Interesting solution to dB limits at race tracks

barstowpo said:

Do you think having the valve open but the pipe closed will effect power?

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The restriction may rob you of a little power but nothing substantial. The pulls I did felt just as strong as "unplugged". Would need a dyno to know for sure though.

wildcatgoal said:

Wait, hold on... the GT350 will exceed dB limits at tracks with the STOCK exhaust, even in the quiet mode (if so equipped with that adjustment)? I can do AMP (BARELY) with my Solo Mach XV and I never knew the stock GT350 would be louder than that.

Like... how do the Miatas that are always present sounding like a swarm of bees get on these tracks? Half of them are incredibly loud after they've been made a race car.

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We're also talking about different AMPs. Arizona Motorsports Park here instead of Atlanta. No idea what Atlanta's sound restriction is.

But yes, wide open without resonators an otherwise stock GT350 runs over 100db depending on distance (of course). It will get kicked out of tracks that have restrictions in the 90 range.

CSL said:

I raced there in November. On Thursday and Friday it was either 89 or 90. On Saturday and Sunday they raised it to 92. I didn't know if that was pretty much their limit.....guess so. I think I saw somewhere that with the valves closed the 350 was still about 96?

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There are unlimited days. There are just a few per year though and most are actual professional races, but I have done an HPDE or two that was lucky enough to be unlimited.

wildcatgoal said:

Wait, hold on... the GT350 will exceed dB limits at tracks with the STOCK exhaust, even in the quiet mode (if so equipped with that adjustment)? I can do AMP (BARELY) with my Solo Mach XV and I never knew the stock GT350 would be louder than that.

Like... how do the Miatas that are always present sounding like a swarm of bees get on these tracks? Half of them are incredibly loud after they've been made a race car.

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The valves automatically open at WOT no matter the setting, it is much quieter and within restrictions if you can give the same effect as "closed" 100% of the time.

Is there anybody who has actually been told to go home from a track running a stock GT 350 exhaust?

iufan993 said:

Is there anybody who has actually been told to go home from a track running a stock GT 350 exhaust?

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Yes

Any risk of damaging the engine or valve doing this from the back pressure?

firestarter2 said:

Any risk of damaging the engine doing this from the back pressure?

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I don't believe there is. It's a single pipe going into the muffler. I'm not sure what routing it takes inside except for that the valved pipe is essentially straight-through, while the non-valved pipe takes a circuitous muffled route. Corking it just adds a bit of dead volume but any pressure should go right back out where they split. The car ran fine, even in the upper range.

iufan993 said:

Is there anybody who has actually been told to go home from a track running a stock GT 350 exhaust?

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Well this was my experience at Laguna Seca on the 30-31st of Dec. Sound limit was 92db...pretty normal for there. I ran my car in the sport mode so valves open BUT I short shifted to 4th gear (4000rpm) going up the hill past sound and didn't get any black flags for sound.

A bit later a friend of mine wanted to video me so I just drove it as I would normally and left it in 3rd up the hill past sound and got in 4 laps before I got the meatball from the flag station heading up to the corkscrew. I had to come in and they told me I was at 98db...a bit more than I thought it would be. But going up the front straight it was LOUD and sounded great. The garages on the left and hill on the right keeps the sound in in that area.

Anyway my session was done...and if I got 2 more they would have invited me to leave for the day...kinda liberal if you ask me. So I wasn't worried about that happening and just went back to short shifting coming out of 5 and had no problems the rest of the event. By the way I was running with the Alfa Romeo Club and they put on very good events...really know what they are doing so if you are looking for a group to run with I would highly recommend them.

I can't imagine running with the valves closed as the sound is one reason I love the car SOOOO much!!! Way to go:ford: super nice job on that. Now FORD you get super bad job on building a track car without tow hooks built into it.:shrug: Did you think we wouldn't take them to the track I mean Porsche and BMW thought of it....geeeze:doh: Maybe they will put some on the new cars.

In case you would like to see the video here's the link: [ame]

I have a vintage race car which is a 289 with resonators only. It ticked 94 dB at Roebling Road. My Gt350 hit 92 only. Their mics are probably 40 ft inside the track surface on a straight away. The Miatas routinely hit 96 dB.

Good to hear the short shift is an effective remedy at Laguna. Any idea if your lap times changed when you went up the hill in third. Those kind of subtle changes typically hurt less than you'd think.

CSL said:

Good to hear the short shift is an effective remedy at Laguna. Any idea if your lap times changed when you went up the hill in third. Those kind of subtle changes typically hurt less than you'd think.

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It was a short shift and watching the RPM's in 4th going past sound...which is measured I understand at 50ft from the right side of the track. I have no idea on lap times as I didn't have a transponder and don't have the app on my cell phone. And I wasn't there trying to be fast..just to have fun. But I know I was going up the hill to 6 a lot faster in 3rd. Still a very fun event and that track is getting harder to get on all the time.

iufan993 said:

I have a vintage race car which is a 289 with resonators only. It ticked 94 dB at Roebling Road. My Gt350 hit 92 only. Their mics are probably 40 ft inside the track surface on a straight away. The Miatas routinely hit 96 dB.

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Laguna I believe is 50ft from track out between 5 and 6 and on a hill so you are under load going up to turn 6.