Does anybody think custom fabbing a 3.5 or 4 inch downpipe would help once your above 6ooHP, and then making a custom 4 inch exhaust , pretty much a straight peice of pipe , a 4inch in 4 inch out borla type muffler and then just have it turn out right before the rear tire? jack ostrander
Bigger down pipe
- Thread starter FLSY2730
- Start date
Christian Dionne
Member
On the 1000HP plus single turbo (T88+) cars I know of, Most have a 5" 90 downto a 4" then later on to a 3 1/2"
Although I do know of a 800rwhp car with single 3" from turbo back as well. He plans on upgrading the DP like above.
You need the bigger pipe closer to the turbo as the hot gas expands more. Further down as the exhaust cools a smaller pipe can flow the same amount.
I know a 3 1/2" DP will fit with the A/C box as my header guy said there's plenty of room for it. 4" might be tight unless that box is removed. I would think single 3" cat-back would be plenty with what you're runnin.
HTH,
Although I do know of a 800rwhp car with single 3" from turbo back as well. He plans on upgrading the DP like above.
You need the bigger pipe closer to the turbo as the hot gas expands more. Further down as the exhaust cools a smaller pipe can flow the same amount.
I know a 3 1/2" DP will fit with the A/C box as my header guy said there's plenty of room for it. 4" might be tight unless that box is removed. I would think single 3" cat-back would be plenty with what you're runnin.
HTH,
ghettosled
SYTY SUPERSTORE
depends what turbo wheel you have. P trim can only flow so much. A Q trim is 3.11" so you must use a 3.5" dp if you want it to function.
if you are going to run a 3.5" or 4" then it would be best to do that all the way back and not bottleneck the system regardless if it cools or not. 3.5" fits b/t the frame and the motor.
if you are going to run a 3.5" or 4" then it would be best to do that all the way back and not bottleneck the system regardless if it cools or not. 3.5" fits b/t the frame and the motor.
10secTy
Sy-Ty builder and Tuner
Hey Mike I just want to clarify something.
The Innovative catalog lists the Q trim Exducer Diameter as 2.693" and Major Diameter as 3.111". So in other words the outlet of the turbine housing would be 2.693" which would mean a 3" downpipe would work alright with the Q. Does this look right to you? It lists the R trim with a 3.111" Exducer which would need a 3.5" down pipe.
Nolan
The Innovative catalog lists the Q trim Exducer Diameter as 2.693" and Major Diameter as 3.111". So in other words the outlet of the turbine housing would be 2.693" which would mean a 3" downpipe would work alright with the Q. Does this look right to you? It lists the R trim with a 3.111" Exducer which would need a 3.5" down pipe.
Nolan
vortecfiero
New member
from what i ve learned so far,
3" will support about 725 hp
going too big will kill velocity which is still important in the down pipe
3.5" will support about 900 hp
try to keep velocities as close as possible to 250 ft/sec
some experts (ive seen this work on a GNX)
recommend going 25% (area)
larger and a 90 deg bend for about 12 to 18" to smooth out the turbulance out turbine
_________________
94/5 Vortec 4300
84 Fiero Phantom GT:
Best ET 14.445 @ 95 mph
Goin' turbo
<font size=-1>[ This Message was edited by: vortecfiero on 2002-03-17 09:44 ]</font>
3" will support about 725 hp
going too big will kill velocity which is still important in the down pipe
3.5" will support about 900 hp
try to keep velocities as close as possible to 250 ft/sec
some experts (ive seen this work on a GNX)
recommend going 25% (area)
larger and a 90 deg bend for about 12 to 18" to smooth out the turbulance out turbine
_________________
94/5 Vortec 4300
84 Fiero Phantom GT:
Best ET 14.445 @ 95 mph
Goin' turbo
<font size=-1>[ This Message was edited by: vortecfiero on 2002-03-17 09:44 ]</font>
20psiGMC
Member
Having to put more severe bends in a larger pipe because of the routing path can negate the advantage of more area. There is a point of diminishing returns.
[thinkingoutloud]
On a <500hp truck, I wonder if anyone has done any “before and after” testing via a DP swap – just the DP – and recorded the difference. I’d like to know the proven level at which the factory 2.5” DP becomes a significant limitation. I realize the PTE set-up has a dump port plumbed into it, but I bet many owners will never use it. I would be willing to bet that the factory DP with a Saudi Resonator would out flow any 3” DP/catcon combo you could come up with….
[/thinkingoutloud]
[thinkingoutloud]
On a <500hp truck, I wonder if anyone has done any “before and after” testing via a DP swap – just the DP – and recorded the difference. I’d like to know the proven level at which the factory 2.5” DP becomes a significant limitation. I realize the PTE set-up has a dump port plumbed into it, but I bet many owners will never use it. I would be willing to bet that the factory DP with a Saudi Resonator would out flow any 3” DP/catcon combo you could come up with….
[/thinkingoutloud]
Christian Dionne
Member
Keith and I both would like to make a couple 3"ers happen, but the flange is the kicker. Dinging the pipe and reducing it like mine from 3 1/2" down to 3" isn't that hard. If you want, email me Sy1252@aol.com and I'll see if the asshole(long story) in KY will make you the flange or partial DP.
Later, Christian
Later, Christian
ghettosled
SYTY SUPERSTORE
Nolan you are correct on the wheel specs. However, You should still run a 3.5" downpipe with Q or R trim. Pretty much any knowledgeable turbo guy will agree. When you take into consideration ID of the 3" pipe, and the actual size of the Q/Rturbine wheel, there is a restriction.
As for custom downpipes. The only thing i can do without the truck is a 3 or 3.5" for the KB headers. thanks
As for custom downpipes. The only thing i can do without the truck is a 3 or 3.5" for the KB headers. thanks
InvisiBill
Active member
As a pure bolt-on, would a bigger downpipe do anything on a stock truck? Fitted to the stock exhaust housing and the stock exhaust, with no other mods... Would it spool up faster, or would it be too big and kill the velocity? Would it be pushing it on the stock wastegate? Just trying to get an idea of what can/should be done when the time comes...
Hey Guys fabriaction is pretty easy if you have the right tools. A buddy and I made my 3" DP for the PTE exhaust housing with the exhaust flange and integrated wastegate flapper. Took two 180 degree manderal bends and a couple feet of 18 gauge 3" pipe. check it out at http://syty.net/phpBB/viewtopic.php?topic=12067&forum=13&1
Spencer Johnston
PA Syclone
Spencer Johnston
PA Syclone
Christian Dionne
Member
Hey Bill, the 3" DP on a close to stock truck like mine makes spoolup insane. I'm sure Adam, Ian and Mike can vouge for me on this one. I do have a bit of trouble controlling boost, however my wastegate has its own hole into the DP. If I could just get a bigger puck and some porting, my boost control would probably be pretty decent. I recommend it as long as you're doing something with the wastegate, or installing an external as well. HTH,