Fun In B.C.  

Welcome to the Fun In B.C. forums. your outdoor adventure headquarters.

As guest on our site, you have the chance to take a look around and get an idea of what we're all about. Feel free to check out some of the current topics of discussion and some of the stories of adventure gone by, by clicking on the top right picture to view past "Pictures of the week" .

Don't be shy, come on in. By joining our free community you'll be able to join in the fun with other outdoor adventurers and find out about upcoming events. you will also get access to View posted pictures. Stop sitting on the outside looking in, join today it's easy and it's FREE.

It's time for you to start having FUN..... in BC!!

If you have any problems with the registration process or your account login, please contact contact support.

HOTMAIL USERS: Check your 'junk mail' folder for the confirmation message and add 'funinbc.com' to your safe list so you don't miss anymore important emails from us.

Go Back   Fun In B.C. > All about your Ride > General 4x4 Discussion

General 4x4 Discussion General discussion and questions that would apply to all makes.

Reply
 
Thread Tools
  #1  
Old 02-19-2007, 07:37 PM
Tunabomber's Avatar
Tunabomber Tunabomber is offline
665 neighbor of the beast
 
Join Date: May 2006
Location: coq bc
Posts: 8,923
Tunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond repute
Reputation: 1000001
back pressure question

ok so im used to haveing big motors that seem to do better with less back pressure ie. freeflow type thing.

but now i got a jeep with 4.0 ho streight 6 and as always first thing i did was hollow the cat and put on a flowmaster .
but i didnt seem to make any difference in fact now it kinda pops almost like a backfire on the decel but only when i go over 3000 rpm.

whats your opinion

to much flow ?
__________________
Reply With Quote
  #2  
Old 02-19-2007, 07:49 PM
Andrew Goll Andrew Goll is offline
Prospect
 
Join Date: May 2005
Location: Kelowna, BC, Canada.
Posts: 243
Andrew Goll bad newbie
Reputation: 0
im callin the dot thats illegal
Reply With Quote
  #3  
Old 02-19-2007, 07:55 PM
MetalMan MetalMan is offline
Manlier than a pirate
 
Join Date: Dec 2004
Location: Abbotsford, BC, Canada.
Posts: 2,059
MetalMan bad newbie
Reputation: -1
Sounds like an exhaust leak, or you might have an O2 after the cat that you have to bypass. One way or another, putting a length of pipe in place of the cat is always a better idea. If you need the cat for aircare, make it as a test pipe, when airscare comes around you just unbolt the pipe and bolt in the cat.
__________________
http://i83.photobucket.com/albums/j317/allpontiacs/DSC00185.jpg
Reply With Quote
  #4  
Old 02-19-2007, 07:58 PM
epic3's Avatar
epic3 epic3 is offline
cornbinder on coils
Swollen Member
 
Join Date: Dec 2004
Location: Richmond, Canada.
Posts: 13,725
epic3 bad newbie
Reputation: 2
the cat is supposed to burnup unburnt fuel in the exhaust so without it if your a touch on the rich during initial decel then you may get a backfire or popping sound from your exhaust try advancing your timing a little more to give a bit more burn time
__________________
founding member of A.A.
Reply With Quote
  #5  
Old 02-19-2007, 09:15 PM
Moondog's Avatar
Moondog Moondog is offline
Make your own-iEdit Title in 'User CP'
Swollen Member
 
Join Date: Nov 2004
Location: Mission
Posts: 5,514
Moondog bad newbie
Reputation: 4
I have a k&n on mine flowmaster with 3" pipe and a high flow cat I have had no problems
Reply With Quote
  #6  
Old 02-19-2007, 09:32 PM
DirtyComanche DirtyComanche is offline
Not a Newbie
 
Join Date: May 2006
Location: PG
Posts: 572
DirtyComanche Unknown Newbie
Reputation: 10
Mine makes a pop when I come off the throttle... Straight through, just a glasspack. Oh, and a cracked header. But what 4.0 header isn't.




