I see this car has three cats on it. They have got to be restricting the exhaust flow. I'm thinking of getting a spare downpipe and gutting the cats to test out what kind of difference in horsepower and sound that would make.
Derrick824
I don't want to take any chances on voiding my warranty. Some dealerships can be picky @ssholes. That's why I only plan on doing things that I can bolt on/off. Also I don't plan on spending $400-500 on a Stillen or CE downpipe. I was simply thinking of getting one out of a junkyard and gutting it.
I've been seeing headers + down pipes on ebay lately for like 200 shipped to your door.
uhm removing a restrictive item from the exhaust will have gains in hp and mileage.
especially if some mods have been to done to improve air into the motor.
get it in and get it out....
I was a 5.0 racer for years and saw stock cars 1/4 et's drop by 2 to 3 tenths just from hollowing cats or installing off-road pipes.
Man forget trying to hollow out the cat unless you have a respirator or something. You do not want to inhale the dust and crap thats going to come out of that thing do you?
my .02
uhm removing a restrictive item from the exhaust will have gains in hp and mileage.
especially if some mods have been to done to improve air into the motor.
get it in and get it out....
I was a 5.0 racer for years and saw stock cars 1/4 et's drop by 2 to 3 tenths just from hollowing cats or installing off-road pipes.
Man forget trying to hollow out the cat unless you have a respirator or something. You do not want to inhale the dust and crap thats going to come out of that thing do you?
my .02
glFirst of all its a bad assumption that catalytic converters increase pressure drop. On most cars they do not. Using bad gas, modifications etc can affect the catalytic structure and that will increase pressure drop. Age of course will, too.
Second, if you want to risk having your car confiscated, incur large fines, and/or prison time, if you want to 'gut' the cat you'll have to open them up and substitute smooth walled tubing and not just 'rod out' the cat. That will aqlmost surely increase pressure drop simply because the exhaust gas bounces, wanders, and deflects off many surfaces before being squeezed to exit the cat. I've seen an Eclipse lose 14 HP from 217 hp gotten on a 'straight pipe' in the cat just by substituting a 'rodded out cat. (it started at 200 hp stock. As some people have pointed out there are better ways to reduce back pressure and increase hp. Don't forget when you change the exhaust pipe diameter/back pressure the pipe length will likely need changing, too.
Second, if you want to risk having your car confiscated, incur large fines, and/or prison time, if you want to 'gut' the cat you'll have to open them up and substitute smooth walled tubing and not just 'rod out' the cat. That will aqlmost surely increase pressure drop simply because the exhaust gas bounces, wanders, and deflects off many surfaces before being squeezed to exit the cat. I've seen an Eclipse lose 14 HP from 217 hp gotten on a 'straight pipe' in the cat just by substituting a 'rodded out cat. (it started at 200 hp stock. As some people have pointed out there are better ways to reduce back pressure and increase hp. Don't forget when you change the exhaust pipe diameter/back pressure the pipe length will likely need changing, too.
yeah i agree with mahout. the nissan cats are known to be very low restriction cats. theres almost no point in changing them out. this isnt old school 1978 technology you have here guys.
This is limited to my V8 knowledge, but I'll try to stay on topic.
With an LS1, removing the cats is good for about 5-6rwhp, and it'll increase the rasp in the exhaust. There are ways around engine codes caused by removing the cats (beating them with a stick would cause the same codes) such as O2 simulators, and reprogramming the rear cats out in the ECU.
As it is, having no cats, or hollowed out cats, in any state is illegal. Een if you don't have emissions testing, it's illegal, and I have no illusions about how fast a Nissan dealership would be to void ANY and ALL warranties pertaining to the car if they found out you either removed the cats and replaced them with a test pipe, or hollowed them out using whatever method. I seriously doubt that hollowing out the cats, and doing nothing else to your exhaust system, would result in any appreciable gains. Even in an LS1, which is a very free-flowing engine, as I said, gains are minimal, and I'd assume they'd be even less with the vg35 (due to displacement).
If you remove the cats without putting rear O2 simulators where the post-cat O2 sensors would go, your car will probably kick into limp mode and you'll not realize ANY gains except for having to unbolt the test pipes and stick the cats back in.
