- Non-R Track Day Drive-by Noise Level—OEM exhaust?

Wondering what drive by noise levels non-Rs have been registering with OEM exhaust, to include intact resonators being in place.

Couple tracks in the area have a 92 or 95 dB noise limits.

Go or no-go?

Measured at what distance?

Right at the exhaust it's going to be significantly higher, but if they are measuring at the walls of the track (which could be 50m away), it would be a lot quieter but probably pretty close to those numbers.

Is there a way to program the valves to stay closed? Or change the wiring around to keep them closed?

Austinj427 said:

Measured at what distance?

Right at the exhaust it's going to be significantly higher, but if they are measuring at the walls of the track (which could be 50m away), it would be a lot quieter but probably pretty close to those numbers.

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Good point. Looking for experience with drive-by (pass-by) measurements. Microphone placement varies per track, so just trying to get a general feel.

I feel like someone should produce a removable tail pipe resonator for these cars so they could be quieted further easily. I has a Bassani Catback on my 04 Cobra and it had removable inserts for the tailpipes (they were 4" tips so there was space). But they worked well and could be removed in 2 min with one set screw. Because these cars have 2 exhaust outlets the diamter might cause restriction though.

You can use the Grimmspeed exhaust valve delete plugs (buy two and it's much easier to buy and use with the extension cables) to disable the exhaust valves so they stay closed.

DocWalt said:

You can use the Grimmspeed exhaust valve delete plugs (buy two and it's much easier to buy and use with the extension cables) to disable the exhaust valves so they stay closed.

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Why plug or close?

So you don’t kicked off the track for being too loud. Very hard to meet 92db sound restrictions even with resonators as valves open under WOT regardless of the mode you’re in.

At my autocross chapter I was clicked in at 95 or so @ 50 feet. With my resonator delete I'm now pretty much right at 100 on the nose.

Old school, lift off the throttle when passing by microphone.

chedder said:

Old school, lift off the throttle when passing by microphone.

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Lifting is no fun....you know that!!

depends of weather and wind also. Learned that recently at laguna seca.

DocWalt said:

You can use the Grimmspeed exhaust valve delete plugs (buy two and it's much easier to buy and use with the extension cables) to disable the exhaust valves so they stay closed.

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Grimmspeed valve defeat does not get the valves to stay closed. It keeps the exhaust valve in the state it was in when the module was plugged in. So if you had it in loud mode when you put the modules in, then the car will not go into quiet mode. So the idea will be to put the modules when the car is in quiet mode so it stays that way. The extension cables make installation easier. All in, it is a solution for a little over $100

I spoke with a guy who ran his GT350 at Laguna Seca with Grimmspeed modules so his car stayed in quiet mode. He asked the sound guy what he was getting and apparently just under 91db. The limit that day was 90 but they give you a 1db grace. Other people in GT350s had to lift by the sound trap or they would get meatballed (apparently hitting around 97db).

I used this setup at Laguna Seca (90db day) and no issues. I did run one gear higher past the sound booth just to be safe though.

Grimmspeed exhaust defeat module (you need 2 of them):
http://www.grimmspeed.com/exhaust-valve-defeat-module/

Extension cable Ford part numbers:
FR3Z 14A411 H (Driver Side)
FR3Z 14A411 J (Passenger Side)

Update: ran at Laguna Seca on a 90db day. Passed no problem using the Grimmspeed modules. Note that sound db is dependent on lots of variables including distance from the sound meter and even things like cloud cover that can make the sound seem louder. So just because I passed on this particular day does not mean that a different car on a different track would make a 90db limit...or even if I would pass on a day with low clouds. What I do know is that it would have been very unlikely to pass sound if the car was not kept in quiet mode.

nordique14 said:

Update: ran at Laguna Seca on a 90db day. Passed no problem using the Grimmspeed modules. Note that sound db is dependent on lots of variables including distance from the sound meter and even things like cloud cover that can make the sound seem louder. So just because I passed on this particular day does not mean that a different car on a different track would make a 90db limit...or even if I would pass on a day with low clouds. What I do know is that it would have been very unlikely to pass sound if the car was not kept in quiet mode.

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Good to hear. I was there Sunday.

At Laguna it also helps to turn in and get further left from the tower and to try to get bunched up with other cars.

If there’s a group of 2-3 cars they typically won’t meatball any.