harrydirty

At my last Laguna track day, it turned out to be a 90db (!) day. Turns out the locals are winning the noise battle and it appears many Laguna days from here on will be 90db ones. I flunked during my last session (92.2db) in my stock C6Z, so I decided I needed a bolt-on exhaust diverter like so many others do. However, I did not want to damage my exhaust tips, but the more I looked into it, the more it seemed difficult and expensive, and jerry rigged at best.

So I decided to use the stock exhaust valve system in my z (I'm assuming that it will be quiet enough with the valves closed). I had some mini spdt toggle switches around and plenty of wire and had previously purchased an add-a-circuit and an LG exhaust valve harness with the switch in the shift ****. The idea was to cut the 12v feed to the exhaust solenoid and use the spdt toggle to switch the solenoid to connect to either the exhaust control module (stock config) or to 12v (controlled by the shift **** switch). This way I could close the exhaust valves when passing the sound shack at T5 exit and leave them open during the rest of the lap.

I also decided while I was wiring things up to install another toggle switch to control my AMB transponder.

I took my time, and it got it done in three days (a few hours each day) despite a few surprises. The exhaust control module was not where I thought it was. Some previous posts indicated it was behind the passenger side rear side carpet, but it was in the battery compartment. Also, I assumed that once I removed the tombstone there would be plenty of room to run wires and connectors, but there is a big piece of foam that surrounds the cup holder and part of the shift area. I had to pull out the center console to get enough room to run the shift **** connector to the tombstone cavity. Also, I decided not to use the usual exhaust module fuse location for 12v since I did not want to worry about the constant power with ignition off. The seat heater did not work because the add-a-circuit would not fit right side up (more on that later). I was surprised that most of the 10A fuse locations are powered with ignition off. I finally decided to use the cruise control fuse location; it is a 2A location, but assumed that all the wires are the same size to the fuse panel so there should be no issues with the small additional load of the solenoid.

I ran the wires from the exhaust controller in the back along the passenger side rear speaker, down the back carpet and along the central console to the tombstone cavity. The wires from the fuse panel I ran under the "hockey puck" trim piece, under the cup holder cover, and into the tombstone cavity.

It turned out the trickiest wire run was running a ground wire from the engine compartment to the console. I could not find a suitable entry point so I ran the wire along the bottom windshield trim, under the A pillar, under the door forward opening trim, then under the passenger kick panel into car. After that it followed the 12V run from the fuse panel.

I soldered all connections and used shrink tubing for protection. For the exhaust control module harness mods I used crimp connectors so that the harness could be easily returned to stock. After soldering the switches up I fired it up and everything worked. I then put all the panels back on and cleaned up......can't wait to try it on the track!

BTW, the earlier comment I made about the add-a-circuit being right side up or upside down.............when I checked out the fuse panel, all the circuit locations had the right fuse terminal being hot. This meant that if the add-a-circuit was installed right side up (fuses up or the red lead on the left), then both fuses were protecting their respective circuits. However, if the add-a-fuse was installed upside down (red lead to the right), then the "new" circuit is now dependent on the original fuse. Not a big deal, especially if both fuses are the same size, but I just wanted both to be independent so I went with a different location.

Bedouin

Curious what year your Z06 is?

I've not heard of any stock Z06's failing the 90db test, I ran there twice in '12 & none of the 4 Z06's running got flagged, but perhaps yours is a newer Z06('11-'13?) with updated bi-mode mufflers? Earlier versions had a quieter perforated bypass pipe, newer bi-mode versions are louder straight pipe w/ no perfs.

I also added an add-a-fuse circuit w/ rocker switch behind the glove box, but I just leave/left it open all the time at Laguna on my '12 LS3 (which is quieter than your LS7).

harrydirty

Actually, 90db is fairly new so I'm not sure if many Z06 drivers have run against the lower limt yet. My first 90db Laguna date was in November 2012 (I'm running a stock '07 Z06). I have never been flagged at Laguna when their lowest days were 92db, but as I mentioned, I did not pass their new 90db limit. Curiously, I only flunked during my last session, which meant that I passed during my first four sessions. Sound is certainly "black magic"!

