How to reduce noise for track db limits?

[Fatboy 18]

I'm on track next year at Spa in Belgium, I believe the Db noise limit is 100db.

My 2000 Gen II GTS currently has Stock headers, full decat pipe and Belanger cat back rear exit exhaust. Its currently kicking out 128db

What is the best and cheapest way to meet the db track limit? (apart from not starting the engine)

What do you guys fit?

Thanks Mark.

[plumcrazy]

throw a muffler in where the cats used to be ?

[ViperTony]

I used Vortex cones a long time ago they dropped the db level 4-5db at most. Not really going to help you. I put in additional Dyno Max race bullet mufflers where the stock resonators used to be. (I run Belanger headers and catback, no cats). It didn't do anything for noise level but got rid of most of the drone at least whatever little drone I hear over the loud exhaust. Some guys gave installed Spiral Flow mufflers where the cats used to be. That may be a good option.

[rw99]

I'm on track next year at Spa in Belgium, I believe the Db noise limit is 100db.

My 2000 Gen II GTS currently has Stock headers, full decat pipe and Belanger cat back rear exit exhaust. Its currently kicking out 128db

What is the best and cheapest way to meet the db track limit? (apart from not starting the engine)

What do you guys fit?

Thanks Mark.

Jeebus, 128 dB... at what distance? Is there a single monitoring station at Spa?

Laguna Seca is our local "problem track" for noise, with increasingly restrictive limits. There's one stationary meter on the uphill T5-T6 straight that's always used, although they say that there's also roving monitoring. Standard Viper practice here, if you're at all modified, is to short-shift to 4th on that section and downshift when you're past it and setting up T6. If Spa has a similar, static meter, you could sacrifice some speed to pass the dB restriction.

A variety of solutions are seen among other cars, including funky "redirectors" bolted onto 911s (to direct outlet up and opposite the trackside meter) and Supertrapps-type suppressors.

Jealous of your visit to Spa already... I would love to drive that track. True bucket list item!

[Fatboy 18]

OK what seems to happen every time I turn up at a track is in the corner of the pits you have to do a static DB test, this is done by a marshal standing behind the car with a hand held Db meter attached to a 3ft cane which they rest on your exhaust tips. ( the cane is so they measure equal distance on all competing cars), next they ask you what the car will rev to, I tell them 6000rpm so they ask me to rev the car and hold it at 4000rpm.

It always fails. and I am only ever allowed on track for a Parade lap behind pace cars and told to short shift.

As for Driving on track and backing off near Db monitors, Fat chance.

The only time I get to have real fun is at Le mans on the so called parade laps, and if I do charity days on the Top Gear Test track and the occasional Hill climb event.

Surely there must be other Gen II cars out there with the exact same set up and problem, or is it that you measure the sound in a different way?

[Heysie]

My 94 RT/10 did 122 dB. Never had problems on Spa.
On Zandvoort is a 96 dB limit and also there no problems.
Never seen them measuring in the pit on Spa.

[Fatboy 18]

Great, Good to know, Thank you.

[Redsled]

Usually in the states most racing tracks who measure sound measure it at 50 ft from track surface. They do not do any type of testing in the pits like I've seen on European tracks.

[Drumrboy]

I'm surprised that they measure so close. As Red stated, in the US measurements are taken by the side of the track (more realistic measure of the invasiveness of the sound) and I usually score around 188-120. If one knows where the measuring devices are, one can always go easy there, OR I use turn downs (which are fitted to the exhaust holes and sheet-metal-screwed in place) so the sound hits the ground and bounces up or gets otherwise diffused. With the turn downs and no driving/throttle adjustment, the approach is good for about 6 dB.....not enough to help you but perhaps good to know as a cheap way to knock 6dB off your volume for about $10 and 10 minutes work.

- - - Updated - - -

118, sorry

[Fatboy 18]

Thanks for the feedback

[Fatboy 18]

Been invited to another track day at Goodwood, here are the rules

For your track sessions you will be called forward into the pit lane by the marshals in good time to enjoy your Goodwood circuit experience. The noise limit for the day is 105DB @ three quarters maximum revs when measured at 0.5 meters from the exhaust. See Maplin mini sound meter here.
During the day there will also be an ARDS instructor on hand to give you tuition/advice on the Goodwood circuit and also coach you on driving technique.

No Idea how to get down to that level? Don't start engine and just push the pedal down?

[cashcorn]

tell them the car only rev's to 4k. then they will have you rev to 2,500. play the game to pass.. just trying to help.. really