PowerLabs

I bought my car with 9000 miles and it was stock, aside for the GHL exhaust. I always liked the system; I've driven and ridden in stock C6s before and they are WAY too quiet: I like to know the car I am driving has an engine in it and the stock exhaust has zero character or sound.
The GHL, on the other hand, idles quietly but with a distinct rumble, and wakes up into just the right amount of sound when I'm on the gas.
Adding headers (Kooks 1 3/4 with a catted X-pipe) to the system did not change the exhaust sound in any way (or affected drone in any way) below about 3000RPMs, but after 3K it gave the car a wail that could only be described as exotic. I absolutely loved it.
HOWEVER, as with most (all?) Corvette exhausts, there was drone. Drone is the ressonance you hear at a certain RPM wen the timing between the exhaust pulses matches up with the time it takes for them to travel to the back of the mufflers. I have always been told that GHLs have mininal or no drone, but between 1500 and 1700RPMs it is DEFINITELY there.
I drove the car from Florida to Los Angeles.
Then I drove it from Los Angles to New Jersey
And now I am daily driving it about 70 miles a day. The drone, which happens exactly at the speed traffic flows on the highway, was starting to really get to me! It didn't bother me before but with the amount of driving I have been doing it was driving me insane. Also, everyone who rode with me for long enoug would eventually complain.
It was time to do something.
I had gathered from feedback on the forum that the Corsa Sport exhaust was supposed to have the least drone of all. Some even said it had no drone. It was time to give it a try:

Almost ready to begin. I have my Craftsman wrench set in the trunk and I haven't fetched the car jack yet:


And here are the two side by side. The Corsas are upside down and the pipes on the GHL aren't staight, but you get the idea. Notice how much larger the GHL tips are, and also the fact that both sides are united and install together. Also notice how much bigger the mufflers on the Corsas are:


I didn't get a picture after the job was done because it was already dark once I was done.
Now, my observations:
First and foremost, those Corsas are HEAVY! Their massive mufflers weight over 22lbs more than the GHLs they replaced. Granted the weight is down low and in the back so it won't affect the CG or the balance of the car much, but still, 22lbs is just two pounds less than what you save by ditching the run flats and going to light non run flat tires like the PS2s. If you autocross, it is significant!
Here are the measured weights as per my bathroom scale (there may be up to 2lbs error here):
Corsas: 56.8lbs
GHL: 34lbs
Z06 W/Actuators: 52lbs

They were a pain to install on jackstands too; I barely had enough clearance and I ended up scratching the bottom of the tips slightly because they had to rub up against the ground before I could wedge them in there.
I do like the smaller tips though. It looks more refined, to me.


NOW... The million dollar question: Is the drone gone?
In short... NO! Here is the breakdown:
The Corsa Sport idles louder than the GHLs. The idle is very noticeable inside the car now.
They still drone at 1500 to 1700RPMs.
They pop and crackle on deceleration as much if not more (it seems like more) than the GHLs. I do like that though; this isn't a complain.
They sound different. A little more metallic; not raspy, but rather a more exotic sound, more ferrari-ish if I dare say... Not the low bassy tone you'd expect from a muscle car. The GHLs already didn't have much bass but the Corsas have even less.

The veredict? I really like the way Corsas look (better than the GHL) and I like the way they sound. The idle could be a tad quieter but everything else is perfect. I THINK they drone less, but I need to determine this with a longer drive in traffic. I will drive them for a week. If I feel like the drone hasn't been reduced drastically I will sell them back on the forum for the only reason that a 22lbs weight increase is too significant for a minor increase in muffling performance. If that becomes the case I will put the GHLs back on and instead add a little bit of weight from sound dampening in the trunk, or also possibly have resonators welded in between the X-Pipe and the mufflers.


This has been a rather expensive piece of knowledge for me to aquire. I hope I can make back some of this cash by selling whichever system I end up not sticking with. Look forward to final photos and a final review later on.
Cheers!

PowerLabs

Drove it to work today. Yes, it is a bit quieter and it does seem to drone less too... But is it worth adding 22lbs to the car? And, most importantly, couldn't I achieve the same reduction in sound with a lot less than 22lbs of sound deadening material in the trunk, or through aftermarket resonators between the X pipe and the GHL mufflers?
Comments?

FloydSummerOf68

My suggestion is probably stick with GHL and throw some sound deadening material in the back. ...I've heard corsas mated with longtubes and it sounds like a tin can.

BigSlick

thx for the write up...

holdin5aces

We have a full Corsa Sport system front to back and it has zero and in none of the dreaded drone.

NormWild

This is the first I've heard of the weight discrepancy, that is pretty huge IMO. I was just getting ready to finish my exhaust with the Corsa, but I doubt it now, I think I'm going with GHL.

