http://tinyurl.com/2ucpzx

What do you think about this discussion?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

That's a Helmholtz resonator he's describing and has built. If you can tell me what the insulation stuffed in the tube does I'll Pay Pal you $1.

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Joshua

reduced the affectivness of this type of resonator.

I am going to sleep on an adjustable lenght resonator to bolt on to the 3"cutout dump. I assume that this port dosen't need to be straight. Any guess with regards to length and diameter.
I am thinking a 2.5" tube about 17" long minus the length of the cutout stub.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Nope. Slows down the acoustic wave to make the pipe appear longer. Also works for speaker cabinets.

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Joshua

Edit: look up

If the resonate tube in question where the optimum lenght, then adding insulation to it would slow down the wave pulse and make the tube seem longer and therefor less effective.
So under certain conditions we both could be right.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I think it will need to be longer. Probably around 24", but that's just a guess. That's why I suggested something adjustable.

Now that I think about this some more the resonator will need to be after the muffler if it's the tailpipe that is resonating. Assuming that the muffler is dividing the exhaust into two different resonant chambers that is.

I'm going to eventually try full 3" single exhaust with a Magnaflow muffler. 3" tail pipe too. Might be a while before it's together though so don't hold your breath.

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Joshua

What do you mean here?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

I mean if the tailpipe is resonating then the helmholtz resonator needs to be part of the tailpipe. Your cutout is before the muffler so adding the resonator to that part of the exhaust won't solve the problem.

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Joshua

Bren,
i had my exhaust system assembled almost exactly as yours.
but i used a very large glas-pak and another pak as a resonator after the axle.
i don't have the drone. all i have is wind blowing thru the worn window rubber. since i have a van, i have a lot more room than u under the vehicle, but the glass pak worked great for me.

the stuffed resonators ur thinking about sound fascinating. it mite be ur cheapest solutuion. it probly will need to be attached to the offending pipe. i agree that ur cut-outs may be the wrong place to put them.
have u tried running with the cut-outs open? what happenes to the drone then?
if it persists, the cut-out location is wrong for these resonators.


D~~~!

You are beating a dead horse (again?). Get rid of the flowmaster. They really don't flow that great anyway. It's just a can with baffles, no acoustic engineering or attention to flow. It is another one of those popular parts that suck. Leave them to the mustang crowd.

The drone is in the muffler, but it is sent back up the pipe as a reversion wave and actually amplified. You cannot really get rid of it by playing with the pipe without restricting flow quite a bit. The best fix I have seen without changing mufflers was a steel insert that looked like a venturi and was installed right in front of the muffler. It necked a 2.5" pipe down to 1.5" for about an inch. If you head in that direction, why even have a big pipe?

The Walker ultra flow is a much better flowing muffler if loud is not a problem.

I would get a slip on collector that goes from 3" to 2.5" and put it right behind your cut-out. Then run 2.5" pipe back to a 2.5" Hooker aero chamber. They have a powerful and clean sound outside the car, but I have not had droning problems inside the car with them. Droning is especially bad with a 6 cylinder and the Aero chamber is the only muffler I have used that really got rid of it. The flow is outstanding, with the straight thru Ultra flow being better, but loud.

Even being 2.5" this should out flow your Flowmaster and weigh less. A single 2.5" Aero chamber is well up to the the task of flowing the exhaust for a 225 horsepower engine without cutting power.

With an exhaust system, enough is enough. Ten free flowing mufflers will not make a car faster. A sewer pipe will not make more power on a setup that only needs a 2" pipe.

I have run a stainless flowmaster 50 for years (3" inlet/outlet) with no problems. Spending more money on essentially the same muffler from Hooker or Magnaflow makes little sense.

If it is Muffler related you should be able to feel the muffler vibrating at an idle. ....kinda like a sex toy.

Necking a pipe to 1.5".....I wont even commment.

Your compression ratio and cam timing have an effect on many things .....like drone. I bet it is worst at peak torque.

To comment on the 2.25 pipe with OEM style muffler that drones.....Im mystified....I have run that for 7 years and have no drone.

Do you get drone with the cutout open?

Have you tried dumping behind the muffler?

I would vary pipe length after the muffler (just straight pieces of scrap pipe) to see if the drone is affected by length.

Try some variables to see if you can change the drone.....then tune till you get what you need. The term tuned exhaust is where you want to be. Its like the rest of the car....some tuning required. You are makin progress ....hang in.

There is always Super Trapps......

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Yeah....Im the one who destroyed this rare, vintage automobile.....

What are these?

No drone with the dump open.
The tail pipe is vibrating. I also took a 4 foot peice of pvc (2") and stuffed it in the end of the crome tip. I dosen't seal or anything but the tone drops alot. Sliding it in and out a little changes things a bit. I drilled a 1.25" hole in the tail pipe elbow as it maks it turn up to go over the axle. You can see inside the muffler with this hole. Tone dropped the most with this modification, almost driveable now. Holding your hand by this new hole you can feel vibrations. Not the puff puff kind, but the electric razor kind.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Super Trapps

http://www.supertrapp.com/product_secti ... /index.asp

Bren have you ever seen the dual pipes on an early 60s Jaguar XKE?

They are very long and tip up into the area behind the trunk.....
Your PVC experiment is kinda similar.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

run open headers for a while...it won't sound so bad when you hook it back up.

I run a summit glasspack but the turbo does some muffling too.