Reason for Down Pipe Mod
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Junior User
Joined: Feb 2011
Posts: 95
Likes: 0
From: Phoenixville, PA
Reason for Down Pipe Mod
Checking out Exhaust options dont really know what is on my truck possible reasonator or cat I know it has muffler. The futher up towards the engine is what I dont know. Is that were the down pipe is and why replace it small dia. ? Also people have 3in. down pipe with 4in. exhaust pipe after it. Why not 4in down pipe to 4in. exhaust not enough back pressure ? Thanks I just want to get this right the first time !
Hotshot
Joined: Feb 2009
Posts: 10,410
Likes: 77
From: Plankinton, SD
There's not room for a 4 inch without a LOT of modifying to the tunnel, firewall, etc. It's not necessary also unless you're going for 500+hp. I've just got a 3-4 inch dp from tymar, and straight pipe exiting in front of the rear tire.
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
Here is a picture of the stock down pipe. You can see how squashed it is so flow is restricted. A 4" down pipe won't fit very well because there is not enough room. With a 3" down pipe you still have to bend the firewall seams a bit to get it to fit. Most aftermarket down piper are 3" up top then expand to 3.5 inches down towards the bottom where it connects to the CAT. There is no back pressure issue regardless what you install because the turbo creates all the back pressure required.
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Junior User
Joined: Feb 2011
Posts: 95
Likes: 0
From: Phoenixville, PA
Great, guys at work by law can't delete there cats so they make up back pressure issue's and I tell them all is good their just jealous because there trucks have asthma with no cure. So straight pipe's delete all is the way to go just a bid noisy when your on it or should I consider a muffler.
Disabled USMC Veteran
Joined: Jan 2011
Posts: 637
Likes: 2
From: Pilot Point, TX
i was running just a 3" down pipe with nothing else... the turbo screamed like a banshee (such a sexy sound), and i had to crank the radio to hear over the exhaust... now i have a 3' long 4" pipe right after the DP, so it stops right before the bed (on my crew cab). it gets loud when you get on it (about 2300 rpm), but other than that it's not that loud.
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Junior User
Joined: Feb 2011
Posts: 95
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From: Phoenixville, PA
So if I run it out to the back of the bed just a little louder then stock. All I can find is aluma-something, no stainless DP. Tymar products are next to impossible to find. Mix alum with stainless Should be alright.
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Disabled USMC Veteran
Joined: Jan 2011
Posts: 637
Likes: 2
From: Pilot Point, TX
i'm running the Diamond Eye 3" DP from riffraff, and the rest of my pipe is actually part of the factory exhaust. and just to clarify, my truck is quiet INSIDE the cab, but not necessarily outside the cab. YouTube - my slightly modded '94.5 7.3 powerstroke this is my truck with just the down pipe, and i'll get a video of the current exhaust on here in about 30 minutes.
Disabled USMC Veteran
Joined: Jan 2011
Posts: 637
Likes: 2
From: Pilot Point, TX
that was just DP, this video is the current setup with the DP and about 2' of the stock 4" straight pipe. just the DP stops right under the passenger's feet, and now it extends to just before the end of the cab. YouTube - my slightly modded 94.5 7.3l powerstroke "custom" exhaust