Topic: GXP Coupe w/Solo RCD and CAT drone fix

[DeepBlueGXP]

Last summer Deedle drove here Coupe to Buffalo for Solo Performance install of the high flow cat and dual center exit exhaust.  Basically it's a Mach Shorty with center exits.   

The problem was the noticable drone, this wasn't typical of any exhaust from Solo Performance.  It had to be the way the coupe was designed.  The sound wasn't captured in the sealed trunk like the vert.  It bounced off the rear hatch in the car and made for a not so enjoyable ride.   So I talked to Jeff and he said he had a new designed resonator that can be welded in to resolve the issue but I had to wait for them to be built. 

In the mean time I tried to reduce the affect of the drone by installing sound proofing in the trunk area.  That didn't help.

Jeff contacted me and said they were ready and last weekend I attempted to install the resonators.
They are completly free flowing.


I dropped the exhaust, cut off the ends of the resonators as per Jeff's instructions and then cut into the exhaust.  I laid the resonator next to it, used a square to transfer the measurement and a saws-all to cut the section out.  I then tried welding it in but my welder wasn't cooperating.  I took them to a shop and paid $40 to get it welded in. 

The difference is fantastic.  It's not a complete fix to the drone but about a 85% to 90% fix.  It sounds great now and you can hear the burble as you decelerate/downshift.   Thanks Jeff

There isn't any clearance issues with the resonators installed.

[Sly Bob]

Joe, how did it change the sound of the exhaust other than virtually eliminating the drone? The resonator that I installed from Jeff, reduced the wide open throttle sound but I don't notice any other difference. I do know that there is a little difference as far as restriction goes though.

I sent you a picture to illustrate the resonator on my car when you first realized that there was an issue with the coupe.and I am really wondering if your solution is the better one.

What other difference other than the reduction  of the drone have you noticed?

[JimmyBaja]

Oh man I'm glad to hear that! I really like that exhaust but I started to lose interest when I saw your earlier thread & watched/heard the video. Glad to hear it's getting worked out - I'm interested again!

[Sly Bob]

It seems to be a problem with the coupe in particular with this exhaust. Be assured that Jeff and Steve at Solo Performance will do whatever is necessary to make the system right. If you are not entirely happy after the sale (which is extremely rare in my experience), they will not let it go until you are.

Don't hesitate to pull the trigger. I can assure you, you won't regret it!

[JimmyBaja]

Thats good to hear. 

[Gentleman Jack]

Joe-
you drove the coupe from your house to Buffalo NY?  That is a heck of a trip for and exhaust system... is there another Buffalo?

GJ

[DeepBlueGXP]

8.5 hours, but I'm from there so we visit family.

Jeff said my resonators are different than yours Bob.  The coupe is much much better now with the two resonators installed.

[jonymac]

I installed a couple of resonators inside my RPI exhaust pipes when I deleted the cat - made a big diff - bought them from some company in Texas - nice snug fit - really helped.

[Critterman]

I drove from my house to Buffalo to get my exhaust done.  From there I drove to Detroit for a tune, that I ended up not getting.  Then back home.  All in a long weekend.  Hell it is a Kappa, meant to be driven.

[Sly Bob]

8.5 hours, but I'm from there so we visit family.

Jeff said my resonators are different than yours Bob.  The coupe is much much better now with the two resonators installed.

That's why I am asking, I am trying to figure out if I should be changing resonators.

Joe, how did those resonators change the sound of the exhaust other than virtually eliminating the drone? The resonator that I installed from Jeff, reduced the wide open throttle sound but I don't notice any other difference. I do know that there is a little difference as far as restriction goes and of course I am trying to eliminate the restrictions were possible..

I sent you the the picture of the resonator on my car when you first realized that there was an issue with the coupe.and I am really wondering if your solution is the better one.

What other difference other than the reduction  of the drone have you noticed?

[spicy3480]

The resonators are a new design and work very well.  Jeff engineered them himself.  The drone associated with the exhaust is coupe specific.  The design of the coupe will cause a drone when you install a free flow converter in there.  It is not there with an exhaust itself, but the converter seems to cause it.  The resonators are, as Joe said, an 85-90% fix to this.  On the convertible, drone is not an issue.  The coupe seemed to not want to cooperate, but we have it under control now.  

Usually, adding a resonator like that will slightly reduce the volume, and smooth out the tone a little.  Other than that, there should not be much difference besides getting rid of the drone.  Can you confirm this Joe? 

[DeepBlueGXP]

I can't speak for what you are asking Bob since the drone was so bad I didn't have anything to compare it to.  Now it's actually quite when cruising and you can hear the exhaust notes and burble now.  It sorta sounds like my vert with the Mach Shorty in it now.  Just a bit louder.  Anyway  Dee is very happy now.

