mikymu

It will be nice to control the loudness of our exhaust at our finger tip especially for those of us with after market exhaust or track time at Laguna Seca since it impose sound limit of 92 db. Wait, if you drive with the sport button off should solve the problem right? Well, no. Even with sport button off, the lower exhaust valve open up to allow better exhaust flow past 4K RPM. This is why you can't pass the 92 db sound limit at Laguna Seca even with stock exhaust and sport button off.

So far the only solution is manually connect the lower exhaust flap vacuum line together so the lower exhaust valve remained closed all the time which mute the exhaust by directing exhaust flow through all chamber of the two main side muffler. Restrict the exhaust flow lead to 8.2 lb-ft of torque and 9.3 hp loss but most importantly 17.2 lb-ft loss of torque at 4300 RPM but sometime you have to pay to play.

So I set out to find ways to make the exhaust flow control less painful and easy with a flip of a switch. First I need to know what voltage trigger the electronic vacuum valve and also find out ways to route the wire from driver compartment to engine compartment.

Blue collar way to manually close the lower exhaust flap as demonstrated by my earlier Laguna sound buster write up





Let's tap into the electronic vacuum valve to find out what voltage turn it on and off



13 volts to the electronic vacuum switch close the lower exhaust flap. It turns out 12V from inside of the car also works



Zero volt turn the lower exhaust flap open regardless if you have sport button on or off



Here is a video of the lower exhaust flap in action with voltage change to the electronic vacuum valve

http://www.youtube.com/watch?v=3Bwyqg3NrTA

Now we need to find ways to control the electronic vacuum valve with a simple switch from inside of the car. Radio Shack is a great source for the occasion



The 12 volt outlet on the passenger side is a good source for the juice needed to control the vacuum valve. A simple cigarette lighter plug does the job



Lift the flat rear carpet and expose the panel that house the DME. Remove three 10 mm nut and lift the panel away to reveal a round plastic body plug. Remove the plug then you can gain access to the engine compartment.



Thread the wires down through both round openings and it will pass next to the transmission



Route the wires to the electronic vacuum valve and try to avoid moving suspension parts and contact with the engine



Lift up the electronic vacuum valve from the metal bracket. to reveal the under side of the plug receiver. I used two small insulated plugs and cup away the insulation at the top of the pug to make it fit in the vacuum valve plug receiver. I tested the polarity of the original plug and made sure the modified plugs also carry the same DC polarity. I don't know if the electronic vacuum valve can be damaged if polarity is switch around. Best to play it safe since they are $135 each to replace!





I used a simple on and off switch with a long handle that you can toggle from side to side. It was secure to the underside of the center console with double sided tape. These double sided tape can be had from any hardware store (I got mine form home depot) and it will not fall off. I had one heck of a time removing it to reposition the switch. The whole setup was perfect even on the track. Super easy to operate just by touch!



Here is a video demonstrating the switch operation

http://www.youtube.com/watch?v=rI_VFuACtjg

I had so much fun with this switch and kept on toggling back and froth driving to Laguna Seca couple days ago and end up burning the 12V outlet fuse lol. It did not help that both 12V outlet were being used in the same time (the other one was connected to traqmate). I swap out the 7.5A fuse with a beefier 10A fuse and switch my traqmate to the center console cigarette plug and had no issue with the fuse since. Here is a picture of the 12V power outlet fuse if you need to gain access. It is the one with the yellow fuse puller - I replaced it with a 10A fuse



Now we need to label the toggle switch to help ID the correct side for on and off operation. Right side = more power and sound. Left = quiet and less adrenaline. I made a few suggestion as follow







I think I like this one the best



So far I am super pleased with this in-car exhaust sound switch and it has been a blast! With a flip of a finger you can reduce the exhaust note for long trip comfort and Laguna Seca sound requirement. Toggle it back if you are trying to pass a CHP lol. This give us another option to control our exhaust note at the touch of our finger.

russo

Cool. Not to change the subject, Laguna Seca has noise restrictions of 92 Db?

malmasri

Yet another nice project by Mikymu.....
Guess my kids won't be visiting Laguna Seca anytime soon.....

mooty

yes, usually.
unless it's pro events or some very rare "uncorked" events where there's no sound limit.

stock 997gt3 will NOT pass sound, even with the sport exhaust set to the "quiet" mode.

mikymu

LOL

I brought my kids to Laguna for the ALMS race thinking same sound restriction will apply and I was so wrong! I had to cover my sons ears the whole time. My exhaust is always on mute ... your kids are safe

Love your avitar!

now with this mod any GT3/RS will pass sound

fc-racer

Mikymu, I'm loving your DIY articles!! How hard is it to remove the carpet on the rear deck above the ECU? I'm thinking of mounting the data acquisition ECU down there and will need access to the unit to hook up the dash at track events. Wondering if it's a pain to remove the carpet or if it's trivial.

Thanks!

mikymu

You are welcome

It is super easy. The carpet cover can be easily removed by lifting up the center portion and the carpet piece will fold slightly and out it comes. It will go in the same way. Hope that helps

Mike

HRMinHawaii

You have the most useful mods. Unfortunately I won't be able to do this before the next event at Laguna Seca March 4&5. As you noted, I got a black flag at 95.9 dB. Short shifting to 4th and reducing throttle got me through the next four sessions safely.

Mike

mikymu

Thanks Mike. You still got time. I knock this mod out in one night - took me a while because I was taking notes and picture. You should be able to do it in 2 hours or less if you have all the right parts, wire etc. Alternatively you can just connect the vacuum hose together like below. I will be at Laguna too on 3/4. I will bring an extra vacuum hose connector in case you need it ... but taking off the OEM hose clamp was a major PITA. Look for me in the green RS

On Pole

Nice post! What fuse controls the electronic vacuum valve?

mikymu

I don't know off hand without looking at the small pamphlet included in the fuse box cover. It should be easy to figure out

brim

I made this mod over the weekend and have to say it was the best $30 and 4 hours I could have spent. I took apart the center console and hid all the wires appropriately. Once installed you can barely notice anything different from the appearance...but the sound...oh the sound!

I was tired of pulling the plug when I wanted the car to be a bit louder and then wound up not being able to take a call or keep the police from staring, so I figured I'd give this a shot and see how it worked. Well, it's perfect. Now, at the flick of a switch I can have the untamed beast from 0-redline. I have the RSS exhaust bypass and it's got a great sound uncorked. When I am on a call or my wife is in the car with me, I keep the exhaust closed and it remains relatively quiet (for a GT3). So now I have the best of both worlds with the flip of a switch, rather than having to drive the car in a certain manner based on the occasion.

Thanks for the post Mikymu!

JohnnyBahamas

Geeks RULE.

Great post.

tcsracing1

another fantastic post!

love the "labels"

micahbones

Mikymu you did not have an '04 VW R32 previously did you? Similar procedure for modifying the flapper valve actuation, although I used the cheap $1 beer clamp method to pinch the vacuum line that controlled the exhaust flapper when I wanted it loud/more torque throughout the rev range. Nice work!