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4" down pipe?

  #1  
Old 05-19-2018, 05:15 PM
Amicus
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4" down pipe?



just in stalled a 4" down pipe. It is louder for sure. Also I seem to have some vibration some where. The bend behind the turbo is up against the fire wall. I don't think I can do anything about that? Just wanted to see if anyone had some advice or ideas about the vibration or anything else. Also there is a tranny pipe that runs right next to the down pipe. Do I need to try and move?

Thanks
 
  #2  
Old 05-19-2018, 11:11 PM
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This won't really help you but might help others. The general consensus is to get a 3.5" downpipe for these trucks because of the issues you're having. Then a 4" exhaust from the downpipe back fits ok. But due to the issues you're having, a 4" downpipe isn't great. You'll have to decide if you want to change to a 3.5 or fix your issues.
 
  #3  
Old 05-20-2018, 12:51 AM
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Loosen the clamp on the turbo and rotate the down pipe until you find the sweet spot then tighten the clamp. I have a 4” turbo back and haven’t had any clearance issues. It’s close to the uppipes but it will fit. What brand did you purchase? That could also be an issue.
 
  #4  
Old 05-20-2018, 07:48 AM
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Originally Posted by FiznUKa View Post
Loosen the clamp on the turbo and rotate the down pipe until you find the sweet spot then tighten the clamp. I have a 4Ē turbo back and havenít had any clearance issues. Itís close to the uppipes but it will fit. What brand did you purchase? That could also be an issue.
Which brand do you have? Iím interested in getting a 4Ē downpipe
 
  #5  
Old 05-20-2018, 08:43 AM
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On the down side.... the 4 inch offers no benefit, the 3.5 helps with back pressure on the turbo which is necessary and performs better. Stock is 3 inch with a resonator for my 2003. If you want the 4 inch down to fit, you may have to hammer back the pinch welds on the cab to keep it from rubbing.
 
  #6  
Old 05-20-2018, 08:49 AM
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Originally Posted by Maxium4x4 View Post
On the down side.... the 4 inch offers no benefit, the 3.5 helps with back pressure on the turbo which is necessary and performs better. Stock is 3 inch with a resonator for my 2003. If you want the 4 inch down to fit, you may have to hammer back the pinch welds on the cab to keep it from rubbing.
FWIW--I've never had EGT or spool issues with my 3.5" downpipe. I got it because Magnaflow testing way back in the day found there was no benefit (actually less) using a 4" downpipe. The fitment issues are obvious.
 
  #7  
Old 05-20-2018, 08:50 AM
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Originally Posted by Maxium4x4 View Post
On the down side.... the 4 inch offers no benefit, the 3.5 helps with back pressure on the turbo which is necessary and performs better. Stock is 3 inch with a resonator for my 2003. If you want the 4 inch down to fit, you may have to hammer back the pinch welds on the cab to keep it from rubbing.
So should we go with a 2Ē downpipe to get more of that turbo performance enhancing back pressure?
 
  #8  
Old 05-20-2018, 08:57 AM
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Originally Posted by tfunk88 View Post


So should we go with a 2Ē downpipe to get more of that turbo performance enhancing back pressure?
Seriously, you're going there?
 
  #9  
Old 05-20-2018, 09:02 AM
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Originally Posted by npccpartsman View Post
Seriously, you're going there?
Iím simply asking a question.

Do you ha e a link to the Magnaflow testing? Iíd be interested in reading it.
 
  #10  
Old 05-20-2018, 09:03 AM
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Originally Posted by tfunk88 View Post


So should we go with a 2” downpipe to get more of that turbo performance enhancing back pressure?


I wouldn't but it is your engine.

As an owner you can choose what to do. Introduced in the year of 2003 and the DYNO time I an others have spent since then, my advice is pretty solid but ultimately it is up to you to decide what is right. To clear a 4 inch down you will have to adjust, make room, and live with rubbing if not done correctly. if you are planning on compound turbo's and aiming at 1000+ HP then the 3.5 down may not apply.

I and other members only offer advice, the final out come is in your hands.
 
  #11  
Old 05-20-2018, 09:07 AM
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Originally Posted by Maxium4x4 View Post
I wouldn't but it is your engine.

As an owner you can choose what to do. Introduced in the year of 2003 and the DYNO time I an others have spent since then, my advice is pretty solid but ultimately it is up to you to decide what is right. To clear a 4 inch down you will have to adjust, make room, and live with rubbing if not done correctly. if you are planning on compound turbo's and aiming at 1000+ HP then the 3.5 down may not apply.

I and other members only offer advice, the final out come is in your hands.
On the dyno the 3.5Ē pipe outperformed the 4Ē? Thatís definitely interesting. And no, Iím not being sarcastic.
 
  #12  
Old 05-20-2018, 09:12 AM
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Back to the subject on hand another option would be to mark the pipe with it installed and pull it back out and flatten it with a hammer wherever needed.
 
  #13  
Old 05-20-2018, 09:13 AM
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Originally Posted by tfunk88 View Post


On the dyno the 3.5Ē pipe outperformed the 4Ē? Thatís definitely interesting. And no, Iím not being sarcastic.
We did hours of testing, you have trade offs for each system. 4" is not wrong or right but to answer, the VGT performs better with back pressure.
 
  #14  
Old 05-20-2018, 09:20 AM
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Originally Posted by FiznUKa View Post
Back to the subject on hand another option would be to mark the pipe with it installed and pull it back out and flatten it with a hammer wherever needed.
Every truck model year is just a tweak different on clearance, I would not recommend hammering the pipe into submission. Just massage the cab area where you find the pipe rubbing.
 
  #15  
Old 05-20-2018, 10:25 AM
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Im not sure how back pressure would have any bearing on the VGT operation? I have had 4" AFE turbo back exhaust for many years now. My truck runs great. I pull a heavy Toyhauler without issue. I think the larger down-pipe is an excellent mod.
As stated earlier, just loosen the clamp and re-position. Also, keep the tranny lines from touching it.
 

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