Pros and Cons of Duel Exhaust.

I have a 1991 Chevy Silverado with a 350 in it. It still has the cat on it but where I live we don't have to get those emission tests before we get tags, so im not worried about cutting it off. I have heard that duel exhaust will eat more fuel and give you less power, any truth to this? I have been thinking about dueling it out for a long time now but the thought of it drinking even more gas is a bummer. I don't want that Y'ed off bull**** where 1 pipe Y's off into two. Any reccomendations?

Going to a dual system especially on a 350 with the cat removed will definetly increase the hp and fuel mileage. I am not saying that it is going to be a huge savings, but you will notice a differnece. Also another good addition for helping in the hp and fuel mileage is a k&n filter at the least, if not an entire cold air intake setup of some kind. I used to have an 88 K1500 jimmy and noticed a big improvement in low end throttle response by upgrading to a k&n air filter.

Is Flowmasters any good? They guy at the exhaust shop seemed to be a total flowmaster freak, going on and on about how great it is....then he said "we start with "3 pipe into a duel outlet flowmasters muffler and Y them either to the sides or the back, whatever you prefer." His estimate was 250$ **** that...... Are stright pipes any good? I can get a duel stright pipe setup for 75$ from a guy a few blocks from me. You need some kind of resistance in the exhaust system don't you?

Anyone?

I just went with the Meineke Votex's on mine. VERY happy with them. The Flowmaster's are also good, but a little louder than I wanted. Check out the Vortex, it's fairly reasonable, good warranty, and a GREAT sound. Oh yea, watch out for the whole "Federal law" thing when removing your Cat, regardless of where you live, it's gotta be on there. Just FYI.

I may be wrong here but aren't there oxygen sensors in the cats?

No, the O2 sensors are before the cat on his model. Some newer ones also have post cat sensors to monitor catalytic converter efficiency.

What about stright pipes? I heard that if you run stright pipes it reduces HP and makes you guzzle gas.....I can get stright pipes for cheap but, if its going to eat gas and make me loose hp forget it.

the ultimate set up for your truck is true duals from the block
after u run the true duals, let it run for a while to get real heated up and using a IR thermometer, find the hottest place on both pipes(where the exhaust pulses stop) and put a x pipe right there.
use flowmaster mufflers or the equivalent
it doesnt matter whether u run straights or not as far as gas mileage goes
the only thing i think your gas mileage would do is increase, by the least bit u probly wont notice it.

by the way, true duals will not hurt your power, they will only increase it
and keep the cat, but if u really wanna get rid of it, id atleast go with a high flow cat

Hey I have a 2000 Silvy with the 5.3 and my duals sound great. It's got true duals from the cats back and no mufflers. My friend and I (an excellent welder) cut the pipe right before they come together and ran new pipe from there. I started out with 40 series flowmasters but it wasn't enough for me :evillol: so we cut em out and put in straight pipe. I was just fortunate enough to have 2 factory cats so I didn't have to buy another.

"Mufflers are for wimps!"-I concur.

Tell me if I'm a dumb $ss but I just cut off the muffler on my 2000 5.3 and it put a pipe in place of the muffler. So your telling me that it will not reduce MPG nor horsepower?


Hey I have a 2000 Silvy with the 5.3 and my duals sound great. It's got true duals from the cats back and no mufflers. My friend and I (an excellent welder) cut the pipe right before they come together and ran new pipe from there. I started out with 40 series flowmasters but it wasn't enough for me :evillol: so we cut em out and put in straight pipe. I was just fortunate enough to have 2 factory cats so I didn't have to buy another.

Hey I have a 2000 Silvy with the 5.3 and my duals sound great. It's got true duals from the cats back and no mufflers. My friend and I (an excellent welder) cut the pipe right before they come together and ran new pipe from there. I started out with 40 series flowmasters but it wasn't enough for me :evillol: so we cut em out and put in straight pipe. I was just fortunate enough to have 2 factory cats so I didn't have to buy another.

I also have 2 factory cats. Do they not all come like this? Why would they offer two seperate systems from the factory?

You do lose power when running straight pipes.

Ok im not really an expert when it comes to exhaust systems, but i know a bit about engine efficiency and heres where people get confused: you have to elaborate on what u mean by "power".its not an absolute that straight pipes cut power. losing the system as a whole cuts torque, not horsepower.at low rpm backpressure helps the engine completely burn gasses in the cylinders, whereas at high rpm the engine needs to be able to vent old gasses and get new fuel/air in at a higher rate-obviously.headers add higher rpm horsepower but not neccesarily torque.so straight pipes will help power at high rpm because it allows the engine to operate more efficiently.most people however have no need to run their engines at this rpm on the street so they dont see the increase.go and unbolt the exhaust at the manifold and u will see the decrease in low rpm torque definitely.the other need for an actual exhaust system is to get rid of heat.no, u dont need mufflers, but if u only run drag pipes-headers only-they will not dissipate heat and the exhaust valves will burn.i do agreee however, mufflers are for wimps.run the sraights all the way back if u can do it without gettin a ticket where u live.if u dont have the low rpm grunt u want, put mufflers on and see if it helps.just remember that only by increasing the stuff that goes into the engine-air and fuel-along with the stuff that comes out will u see the full benefits of a free flowing exhaust

some people think that changing the exhaust on a truck drops gas milage but what happens is guys drive harder to make more sound and burn more gas

on the 350's true dual exhaust might be good but i have heard nothing but bad stories about dual exhaust put on the new body style trucks. kills low end torque and horsepower. im personally replacing my single muffler with a gibson and thats as much as ill do to the exhaust :smokin:

Something that many people do not realize is that to have true dual exhaust, you don't have to have two 4" pipes running out of the headers to the tail pipe. I have dual exhaust on my truck, with the stock 2 1/4 pipes, and going from factory style mufflers to glasspacks (mufflers required here, $50 ticket), there was no noticable decrease in torque. If you stay at a reasonable size pipe (I'm going a bit smaller when mine rusts through, thinking 1 7/8), you won't have a decrease in torque because the friction between the air and the pipe comes close to what a muffler creates in a larger diameter pipe.

Also, can anyone find a report from a respectable third party organization on torque loss with no backpressure? I've heard that from a lot of people, but I have a buddy with a 388 stroker (he swears it's not a 383) with straight pipes off the headers (3" pipe all the way back, no cats, no bends) and he's got 600-some ft-lbs torque at the wheels on the dyno, with 3.73 gears and 35" tires.

j-ri: you said it right.....as long as you dont go crazy with pipe size, you dont kill your torque.

internic: true duals let the engine breathe better, OBS or NBS, basically any v8 will benefit from true dual exhaust; if its done right.

i have true duals and before i could not pull on my bro in laws truck from the line...exact same truck, except for his has fake duals...now i can pull on him from any speed, or from the hole.

bottom line--true duals help make power, if its done right, like i said

if you feel ambitious buy 2 flowmaster mufflers, some exhaust tubing and start welding :P, its not that hard to do, I did my trucks exhaust using a single 3" in and 3" out muffler with a custom pipe reducer to run a small piece of factory pipe (2.75" i think was the stock) so I still have the cat's, Cost me bout $50 all together and it sounds great, i got a few small vid's of my silverado (99 silverado) when i was testing the sound ill post them soon

One person has it completely correct, if you go dual pipes you need to increase air flow in as well as out. You could see as much as a 20% HP gain. If you only do the pipes you may see a gas mileage drop.

I don't think you're going to see a 20% horsepower gain, on a 350, from true duals. I dont care if it's done correctly or not.