Mpg

[03slvrdo]

I know we all heard this before but I'm doing it again. I recently put on a dual exhaust with a super 40 flowmaster. I was looking for more HP and a better MPG for my 03 silverado. I was getting 400 miles to the whole tank and now after having the exhaust, its dropped to 380 miles to the whole tank.
WHATS UP WITH THAT !?

Any inputs on tuners would be nice

[pbergmann]

Dont mess with mother general! If the dual exhaust was such a good thing (other than making the truck sound powerful) Dont you think GM would put it on and advertize it? OR better yet sell it as an option?
They have been building vehicles for 90 years, In general they know what there doing. Enjoy the sound and drive like theres an egg under your foot.

[BlenderWizard]

Well, they do put duals on the SS model

[jethro_3]

Why don't they? Cost, cost and cost. On most engines the gain in power is not worth the cost. If the duals are set up properly they can help facilitate great horsepower and in some cases mpg. You have to know the size of the pipe needed by the engine and amount of backpressure the engine requires to stay in the curve. Each engine has a sweet spot for power, horsepower, and mpg. Gains in one sweet spot does not mean gains in the other, sometimes they do but not always.

[dr_of_lovephd]

Did you leave the cat. converters on? The new trucks require a certain amount of back pressure in the exhaust sysem. So if you make the exhaust too free flowing, it could rob your power and mpg. I think most people get better results getting air into the engine than improving exhaust.

[jethro_3]

Originally Posted by dr_of_lovephd

Did you leave the cat. converters on? I think most people get better results getting air into the engine than improving exhaust.

You got that one right, you can stuff a lot more air in before you require a larger exhaust. Read this post about half way down by Hit Man X and you will see the size requirements for the different engines and horsepowers. Those guys over there are doing serious engine mods, they know their sh!t.

http://forum.ls1truck.com/index.php?...l=exhaust+size

[BlenderWizard]

Originally Posted by jethro_3

You got that one right, you can stuff a lot more air in before you require a larger exhaust. Read this post about half way down by Hit Man X and you will see the size requirements for the different engines and horsepowers. Those guys over there are doing serious engine mods, they know their sh!t.

http://forum.ls1truck.com/index.php?...l=exhaust+size

Well, that makes me feel better about having my single in/dual out flowmaster

[jethro_3]

The most restrictive part, your single in, is the point that dictates the size of the pipe. Dual out always sounds better but gains you closer to nothing when it comes to performance or mpg. Don't be discouraged, you did make it sound better and releive yourself of some cash .....

[BlenderWizard]

Originally Posted by jethro_3

The most restrictive part, your single in, is the point that dictates the size of the pipe. Dual out always sounds better but gains you closer to nothing when it comes to performance or mpg. Don't be discouraged, you did make it sound better and releive yourself of some cash .....

Nope, I left that part up to the original owner; the exhaust setup was in place when I bought it.

[Silverado Brethern]

I myself believe that any decrease in mpg with the install of an exhaust can be linked directly to increased weight in the right foot. Meaning that the louder your truck is the more your gonna romp on it to hear it rumble. I never really have been one to give a rats ass about mpg but i ususally get around 320-340 miles out of a full tank.

[jethro_3]

Now please do an experiment for us. Drive like hell and don't get out of the gas for a tank and tell us the mpg and performance. Next take the exhaust off at the manifold and then drive like hell agian and tell us the results.........

A few motorheads have done dyno tests and shown us that engines require backpressure dependent on the build of the engine.

[twomorestrokes]

Originally Posted by Silverado Brethern

I myself believe that any decrease in mpg with the install of an exhaust can be linked directly to increased weight in the right foot. Meaning that the louder your truck is the more your gonna romp on it to hear it rumble. I never really have been one to give a rats ass about mpg but i ususally get around 320-340 miles out of a full tank.

I agree.

[jeverett]

BUT, in certain situations it does help though correct? Like my cats for example. they're stopped up, and if I cut them will I loose too much backpressure and it hurt instead of help? What about using a factory muffler with no cats.??

[TexasF355F1]

Originally Posted by jeverett

BUT, in certain situations it does help though correct? Like my cats for example. they're stopped up, and if I cut them will I loose too much backpressure and it hurt instead of help? What about using a factory muffler with no cats.??

Removing cats is completely unecessary. It doesn't add any hp so why do it? Get a performance cat if anything. Trucks just sound terrible with them off. Whenever i think of a truck with no cats, i think of hillbilly redneck country bumpkin with big super swampers in the rear and stock tires in the front with a rake of like 45 degree. Not to mention its absolutely annoying.

[jeverett]

They're stopped up, I just want them gone to rid me of the smell, and shitty mileage.