Last night at the track I tried running with the cutout open and I ran slower...

Here are the times:

Closed
2.0 60ft
5.88 @ 58.8 mph 330'
8.9 @ 78 mph 1/8

Open
2.1 60ft
5.84 @ 59.3 mph 330'
9.0 @ 79mph

I only ran once with it open, but I ran 3 other times with it closed and always got a 2.0 60ft.... I guess the 4.8 does not like the cutout, my regular exhaust consists of 2 magnaflow 18" run in series and a full tailpipe exiting behind the bumper.... I figured that much muffler and pipe was holding me back, but I guess not....

 

my friend had the same problem with his SS 408..

 

Mine runs slower if I launch from the hole with it open. Being electric I can open it after I launch and it will run better times.

 

try flipping the switch when you go into 2nd gear, it might help Ive been wanting to try that with mine

 

same thing happens to my friend with a 5.3..... its almost a stock truck except for tune and headers, but it runs better with cutouts closed ......

 

yeah i would say if it's electric begin opening after you get going. since open you loose torque down low from what I understand. So get off the line then open them.

 

seems odd to me. My 6.0 is very noticeably stronger everywhere in the powerband with the cutout open.

 

I might try opening it mid track next time, but other than that IMO it was a waste of money.... More than likely I will be giving it to a friend that needs it...

 

yeah I would think if u dump everything (cut out open) u lose that low end. if u had a cat and then the cut out after that u might get better results. I noticed after I put the headers on with no muffler it was a dog

 

my cutout is after the cats maybe that's why. I run the magnaflow 22" case which is supposed to be non-restrictive but like I said the cutout gains significantly over the muffler. I'm gonna have it dyno'd open and closed just to confirm.