Exhaust opinions - Hey Petek....

[jdean]

Pete,

I know you replaced the stock CR muffler with less restrictive ones, and I saw on your web site that you are using a SS clamp to hook it up. I also have a better set of mufflers to put on, and they have a straight 2 1/2" hole through them, with a spiral of little "scallops" that I suppose will muffle a bit.

My questions:

1) Are they too loud (subjective opinion, i know)
2) How do you like the clamps? Any leaks etc.?

With the 460, I am thinking I will add the disks inside the collector to reduce noise by about 7 decibels, BUT, if I use a clamp to make them removeable, i could easily change to a straight pipe if I wanted to be really obnoxious, which if foresee being from time to time, or at the track.

Thanks,

John

[Jack21]

Working on similar issue to make mufflers easier to swap with 3 bolt collecter flange rings.

Slip fit, as now using, tend to leak at first. When sealed with RTV copper they're difficult to separate.

Chirp test for Cobra mufflers. Drive into any enclosed parking garage.

1) With engine idling as you roll by parked cars, Cobra exhaust sets off virtually all car alarms. This is a Stage 1 exhaust. Too loud, and likely to cause permanent loss of hearing unless ear protetion is worn.

2) Blip the throttle as you roll by parked cars, exhaust then sets off virtually all car alarms nearby. Most of the rest of the car alarms located further away will chirp. This is a stage II exhaust. Too loud for street use, but may be OK for track use if helmet with hearing/ear protection is worn.

3) With engine idling as you roll by parked cars, some nearby car alarms will be set off. Most nearby car alarms will chirp. This is a stage III exhaust, and about as loud as you can stand it for street use.

4) Blip the throttle while rolling by parked cars. Some nearby cars will chirp, but none will set off. This is a stage IV exhaust and you can comfortably live with it on the street.

5) Rev the engine while rolling by parked cars. If one or two nearby cars chirp, this is a stage V exhaust. Pleasant for street use on a Cobra for top off, fair weather use.

6) Rev the engine while rolling by parked cars. No parked cars so much as chirp. This is a stage VI, or nearly stock exhaust. Car should not sound like riding inside bass drum with top on, and and sidewindows in for cold or inclement weather use.

Using 2 1/2" x 4" x 30" glasspacks (with the spiral scallops) and they're not bad sound level wise. About Stage IV on the Chirp Test. For top off use, they're fairly mellow for cruising. For top & sidewindows use, they have the "Riding inside a bass drum" effect.

Have 2 1/4" x 4" x 36" glasspacks and they're very mellow. About Stage VI on the chirp test. Minimal bass drum for buttoned up cruising. But the car is not as responsive to throttle input, so it takes a hit in the torque curve. Have pair of 2 1/2" x 4" x 36" that I'm about to substitute for the 2 1/4" and see if I can get around Phase V for winter driving.

And, Jones Exhaust has a "Stallion" muffler with a 4" case, 2" straight through core, 30" length, and "Car Chemistry" style perforated disk inserts around the core that is (according to Jones) quieter than glasspacks.

Keep you posted as I try different styles are tried.

[petek]

I haven't had any leaks since retightening the clamps (after about 200 miles or so). Sound is just fine, not too loud ... well nobody is complaining, so maybe it's not loud enough!

I'd try the straight muffler first ... and then decide if it's too loud. I think you'll be surprised.

[Aussie Mike]

I've just built a set of side pipes for mine. I've used a slip joint system but the clamp is part of the pipe where is slips over the flange and is invisible. With a bit of high temp RTV it should seal well. I've built mufflers this way for my bikes in the past and had no problems. I've also put cat converters in them as they are required for emissions down here. They are part of the baffle structure and are held in with grub screws so I can remove them and repack them. The baffle is a 2-1/2" perforated tube that's welded onto the back of the cat (I haven't got a pic of this yet). The baffle is wrapped with stainless steel swarf and fiberglass and is easily repackable or I can unbolt the baffle and change it for a different design. There was a bit of machining involved in making the flanges but I think they turned out nice.

Hope this gives you some ideas. There's more pics in my gallery.




Cheers

[jdean]

Jack 21 - I'm looking for something on the Stage V scale, and really plan to go topless all the time. I have some Car Chemistry disks ordered. They claim to reduce the droning effect, which I find more annoying than the actual loudness.

Petek - Thanks for the reply.....would you say your car is about the same or louder than with the restrictive CR version? I think i will take your advice and mock them up as is to try out, then see if i can insert the disks temporarily as well and then decide. But if I can make the mufflers removeable, then I can loud by swapping out.

turk had some interesting couplers from Burns stainless on his last car, looked pretty solid, but a bit pricey at $160.