Anyways, if you want more or less back-pressure with a 4-oh is pretty much entirely up to you. What works better? Who knows. People swear one side, others swear the other.
__________________
1 working dodge, 1 sorta working GMC, 2 not working jeeps.
Reply With Quote
  #7  
Old 02-19-2007, 09:41 PM
Dieseljeep Dieseljeep is offline
Not a Newbie
 
Join Date: Apr 2005
Location: Chilliwack, Canada.
Posts: 500
Dieseljeep bad newbie
Reputation: 0
I think that back pressure for those motors is around 3 pounds.I think some exhaust shops have a guage they plug the pipe with and take a reading . The back pressure is a balance from the intake of air.
__________________
A recession is when your neighbour is outa work, a Depression is when you are outa work.
Reply With Quote
  #8  
Old 02-20-2007, 06:11 PM
MetalMan MetalMan is offline
Manlier than a pirate
 
Join Date: Dec 2004
Location: Abbotsford, BC, Canada.
Posts: 2,059
MetalMan bad newbie
Reputation: -1
Quote:
Originally Posted by epic3 View Post
the cat is supposed to burnup unburnt fuel in the exhaust so without it if your a touch on the rich during initial decel then you may get a backfire or popping sound from your exhaust try advancing your timing a little more to give a bit more burn time
It won't pop from a rich condition, the popping is the ignition of unburnt gasses. But it doesn't just ignite itself, it needs oxygen, hence air is getting into the exhaust at some point where the gasses are still hot enough to ignite. Unless the vehicle has an active AIR system, a leak is the only way for oxygen to get in.
__________________
http://i83.photobucket.com/albums/j317/allpontiacs/DSC00185.jpg
Reply With Quote
  #9  
Old 02-20-2007, 07:39 PM
Tunabomber's Avatar
Tunabomber Tunabomber is offline
665 neighbor of the beast
 
Join Date: May 2006
Location: coq bc
Posts: 8,923
Tunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond repute
Reputation: 1000001
hmmm i like poping noise on decel its very suttle and i have to give it a little gas to make it happen .

its when i acel up past 2900 rpm and hit the clutch that it makes the slight backfire noise
__________________
Reply With Quote
  #10  
Old 02-20-2007, 07:59 PM
Trooper Trooper is offline
Fisting for dollars
 
Join Date: Aug 2005
Location: Vancouver, Canada.
Posts: 1,543
Trooper bad newbie
Reputation: 1
If your exhaust is to large and you dont have enough back pressure it will pop too wont it?

I have a little MG that pops and flames out the back but thats a whole other story
__________________

Taint nothin'
Reply With Quote
  #11  
Old 02-20-2007, 08:26 PM
u2slow u2slow is offline
Not a Newbie
 
Join Date: Aug 2003
Location: Southwestern BC
Posts: 691
u2slow bad newbie
Reputation: 0
When I upgraded to ram's horn manifolds and dual exhaust with dumps (350 TBI) I got lots of popping and banging when riding a gear down a hill. So bad it actually slit the seams on the muffler. Still no idea why it did it.
Reply With Quote
  #12  
Old 02-20-2007, 08:26 PM
MetalMan MetalMan is offline
Manlier than a pirate
 
Join Date: Dec 2004
Location: Abbotsford, BC, Canada.
Posts: 2,059
MetalMan bad newbie
Reputation: -1
I had a Chevette that popped and shot flames out the exhaust, that was an extreme case mind you. I'm fairly certain the cause was a shot cat coupled to an active AIR system. It's pretty tough to totally seal an exhaust system, so it almost always happens to some degree. Check to make sure you don't have a smog pump, I'm not on the up and up with those Jeeps.
__________________
http://i83.photobucket.com/albums/j317/allpontiacs/DSC00185.jpg
Reply With Quote
  #13  
Old 02-20-2007, 08:27 PM
MetalMan MetalMan is offline
Manlier than a pirate
 
Join Date: Dec 2004
Location: Abbotsford, BC, Canada.
Posts: 2,059
MetalMan bad newbie
Reputation: -1
Quote:
Originally Posted by u2slow View Post
When I upgraded to ram's horn manifolds and dual exhaust with dumps (350 TBI) I got lots of popping and banging when riding a gear down a hill. So bad it actually slit the seams on the muffler. Still no idea why it did it.

Refer to everything I've said so far...
__________________
http://i83.photobucket.com/albums/j317/allpontiacs/DSC00185.jpg
Reply With Quote
  #14  
Old 02-20-2007, 08:44 PM
Tunabomber's Avatar
Tunabomber Tunabomber is offline
665 neighbor of the beast
 
Join Date: May 2006
Location: coq bc
Posts: 8,923
Tunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond reputeTunabomber has a reputation beyond repute
Reputation: 1000001
thanks for the input guys
__________________
Reply With Quote
  #15  
Old 02-20-2007, 10:27 PM
Trooper Trooper is offline
Fisting for dollars
 
Join Date: Aug 2005
Location: Vancouver, Canada.
Posts: 1,543
Trooper bad newbie
Reputation: 1
Wont an intake leak cause popping too? Do the old intake cleaner test to see if its a intake leak
__________________

Taint nothin'
Reply With Quote
Reply


Thread Tools

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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Style Design By: Resourcelabz.se