How to quiet car with out loss of power?

[crashmy911]

Right now I have headers into straight pipes. Car is loud. 102 decibels and I need to find something that doesn't loose power or torque. Anyone?

[crashmy911]

911sc w twin plug and race cams. individual throttle bodies.

[TimT]

Quiet Horsepower

[Dave at Pelican Parts]

ITBS are noisy, as well. I am told that a surprising amount of sound can come from the induction side of things. A decent airbox can help with that, or possibly just insulating the engine lid. (Yes, more weight where you don't want it--in the back.)

Tim has posted something that looks like the Tangerine Racing Phase 9 silencers, with a muffler on the end. (For a mid-engine'd setup, yet!) While I'm not sure that would not have any impact on the power or torque levels, I would bet a shiny nickel that it is one of the best power/torque/decibel tradeoffs you can make. Chris knows his stuff, and has been helping cars get under dB limits for decades. Tangerine Racing Home

--DD

[safe]

My car is pretty loud, from the side of the track I was messured at 99.6 db, on some tracks its been over 100db.

A trick I have used is tips (I have dual exhaust) like these, angeled down or slightly away from the soundmeter....
That usually gets me under 95 db, or at least close enough so they wont care.

It doesn't show in the picture, but there is a disc with holes just before the bend. Don't know if that does much, I think its the bend and deflection that does the trick.



They are ~$15 items....

[Mahler9th]

There are quite a few ways to skin this cat. I usually recommend starting out by identifying local resources by asking about local cars with similar configurations, specs and sound constraints. PCA is usually a great resource for that. In most areas, there are some commonly used approaches.

Quiet Horsepower is right near my house. The proprietor, Pete, is a a really, really good guy with tons of experience in many forms of racing. He has done some fab work for me through the years. First rate in all ways. We have been extremely fortunate to have him as a resource in the racing community. This includes pro teams.

Tangerine Racing is a distributor of some of the Quiet Horsepower products.

The Phase 9 muffler was co-designed by the father of Jan Beekius, who you can see on TV as a race reporter. Jerry Woods is a co-designer as well as Pete.

The design works very well and has been implemented and tested in a wide variety of configurations and applications. Note that it the mufflers can be made in several different sizes, and some system designs include the rear chamber while others do not.

Quiet Horsepower is an excellent global resource, and you cannot go wrong having Pete create a system that meets your needs.

[PCA7GGR]

It also depends on how loud your exhaust is. At Laguna, a tip like the one on theabov post mounted to the left and slightly downward helps lower the dB reading at the sound station between T4 and T5 which is located at the right of the track.

[stownsen914]

To the OP, are you just trying to quiet the car a little for your own benefit, or do you also need to make sound at noise-restricted tracks? If you just want to quiet the car a little, Phase 9's do a good job as noted above without killing power. But they won't be quiet enough to make some noise restricted tracks like Laguna or Lime Rock. Lime Rock is 88 db these days, which is not easy to make. I've managed to do so with my 914/6 racecar with a 2.7L race motor using a custom muffler that I fabbed up. I know of at least one car with a 3L race motor that has made Lime Rock's limit using the full Quiet Horsepower setup pictured above. If you're trying to make a restrictive limit like 88 db, you may need to address intake noise as well, as Dave suggests.

Scott

[bpu699]

How much horsepower difference is there between an open exhaust, a cherry bomb type muffler, and a stock muffler?

There was a car show I saw once where they had a motor with race headers on a dyno. They wanted to see how much damage one could inflict to the headers by denting them and crushing them, before power was effected...

Very interesting data. They dented the headers to less than 50% of their normal diameter with no loss of power. Some were dented to less than 10% of normal diameter before any loss in power. Even with the headers damaged to the point of being almost completely restricted, power loss was less than 10%...

Trying to remember the name of the show, its on youtube. I think its called "Roadkill."

Google it, as it was fascinating...

There is very little power gain with a free flow muffler, assuming all else stays the same...

