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Corsa Sport Catback - very disappointed with boom/drone in AFM mode.


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Well, after 1000 miles in our new to us 2015 Tahoe PPV (had 12500 miles when we bought it) it was time to try out a the Corsa Sport exhaust.

 

The 1000 miles run up was a mix of city, country, freeway, dirt road and even a couple full throttle starts. 1 tank 87 octane (16.8mpg), 1 tank 91 octane (17.2mpg) and 1 tank e85 (12.6mpg so far)

 

Truck is awesome with stock exhaust, silent, smooth and - well too under-stated ;)

 

Remote start video of the stock truck:

 

So a Corsa Sport cat back was purchased, mostly based on the Corsa YouTube video and discussions directly with Corsa.

 

 

The reality is a little different.

 

The exhaust sounds great outside at startup - great at idle - great from inside the truck at startup and great at idle from the inside.

The exhaust sounds fantastic on the throttle accelerating from a stand still, great when it kicks down at freeway speed to pull off a passing maneuver.

The exhaust even sounds pretty good around town in stop and go traffic.

 

Remote start video of the truck with the Corsa Sport installed:

 

All these scenarios have a sweet blubba-blubba-blubba throaty V8 sound, subdued and tasteful.

 

The wife, daughter and most importantly the family dog does not mind the sound.

 

The problem is steady state cruising at ANY speed that invokes AFM.

 

In V4 mode the truck sounds horrible - with a low booming thumping glob-glob-glob-glob sound, not unlike as if there is a rubber hose flapping in the wind. This booming drone visibly irritates the dog - and if my dog is not comfortable driving in the truck then its a non-starter. ;)

 

I do not believe Corsa Performance did any AFM V4 mode testing, or if they did, they chose to ignore the horrible drone that this exhaust causes.

 

I just figured I would just put this out there and save other folks the $1100 of frustration.

 

I will try install a Touring muffler from an '07-14 system and see if that helps, if not the stock muffler is going back on.

Edited by RC45
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Some food for thought on this as people have run into the issue you are having with the STOCK exhaust:

 

Some owners may comment on a buffeting vibration drone type noise, exhaust tone change, and/or body pressure booming.

These concerns may be caused when the Active Fuel Management (AFM) system changes into 4 cylinder mode.

While some slight changes in exhaust tone and/or vibration/drone type noises can be normal when AFM is in 4 cylinder mode, there have been some complaints of them being excessive.

If the concern is excessive, it may excite the roof sheet metal and compound the issue. (See the latest version of PIT5318.)

 

Tip: Verify the concern by test driving the vehicle at the vehicle speed and engine RPM range of the customer concern. If equipped, use the colored DIC Display to monitor the AFM V8 to V4 cylinder activation. For vehicles without color DIC display, use a scan tool to monitor AFM V8 to V4 cylinder activation. Confirm the concern is present during V4 mode. The concern may be most noticeable in the 1,100-1,400 engine RPM range. Place the transmission in manual mode 5th gear to force the engine to stay in V8 mode. Then operate the vehicle at the same speed and engine RPM range to confirm that the concern is no longer present in V8 mode.

 

There are a few booming/buffeting threads on this forum with 100% stock trucks. There is a repair to install added panel vibration control material on certain roof bows.

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Thanks, sounds plausible, but I wonder why we only started to notice after the Corsa went on?

 

Perhaps in the PPV format (no roof rack mounts, no third row seat etc.) with its different body torsional resonance layout, the stock sound waves don't get a chance to "excite" the roof panel and once the Corsa went on the sound waves are now in the "excite the roof panel" frequency and resonance range.

 

I will look into this - I will need to find and work with a friendly GM dealer - I spent the first 36,000 miles of C5 Corvette ownership fighting with GM over the excessive oil consumption in my 2001 Vette, they fought me till the day the car was out of warranty and only capitulated under threat of law suit to finally replace my 1 quart of oil per 150 miles LS6 with a 1 quart of oil per 200 miles LS6 at 36,500 miles :) - so I abandoned GM many years ago due to their arrogant ignorance and very poor customer service - the 2015 Tahoe PPV brought me back.

 

From what I have read GM is still the same and I should expect un uphill battle to get these types of issues addressed under warranty.