The best way to look at an engine is as a massive air pump. You want the intake and exhaust to be as free-flowing and smooth as possible. Any modification you make to the intake (say a WAI, or a better intake manifold) will see much better gains if you similarl mod the exhaust side of the engine to flow more. If your engine can't push air out any more efficiently, it's not going to be able to do a whole lot with just an intake. The same goes for the exhaust - unless you remove restrictive parts (exhaust manifolds, small diameter exhaust tubing) doing a single thing like gutting/removing the cats really won't make a huge difference.
All that said, I picked up 38rwhp in my car by installing long tube headers, 3" true duals with no cats and 12" Dynomax Bullet mufflers (basically a straight-through, chambered wall design) and having it dumped at the rear axle. If I had only changed the system so that the cats were removed and everything else remained stock, I probably would have only picked up 5rwhp. Just some things to think about.
With an LS1, removing the cats is good for about 5-6rwhp, and it'll increase the rasp in the exhaust. There are ways around engine codes caused by removing the cats (beating them with a stick would cause the same codes) such as O2 simulators, and reprogramming the rear cats out in the ECU.
As it is, having no cats, or hollowed out cats, in any state is illegal. Een if you don't have emissions testing, it's illegal, and I have no illusions about how fast a Nissan dealership would be to void ANY and ALL warranties pertaining to the car if they found out you either removed the cats and replaced them with a test pipe, or hollowed them out using whatever method. I seriously doubt that hollowing out the cats, and doing nothing else to your exhaust system, would result in any appreciable gains. Even in an LS1, which is a very free-flowing engine, as I said, gains are minimal, and I'd assume they'd be even less with the vg35 (due to displacement).
If you remove the cats without putting rear O2 simulators where the post-cat O2 sensors would go, your car will probably kick into limp mode and you'll not realize ANY gains except for having to unbolt the test pipes and stick the cats back in.
The best way to look at an engine is as a massive air pump. You want the intake and exhaust to be as free-flowing and smooth as possible. Any modification you make to the intake (say a WAI, or a better intake manifold) will see much better gains if you similarl mod the exhaust side of the engine to flow more. If your engine can't push air out any more efficiently, it's not going to be able to do a whole lot with just an intake. The same goes for the exhaust - unless you remove restrictive parts (exhaust manifolds, small diameter exhaust tubing) doing a single thing like gutting/removing the cats really won't make a huge difference.
All that said, I picked up 38rwhp in my car by installing long tube headers, 3" true duals with no cats and 12" Dynomax Bullet mufflers (basically a straight-through, chambered wall design) and having it dumped at the rear axle. If I had only changed the system so that the cats were removed and everything else remained stock, I probably would have only picked up 5rwhp. Just some things to think about.
We have done a lot of experimentation on Honda, some others & Chevy engines exhaust. (what? you thought SSS was really showroom stock?) On 1990's Chevy, Mitsu, Nissan & Honda engines just gutting the cats cost us torque (and thus HP, too). We had to adjust the length and pipe diameter as well to minimize loss. Putting smooth bore pipes in the exhaust and changing diameter and length yielded 15 to 18% gain in torque, (and HP) which was very good considering customers had to meet 78 db max at 50 feet. We have yet to see a significant gain (>5%)from cat-back exhausts that were worth the $500 costs except to those who like different sounds or looks.
The only way to 'gut' cats for performance is to disassemble and weld nice clean smooth thru pipes in your cats and probably install cat-back systems, but you'll advertise to feds. Just because its loud doesn't mean there's more power; the sound is most often not related to power.
But if you run on the street and get 'tagged' you will lose your car and perhaps freedom for a while as well as a much lighter pocketbook. And don't tell me about it. Or anyone else either.
The only way to 'gut' cats for performance is to disassemble and weld nice clean smooth thru pipes in your cats and probably install cat-back systems, but you'll advertise to feds. Just because its loud doesn't mean there's more power; the sound is most often not related to power.
But if you run on the street and get 'tagged' you will lose your car and perhaps freedom for a while as well as a much lighter pocketbook. And don't tell me about it. Or anyone else either.
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
