Lack Of Exhaust And Mpg

[ruggedlife]

so i recently purchased a 2009 1500 RCSB z71 with a 5.3L, 4speed trans and 3.73 gears. it originially did not come with a DIC, before i installed the DIC i installed a drop in filter and MIT and also cut the exhaust off right before the muffler and just left it as is, since then i installed the DIC and it seems to show low average MPG like anywhere between 12 and 14...

my real question is... with a lack of exhaust could this hurt my MPG?

[dlstewart01]

In my opinion....Yes.

[ruggedlife]

would this be due to lack of back pressure i assume? i know my 09 has two cats and then some big resonator/cat looking thing on the Y pipe, wasnt sure if it was enough or not... or if it really made a difference...

[elcompalaline]

Lack of back pressure IMO, had a similar problem. My exhaust pipe was too wide (3") and fixed it with 2 1/2". MPG and low-end greatly increased after.

[ruggedlife]

well i know the Ypipe merges into a 3 inch pipe, do you think putting it into a flowmaster or cherry bomb and still dumping it under the truck would be enough? i dont like the look of an exhaust pipe sticking out the back of the truck IMO it looks alot cleaner without it so i'm looking to keep it under the truck before the rear axle... but i would like to gain some more MPG...

[elcompalaline]

Here is a side shot of the pipe tucked in under the rear fender all the way back, can't see it.

 

[elcompalaline]

And in this one you can see how the pipe was up high and then dumped.

 

 

Hope it helps.

[ruggedlife]

that does look pretty nice, and not to get side tracked but could i get some better shots of your taillights? i was thinking of doin the same but wasnt sure how it would look. i figure a can of night shades is alot cheaper than a set of recon taillights. do you ever get hassled by cops for it? i like the look of your pipe, which muffler are you running?

[pm26]

Why don't you remove the entire exhaust, including the manifolds and see what happens.

[ruggedlife]

oh hey thanks thats a helpful answer to my question thanks for the input..........

[pm26]

oh hey thanks thats a helpful answer to my question thanks for the input..........

 

Just kidding, but why remove the muffler on a brand new truck? Try a good after market exhaust if you cannot stand the stock one for whatever reason. These trucks run at very low RPM most of the time, and shift at low RPM so proper exhaust back pressure is very important for good fuel economy and proper performance.

[ruggedlife]

last truck was a strait piped duramax, before that was a jeep cherokee with no muffler, before that was a wrangler with no muffler...im not sure but you may be noticing a trend here... i like a loud exhaust, i was planning on swapping in a gibson muffler originally but after i cut off the factory one i couldnt resist starting it up, the exhaust really isnt all that loud it has a decent sound do it, it almost sounds like a older body style with a flowmaster kit on it. i guess i'll try some sort of muffler and tail pipe and see what happens, i'd rather spend money on other things than a stainless exhaust but i guess its inevitable

[vdubmurray]

...Just kidding, but why remove the muffler on a brand new truck? Try a good after market exhaust if you cannot stand the stock one for whatever reason....

 

As far as I can tell, Magnaflow is the only one with a bolt on cat back exhaust for the 2009's? Correct me if I'm wrong.

[REV353]

Here read this. I was looking into Shorty vs long tube headers. This will help explain how the length of exhaust works, its not always back pressure. This link will just help you understand how and why.

 

 

http://www.fourwheeler.com/techarticles/en...ders/index.html

[uh6tdrvr]

That big thing you are calling is another cat. With the 09's the emmission restrictions went up so they added another one. Its on most of the 09.5 Vehicles. My early 09 G8 doesnt have it but the later ones have 3 cats and a 6 HP decrease (361-355) but Tq went from 380 to 385 according to GM that is.