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If it were me, I would have left off the last 90 degree bend at the top and used the exhaust for down force! On a more serious note, many times at an event you will see the exhaust turned away from where the sound meter is supposed to be and those tricky tech people move it to the other side of the track!

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Thanks Grant...I am really feeling the heat to get this thing to make sound.

I have a stock 911 carb air box on the way. I will do the same set-up Randal did with the K&N Airfilter and turbo bellmouth.



As for the muffler, Jeff at Rothsport is going to let me borrow a couple of different configurations. I would like to test some locally before I got to get a baseline on where I am at.

In the power department, I am going to up the timing a bit from 32degs to 36degs...but that is all I got.

-Britain

My dual quiet pack exhaust with no intake mods, was 89dBa at Laguna.


KT

According PCA SDR I managed 95db at Qualcom in a box stock Caymen S so I think it all comes down to the way that it is measured, good luck with it and I look forward to seeing what you find.

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There are a couple of things to try, one is to cover the engine cover with foam, the very porous type several inches thick which will deaden the sound but still let air in. Another is to close off the engine cover completely and run air intakes through the firewall to carb boxes but the downside to that is it requires cutting holes and on a street/track car that is not a great idea. Many vintage racers (Frank Beck for one) do that to get a better and cleaner flow of air that trying to suck it down behind the roof line. Finally many many years ago I saw a 914 that had the rear of the roof raised a couple of inches and a cover that came down from the roof to the rear deck lid between the sail panels and that car had a six with stacks and no air cleaners at all and had NO intake noise. The panel was added after work was done on the engine and was not visible except from the back of the car.

We have to make 90 db at Lime Rock, measured at 50 ft. They usually measure in the middle of the front straight. Most 911 based cars seem to make sound with factory-style sport mufflers. Phase 9s and Supertrapps are usually too loud from what I've seen. Personally I use a single Flowmaster on my 2.7L 914/6.

Scott

I am so frustrated and stress out about meeting the sound requirements. AHHH!!

Got a new muffler, but it will take some fab work to mate up to my headers!

Got an air box for the carbs, not the engine lid doesn't close!

-Britain

I know your car is radically different than mine was but with a 2056cc T4, 290 duration .507 lift cam, duel 40mm carbs with 6" air filters, and a Tangerine Racing Header with only Chris's version of a phase 9 for muffling. I was 96db at 100 feet and ~7200RPM. I had a stock engine lid, and was running full engine tin though so these may knocked down the noise a little but with a different muffler and an air box, I am fairly certain I wouldn't have had a problem making 92db, though I would have lost a little top end power. Fortunately, El Toro does not have any sound restrictions though so I just stopped going to SD AX's.

Stick with it and I am sure you will get it to pass. If the rotary cars can do it, you should have no problem.

All SCCA National events now have gone to a 100 db sound limit if no local rules exist. Our local region is doing the same.

17.2 A
Grills may be removed, modified, or substituted.

BTW, IMO, modify the muffler not the headers.

My first year at Laguna with my 914-6 I made an aluminum and foam cover that fit on the inside of the engine grill and put on two mufflers that my local shop promised would make sound. Didn't make sound and had to lift all weekend before the microphone so I could run.
Next year I used the same foam cover for the intake and modified a stock 914 muffler to mate to my headers. Didn't make sound, but close at like 95db. Had to lift before the mic to run the weekend.
Next year I used the same stock muffler with a stock 911 intake and filter. The grill wouldn't close so I took it off. Made sound but the car was so down on power that it wasn't much fun and I would have rather been lifting at the mic and being able to enjoy the rest of the track with some power.
Bottom line is the intake is just as important as the exhaust for sound control with the webers.

BTW, it is 93db at 50ft.

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