Quietening Sidepipes

[FatBoy]

I'd like to do some track sessions in my Kirkham, but we have a strictly imposed maximum noise limit on pretty much every race track in the UK of 105dBs.
Can anyone recommend a permanent solution for getting the standard steel Kirkham side pipes down to this level? I measure the noise on mine at 120dB. This was static at 4,000rpm.
If I was to cut the cans open, what type of baffler works best?

Thanks,
Paul

[garry viohl]

http://www.summitracing.com/parts/DTC-72-32520/

these will take the bite out of the noise

I use them and they work. 2 or 3 decebile less

Did not notice HP loss

[FatBoy]

Thank you, but "2 or 3 decibels less" isn't going to be anywhere near enough. I need to lose at least 15dB.

Paul

[garry viohl]

I have seen guys at the track use these:

http://www.summitracing.com/parts/SUP-544-3003/

[Don]

Paul, another alternative is to determine if any of the various motorcycle baffles might work. As an example, Harley Davidson has a low end " Power Baffle " part # V21299 , along with other baffles that are more/less restrictive. Baffles might require modification. Or, a combination of baffles that have been mentioned.

There are reverse flow mufflers, which would need to be modified, used for Corvette side pipes.

Take it that you are going to place the baffle internally and/or modify the turn out. Challenge will be not knowing how effective the solution is and the impact to performance/HP, such as reverse flow mufflers, until the side pipes are reconstructed

[FatBoy]

Thanks for the suggestions.

The elliptical shape of the exhaust exit due to the turnout makes adding anything onto the end problematic and I don't want to change the original appearance too much.

One suggestion has been to modify the tailpipe section so that the outlet can be rotated to face the ground when being used on the track. This could easily be achieved, but I don't know how much effect it will have on the noise levels. But maybe used in conjunction with some of the other suggestions, it could be enough.

Thanks again.
Paul

[mickmate]

What's your HP? I have used the Cobrapacks with great success. I face the louvres towards the motor and run them packed with the smallest ID I can match to the HP requirement.http://www.classicchambered.com

[FatBoy]

I don't know the prcise figure, but it will be in the 450-500 range.
It is a pretty modest setup 427 S/O with around 10:1 compression.

I've looked at the website and the insides of the Cobrapacks look the same as the internals of the Kirkham sidepipes. Does anyone know if that is what Kirkham use?

Paul

[mickmate]

Eric says 450HP for the 2-1/2" ID mufflers. I think they'll work fine for you. Bear in mind you can get a little more muffling by making them an inch or two longer and you'd be the only one that knew they were longer by looking at them. As you suggested turning the tips down on a slight angle (about 15 deg) helps some but if you have then going too far down the sound bounces right back up from the road.

[Ronbo]

Another option...

http://www.spiralturbobaffles.com/

Don't have any experience with these but some other members here have used them.

[Don]

Paul, taking into consideration that loss of HP/performance was accepted in order to have quieter pipes:

Used 3 1/2 " round exhaust tubing, reducers at both ends to go from the 3 1/2 " to 3 ", filled the joints. The modified reverse flow muffler was placed inside the tubing with ends to act as a seal as I wanted to maintain the stock appearance of the side pipes. 3 1/2 " tubing is as long as possible to still be able to attach the turnout

Attached the front to the header extension/connection and the rear to a turn out, all joints were filled. Looks like conventional side pipes, used the same mounting hardware.

The cones mentioned by Garry are in the front. The motorcycle baffle was placed internally after the muffler. Reduced the dB , but do not have a measurement. For normal street only driving, never noticed the reduced HP. Will satisfy the dB reduction needed for use within a " retirement "community

Summit sells the tubing, reducers and turnouts

A consideration when pointing the turnouts down depending upon conditions is the " possibility " of blowing dirt and other debris onto adjacent cars, in the pits, on the street etc.

[Learjockey1]

I feel your pain on the loud exhaust, I am in Europe and have the older style ERA/ Stainless Steel Specialtes sidepipes. I wear ear plugs. Folks cannot believe my car has not been towed, I hurt my ears after 60 mph. I do not believe I am losing any power. They must sound just like they did in 1965. I do not know how Ken Miles and the other men did it.

