's two waves. Crap , I'm beat lol. I'll see if i can find something to copy and paste real quick lol.

Right, read this, they shouldn't say there's any loss, -because it's so minute,- it doesn't harbor a thing either way, but here, you can sub in the thumb/hose theory -

The exhaust valve opens, two things immediately happen. An energy wave, or pulse, is created from the rapidly expanding combustion gases. The wave enters the exhaust pipe traveling outward at a nominal speed of 1,300 - 1,700 feet per second (this speed varies depending on modifications and is therefore stated as a "nominal" velocity). This wave is pure energy, similar to a shock wave from an explosion. Simultaneous with the energy wave, the spent combustion gases also enter the exhaust pipe and travel outward more slowly at 150 - 300 feet per second nominal (maximum power is usually made with gas velocities between 240 and 300 feet per second).
Since the energy wave is moving about 5 times faster than the exhaust gases, it will get where it is going faster than the gases. When the outbound energy wave encounters a lower pressure area such as a second or larger diameter section of pipe, the muffler or the ambient atmosphere,a reversion wave (a reversed or mirrored wave) is reflected back toward the exhaust valve without significant loss of velocity.

 

How the frick did I double posteded ??? I hit submit , then I don't know what happened ? It got all black until a few hours ago.

I've heard others complaining about DP's lol, - I thought , well if you hit submit just once, it wouldn't happen durrr

So, I'm positive I only submitted once...., -honest. Unless it was my evil twin.

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ef, - Mike explains it best. The old Troyer articles that are f150 specific. Sort of write-ups he's posted in the past. I'm sure you seen a few. - I need an X-pipe like avfrog has, still haven't done that one