Down Pipe Issues
Hotshot
Joined: Jul 2008
Posts: 11,231
Likes: 130
From: Thomasville, GA
Sawzall to cut the seam in two places and then a 2x4 or portapower to bend it. Should fit pretty well.
A 3" downpipe will let the turbo spool faster and lower EGT's. WOrth the upgrade.
Posting Guru
Joined: Nov 2009
Posts: 1,569
Likes: 2
I apologize, i was a little hot headed on this project today. After i cooled down i figured out how to get my sawzall into the place to cut the seam..Then after looking i found my attachments for my porta power. After bending it a little bit it fit like a glove. HOWEVER! while cutting the down pipe from the top side, i hit the up pipe to the turbo...Bone head move. So i had to stop and weld it. So all in all its been a blast. but it seems worth it i guess. I just have alot of vibration so i have to adjust a few things. Does anyone have vibration?
Posting Guru
Joined: Mar 2008
Posts: 1,669
Likes: 1
From: Billerica, MA
The vibration is from the DP hitting the firewall. You just need to "massage" the wall some more lol, now that you have the atachments for the portapower (did you find the one that I was talking about?) it shouldn't be a problem at all, 20 min tops.
Posting Guru
Joined: Nov 2009
Posts: 1,569
Likes: 2
oops...its all in and welded. haha maybe i can do some more fixin. And yes i did find the piee after i got off the phone with you. LOL it sounds soooooo good...my trucks just so long its hard to hear. Now i need that tip from you. I wasnt able to make it to the get together, maybe we can meet up this weekend?
Senior User
Joined: Jan 2005
Posts: 222
Likes: 0
From: pennsburg Pa
this might be a stupit question but thought of it after i replaced my stock DP with a 3 inch tymar, The stock pipe is 4.5 inches by 1.5 inches which = 6 inch total diamater and a 3 inch round pipe would also be 6 inch total. What am i missing here?
Fleet Mechanic
Joined: Mar 2007
Posts: 1,313
Likes: 6
From: Rio Rancho NM
Your figures don't add up to the "diameters." If your measurements are correct and are internal dimensions, the stock pipe would have 6.75 sqin of cross sectional area for exhaust flow. The problem is that it's narrow, has a sharp bend or two and is a huge restriction to flow. This slows turbo spooling, robs power and builds up excess heat. The 3in round pipe has about 7 sqin cross sectional area, not much more than the stock DP by your measurements. But compare them side by side. How can you not see that the 3in round DP will flow way better than the stock DP. If you've ever taken fluid dynamics (gases are fluid), you'll understand that fluids flow best in a round pipe or tube with gradual bends and minimal cross sectional area changes and other interruptions to flow. These interruptions to flow define the stock DP - rectangular, tight, sharp bends, etc. If you plan on other go fast goodies, a good DP is an absolute MUST.
Fleet Mechanic
Joined: Mar 2007
Posts: 1,313
Likes: 6
From: Rio Rancho NM
Here's my cut up stock DP, the stock DP next to my first 3in DP, and finally my aFe 4in exhaust kit with a DP that starts out 3in, then goes to 3.5, then 4in. I straight piped the whole exhaust. No muff or kitty. You have to agree a round DP is way better than the stock one. If you still have your cat you may want to think about gutting or removing it too. All they do is collect soot and restrict flow.
Posting Guru
Joined: Mar 2008
Posts: 1,669
Likes: 1
From: Billerica, MA
oops...its all in and welded. haha maybe i can do some more fixin. And yes i did find the piee after i got off the phone with you. LOL it sounds soooooo good...my trucks just so long its hard to hear. Now i need that tip from you. I wasnt able to make it to the get together, maybe we can meet up this weekend?
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Posting Guru
Joined: Nov 2009
Posts: 1,569
Likes: 2
lol, i brought my truck to my buddys shop to have him piece some pipe from the dp to the exhaust system...because i removed the cat and needed about 2 feet to make up the difference. And i left for a second to get a drink and cameback and he frigging welded it. I was not happy....
Cargo Master
Joined: Nov 2009
Posts: 2,558
Likes: 19
It is a fluid dynamics thing. Turbulant flow vs Laminar flow I believe. The circular pipe has more are that is not effected by the exhaust passing the wall of the pipe. The best way to think of it is breath through a straw then flatten it out and try to breath through it. Kinda gives you the same effect of the stock DP vs the 3" DP.
Hotshot
Joined: Jul 2008
Posts: 11,231
Likes: 130
From: Thomasville, GA
I had some vibration that started a few months after the downpipe install. Just shifted around a little bit while driving so I adjusted it and tightened it back up and it's great now. Also ditched the u-bolt clamp and got a stainless band clamp instead, fits a lot better.
Hotshot
Joined: Feb 2009
Posts: 10,410
Likes: 77
From: Plankinton, SD
I just put some heat wrap on mine where its close to the tranny and noticed the bulky u bolt clamp is against my floor and has worn a one inch square hole in it. I think I might have one of the other clamps, gotta look and see.