backpressure loss?

[Four0Sport]

every joint and weld on my exhaust either is or is about to have a hole/leak in it. mainly from the truck sitting for over a year but partially bc everything except the muffler and tail pipe are the stock pieces. when my truck blew, gas was pouring out through the exhaust and heating up in the cats. i know this cant be good so i was thinking about cutting off the the entire exhaust in front of the cats and running 2 1/4 back to a decent muffler and a dump tail pipe after the rear end.

getting rid of the cats is gonna effect the backpressure i know. but how much? a friend of mine and i were talking about this and we thought that worst case is i might lose a little low end torque, but i would be freeing up the exhaust and helping the truck breathe, well exhale, a little better.

am i missing anything? any feedback is appreciated.

 

[leefhead]

its illegal to drive with no cats....get a high flow mini cat at least.

 

[Rosscup]

its only illegal in some places not all. i took bolth my cats off and am running 2 1/2" all the way back and i know i lost some back pressure but not a TON. i didnt notice any power loss, some gain. you will lose a couple mpg ill warn you.

 

[Anime]

No, it's illegal in all places for an on-road vehicle. If you're lucky, you'll just get a $5000 fine. If you're unlucky, you'll get a $5000 fine and some time in jail. Not to mention the toxic fumes that will come out of the exhaust for you and your passengers, along with anyone who's unlucky enough to be near your exhaust pipe exit at a stoplight, to inhale.

The easiest route is to get a replacement set of bolt-on OEM cats (Walker and Magnaflow sell them for ~$200) and then a cat-back exhaust system (something like a Dynomax Super Turbo system for another ~$200 or less). Pay up, bolt on, you're done.

Otherwise, you can get an exhaust shop to weld in a single high-flow 3-way cat to replace the two OEM ones, and then get whatever muffler you want welded up to new 2.25" pipe all the way back.

You could also do a combo of the two, and get an exhaust shop to weld in a high-flow cat, but leave the factory muffler flange so you can just bolt up a catback system instead of having them fab the muffler pipe.

 

[Four0Sport]

bolt up hardware isnt really an issure, i would rather have something professionally bent and welded. i may go with a universal 2 1/4 mini cat which i can get from work for around $50 just to eliminate excess gasses. $400 for an exhaust sounds ridiculous when i can get a $20 muffler, $50 cat, and $40 in bent and welded pipe. thanks for the quick feedback though.

 

[91exploreron37]

bolt up hardware isnt really an issure, i would rather have something professionally bent and welded. i may go with a universal 2 1/4 mini cat which i can get from work for around $50 just to eliminate excess gasses. $400 for an exhaust sounds ridiculous when i can get a $20 muffler, $50 cat, and $40 in bent and welded pipe. thanks for the quick feedback though.

Exactly thats why I say screw the cats and the guy sitting behind you and run muffler and pipe.

 

[Reejerey]

Its a federal law that you have to have Cats on a road vehicle.

On to the next issue... Backpressure is bad anyway. Its caused by restrictions in your exhaust system. Thats why you typically see an increase in power when you bolt on high flow cats and a less restrictive exhaust.

The myth that backpressure was good was started long ago when people started putting small diameter long tube headers on vehicles and noticing an increase in torque, but its not the back pressure that causes that increase, its the increased scavenging effect from the long tube headers being able to pull more air into the combustion chamber. A set of large diameter short tube headers wouldn't offer the same low end gains, but it would offer more airflow for high end power. Anything beyond the headers that adds "backpressure" and that isn't a turbo is just going to be a restriction and is going to cost you power.

 

[seth247]

Wait I'm confused...

I have a cat, his name is evinrude. But he does nothing to help my exhaust...

He just sits around and sheds on stuff.

 

[91exploreron37]

Have tried taping him to the muffler? and isnt this thread like a year old?

 

[robmurt04]

Have tried taping him to the muffler? and isnt this thread like a year old?

Yeah but it's a classic now. :

 

[seth247]

Have tried taping him to the muffler? and isnt this thread like a year old?

hhhmm I don't know, he's kinda old.

Maybe get a new one for better efficiency?

 

[robmurt04]

hhhmm I don't know, he's kinda old.

Maybe get a new one for better efficiency?

if you want the best efficiency just hallow him out.

 

[Four0Sport]

if you gut the cat you wont be able to get money for it when you bring it to a recycler. so keep your cat full.

 

[seth247]

Wait, wait, wait, you can get money for em after they kick the bucket?


How Much? It might be 'ol rudy's time to go...

If you want the best efficiency just hallow him out.

What... Turn him into a saint?

 

[Four0Sport]

i got $75 for mine. well it wasnt mine, i found it wandering around my year.

 

[Reejerey]

Yeah, you've got to take them to a chinese resturant to get money for them. you don't really think that's beef do you?

Also sorry for dragging up the old thread, didn't realize I was that far back in the forum when I posted. My mistake.

 

[robmurt04]

I'll have to go steal some of my neighbors cats. The one guy needs a new one anyone it's starting to smell funny and has dirty emissions.

And it's okay we'll forgive you... This time.

 

[91exploreron37]

This is going to end up like IZwack's thread... just 41 more pages to go

 

[seth247]

I hear izwack got his stimulation bill past the senate.

May be he can use this new dead cat recycling program to help fund it...

 

[robmurt04]

Yeah but then everyone will be taking theirs to the scrap yard and there will be a lot of poor emissions and burning all those cats would smell! Not to mention who would eat all the cat food?