BTW, what exactly do you mean by "adding an add-a-fuse circuit w/rocker switch"? Did you install the "Mild to Wild" setup? Or is it a homebrew? If it's something you designed, what exactly does it do?

Bedouin

I did this method; http://www.digitalcorvettes.com/foru...d.php?t=158862

It's a 1" rocker switch, installed behind the glove box door, to manually open or close the bypass valves, but when closed they still operate/open per factory rpm-throttle spec's. It doesn't manually close/override the valves through all RPM ranges.

I just wanted a clean way to keep them open 99% of the time, but easily close them on long hwy trips. Note; I've read that the valves need to be left in the open position when the car is turned off to prevent battery drain, & I keep mine on a BTjr. anyway.

I also ran laguna in May & July of '12 w/ CFRA, & by your post it sounds like sound db has recently dropped from 92db to 90db. Not good. Strange that you got flagged on your last session...sounds like the person(?) operating it maybe decided to give you a heads up on your last session...

Andrie

Thanks for guiding me here from the other thread. However, I still don’t know what you actually did. LOL.

How does thw valve actually work? All you said is running wires, but what wires? How do you actually keep the valve closed?

harrydirty

Sorry........basically, I cut the wires from the exhaust controller to the exhaust solenoids and used the shift **** switch to either supply 12v to the solenoids (flaps closed) or 0v to the solenoids (flaps open). I used a separate toggle switch mounted on the "tombstone" to do this; thus the solenoids were getting 12v/0v from either the shift **** switch (manual control) or from the exhaust controller (normal operation). I've been using this setup for over 50 track days with no problems. At tracks with no sound restrictions I just run with the flaps open; at Laguna I close the flaps just before the sound station as I enter T5, and open them up at the entry of T6.

btw, I once forgot to open the flaps back up at T6 and opened them on the uphill straight after T6 and my butt-o-meter indicated there was a definite increase in power when the flaps opened up.

Hope that helps.

Andrie

Thanks that’s really simple and I’ll do that. Just need to buy the shift **** as it is the most convenient location.

Just FYI on my F430, the difference on the hp between valve closed and open is staggering 70 WHP verified on dyno. However I think this is because of difference in piping size. The one without the muffler is basically a straight pipe with 2.5” piping while the one with the muffler is 2” piping.

That being said, my GT4 also noticeable when I had he valve closed and open. However, I never verified on dyno.

I will I’ll try to go to dyno once I run the wiring to do the switch.

Also, the Porsche community creates a gps based box. It is geo-fenced so the valve closed automatically when you are in T5 at and open again once you passed T6. Really tricked and awesome. I had it on my GT4. Maybe I’ll look into ways to make it work for the Corvette. Your solution sound simpler and I do believe in the old adage of KISS (keep it simple stupid). LOL.

Thanks and and hope to run to you in one of the track days. I usually go to Speed SF for my street cars.

harrydirty

Same here...........I usually run with TrackMasters, HOD, or Checkered Flag, but just the same, I run a black C6Z number 152.......hope to see you one of these track days.

Good luck with whatever you decide, and let me know if you have any other questions about my setup.

Nowanker

Thanks for the sound advice, HarryD!
I'm signed up to run Laguna with NCRC end of October.
Silver Z, number TBD. Maybe I'll see you there?
Planning to do something similar with the exh flaps, also thinking of some turndowns if I can find a good slip over size and band clamps to match.

harrydirty

I was also thinking of turndowns or diverters, but did not want to scratch up the tips, and jamming something into the tips did not seem very secure, hence using the flaps was the way to go for me.

Thanks for the heads up on Laguna, maybe I'll see you there.

hungryhippo

I have a C6 z06 borla touring exhaust if someone wants it for 400 bucks(or make an offer)? It is pretty quiet and i think it would pass sound on a car with cats.
Laguna seca is not convenient for me so i don't go.