Pennock's Fiero Forum
  Technical Discussion & Questions
  stock exhaust on 3800 swap

Post New Topic  Post A Reply
Email This Page to Someone! | Printable Version


next newest topic | next oldest topic
stock exhaust on 3800 swap by lowtrickry
Started on: 07-02-2013 11:26 AM
Replies: 6 (1228 views)
Last post by: 86GTFastback on 07-03-2013 09:44 PM
lowtrickry
Member
Posts: 333
From: Leominster,MA,U.S.A.
Registered: Feb 2008


Feedback score: N/A
Leave feedback

Rate this member

Report this Post07-02-2013 11:26 AM Click Here to See the Profile for lowtrickryClick Here to Email lowtrickrySend a Private Message to lowtrickryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Entill I have the money to get the parts and time to put together an exhaust for my 3800 series II s/c can I run the stock dual out single in exhaust I got from the Fiero store ? Anyone see any problems with it? Will it cause to much back pressure since its ment for such a smaller engine?
IP: Logged
PFF
System Bot
Darth Fiero
Member
Posts: 5888
From: Waterloo, Indiana
Registered: Oct 2002


Feedback score: (5)
Leave feedback





Total ratings: 360
Rate this member

Report this Post07-02-2013 12:35 PM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by lowtrickry:

Entill I have the money to get the parts and time to put together an exhaust for my 3800 series II s/c can I run the stock dual out single in exhaust I got from the Fiero store ? Anyone see any problems with it? Will it cause to much back pressure since its ment for such a smaller engine?


I would not run any exhaust system designed for a 2.8L on a 3800 SC engine. These systems are just too small and too restrictive for any supercharged 3800. Using too restrictive of an exhaust system on a 3800 SC engine can result in KR (detonation) problems among other things.

I would recommend nothing smaller than 2.5" diameter pipe using mandrel bends (single pipe systems) and low restriction mufflers and catalytic converters (if those are used). 3.0" mandrel bent tubing is the way to go if you want the best performance.

-ryan

------------------
OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

IP: Logged
JamesCurtis
Member
Posts: 2017
From: Omaha, NE
Registered: Oct 2003


Feedback score: N/A
Leave feedback





Total ratings: 64
Rate this member

Report this Post07-02-2013 01:03 PM Click Here to See the Profile for JamesCurtisClick Here to Email JamesCurtisSend a Private Message to JamesCurtisEdit/Delete MessageReply w/QuoteDirect Link to This Post
Something like the picture below is usually what people go for if they are not modifying the trunk. Finding a shop to do this with a 3" downpipe would be pretty difficult. The shop that did mine with 2.5" mandrel almost turned me down and they didn't see how a 3" downpipe in my configuration would work.



Here's how much I ended up paying to have it done (~$520 + tax):

Muffler - ~$160
Labor - $120
Flex joint and tubing - $230
Flange - ~$10

------------------

IP: Logged
lowtrickry
Member
Posts: 333
From: Leominster,MA,U.S.A.
Registered: Feb 2008


Feedback score: N/A
Leave feedback

Rate this member

Report this Post07-02-2013 05:47 PM Click Here to See the Profile for lowtrickryClick Here to Email lowtrickrySend a Private Message to lowtrickryEdit/Delete MessageReply w/QuoteDirect Link to This Post
I already have my exhaust designed and im building/welding it my self....just out of project money at the moment and wondering if that stock muffler was to restrictive
IP: Logged
1fast2m4
Member
Posts: 513
From: Frederick, MD (U.S.A)
Registered: Feb 2013


Feedback score: N/A
Leave feedback

Rate this member

Report this Post07-02-2013 08:19 PM Click Here to See the Profile for 1fast2m4Send a Private Message to 1fast2m4Edit/Delete MessageReply w/QuoteDirect Link to This Post


Mine cost $65 ($95 if you count the resonated tip)


I don't see how you could make the bend from the stock 3800 manifold around to the stock Fiero muffler. that cramped set of bends would probably be more restrictive than the fiero cat back.

------------------
1986 SE 3800SC/4t65eHD (12.871@104.96) I'll Sell it if you like
1985 GT 3800SC (swap in progress)

IP: Logged
Darth Fiero
Member
Posts: 5888
From: Waterloo, Indiana
Registered: Oct 2002


Feedback score: (5)
Leave feedback





Total ratings: 360
Rate this member

Report this Post07-03-2013 02:06 AM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can buy 3" diameter, 3" radius mandrel 90 deg elbows from Walker/Dynomax (p/n: 41221) directly or plug that part number into Summit or Jegs.

These tight bends work great for exiting the stock 3800 rear exhaust manifold and getting the exhaust system to hook up to a muffler in the stock Fiero muffler location WITHOUT cutting the trunk. I've built many systems like this.

In regards to restrictions, even using these tight mandrel bends, the backpressure tests I did on my custom exhaust systems showed my setups had less backpressure than most of the performance systems people put on Grand Prixs and Regals.

Having said that, the picture of the system JamesCurtis showed should work very well. Just make sure that the flex section you use has NO INTERNAL BRAID in it. The higher exhaust temps the SC (and Turbo) engines run will melt, distort, and collapse the internal braiding some manufacturers put inside of their exhaust flex joints and this will cause a huge restriction if it happens.
IP: Logged
86GTFastback
Member
Posts: 347
From: Marion, OH, US
Registered: Apr 2009


Feedback score: (3)
Leave feedback

Rate this member

Report this Post07-03-2013 09:44 PM Click Here to See the Profile for 86GTFastbackSend a Private Message to 86GTFastbackEdit/Delete MessageReply w/QuoteDirect Link to This Post
I just made mine out of three of those 3" bends (over the last weekend), the walker 41221's Darth had mentioned, and I added an inch of pipe to push it to one side, and I'm not a very good welder, in fact this was my first actual project. I ordered a 3 inch flange from jegs, but I got the 41221's from advance just because it would have been easier to return them if I decided to have a shop do it. Mine is very similar to the first one pictured above. I also ended up using the flowtech muffler mentioned on another thread. I'll be figuring out my exhaust tips in the next week or two.
IP: Logged

next newest topic | next oldest topic

All times are ET (US)

Post New Topic  Post A Reply
Hop to:

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock