No muffler. Problem?

uh6077 · October 24, 2006

I just picked up a 99 Chevy 1500, 5.3, 4x4 last week. I am noticing little things here and there so I will be asking lots of questions in the coming weeks. The truck does not have a muffler. It does have a cat though. Not near as loud as I thought it would be. Will this cause any problems? Will it affect gas mileage either way? Thanks

lerbud · October 24, 2006

i have had straights on all my trucks with no problems. some others here will say you shouldnt do it. After reading all the posts about an x-pipe I finally put one on my 06. its not near as loud as straights but i know i have plenty of back pressure just in case.

4doorluv · October 24, 2006

i dont have one on my 07 sounds good had no problems yet

thecraft · October 24, 2006

Nothing wrong with it unless you have inspections... or bitchy neighbors.

BTW, there are rumors floating around that say you will lose low-end torque by removing too much backpressure. That is completely FALSE, power loss will only occur when you use pipe so large that the exhaust slows down and cools.

eshoremd · October 25, 2006

i wish i could hear what that sounds like. ive been thinking about it.

uh6077 · October 25, 2006

i wish i could hear what that sounds like. ive been thinking about it.

<{POST_SNAPBACK}>

I will make recording and post it later if you want.

pwall · October 25, 2006

Yes please....I'm interested to hear what it sounds like too.

eshoremd · October 25, 2006

that would be great, thanks

uh6077 · October 28, 2006

I didn't forget about this. It has been raining here for the last few days. I am not in a hurry to take my laptop out in the rain. Maybe tomorrow will be nice.

mudbug660 · October 28, 2006

I'd also be interested in some sound clips

Mark_in_Tulsa · October 28, 2006

Nothing wrong with it unless you have inspections... or bitchy neighbors.

BTW, there are rumors floating around that say you will lose low-end torque by removing too much backpressure. That is completely FALSE, power loss will only occur when you use pipe so large that the exhaust slows down and cools.

<{POST_SNAPBACK}>

FALSE.

If you remove the muffler you will reduce back pressure. Which will lower your low end TQ. Which is where you spend all day driving and also what you need a lot of to launch these 5000lbs shaped bricks.

During the combustion process, when the exhaust valve is open, all of the compressed (and depeleted) air-fuel mixture spills out from the cylinders as fast as it can, through your exhaust manifold, into your catalytic converter(s), the muffler, and finally out the tail pipe. The problem with this is, just before your exhaust valve is about to close again, your intake valve opens up, allowing the fresh air-fuel mixture to rush into the cylinders. This is called overlap, and one of the things you take into consideration when choosing a cam, because it can be used to your advantage.

If there was no valve overlap, it would be 100% impossible to completely irradicate all of the spent gases from the cylinder. This has a two-fold effect on power output, depending on what RPM the motor is running at. At low RPM, this effect actually increases torque, because the least amount of compression is lost during the intake stroke, and the ratio of intake to exhaust gases is high. Unfortunately, as the RPMs increase, there is increasingly less time to evacuate the exhaust gases during the exhaust stroke, and more and more depleted air-fuel remains in the cylinders when the exhaust valve closes. The motor becomes incredibly inefficient near its readline. A motor designed for high-torque applications, such as towing, tends to exhibit less valve overlap then normal. The type of cam used in this application is often called an "RV" cam, because a recreational vehicle doesn't need horsepower as much as it needs low-end torque to get it moving.

Your truck would also run terribly if there was too much valve overlap as well. When exhaust gases rush out of the cylinder to fast, they create a low pressure area in the cylinder and the exhaust system, sucking the intake charge right into the cylinder, and right back out into the exhaust system. This is called scavenging. When that air spills out, so does the fuel it was carrying, so the O2 sensor reports a rich condition to the computer, often causing further decreases in the amount of fuel the computer injects. At low RPMs, this effect is most pronounced as there is sufficient time to suck out a significant portion of the intake charge, reducing torque. As the RPMs increase, however, the extra velocity imparted to the intake charge increases the amount that squeezes into the cylinder after the exhaust valve closes, as the valve closes so quickly at high RPMs that barely any intake charge escapes through the exhaust system.

uh6077 · October 29, 2006

Got clip recorded. I recorded it inside the cab to get a better idea of how it sounds while driving. It is not as loud when driving since it is under a load. I recorded it just siting in the driveway. Drop me a PM with your email and I will send it to you. It is only like 30 seconds or so.