When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Open NPP, LT headers with no cats, still not loud enough for me..
So i've got ARH 1 7/8" long tube headers, with no cats, which also includes their catless X-pipe, and factory NPP exhaust (yes the valves are already open) and the car sounds great at WOT. But, Im looking for it to be even louder than that, especially at idle. Right now at idle its just not that intimidating.
What options do I have at this point? Since my car is a M7, fully tuned with HPT, my Eco mode has already been disabled. I ASSUME that means my AFM valves are always 100% open already correct?
Would changing the axle back get it louder? I love the raspy sound of the NPP with headers and do not like the bubbly sound of some of the exhausts out there so if I did change the axle back it would be for a Borla/Corsa exhaust.
I'm thinking that you might need to replace the axlebacks with straight pipes. The Borla and Corsa options are still going to have mufflers which will muffle the sound.
I had a 2009 Pontiac G8 GT with headers, high flow cats, with solo brand axle backs which were essentially straight pipes (see example photo below) and it was definitely louder at idle compared to the set of GXP axlebacks I had which sounded very similar to our NPP axlebacks. It doesn't appear that solo offers axlebacks for Corvette, but I know that I have seen some folks post manufactured staight pipes here. Just some food for thought...
Whatever path I take, it must retain NPP functionality. I need to still be able to take it down a notch on command. Straight pipes will be an absolute last resort..
Whatever path I take, it must retain NPP functionality. I need to still be able to take it down a notch on command. Straight pipes will be an absolute last resort..
Ok, scratch the straight pipes then...didn't realize that was a requirement for you. I wouldn't want to lose that functionality either. No need for Jake to chime in now...
If you have a welder you can make it louder without it costing you a penny. For many years and on many cars i have done this. Remove the stock mufflers. Cut open the upper portion with a wiz wheel. Then using the wiz wheel cut out the baffles of the interior of the muffler. Make sure you get all the loose stuff out so it doesnt rattle around. Then weld the portion door you cut off back on. It will be on the top against the body so know one will ever see it. Your NPP wil still work and you car will be loud with that straight through sound just like Magnaflow advertises. Haha. this is by far the best idea to get what you are going for and the best part is it is cost efficient. I firts did this with an e36 M3 I owned backk in the day and it sounded amazing. Everyone would ask what brand exhausts i was running. HaHa
If you have a welder you can make it louder without it costing you a penny. For many years and on many cars i have done this. Remove the stock mufflers. Cut open the upper portion with a wiz wheel. Then using the wiz wheel cut out the baffles of the interior of the muffler. Make sure you get all the loose stuff out so it doesnt rattle around. Then weld the portion door you cut off back on. It will be on the top against the body so know one will ever see it. Your NPP wil still work and you car will be loud with that straight through sound just like Magnaflow advertises. Haha. this is by far the best idea to get what you are going for and the best part is it is cost efficient. I firts did this with an e36 M3 I owned backk in the day and it sounded amazing. Everyone would ask what brand exhausts i was running. HaHa
Or like MikeLsx said, a cam swap for noise and more hp/tq.
If you have a welder you can make it louder without it costing you a penny. For many years and on many cars i have done this. Remove the stock mufflers. Cut open the upper portion with a wiz wheel. Then using the wiz wheel cut out the baffles of the interior of the muffler. Make sure you get all the loose stuff out so it doesnt rattle around. Then weld the portion door you cut off back on. It will be on the top against the body so know one will ever see it. Your NPP wil still work and you car will be loud with that straight through sound just like Magnaflow advertises. Haha. this is by far the best idea to get what you are going for and the best part is it is cost efficient. I firts did this with an e36 M3 I owned backk in the day and it sounded amazing. Everyone would ask what brand exhausts i was running. HaHa
Do I have a welder, yep. Can I actually weld worth a crap, nope. LOL
Originally Posted by MikeLsx
back in my LS3 camaro i had this problem.
you are at the point of doing a cam swap for more noise.
Man I was afraid it would come to that
Originally Posted by spearfish25
The NPP when open (or Track mode) IS a straight pipe. The axle back flow is directly through the pipe that bypasses the muffler.
Yea I thought so. Was hoping an aftermarket exhaust would use the muffler to amplify the sound though. Guess not..
You can get a little more out of the car by pulling all the cats off. Are if you still have the front cats pulling them and knock out all the inside of them out.
With what you have done all other thing is to do what the one guy has said cut open the mufflers and pulling out all the inside of them.
I may sale my Borla NPP ATKA cat backs and do that to my stock mufflers. Just to see what this sounds like after I get the blower on the car. Should have that on the car in less than 3 weeks but should have it from Andy by the end of next week. Robert
Last edited by robert miller; 01-15-2017 at 12:06 AM.
I'm thinking that you might need to replace the axlebacks with straight pipes. The Borla and Corsa options are still going to have mufflers which will muffle the sound.
I had a 2009 Pontiac G8 GT with headers, high flow cats, with solo brand axle backs which were essentially straight pipes (see example photo below) and it was definitely louder at idle compared to the set of GXP axlebacks I had which sounded very similar to our NPP axlebacks. It doesn't appear that solo offers axlebacks for Corvette, but I know that I have seen some folks post manufactured staight pipes here. Just some food for thought...
Man with all of these strong bends in these pipes other than sound did it add any rwhp to the car on the dyno. Robert
The NPP when open (or Track mode) IS a straight pipe. The axle back flow is directly through the pipe that bypasses the muffler.
It will get louder if the baffle is remove from the quiet side. Then both sides of the muffler will be bypassed. It will also be louder with NNP closed.
You can get a little more out of the car by pulling all the cats off. Are if you still have the front cats pulling them and knock out all the inside of them out.
With what you have done all other thing is to do what the one guy has said cut open the mufflers and pulling out all the inside of them.
I may sale my Borla NPP ATKA cat backs and do that to my stock mufflers. Just to see what this sounds like after I get the blower on the car. Should have that on the car in less than 3 weeks but should have it from Andy by the end of next week. Robert
I have no cats on the car at all. All are removed already.
I was like you with wanting more and a cam got me there. Certainly not cost effective, but has the additional benefit of fueling and HP in addition to the lovely lope.
01-14-2017, 08:15 AM
Open NPP, LT headers with no cats, still not loud enough for me..