[wspohn]

The resonators are a new design and work very well.  Jeff engineered them himself.  The drone associated with the exhaust is coupe specific.  The design of the coupe will cause a drone when you install a free flow converter in there.  It is not there with an exhaust itself, but the converter seems to cause it.  The resonators are, as Joe said, an 85-90% fix to this.  On the convertible, drone is not an issue.  The coupe seemed to not want to cooperate, but we have it under control now. 

How do you  control it?  Other than the resonators, which don't do the job, what can you do for me?

[spicy3480]

How do you  control it?  Other than the resonators, which don't do the job, what can you do for me?

I'm not quite sure I understand.  The resonators do quiet it down.  They are what take the drone away from the exhaust/HF cat combo in the coupe.

[wspohn]

I'm not quite sure I understand.  The resonators do quiet it down.  They are what take the drone away from the exhaust/HF cat combo in the coupe.

Unfortunately that is not true.  While they may be effective when used in combination with the Mach Shorty, they are not effective when used in a Street Race system as I have.  In that case, the drone remains and is objectionable.

Am I stuck with this?

[Gentleman Jack]

I'd use glasspacks.  They worked great in the 70's and 80's!

No, really though, what is is about the coupe that makes the exhaust resonate?  It must have something to do with the length of the pipes.  The resonation is just a natural frequency.  What about putting a big bow in the pipes to change the overall lenth?  Curly Q?  What about using a different thickness pipe that has a different natural frequency?  Different type of metal?  Stainless vs aluminum?  If this is for a race set up (as they seemed to have solved the street version with resonators) you could do just about anything.  Dump the exhaust in front of the rear tires to shorten the length?

Am I way off base here?  It would seem a simple harmonic frequency issue (he says with no clue of what that means )

GJ

[Sly Bob]

Thanks for that Joe. I didn't realize that the drone was that bad on your car as it was non existent on mine. Mine, like yours, is quiet while cruising.

[DeepBlueGXP]

The problem with the coupe is the cabin area amplifies the sound because it isn't cut off from the trunk area like the convert

[JimmyBaja]

One good way to find out how much certain frequency noises are amplified in the coupe is take the top off. Even sitting still in the driveway idling any engine or exhaust noise drone goes away. The shape of the coupe does amplify certain frequencies really bad - I had a hell of a time tuning out certain overpowering base frequencies when I added an amp & subwoofer - take the top off, no problem - put the top back on, drive you nuts. It would be interesting to get an audio frequency response of the coupe, maybe this would help with exhaust tuning.

[spicy3480]

Unfortunately that is not true.  While they may be effective when used in combination with the Mach Shorty, they are not effective when used in a Street Race system as I have.  In that case, the drone remains and is objectionable.

Am I stuck with this?

I was referring to the resonators as a solution with the Mach Shorty.  The absence of a muffler in the Street Race makes it a bit more difficult.  I will talk to Jeff about this one.  Feel free to give him a call...he is great and will be able to offer you some solutions.

[spicy3480]

Thanks for that Joe. I didn't realize that the drone was that bad on your car as it was non existent on mine. Mine, like yours, is quiet while cruising.

Joe is spot on with this.  We found the same problem in the G8.  Trust me when I tell you that we have worked for a few months on tuning the G8 exhaust using the Hemholtz formula.  The G8 has a spare tire well that seems to cause the same interior resonance that the coupe displays.  We might be able to incorporate some of that technology into the exhaust for the coupe.  Are there any coupes near Buffalo,
NY that would want to come by and let us test on their car?

[JimmyBaja]

Man I wish I lived closer, I would be glad to help out. How many day's would you need the car?

[spicy3480]

I spoke with Jeff today about this issue.  Our new QR resonator has worked with the Street Race kit.  It lessens the noise by 35% on this setup.  

The J-pipes on a 4 cylinder would have to be 70+ inches in order to work, and we don't have that much room for them on the Solstice or Sky. 

WSJOHN,
I am seding you a PM.

[LiquidPT]

I spoke with Jeff today about this issue.  Our new QR resonator has worked with the Street Race kit.  It lessens the noise by 35% on this setup. 

The J-pipes on a 4 cylinder would have to be 70+ inches in order to work, and we don't have that much room for them on the Solstice or Sky. 

WSJOHN,
I am seding you a PM.

I know (think) Solo sent wsphon some resonators already. I guess they didn't really solve his problem though.

[wspohn]

I know (think) Solo sent wsphon some resonators already. I guess they didn't really solve his problem though.

That is correct - I already have the resonators - that's how I built the system to start with.

They do a great job of making it quiet enough - no complaints there.  They just don't address this resonance issue so I am stuck with this annoying droning.