Cat Back?
Thread Starter
|
Senior User
Joined: Feb 2005
Posts: 102
Likes: 0
Cat Back?
Does 4" cat back exhaust really make that much of a difference? It seems that the exhaust is only capable of flowing as good as the smallest exhaust (stock down pipe and cat) component will let it.
Senior User
Joined: Jan 2007
Posts: 393
Likes: 0
From: Bountiful, Utah
Do a 4" Turbo back Exhaust system. If you only do a Cat back you will not see any big increase performance and MPG's. By removing the Cat I have noticed that my other truck had lower MPG's and slower Turbo spooling.
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
Originally Posted by hangon2me
Do a 4" Turbo back Exhaust system. If you only do a Cat back you will not see any big increase performance and MPG's. By removing the Cat I have noticed that my other truck had lower MPG's and slower Turbo spooling.
Senior User
Joined: Aug 2006
Posts: 336
Likes: 0
I got increases in the MPG as well as i lowered the spool up time of the turbo, interesting how your results are backwards
The turbo back is more work and unless you do towing or run the truck at WOT all the time, its not neccesary to do it
Bruno
The turbo back is more work and unless you do towing or run the truck at WOT all the time, its not neccesary to do it
Bruno
Trending Topics
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Elder User
Joined: Dec 2001
Posts: 578
Likes: 0
From: Massachusetts, USA
huh?
sorry hang, but those figures may be true for you but the majority of us would disagree. SInce I am not running a tuner and have a straight out exhaust leaving my stock downpipe is reducing my numbers by a negligible amount ( besides its to friggin cold up here to spend the extra 30-45 min messing with it 
) The 4" downpipe will cause fit problems and give you a fit as well.
Gonein60 if you decide to go turbo back get a 3.5" DP and delete the cat but save the cat if you are concerned about the emissions monster. And remember MPG's are directly proportional to the weight of your right foot
I will be doing about 350 miles tomorrow and possibly towing a trailer thru the mountains of VT I will definitely get back to ya'll on the performance.
) The 4" downpipe will cause fit problems and give you a fit as well.Gonein60 if you decide to go turbo back get a 3.5" DP and delete the cat but save the cat if you are concerned about the emissions monster. And remember MPG's are directly proportional to the weight of your right foot
I will be doing about 350 miles tomorrow and possibly towing a trailer thru the mountains of VT I will definitely get back to ya'll on the performance.
Senior User
Joined: Jan 2007
Posts: 393
Likes: 0
From: Bountiful, Utah
My 4" Turbo down pipe was no problem to install. You really need to remove the stock Turbo-up pipe , get rid of the restrictions and install the EGR delete plate . I now have no Turbo Lag and my MPG's are in the 17's, before 14's or less. Max EGT's are 1200 pulling a 10,000 trailer in the summer. On my old 2004 6.0L with the Cat removed I had major Turbo Lag and the MPG's were 12's after the Cat was removed. The Cat has almost no restriction in it going 4" in and 4" out. I have no tuner and I need to keep mine in because I get Smog checked every year.
Thread Starter
|
Senior User
Joined: Feb 2005
Posts: 102
Likes: 0
Originally Posted by hangon2me
My 4" Turbo down pipe was no problem to install. You really need to remove the stock Turbo-up pipe , get rid of the restrictions and install the EGR delete plate . I now have no Turbo Lag and my MPG's are in the 17's, before 14's or less. Max EGT's are 1200 pulling a 10,000 trailer in the summer. On my old 2004 6.0L with the Cat removed I had major Turbo Lag and the MPG's were 12's after the Cat was removed. The Cat has almost no restriction in it going 4" in and 4" out. I have no tuner and I need to keep mine in because I get Smog checked every year.
Elder User
Joined: Nov 2001
Posts: 892
Likes: 1
From: Duluth, MN
Duals aren't going to increase turbo spool up time. The turbo is VGT operated and is already at max duty cycle(around 65%) when at idle or light cruise. Back pressure is measured in the exhaust system pre turbo also(so duals have no effect). They will give you good sound though....
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
Originally Posted by Wilber15
Duals aren't going to increase turbo spool up time. The turbo is VGT operated and is already at max duty cycle(around 65%) when at idle or light cruise. Back pressure is measured in the exhaust system pre turbo also(so duals have no effect). They will give you good sound though....
Postmaster
Joined: Apr 2006
Posts: 3,294
Likes: 1
From: Neptune Beach, FL
Diesels are generally a 0 BP operation.. Cat addition is the work of the EPA (rejects).. Removing the CAT provides less spool time, less back pressure and slight increase in pressure.. If the MPG drop, its due to the driver and his foot.. There is no "Negative" advantage with a Turbo Back Straight.. That is why "technically" diesels are authorized for Inspections in some states with Straight systems and do not require an emission test. Here in Texas you can walk up and tell an Inspector "I have a straight exhaust, no cat or muffler".. He won't say a thing and you'll still pass.
The effectiveness of the exhaust also plays a vital role in lowering the EGT's. It's more ratio'd towards effectively lowering EGT by increase volume for air and reducing resistance (back pressure). You can see upwards of 200-400* in temperature drop with moving to a free flowing 4" systems versus a stock system.
The effectiveness of the exhaust also plays a vital role in lowering the EGT's. It's more ratio'd towards effectively lowering EGT by increase volume for air and reducing resistance (back pressure). You can see upwards of 200-400* in temperature drop with moving to a free flowing 4" systems versus a stock system.
Elder User
Joined: Dec 2001
Posts: 578
Likes: 0
From: Massachusetts, USA
Gonein60
My mpg's went almost 2 miles per gallon in the first tank after exhaust and cat delete.
Listen to the the Green Beret he explains it right on the money, if it has a negative effect either its your driving your math or something else but not the exhaust and cat delete. Its kinda like saying rain pours up to the clouds not down, it could only happen in bizzaro world
my $.02 ..... I might need change
My mpg's went almost 2 miles per gallon in the first tank after exhaust and cat delete.
Listen to the the Green Beret he explains it right on the money, if it has a negative effect either its your driving your math or something else but not the exhaust and cat delete. Its kinda like saying rain pours up to the clouds not down, it could only happen in bizzaro world
my $.02 ..... I might need change