3" downpipe - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

Reply
 
 
 
Thread Tools Search this Thread
Old 05-31-2004, 06:20 PM   #1
Senior Member
True Car Nut
Thread Starter
 
Join Date: Dec 2002
Location: Sauk Centre, MN
Posts: 5,458
Thanks: 0
Thanked 0 Times in 0 Posts
OLBlueEyesBonne is on a distinguished road
Default 3" downpipe

I can get a 3" downpipe and have it installed (parts and labor for $45) when I get my new tips installed. Is it going to be worth it with my level of mods? Am I going to need an o2 spoof? Keeping stock cat, so I'm assuming no spoof is needed yet.
Also, will I see much more power?
Thanks in advance,
Martin
OLBlueEyesBonne is offline   Reply With Quote
Old 06-03-2004, 10:14 PM   #2
Senior Member
True Car Nut
Thread Starter
 
Join Date: Dec 2002
Location: Sauk Centre, MN
Posts: 5,458
Thanks: 0
Thanked 0 Times in 0 Posts
OLBlueEyesBonne is on a distinguished road
Default

Anybody??
OLBlueEyesBonne is offline   Reply With Quote
Old 06-03-2004, 10:41 PM   #3
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Unless you're going 3" full exhaust (I don't recommend it unless you mod like Rogue or Scott Cook), no.
willwren is offline   Reply With Quote
Old 06-04-2004, 01:19 AM   #4
Senior Member
True Car Nut
 
Join Date: Feb 2003
Location: Bloomington-Normal, IL 1997 SE
Posts: 3,734
Thanks: 0
Thanked 0 Times in 0 Posts
macho_mike21 is on a distinguished road
Default

how would it help if the rest of your exhaust is still the stock size?
macho_mike21 is offline   Reply With Quote
Old 06-04-2004, 01:26 AM   #5
Junior Member
 
Join Date: Jun 2002
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
2000SilverBullet is on a distinguished road
Default

If you keep the stock Cat you won't need a spoof.
You may benefit slightly with the supercharged engine if you replace the downpipe including the flex connector because the stock one is only 2" dia. and any decrease in restriction will add power. My guess is about 2 - 4 hp.
2000SilverBullet is offline   Reply With Quote
Old 06-04-2004, 01:39 AM   #6
Senior Member
True Car Nut
 
Join Date: May 2003
Location: Holt, MI & Lima, OH
Posts: 3,022
Thanks: 0
Thanked 0 Times in 0 Posts
dbtk2 is on a distinguished road
Default

You're not removing the cat so no spoof is needed. I don't know why you would need a 3" downpipe, but it would probably free up a few horsepower, as long as you leave the rest of the exhaust stock behind it. If you open up the whole exhaust to 3" you will lose WAY too much backpressure.

If that doesn't convince you maybe this will:

My dads GTP (the one in my sig) runs 12.2'* @ 115mph...it has a 2.25" borla exhaust on it. Yeah, it has headers and a 3" downpipe, but the downpipe then reduces from 3" to 2.5", which then reduces to 2.25" where the exhaust bolts on. Having the big downpipe but keeping the small exhaust frees up any restrictions before the cat-back to give as much power as possible, but keeps the backpressure higher due to the smaller exhaust. The GTP pulled 315.6whp with the 2.25" exhaust on. I can pretty much guaruntee you that if it had a 3" exhuast it would have less power. With open downpipe it pulled 304.9whp. So basically, don't go too big, afterall, it is still a 6 cylinder.

Shawn
dbtk2 is offline   Reply With Quote
Old 06-04-2004, 01:44 AM   #7
Senior Member
Certified Car Nut
 
Join Date: Jun 2003
Posts: 15,928
Thanks: 0
Thanked 0 Times in 0 Posts
BonneMeMN is on a distinguished road
Default

Keeping a 3" pipe between the headers and a smaller exhaust may work like a venturi setup.
BonneMeMN is offline   Reply With Quote
Old 06-04-2004, 01:51 AM   #8
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

I'm not sure the money and effort would be worth the minimal gain, unless you're modded out already, and that'* the last thing left undone.
willwren is offline   Reply With Quote
Old 06-04-2004, 02:33 AM   #9
Senior Member
True Car Nut
 
Join Date: Feb 2003
Location: Bloomington-Normal, IL 1997 SE
Posts: 3,734
Thanks: 0
Thanked 0 Times in 0 Posts
macho_mike21 is on a distinguished road
Default

if you can get it done for cheap great, but maybe you should wait to get a few more mods that will make more of a difference.
macho_mike21 is offline   Reply With Quote
Old 06-06-2004, 03:25 PM   #10
Senior Member
True Car Nut
Thread Starter
 
Join Date: Dec 2002
Location: Sauk Centre, MN
Posts: 5,458
Thanks: 0
Thanked 0 Times in 0 Posts
OLBlueEyesBonne is on a distinguished road
Default

Right now I have no exhuast resonator, and have replaced the muffler with a Magnaflow Wide Open (3" inlet >> dual 2.5" outlets). Otherwise it is still the stock cat and piping.

I'm thinking for $45 I'll be the guinea pig. It may not be all that much power, but $45 for a 3" DP including install is alot less than what some of our 3800 perf vendors are charging.
OLBlueEyesBonne is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
3" downpipe with manifold question chrisdon86 Performance, Brainstorming & Tuning 6 06-26-2009 05:17 PM
3" Downpipe....how, where? Can't seem to get one made. mikey383 2000-2005 3 02-12-2006 09:33 AM
ssei 3" downpipe? syclonegs2003 Performance, Brainstorming & Tuning 7 01-15-2006 11:33 AM
where do i get the 3" downpipe? harofreak00 2000-2005 10 01-06-2006 11:15 PM
"D" or "OD" ? BusMaster007 1992-1999 23 01-09-2003 03:09 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 10:57 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.