cold start vs exhaust crimp sound - Page 2

MR-02 · 10-15-2017, 05:29 PM

Quote:

Originally Posted by cmitchell17

Is the NPP exhaust hollow? I thought I saw pictures of someone cutting open an NPP muffler on a corvette and there being fiberglass packing in it?

I completely agree, it sounds really good at mid throttle under load, but at WOT or startup sounds pretty bad and unrefined.

It cant be from hollow mufflers, because I changed to flowmaster axle back on both my gen5 and now my gen6. My 2011 gen 5 had a nice deep tone start up, but the gen6 now still sounds farty (at cold start up only-warm idle is awesome with flowmaster) , doesn't matter if valves are open or closed. The remaining variable is the pipe diameter before the muffler. Does anyone have info on cold start up sound after cutting out the crimped section, and replacing with consistent diameter pipe????

Here is a youtube link of a gen5 on cold start. ANd my 2011 sounded exactly the same! IT WAS AWESOME! I want my gen6 to sound more like that....check it out and have a listen.

or type into youtube:
FLOWMASTER "American Thunder" CATBACK 2011 Camaro 2SS V8
...tell me that doesn't sound far far better than the gen6.

MR-02 · 10-15-2017, 05:30 PM

WHY DO THE HYPERTEXT LINKS KEEP DISAPPEARING AFTER I POST????????????????????????????????????????

parish8 · 10-15-2017, 09:33 PM

It is under engine/general/catalyst

Snowblind · 10-15-2017, 10:13 PM

The loud start up you are hearing is from a double squirt of fuel. It was advertised by GM that cold start hydrocarbon emissions were cut by 25% in the DI engine by excellerating the warm up procedure.

I briefly glanced in the fuel section of HPT and see the split (double) pulse is "enabled" under cranking...I would try there first if I was looking (but I'm not) to do what I think you are asking.

The exhaust crimp was created for clearance issues and is not a restriction nor does it change the tone.

JFM-jr · 10-15-2017, 10:26 PM

This is definately something that only last about 30-45 seconds on an overnight cold start at wich point there is an unmistakeable change in the exhaust note

parish8 · 10-15-2017, 10:33 PM

Quote:

Originally Posted by JFM-jr

This is definately something that only last about 30-45 seconds on an overnight cold start at wich point there is an unmistakeable change in the exhaust note

I disabled cat warm up and that sound during a cold start went away. I have no cats and It sounds like the fuel is ignighting in the exhaust. Look 3 posts up if you want to turn it off.

Snowblind · 10-15-2017, 11:21 PM

Quote:

Originally Posted by parish8

I disabled cat warm up and that sound during a cold start went away. I have no cats and It sounds like the fuel is ignighting in the exhaust. Look 3 posts up if you want to turn it off.

Oh cool. I thought your pic post was asking "is it" but it clearly says "it is". Disregard my post then, you figured it out.

JFM-jr · 10-16-2017, 04:08 AM

Quote:

Originally Posted by parish8

I disabled cat warm up and that sound during a cold start went away. I have no cats and It sounds like the fuel is ignighting in the exhaust. Look 3 posts up if you want to turn it off.

Thanks Parish , i have hi flow cats do you think i could still disable this? Not sure if this is an emissions focused thing or prevents any sorta damage to the cats.

cmitchell17 · 10-16-2017, 07:48 PM

Thanks for the help guys. I just disabled mine and ill see tomorrow morning how it does. Weird thing is I've been running E85 probably 95% of the time for about 6 months. I was driving down the highway yesterday and noticed a code pop up for bank 2 post catalyst fuel trim too rich. I'm wondering if there is adjustments to something I'm not seeing for E85 either for diagnostics purposes or if the cat is actually getting damaged?

Marty McFlew · 10-17-2017, 12:28 AM

Quote:

Originally Posted by cmitchell17

Is the NPP exhaust hollow? I thought I saw pictures of someone cutting open an NPP muffler on a corvette and there being fiberglass packing in it?

I completely agree, it sounds really good at mid throttle under load, but at WOT or startup sounds pretty bad and unrefined.

No, our mufflers have no packing are are hollow.

blkchevyz · 10-17-2017, 03:24 PM

i just skimmed through so sorry if it was mentioned, but are you just hearing the intake being pipped through the speakers?
i notice mine sounds better since i disabled that when i added a sub.

cmitchell17 · 10-17-2017, 07:02 PM

This is from the outside. But ive wondered if the 2SS actually comes with active noise cancelation, or if that's just the 2.0 turbos?

10-15-2017, 05:30 PM	#16
MR-02 Drives: 2016 2SS M6 Join Date: Feb 2011 Location: ONT Posts: 185	WHY DO THE HYPERTEXT LINKS KEEP DISAPPEARING AFTER I POST???????????????????????????????????????? __________________ 2016 SS M6

10-15-2017, 09:33 PM	#17
parish8 Drives: 17 SS a8 Join Date: Feb 2010 Location: omaha Posts: 1,678	It is under engine/general/catalyst Attached Images __________________ dropped a valve in the 6.2. now running a drop in rods and piston 5.3 best et 5.83@121 with the 5.3 http://www.camaro6.com/forums/showthread.php?t=465472

10-15-2017, 10:13 PM	#18
Snowblind Drives: '16 2SS / '05 SRT10 Ram / '65 bu Join Date: Dec 2015 Location: Philthy Posts: 978	The loud start up you are hearing is from a double squirt of fuel. It was advertised by GM that cold start hydrocarbon emissions were cut by 25% in the DI engine by excellerating the warm up procedure. I briefly glanced in the fuel section of HPT and see the split (double) pulse is "enabled" under cranking...I would try there first if I was looking (but I'm not) to do what I think you are asking. The exhaust crimp was created for clearance issues and is not a restriction nor does it change the tone. __________________ H/C SBE 9.80@140 powered by Texas Speed

10-15-2017, 10:26 PM	#19
JFM-jr Drives: 2016 Camaro 2SS Join Date: Mar 2016 Location: Suffolk Long Island Posts: 954	This is definately something that only last about 30-45 seconds on an overnight cold start at wich point there is an unmistakeable change in the exhaust note __________________ 2016 Hyper Blue 2SS A8,NPP,Moonroof Pray ported factory intake manifold Ported TB Rotofab ARH 1 7/8 longtubes hi flow cats AFM deleted E85 11.0@124.9 11.65@118.8 pump gas,stock tune/exhaust New combo: Pray Performance Heads/cam MSD intake manifold and Circle D 3C 554/491 on E85 all work & tuning done by Pray

10-16-2017, 07:48 PM	#23
cmitchell17 Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016 Location: US Posts: 1,213	Thanks for the help guys. I just disabled mine and ill see tomorrow morning how it does. Weird thing is I've been running E85 probably 95% of the time for about 6 months. I was driving down the highway yesterday and noticed a code pop up for bank 2 post catalyst fuel trim too rich. I'm wondering if there is adjustments to something I'm not seeing for E85 either for diagnostics purposes or if the cat is actually getting damaged?

10-17-2017, 03:24 PM	#25
blkchevyz Drives: 94 z28 and 2017 1ss Join Date: Feb 2017 Location: missouri Posts: 19	i just skimmed through so sorry if it was mentioned, but are you just hearing the intake being pipped through the speakers? i notice mine sounds better since i disabled that when i added a sub.

10-17-2017, 07:02 PM	#26
cmitchell17 Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016 Location: US Posts: 1,213	This is from the outside. But ive wondered if the 2SS actually comes with active noise cancelation, or if that's just the 2.0 turbos?

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