[Bobby Smith]

This

[TimT]

How much horsepower difference is there between an open exhaust, a cherry bomb type muffler, and a stock muffler?

I've posted this before, the link you read can barely read is broken..... but it give some comparisons of dyno runs with only one variable changed at a time, however dyno runs change throughout the day



This is my car, passes sound at Lime Rock with one pipe capped, and a turn down...Remember atmospheric conditions affect sound... at a venue like Lime Rock, which is an old quarry, cloud cover, etc affects the way sound is bounced around... I have run there just with one outlet capped and passed sound, other days. No way!








On edit, my car has M&K header and a M&K Gen 1 RSR exhaust... which screams when uncorked

[stownsen914]

Interesting to see the different hp levels with the various mufflers. I wonder what Borla and Flowmaster setups they were using for the tests - they tested surprisingly low ...

[Mahler9th]

Bruce Anderson's 911 book has some perspective on various exhausts. Includes some dyno results. Worthwhile reading.

Quite a few folks with track, race and mixed use cars have used a variety of approaches. There is also a range of sound requirements at tracks throughout the country, and localized solutions abound.

Simply adding turndowns, et cetera can be great for some situations, but they are not a panacea.

More generalized solutions with specs like "I want to be able to make 92 dB exhaust sound at Laguna Seca" can be easier to find.

In that example, yes, induction noise can also be an issue. For example, when the 993 TT first came out, we had one at a Laguna event that could not make sound due to induction noise. Stock car with stock induction and exhaust.

The sound booth at Laguna is just after the exiit of turn 5, and so the driver just lifted and short shifted. But at Laguna in those days, the testing protocol allowed them to move to different places on the track.

It pays to consider requirements the car will face, and to tap into localized resources that have been there and done that.

Quiet Horsepower has a lot of institutional knowledge from situations all over the country, and it happens a bunch of this is with respect to air cooled Porsche applications.

[Dave at Pelican Parts]

Interesting to see the Triad results. Anderson was not too complementary of the Triad units that he had tested... Possibly different designs?

--DD

[crashmy911]

Going to try turning the pipes down at the ground.

[gtu935]

Timmy T, nice to see you still so active on Pelican. Now to get you back on the track :-)

[stownsen914]

Originally Posted by crashmy911

Going to try turning the pipes down at the ground.

If you're looking to quiet the car from the driver's perspective, the turndowns won't really do anything. They just knock a couple db off from outside the car for the purpose of passing soundmeter tests. If you want to quiet what you're hearing, try getting a pair of Phase 9 cans, or straight-through perforated core mufflers. Coast Fabrication, Burns Stainless, Supertrapp (without any disks) all make good straight-through perforated mufflers.

For what it's worth, in my 914 racecar, I've barely noticed any difference in sound level from the driver's seat when switching from open exhaust to my Lime Rock muffler. The other engine noise, induction, and air noise seem to dominate once I'm up to speed, and I still have to wear my ear plugs.

Scott

[KTL]

I would look into revising the exhaust to have a merge pipe that mixes the headers together. Headers with straight pipes are mega loud on acceleration and also deceleration. Mixing the two banks of cylinders definitely smooths out the sound.

I had a very nice exhaust system on my racecar that was made by MODE. Excellent fabrication from the heads all the way to the tips of the pipes. But my God it was loud.

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/731962-racing-headers-muffler-any-track.html

On decel/overrun it was downright nasty, almost offensive. Watch my car viewed from the rear in this video. My car is the dark widebody 911 two cars ahead on the right at the start and shortly after the start the camera car is right behind me, ready to kick my slow azz out of the way.

https://vimeo.com/groups/63643/videos/14950324

[Olsen911]

On two seasons i did get several warnings and one time black flag because of noise on the track.

Did try different kind of Dansk muffler, but no one did the trick.

So bought Pete's Phase nr. 9 and 10. NOT cheap, but haven't had any kind of problems ever since.


Thanks - Cheers - Olsen911 - Tommy Olsen

[65rsr]

Ultra Lightweight Racing Mufflers - Coast Fabrication