 

FFW, anyone know which GM dealer in Houston is worth a try? (I bought this truck from a dealer in New Jersey)

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FWIW the GM-spec Borla exhaust has absolutely no drone in AFM or at any other time. It is a very subdued cat-back; however. GM did spec an anti-drone flap/valve into the Borla muffler.

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We have heard this same issue from many of our customers, and as such, have the V4 turned off.

 

That being said, I have a Corsa Touring on my 2013 Denali XL, and had one on my 2010 Denali as well as my 2004 Z71 Tahoe. With and without major mods, the tone is just a bit throatier than stock, no issues at cruise. When you open up the throttle, it has a real nice rumble. Touring may be the way to go for you.

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I found an almost new 2014 Touring muffler on eBay, we will see if it disguises the drone a bit better. Corsa where no help at all - in fact all I got was an arrogant "we don't sell parts and have not tested the Touring on the 2015 yet". So even though I said I am willing to take the chance and just want to buy the 2014 Touring muffler, he refused to sell to an existing customer.

 

The guy went on to claim that they did "extensive testing with the Sport before releasing it to the public" - which is odd, they only had a 2015 Tahoe for about a week to test fitment, not design and test all facets of the sound dynamics of the muffler itself.

 

He claimed that the muffler for pickups (short bed, long bed, crew and double cab), Tahoe and Suburban are all different and specially tested against the unique dynamics of the cabs etc.

 

But then went on to claim they don't have access to all these chassis to test on.

 

Either way, its the last Corsa product I buy new - ever. This decision is based on the arrogance of the company reps, not the product itself.

 

Please see follow-up posts for resolution with Corsa.

Edited by RC45
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I have a follow-up to post after again speaking with Corsa.

 

While there is no resolution to the sound issue, there is a resolution to the "perceived arrogance" of their company policies.

 

After a discussion with the corner office, I come to learn it is as I had assumed from the get go - if you want to purchase replacement or alternate parts for your Corsa system they will sell them to you.

 

The funny thing is that this Touring muffler I have coming in from eBay was being sold by a guy that had just bought the exhaust and had changed trucks and needed a longer intermediate pipe - he too ran into a brick wall when as an existing customer tried to buy a replacement part. That's why he parted out the brand new exhaust.

 

It seems both he and I where misinformed as to the replacement/substitution parts reselling policy of Corsa. If you speak to the correct person, it can be done.

 

So, in the end Corsa management and I have cleared the air and any misperceptions either by me the customer or Corsa the vendor with regard to the availability of spare/replacement/alternate parts for existing owners have been put to rest. Their commitment is to better communicate this policy in the future.

 

Folks, please don't take my Corsa experience as the be all and end all, but rather just one persons out of many.

 

Full disclosure - I have invited Corsa to visit this thread, as such I am not going to go back and edit out any of the negatives, but rather leave them along with any resolutions reached.

 

I will try the Touring muffler out and see if it works. The other variable that we never thought of until today was that I am running e85 and as such with the extra timing the truck may simply be louder and stronger even in V4 mode.

 

 

 

 

 

Edited by RC45
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We installed the Corsa Touring muffler form a 2007-2013 Chevy Silverado pickup exhaust system. It was a perfect size match to the 2015 Tahoe muffler.

 

The sound is a bit more subdued of course, wife loves it I am missing the raucous Sport sound - but the good news is the helicopter that used to follow us is now a lot quieter.

 

You can still here when the truck goes into V4 mode, but it is not as pronounced as with the Sport muffler.

 

The only conclusion I can come to is that they did not test the V4 mode as thoroughly or figured that it would not bother folks who went for the Sport sound any way.

 

I will post a remote start/idle video in a few days.

 

I believe this muffler will match the Blower perfectly - it is not loud, but has a "not stock' sound to it. Will let the truck be a great sleeper.

 

Although with the Magnacharger (in low boost) only putting about 430hp to the wheels it will not be much quicker than most minivans these days LOL.

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  • 3 weeks later...

Final followup with all 3 startup samples in one place/ I have settled on the touring muffler.

 

 

Remote start video of the stock truck:

.

 

Remote start video of the truck with the Corsa Sport installed:

 

Remote start video of the truck with the Corsa Touring muffler installed on existing Corsa system:

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