A 14mm wrench and some time later

[UberDude]

and now my 5.7L 07 Tundra has no muffler

holy BA'jesus this truck is loud with straight pipes..

and it sounds mean as HELL sense its true duals.

i'll eventually pipe it out the back or maybe out the pass. side right before the rear wheel..

but having the clean, no exhuast pipe look is workin too.

seriously though if any of you plan on getting an exhuast job done..

take your muffler off and start 'er up.. i think you'll be impressed with how the 5.7L sounds straight piped and true dualed..

[Dana_15]

Only in the South ........


Do you need the muffler for backpressure?

[pushr0d]

I was about to ask the same question.

I'm curious how much fuel economy you lose running the truck like that.

[UberDude]

exactly why do people seem to think back pressure is a good thing?..

ever wonder why Toyota put the effort into making such a complex exhuast manifold? 4 into 2 into 1..

less back pressure..

why do you think magnaflow and flowmaster all brag about having the least back pressure?

that said im sure the 4 cats that are still there are providing all the back pressure the engine needs


fuel economy? any engine that flows better, runs more efficiently, thus saving fuel..

that said, i doubt im going to get better fuel economy because im getting on it more often now..

oh well, maybe someone on here fluent in the ways of technical jargon can tell me im full of it and my engines gonna explode soon.

[kn38ms]

Lets see here.
Increase your interior noise.
Piss off other drivers every time you pull from a stop light.
Lose some of your bottom end torque in the process.
You should market that system.

[UberDude]

Originally Posted by kn38ms

Lets see here.
Increase your interior noise.
Piss off other drivers every time you pull from a stop light.
Lose some of your bottom end torque in the process.
You should market that system.

1. dont care.
2. REALLY DONT CARE.
3. but i pick up top end HP.. AND sense i dont tow.. i dont feel the difference when starting from a stop..
4. i would but they already sell 14mm wrenchs in most stores..

[Jshore76]

You definately notice low end torque more then you would top end HP. Most top end power isn't even usable in day to day street driving. But hey, if your happy with it then more power to you.

[UberDude]

Originally Posted by Jshore76

You definately notice low end torque more then you would top end HP. Most top end power isn't even usable in day to day street driving. But hey, if your happy with it then more power to you.

how exactly is torque affected by back pressure?

as a reference guide to the point... in the Tundra Magazine.. it shows the exhuast manifold.. and then states " Tundra's 5.7L uses a special header that uses a 4 into 2 into 1 design. this is to help reduce back pressure and increase mid-range Torque."

like i said. if someone here schooled in the ways of back pressure would like to step in and explain things then by all means..

[pushr0d]

UD,

Some engines' cam timing can result in both the intake and exhaust valves being open at the same time. Without some resistance to flow, it is possible for some of the intake charge to shoot straight through the cylinder before the exhaust valve shuts.

This makes for very inefficient combustion, obviously, and has a much greater effect at lower engine speeds. You've witnessed this phenomenon when you hear drag racer engines struggle to run at idle, but run fine at WFO.

Now, I'm not saying the Tundra has a problem without a resonator/muffler, but it should be considered. The only way to tell is on a dyno, and to run a A<>B comparison.

The OEM engineers walk a fine line between efficiency and noise and cost. So, what ends up underneath a vehicle is almost always a compromise.

HTH!

[UberDude]

Originally Posted by pushr0d

UD,

Some engines' cam timing can result in both the intake and exhaust valves being open at the same time. Without some resistance to flow, it is possible for some of the intake charge to shoot straight through the cylinder before the exhaust valve shuts.

This makes for very inefficient combustion, obviously, and has a much greater effect at lower engine speeds. You've witnessed this phenomenon when you hear drag racer engines struggle to run at idle, but run fine at WFO.

Now, I'm not saying the Tundra has a problem without a resonator/muffler, but it should be considered. The only way to tell is on a dyno, and to run a A<>B comparison.

The OEM engineers walk a fine line between efficiency and noise and cost. So, what ends up underneath a vehicle is almost always a compromise.

HTH!

well you hit the nail on the head.

i'd have to dyno run it with it off and with it on ..

but as far as the possibility of both intake and exhuast valves being open at the same time.. hardly..

remember the I-Force uses variable valve timing on both exhuast and intake cams

actually at idle the engine is incredibly quite despite the fact that the mufflers missing.. its only when i accelerate that the engine gets loud.. unlike my F-150 with its 5.4L that sounded loud at idle .. but then again the F-150 had 2 cats and not 4 so..

another enteresting note.. this engine makes very few, if any, popping sounds when the engine wind's down from high RPMS ..

[Lumpy_99901]

i done the same thing to my rig. i added an elbow and 12'' extension exit out the passinger side.

i just ordered up a whole JBA kit (headers, Y pipe, 3'' single outlet) it should solve the cab resonation problem. that gets annoying...probably run better too.

[nikita]

I had true duals, without a crossover pipe, but big Cadillac mufflers, on a 1964 Chevy 283 (close to 4.7l) and it made it very "peaky", meaning it pulled best in a limited rpm range. Because it was a three speed stick (no OD) and 3.73 gears, it "worked" well at a 70mph cruise. That was just dumb luck on my part. I went with a high-lift, low-overlap cam, so efficiency was decent for such a low-tech beast. Even with those mufflers, meant for a single exhaust 7 liter engine, it was kind of loud.