lost power after muffler install?

[whiteysrod]

i have a new 06 silverado shortbed regular cab....2wd...5.3 and automatic trans...3.73 gears and posi....truck has 1100 miles on it now......when i first bought it...from a dead stop on blacktop ..it would spin the tires all thru first and shift to second still spinning....and then hookup.......i changed just the muffler to a flow master and now it will not even spin a tire......it was installed correctly and was the muffler flowmaster recommended...it sounds good but i have lost alot of torque.....i also added a k+n filter...dealer has no idea what is wrong...is there anyway i can get my torque back before i swap the muffler back to stock?thanks guys.

[Mark_in_Tulsa]

i have a new 06 silverado shortbed regular cab....2wd...5.3 and automatic trans...3.73 gears and posi....truck has 1100 miles on it now......when i first bought it...from a dead stop on blacktop ..it would spin the tires all thru first and shift to second still spinning....and then hookup.......i changed  just the  muffler to a flow master and now it will not even spin a tire......it was installed correctly and was the muffler flowmaster recommended...it sounds good but i have lost alot of torque.....i also added a k+n filter...dealer has no idea what is wrong...is there anyway i can get my torque back before i swap the muffler back to stock?thanks guys.

 

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Well I can't help out to much, but what I do know is that FlowMaster is an oxymoron.

[whiteysrod]

????????would a programmer help it out?

[fpkelly]

These motors seem to thrive on back pressure. My brother's tahoe lost its low end grunt when he put a flowmaster on it, after a year or so he changed it back and all was good again, just from driving that truck I will not alter the exhaust on mine.

[opsbear7]

Ok...I know the whole flowmaster muffler quality "blowmaster" debate is going to come up here...but i am going to try to avoid it.

 

What muffler from flowmaster did you get? the 40 series mufflers have very little backpressure and i woul dnot suggest those for a 03+ pickup...However, the 50/70 series from what i have heard have a good balance between back pressure and free flow that they improve performance.

 

Now as far as your torque...that just does not seem right to me that after a muffler swap you completely lose the ability to spin your tires....anyone else on this?

[bajakid2]

Hey i have a 2000 with the 5.3and a flowmaster 70series and a turn down and a drop in k&n,and my truck wont burn out from a dead stop....not sure i wonder if id gain any power going to a magnaflow?...thanks-Travis

[ZZebes]

i know i didn't lose squat on my 2006 5.3 when i put my magnaflow on

[whiteysrod]

it was a super 40 muffler.....3 inch in and out....flowmaster said it was the direct fit for my truck....would computer tuning get my torque back?

[pm26]

High flow mufflers are beneficial for vehicles with high revving engines that develop their peak torque and max HP at higher RPMs. Such mufflers do little good for vehicles such as these trucks that develop most of their torque at low RPM and run at low rpm most of the time. In fact, these engines perform off line better with more back pressure.

 

So, just because it is noisy, does not mean it is faster.

[mikez]

I installed a corsa cat-back on my 2003 gmc and it took away some of the low end power but then I added some JBA headers and got it back plus a little. When you make changes to the intake or exhaust you can't just change one component, you have to match the whole system.

[bajakid2]

Should i keep the 2 3/4 piping and just put a magnaflow on?and get rid of my flowmaster...my truck has barly any bottom end compared to my friends with a stock exhaust...thanks-Travis

[rmreid]

If you are running 1 in 2 pipes out I would run 2 1/4" pipes, if you are running 1 in 1 out I would keep the factory exhaust and just change out the muffler.

 

I also agree with pm26's statement 100%:

pm26 Posted Yesterday, 07:24 AM

  High flow mufflers are beneficial for vehicles with high revving engines that develop their peak torque and max HP at higher RPMs. Such mufflers do little good for vehicles such as these trucks that develop most of their torque at low RPM and run at low rpm most of the time. In fact, these engines perform off line better with more back pressure.

 

So, just because it is noisy, does not mean it is faster.

[willfxp]

I installed a corsa cat-back on my 2003 gmc and it took away some of the low end power but then I added some JBA headers and got it back plus a little.  When you make changes to the intake or exhaust you can't just change one component, you have to match the whole system.

 

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Surprised you lost any low end power. The guys at Corsa sent me a dyno showing throughout the RPM range no power loss.

 

Should be on this board somewhere...

[JPB]

i know i didn't lose squat on my 2006 5.3 when i put my magnaflow on

 

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Ditto, except I have the 4.8 with a Flowmaster 40.

[Hecktorx]

I have seen a few instances where a free flow exhaust would cause false o2 sensor readings on a stock truck. With the exhaust flowing easier, the O2 sensor can read a lean condition and will make the truck run rich. This will hurt power, emissions, and fuel economy.

 

A custom turner should be able to help with this.