Gofishracing

tough one.

stownsen914

If you don't mind sharing, are you using a couple of Burns mufflers like this one? How do you have them configured? I'm impressed that a straight-through type muffler (or a pair of them) passes at LRP. I've had no luck with that style muffler in the past.

Gary R.

That's the muffler, the configuration is one muffler each bank, then a convergence after the mufflers to exit out the center rear. The way my buddy did it was to split the two 90 degree exits and make one larger (sort of oval) exit. I converged to one pipe and had a fitting on it so I could add the third muffle at 90 degrees if it was needed. It never was. This was on a stock 3.2 and mine was more restrictive than the "oval" tailpipe.

stownsen914

Thanks Gary for sharing your experience. I'm going to guess that iwth a 3.5L race motor with big carbs that with your setup I still wouldn't make 88 db.

Anyone with a large-engined 911 care to share how they make sound at Lime Rock?

analogmike

IMHO a carbed 911 engine, even with the exhaust exiting somewhere in New York state, would still be too loud for 88db unless the carbs are well-muffled.

Tim

^^ This,

Sometimes running a stock airbox over the carbs is needed..

Lou D

FYI, Hudson Valley Region has an unmuffled event at Lime Rock on Tuesday, July 21, 2015. Register via http://www.clubregistration.net. No muffler required. We currently have room in all rungroups.

stownsen914

(To all) Any suggestions for how to muffle intake aside from going to a stock airbox as Tim suggests? Would a sound deadening / insulation mat over the decklid grill opening help?



I'm planning to be there (and hopefully testing a first iteration of a muffler)!

Gary R.

Honestly, your best bet is to go on unmuffled Tuesday afternoons, to either the Hudson Valley Events or Limerock's Test n Tune Tuesday (if you have a racing license).. By the time you meet 88db you may as well unplug two of your cylinders for the restriction you are going to put on her. I've seen stock street cars flagged there under certain test conditions!

stownsen914

Ha, well you may just be right. But I'm a stubborn bastard so I'm going to try. I'm planning to go to the unmuffled HVR event in a few weeks with a muffler to see how far off I am (and megaphones for the afternoon).

Gary R.

I didn't want to show my secret, but this baby will pass sound AND you can run during a flood..

Gary R.

That upright Burns muffler, with ends lightly tacked on, is still unused and FS if you want to save some $$..

Gofishracing

Gary- does it shoot flames?

CAM14

If you know where the sound station is located and if it is consistently on the same side of the car, then point the muffler tip away from the sound station. Can make a big difference in what the meter picks up. Also, have the exhaust exit under the car by the turbulent air of the tires/wheels will dissipate some of the energy in the sound wave, whilst this might be more difficult with the rear engine layout, worth the effort.

HTH

stownsen914

On the first point, yes absolutely. Very common to see this at Lime Rock. On the second point, yes as well though I don't see as many people doing it, possibly since it's more of a pain to do ... I am planning to do this for whatever I wind up building.