AORoads

I see you haven't called Corsa to ask them a question re drone. Any reason why or why not?

Wicked Weasel

nice to have a writeup from unbiased source.

thanks

BriscoCounty

The Corsas weigh the exact same as the stock, and are actually 1lb less than the NPPs. Its just that the GHLs are obviously a lot lighter.

I have the Corsa Sports for the A6, which comes with its own H-pipe to further reduce droning, and there is absolutely no drone what so ever, at any speed or RPM. Even if there was, these things just aren't loud enough to be of any bother. At highway speeds, these are almost identical to stock; dead quiet.

AutoCutter

I had Corsa Sports in the 05' with no drone-but one person's pleasant rumble sound may be someone else's loud drone! The Corsa Sports have a great sound especially at 2500+ rpm's-I used to hold third gear just to hear the sound!

Anyway, you are going to have a more pronounced exhaust note at 1500 to 2000 rpm with any aftermarket exhaust and, to me, "drone" would be more of a harmonic resonance that is felt as much as heard. I had a set of Borlas on my Gran Prix that had a harmonic resonance at 65mph that drove me crazy (not a very long drive) Heck you could watch water ripples form in a water bottle held in the center console cup holder!

Ben Diss

I wouldn't bother with sound deadening. I have B&B Rt. 66 and tried to tame the drone with two layers of dynomat and Crazy Cowboy's foil backed insulation kit in the trunk. Before the install I measured 110db at 1900 RPM and after the install I measured 110db at 1900 RPM.

When I originally received Crazy Cowboy's kit I installed the front section only and it did make a difference with road noise and cabin heat. I hoped the trunk kit would help with drone, but it did not.

PowerLabs

He answered it best:


Sound is a very subjective thing; you will find a lot of people who say Corsas have no drone, you find people who say GHL has no drone, and then there are people like myself who think the GHLs have way too much drone for a daily driver and Corsas drone too. They sound the way they sound and a phone call to Corsa won't really change that. I am happy with the exhaust and I am happy with the way they sound. I think it is a great product. What I need to decide is wether I am willing to live with 22lbs more weight on my car for that small reduction in the drone.

Currently I am thinking of putting the GHLs back on and doing sound deadening as well as possibly installing 2 small resonators in the system. My main driving force for doing that is not because I don't like the Corsas but rather because it will be a novel approach and it will be lighter.

PowerLabs

Thank you. That is the kind of feedback I was looking for.

OK, so lets scrap that idea. How about I put the GHLs back on and weld two 2.5" x 12" Magnaflow stainless steel resonators in between the X-Pipe and the mufflers? I'm not sure how much weight it will add but it is a cheap mod...

augydog

Nice writeup

augydog

C6NRED

I do not think that adding the sound insulation is going to help much because the dreaded "drone" is a whole-body-structure kind of thing.... as someone posted above, you feel it as much as hear it....the whole car begins to resonate. I've heard it on other's cars and it is NOT a pleasant experience. Like having a hole drilled in the back of your head after about 15 minutes on the highway.........

SanDiegoBert

Nice write-up. I was wondering what the function of resonators is, (Mentioned above several times.)

Ben Diss

I used that exact same approach on my Jeep and it made a significant improvement to the drone. You might also consider the B&B PRT that does the same thing.

http://www.bbexhaust.com/car/corvette/c6/

They don't show it separately, but I asked the question and it can be purchased separately.

PowerLabs

A resonator is basically an in-line muffler that you place on your exhaust system before the mufflers themselves. Their function is to further quiet down the exhaust. I've found them to be very effective at cancelling out higher pitched sounds such as metallic raspyness but without removing much bass from the exhaust note.
Here is what a typical resonator looks like:





A lot of them are a perforated metal pipe inside a larger pipe packed with fibreglass. They are not very restrictive at all.

danl72

Thanks for the write-up.

10mikeymike

I'll be interested to learn if the addition of resonators solves the problem for you. I previously had Corsa Sports on my A6 and ended up replacing them with a complete Magnaflow system because I didn't care for the look of the Corsa's from behind or for the way they trumpeted under accelerated. I can't honestly say that I'm completely satisfied with the Magnaflow's either. While I like the looks, especially from behind, I think they could be a little louder. As for the addition of resonators, I've been told that sometimes all they succeed in doing is changing the RPM range where the drone takes place. I guess that could either be good or bad. As an aside, I previously had a Magnaflow system on my H2. It sounded great as it rolled by, but the resonance under normal acceleration was almost unbearable. I ended up removing it and going back to the stock system. Like you said, sound and drone for that matter are perceived differently by everyone. Hopefully, you will be able to find a happy medium that satisfies your tastes. If you do, please share it with me as I haven't arrived there yet.