OK, here is my idea, nothing revoutionary, but I have not seen it integrated on the Cobras. The Harley guys are doing it using electrically operated butterfly baffles. There is a company in the Netherlands called Jekyl and Hyde that make pipes for all the Harleys even the Vrods. They sound full and throaty on or off. I have looked and the Partriot Exhaust butterfly controlled baffles am working it in my mind to adapt/ cut/ weld/ fit/ reweld/ polish/ to my pipes. I intend this winter to have the best of both quiet around town and open on the Bahn as I do not want I set a bad example. However, the 427 NASCAR style howl at 3000 and up is just too good to lose. Plus many of the Germans grin and get it. I have seen old ladies smile. I had to pack 15 steel wool pads in each pipe held in with the dyna Teck cones (covered in the earler threads) to pass but they blew out.

[Stentor]

You should consider contacting Tom from Tom's Motorsports in Las Vegas. He fabricates custom sidepipes for Cobras--with inserts--that will meet the noise requirements of tracks (and not kill your HP in doing so).

http://www.tomsmotorsportsinc.com/About%20Us.html

Good luck.

[Justin O'Rourke]

Hi Paul; We made your mildsteel sidepipes and can make new ones for you that will be as quiet as you like. But, they will be more restrictive. That will rob some HP. Regards, Justin

[FatBoy]

Hi Justin,
Thank you for your response.
I may get back to you on that, but first I'll investigate what is available on this side of the Atlantic in order to keep the costs down.
Regards,
Paul

[bobcowan]

15dB is a lot. Remember that the scale is not linear, it's logorithmic. To lose 15 Db, you're going to have to work at it. There's no off the shelf baffle that you can stick in the pipe to do what you want.

You're going to need some new mufflers. The two most popular seem to be the spiral/auger type, and the Cobra Pack glass packs. I installed 32" Cobra Packs in mine. A big job, but made a big differance in sound volume and quality. I don't have a dB meter.

Another trick is to bolt on a piece of alum about 4" in front of the pipe opening to act as a baffle. That breaks up the sound waves and the meter reads lower.

[xlr8tr]

does anyone have direct experience/comparison of the classic chamber mufflers vs the auger style, from the perspective of both noise level and power loss?

[RestoCreations]

Glasspack mufflers are glasspack mufflers. The only way that they will be quieter is if the Internal diameter of the muffler is smaller. it will be more restrictive, but you can also fit more packing/sound dampening material around the muffler. Our cars use very short muffler sections, which is the majority of the problem. If you could find someone that would make a 2" or 2-1/4" internal diameter muffler, then i think it would help dramatically.
On a previous car, i custom made a set of 2-1/4" internal diameter chambered mufflers. They worked and they shut the exhaust up a good bit, but it was a huge hassle and a ton of work. Overall i had a 5db decrease across the rpm range until about 65mph where the wind noise took over. I lost about 8rwhp total. However, I could not feel the loss and was more than happy to sacrifice a few hp to quiet the pipes down. I have used mufflers from some of the companies mentioned and i can tell you there is no Decibel difference or hp difference. If you are swapping one brand of 2-1/2 or 3" glasspacks for another brand, there really isnt a difference as far as sound levels are concerned. All are chambered exhaust with small louvers and wrapped with fiberglass. I wish someone would make a glasspack with a 2" or 2-1/4" ID muffler with a smooth transition into from pipe to muffler. Yes, you will sacrifice a little hp, but I am willing to give up 10-15 RWHP, probably even 20 in order to keep more of my hearing.
-One more point. I have heard a car in person with the spiral inserts and they do not sound good unless you like a very metallic sound to your exhaust. It was far too much for me. I have heard that the spiral cones will drop the noise a db or two, but that is not enough for me to bother with the effort of installing them. I have also heard that the Car Chemistry tip inserts work, but that was only from one source. Car chemistry used to offer a full length insert, but i do not see it on their website anymore.

You would really think with all of the complaints that someone would make a better muffler. The small inserts, regardless of brand, seem pricey to me for what they are.