[petek]

Hmmm... a little bit louder than the CR mufflers but at a lower pitch. The only time the sound is a bit bothersome is when I've got the top on the car. With the top on the sound gets a bit "boomy" at times.

[jdean]

Mike,

The pipes look great. The catalytic converter is well-hidden. At least we know there is a nice looking solution for the rest of us who will likely be mandated to add a catalytic converter in the future. They have come a long way since their power-robbing days of the 70's and 80's.

I think adding a catalytic converter would definitely muffle a lot of the sound though.

[Aussie Mike]

I hope the cat knocks out a bit of noise since we have some strict noise laws down here too. Fortunately most of the police turn a blind ear to a Cobra

I think the cat will act as a flame trap and stop the foot long exhaust flames on deceleration. I don't know if this is a good thing or a bad thing.

Hopefully I'll be able to hear what they sound like befor the end of the year.

Cheers

[Jack21]

For a Stage V, you may not need Car Chemistry inserts. Using a 2 1/2" x 4" x 30" glasspack from Page Muffler, Jones Exhaust, J.C. Whitney, or your local Meinikie shop; they're right in the Stage V category.

Lenthening the case from 30" to 36" dramatically improves sound control without inhibiting backpressure and engine torque curve.

[jdean]

Jack, I think the ones I got from Lucien a while back are 36" long. I'm on the road right now so I will confirm when i get home. They are at least as long as the std. CR set.

I started this thread because when I got them out of the box last week and looked through them, that 2 1/2" was quite a bit of daylight, and started me thinking they would be quite loud. But based on feedback here, looks like it might be about right.

In starting it up and driving a little ways, I thought the std. CR set was about the right range noise wise for my tastes, and if tiny 1.5" holes made about the right noice, how much louder would 2 1/2" be? I hope I do not need the CC disks after all. One thing they claim is the reduction of droning, and if that is true i'll use maybe one disk put in right after the collectors. That seems to be a good compromise on sound w/o affecting performance.



John

[petek]

Mike,

Those are some darn fancy side pipes ... works of art!

[jdean]

Aussie Mike,

What have you decided to do with them, paint, ceramic, chrome?

John

[Aussie Mike]

Thanks Pete.

I plan to get them HPC Aluminium/Ceramic coated. To many good benifits to pass up in my opinion. The guy at the exhaust shop I bought all the bends and tube from has been realy helpfull and is quite interested in the project. He's offered to send them away with a batch of his headers and get them done at his bulk trade rate.

Cheers

[cobra427mnsi]

jdean

I was inspired by Petek and others a while back and made the Paige muffler change. I have the 4" X 36" ( not sure about the inside diameter 2 1/2" or 3") I cut out the CR center section and had the Paige section welded in. Ground the welds a bit to hide them and receramic coated the whole thing.

The sound is slightly louder than the CRs but it is definitly a lower pitch. I like the new sound especially at 6000 rpm. Also a better throttle response. Quite noticeable .

Paul

[jdean]

Paul,

I am doing similar surgery on CR pipes with mufflers from Arizona (Lucien). I am mocking them up right now. The only thing up in the air now is whether to use the Car Chemistry disks as well.

Also, my engine is running rich now with the stock CRs, I hope it leans out a bit with better breathing.

John

[Don]

JDEAN:

When replacing the CR muffler with those from Arizona Exhaust, I did install the Car Chemistry discs prior to the muffler.

Used three discs without the center pipe reducer or diffuser which send the exhaust gases into the discs only

System is much quieter than the CR mufflers, with a lower tone. However, difficult to determine the tone change was due to the Arizona Exhaust muffler or the CC discs.

For recreational street driving, did not notice any change in overall performance. Others have mentioned the CC discs create too much back pressure.

[jdean]

Don,

Based on what others have experienced using similar glass packs vs. CR, it seems the lower tone is due to the mufflers. I have everything cut right not in order to re-assemble - except for to have one of my headers modified.

I went to 1" lower motor mounts, and this seemingly minor change has caused a lot of work - modify pass. side header for frame clearance, move alternator, install remote oil filter, changes to radiator hoses etc.

Hope to have it ready to test using the Arizona pipes with and without CC disks. In fact, the CC disk rep had a good idea - just use a couple of stainless rivets to mount the disks, then you can take them out later if you like - as long as you have a clamp for mating the muffler to collector. That's what I am going to do.

John