Restrictive or not? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-29-2012, 09:08 PM
Registered User
 
Join Date: Nov 2011
Location: montana
Posts: 136
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Restrictive or not?

I am running true dual exhaust on a 300 hp crate 360 magnum in a 91 dodge truck the pipe diameter is 2 1/4 and i have an H pipe that is also 2 1/4 and aout a foot long, for mufflers i have 18 inch flo-pro glass packs that have a louvered inside core. But these glass packs did not have any inlets or outlets, we welded our own inlets and outlet on them and they have a 3 inch inside diameter.
I have been told louvered glasspacks are restrictive... But i was thinking since these glasspacks i have dont neck down inside that they'd most likely flow pretty well considering they have a 3 inch inside diameter.
I mean i looked inside these glasspacks before i bought them and they were huge inside 3 inches and they didnt neck down at all becuse they didnt have any inlets or outlets on them we welded on our own wich were 2.5 inches so my exhaust pipe never runs into anything smaller, it only runs into bigger.
So thought i'd ask if this system should give sufficient enough exhaust flow i also have 1 5/8 hedman llong tube hedders. Just wanna make sure i am not choking my engine, there isnt any big bends in my exhaust, for the most part its stright thru exhaust.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-29-2012, 11:34 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,556
Wiki Edits: 326

Thanks: 695
Thanked 877 Times in 745 Posts
You've built it pretty much like I would have, if that means anything to you.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-30-2012, 08:01 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by pjc360 View Post
I am running true dual exhaust on a 300 hp crate 360 magnum in a 91 dodge truck the pipe diameter is 2 1/4 and i have an H pipe that is also 2 1/4 and aout a foot long, for mufflers i have 18 inch flo-pro glass packs that have a louvered inside core. But these glass packs did not have any inlets or outlets, we welded our own inlets and outlet on them and they have a 3 inch inside diameter.
I have been told louvered glasspacks are restrictive... But i was thinking since these glasspacks i have dont neck down inside that they'd most likely flow pretty well considering they have a 3 inch inside diameter.
I mean i looked inside these glasspacks before i bought them and they were huge inside 3 inches and they didnt neck down at all becuse they didnt have any inlets or outlets on them we welded on our own wich were 2.5 inches so my exhaust pipe never runs into anything smaller, it only runs into bigger.
So thought i'd ask if this system should give sufficient enough exhaust flow i also have 1 5/8 hedman llong tube hedders. Just wanna make sure i am not choking my engine, there isnt any big bends in my exhaust, for the most part its stright thru exhaust.
'Packs having louvers- or anything, actually- that protrudes into the flow path of the exhaust, or cores having irregular, rough openings like those w/saw cuts the length of the core are going to be more restrictive than a muffler having smooth, non protruding openings in the core. As you surmise, the saving grace is the 3" ID- which will compensate for the protruding louvers to a large degree. But they'll still not flow as well as they would w/o louvers; the protrusions still will cause some turbulence.

2-1/4" exhaust pipes are the minimum I'd use. IMO 2-1/2 would be a better size; 3" pipes would be overkill unless you had a lot of length and/or sharp bends or a lot of bends of any degree.

I like the use of a connector pipe between the sides, too. There is an optimum place for the connector, but for vehicles w/a full exhaust system, placement isn't super critical as long as the connector is aft of the collector and before the mufflers. I would choose to put it close to the collectors unless there's a fitment problem. That way there will be a sharing between the two sides that much sooner, which could help reduce backpressure when using a relatively small pipe diameter.



But all things considered, you should be fine w/the set up the way it is. Maybe not optimum, but still OK.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-30-2012, 07:37 PM
Registered User
 
Join Date: Nov 2011
Location: montana
Posts: 136
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i was thinking the 3 inch inside diameter would make up for any restriction caused by the louvers.. It seems to run good with this set up and it sure does sound good. I wanted to use 2 1/2 inch pipe but it is a 4x4 truck and space for pipe under neath is pretty limited, its a tiht fit with dual 2 1/4 inch pipe already. my h pipe is closer to closer to my glass packs then to the collectors but i figured any balance pipe would be better then none.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-30-2012, 08:13 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,556
Wiki Edits: 326

Thanks: 695
Thanked 877 Times in 745 Posts
Quote:
Originally Posted by pjc360 View Post
but i figured any balance pipe would be better then none.
Exactly right.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-07-2012, 08:12 PM
Registered User
 
Join Date: Nov 2011
Location: montana
Posts: 136
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
would i see more power going to a dual 2 1/2 inch exhaust system from a dual 2 1/4 inch exhaust system? Or would it be a waist of time and money?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-07-2012, 10:01 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by pjc360 View Post
would i see more power going to a dual 2 1/2 inch exhaust system from a dual 2 1/4 inch exhaust system? Or would it be a waist of time and money?
On a 300 hp engine- unless the system was very long (think school bus) or there are a lot of bends or there are tight bends, going to a 2-1/2" system will not be cost effective looking at it on a dollar-per-hp basis.

If money isn't an object, you could possibly gain a small bit of performance by going to a less restrictive system, but my thoughts are that on a 300-325 hp engine your system is fine as-is.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-08-2012, 02:12 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,686
Wiki Edits: 0

Thanks: 3
Thanked 403 Times in 348 Posts
Quote:
Originally Posted by pjc360 View Post
I am running true dual exhaust on a 300 hp crate 360 magnum in a 91 dodge truck the pipe diameter is 2 1/4 and i have an H pipe that is also 2 1/4 and aout a foot long, for mufflers i have 18 inch flo-pro glass packs that have a louvered inside core. But these glass packs did not have any inlets or outlets, we welded our own inlets and outlet on them and they have a 3 inch inside diameter.
I have been told louvered glasspacks are restrictive... But i was thinking since these glasspacks i have dont neck down inside that they'd most likely flow pretty well considering they have a 3 inch inside diameter.
I mean i looked inside these glasspacks before i bought them and they were huge inside 3 inches and they didnt neck down at all becuse they didnt have any inlets or outlets on them we welded on our own wich were 2.5 inches so my exhaust pipe never runs into anything smaller, it only runs into bigger.
So thought i'd ask if this system should give sufficient enough exhaust flow i also have 1 5/8 hedman llong tube hedders. Just wanna make sure i am not choking my engine, there isnt any big bends in my exhaust, for the most part its stright thru exhaust.
As long as the louvers point away from the direction of flow and open toward the outside casing they do not obstruct flow. When they point inward and/or against the flow or are simple saw cuts then you get obstruction.

Going from a 2.25 inch pipe to a 3 inch pipe is going to drop flow velocity a lot, the potential problem I see is that the flow may act as if it hit the atmosphere and trigger a negative pressure wave. Nothing wrong with that unless its out of synch with the natural beat of the headers. In the bigger picture this is aways a problem when a termination wave forms whether that's in a terminiation box like Dave Vizard recommends, or at the muffler or the end of the pipe. The goodness or badness of this event all depends on the length of pipe back to the collector and engine RPMs. For a 300 horse 360 this probably isn't anything that should keep you awake nights it is what it is and the engine isn't tuned so close to the optimium edge that wave tuning is going to have any useful effect toward ultimate power.

Basically this system sounds plenty good enough.

Bogie
Reply With Quote Quick reply to this message
The Following User Says Thank You to oldbogie For This Useful Post:
techinspector1 (11-08-2012)

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Restrictive Exhaust Question Regal Beagle Engine 13 08-26-2008 07:17 AM


All times are GMT -6. The time now is 03:54 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.