Cutout Before or After Cats, & O2 Simms?
02-07-2004, 02:48 PM
#12
i really have to question the whole loss of low end power from "too little" back presure, i have heard that for ever and kind of think it might just be a perception issue, could it be that it is just soo much louder that your not pushing the pedal as hard.
i have installed quiet mufflers before and the truck felt faster, just because i could completely floor it and not make alot of fuss and run hard.
here is a closed vs open chart from my truck
and here is a chart that shows the actual hp diference of the chart above
you can see from the beging to the end the hp is up, i admit i have the stock restrictive exhaust and not a free flowing cat back but i bet the results would be similar, just not as extreme.
i have installed quiet mufflers before and the truck felt faster, just because i could completely floor it and not make alot of fuss and run hard.
here is a closed vs open chart from my truck
and here is a chart that shows the actual hp diference of the chart above
you can see from the beging to the end the hp is up, i admit i have the stock restrictive exhaust and not a free flowing cat back but i bet the results would be similar, just not as extreme.
02-07-2004, 02:54 PM
#13
TECH Senior Member
iTrader: (1)
Join Date: Jan 2003
Location: Armpit of East TX
Posts: 9,342
Likes: 0
Received 0 Likes
on
0 Posts
If you have the cutouts in front of the cats, you may or may not throw a code, the codes will be something about the rear 02 sensors and can be ignored. They are used for emissions testing and catalytic temperatures. If you do get a light, you can get it checked at AutoZone and have them clear the code.
I have run around on open header for a weekend and didn't throw a code. I have also thrown one on the first WOT run I made after uncorking them too. It just happens sometimes. Either way, you don't need o2 simms. From a performance standpoint you will get better results from putting them in front of the cats, but there isn't much room and it's a tight fit. You may not get as good of a 1/8mile time, but you will probably trap higher speeds due to the less backpressure giving you increased horsepower but reduced torque. It's a trade off some are willing to go with.
If this tells you anything, I always unbolt and remove my exhaust from the y-pipe back when I go to the track.
I have run around on open header for a weekend and didn't throw a code. I have also thrown one on the first WOT run I made after uncorking them too. It just happens sometimes. Either way, you don't need o2 simms. From a performance standpoint you will get better results from putting them in front of the cats, but there isn't much room and it's a tight fit. You may not get as good of a 1/8mile time, but you will probably trap higher speeds due to the less backpressure giving you increased horsepower but reduced torque. It's a trade off some are willing to go with.
If this tells you anything, I always unbolt and remove my exhaust from the y-pipe back when I go to the track.
02-07-2004, 03:53 PM
#15
Originally Posted by jhelms
Good info, guys.
PARISH - is that dyno sheet from a cutout before the cats?
PARISH - is that dyno sheet from a cutout before the cats?
my next trip to the dyno will have no cats and a single 3" electric cut out.
02-07-2004, 03:59 PM
#16
TECH Senior Member
iTrader: (1)
Join Date: Jan 2003
Location: Armpit of East TX
Posts: 9,342
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by parish8
could it be that it is just soo much louder that your not pushing the pedal as hard.
02-12-2004, 08:48 PM
#17
Mortgage Banker Mod
Thread Starter
iTrader: (2)
Join Date: Nov 2001
Location: Columbus, GA
Posts: 1,805
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Flyer
If you have the cutouts in front of the cats, you may or may not throw a code, the codes will be something about the rear 02 sensors and can be ignored. They are used for emissions testing and catalytic temperatures. If you do get a light, you can get it checked at AutoZone and have them clear the code.
I have run around on open header for a weekend and didn't throw a code. I have also thrown one on the first WOT run I made after uncorking them too. It just happens sometimes. Either way, you don't need o2 simms. From a performance standpoint you will get better results from putting them in front of the cats, but there isn't much room and it's a tight fit. You may not get as good of a 1/8mile time, but you will probably trap higher speeds due to the less backpressure giving you increased horsepower but reduced torque. It's a trade off some are willing to go with.
If this tells you anything, I always unbolt and remove my exhaust from the y-pipe back when I go to the track.
I have run around on open header for a weekend and didn't throw a code. I have also thrown one on the first WOT run I made after uncorking them too. It just happens sometimes. Either way, you don't need o2 simms. From a performance standpoint you will get better results from putting them in front of the cats, but there isn't much room and it's a tight fit. You may not get as good of a 1/8mile time, but you will probably trap higher speeds due to the less backpressure giving you increased horsepower but reduced torque. It's a trade off some are willing to go with.
If this tells you anything, I always unbolt and remove my exhaust from the y-pipe back when I go to the track.
Thread
Thread Starter
Forum
Replies
Last Post
jhelms
Tuning, Diagnostics, Electronics, and Wiring
6
02-14-2006 05:51 PM
