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Why do downpipes gotta be so big?

  • Thread starter Thread starter tylerrocks
  • Start date Start date Feb 6, 2007
T

tylerrocks

New Member
Oct 13, 2005
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0
Big Spring, TX
Feb 6, 2007
#1
  • Feb 6, 2007
  • #1
Paul302? 10secgoal? 12sec67?....others?
 
1

10secgoal

Active Member
Dec 1, 2003
2,801
3
49
San Diego
Feb 6, 2007
#2
  • Feb 6, 2007
  • #2
Exhuast systems on a turbo kit can only have a little bit of back pressure. Back pressure in the exhuast(after turbo) can be bad. It can cause a turbo to spool slower. If the exhuast can't cross the turbo fast enough, it can't spin the turbo fast enough. If it backs up there, it backs up in the headers and crossover and over whelms the wastegate. You can over boost your motor, which can be very bad.
Also, you are trying to make a ton of power with one pipe, so it has to be bigger. Lots of guys run 3in into a splitter and 2.5 back like a normal N/A car.
 

classic boost

Founding Member
Feb 3, 1999
709
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0
canton, oh
Feb 6, 2007
#3
  • Feb 6, 2007
  • #3
pretty much what dustin said. also, back pressure before the turbo is already high (2:1), so any bp in the dp will just make matters worse before the turbo.
 
T

tylerrocks

New Member
Oct 13, 2005
514
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0
Big Spring, TX
Feb 6, 2007
#4
  • Feb 6, 2007
  • #4
10secgoal said:
Exhuast systems on a turbo kit can only have a little bit of back pressure. Back pressure in the exhuast(after turbo) can be bad. It can cause a turbo to spool slower. If the exhuast can't cross the turbo fast enough, it can't spin the turbo fast enough. If it backs up there, it backs up in the headers and crossover and over whelms the wastegate. You can over boost your motor, which can be very bad.
Also, you are trying to make a ton of power with one pipe, so it has to be bigger. Lots of guys run 3in into a splitter and 2.5 back like a normal N/A car.
Click to expand...

Thanks guys. The reason I ask it that the pics I've seen look alot larger than 3". But now that I think about it those were probly close to 1000HP builds. what size DP do you guys use?
 

classic boost

Founding Member
Feb 3, 1999
709
0
0
canton, oh
Feb 6, 2007
#5
  • Feb 6, 2007
  • #5
3.5" all of the way back.
 
1

10secgoal

Active Member
Dec 1, 2003
2,801
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49
San Diego
Feb 6, 2007
#6
  • Feb 6, 2007
  • #6
I run a 3. I've seen it said huys have made up to 1000hp with a single 3in. I'm gonna keep my 3in so I can tell customers what my kit can actually do. I'm gonn a be building a 800-1000 hp Maverick which will get probably only a 3.5.

Rich's is getting a 3in DP, and whether he wants to or not it's going to make over 500hp with 7 psi. He doesn't want that much, but can't go much lower on boost.
 
1

10secgoal

Active Member
Dec 1, 2003
2,801
3
49
San Diego
Feb 6, 2007
#7
  • Feb 6, 2007
  • #7
I run a 3. I've seen it said guys have made up to 1000hp with a single 3in. I'm gonna keep my 3in so I can tell customers what my kit can actually do. I'm gonn a be building a 800-1000 hp Maverick which will get probably only a 3.5.

Rich's is getting a 3in DP, and whether he wants to or not it's going to make over 500hp with 7 psi. He doesn't want that much, but can't go much lower on boost. He's whining something about not wanting a new block, or two used four cylinders.
 
T

tylerrocks

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Oct 13, 2005
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0
Big Spring, TX
Feb 6, 2007
#8
  • Feb 6, 2007
  • #8
too much power?!? bah. Thanks guys just collecting info
 
1

10secgoal

Active Member
Dec 1, 2003
2,801
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49
San Diego
Feb 7, 2007
#9
  • Feb 7, 2007
  • #9
tylerrocks said:
too much power?!? bah. Thanks guys just collecting info
Click to expand...
NEVA too much
 
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