Sick of the racket and kids hurling in the backseat so I got off my hump a few wks ago and attacked the dreaded AWD drone.

Everyone said it wouldn't fit but here's the proof - in colour!

I have no extractors, stock cat, but 2.5" from the car, 14" hotdog (waste of time), THEN the round resonator just before the diff. Thats the ONLY feasible location for you AWD owners wondering. I have been looking and measuring for a long time so trust me.

The system then splits into twin 2" pipes with some cheap high flows. Garnished with an SS tip and a Falcon tip - one for each side. Hurricane extractors are on order. Not too fussed about the cat atm. I do have a 3" cat on the shelf at Dad's shop for me if I want some more noise.

The drone has been reduced by a deadset 80%!!!! There is still some underlying note, but the Mrs and Kids are happy to hop in the car for long trips without anyone getting a migrane AND without embarrassing them to death with the drone.

The considerations to be made are in the resonators body diameter (the catalogue said 6", was closer to 6.3/4" including the foldings on the case), get the louvered internal pipe not just simply perforated, and make sure it weighs a ton with lots of quality glass packing in the body.

If people want part numbers or similar let me know by posting up here.

I don't get it... what did you do to reduce drone? Just add the louvre'd resonator?

Bingo. A big slab of absorbtive noise reduction. The hot dogs just dont have enough body to absorb enough drone. Useful information for anyone wanting a good system.

What brand of resonator did you pur in?

I have a big lukey in the center but only a perf and it does SFA, was gunna pput in a hot dog after it to reduce some noise but now i dont know if i'm waisting my time....

I went througfh the 3 types of Redback mufflers on my AWD and ended up going to the stock sports muffler with the single tip due to the unbarable droan with all 3 of them.

I have a standard system to the cat then a 2.5 inch pipe through to the rear muffler.

I tried combonations of hot dogs being 1 then 2 then in different places and they did absolutely nothing. Took them all out completely.

The car sounds great at idle and soft driving, with only a very slight droan which is ok but as soon as you load it hard or rev it hard it sounds like absolute crap. It has a real raspy thrashy sound. It sounds that bad that i never drive hard round people.

Any suggestions without changing mufflers again?

Would hi flow cat make it any better or worse again?

I found when the hot dogs were on, it made that thrashy air noise even worse. Taking them off opened it up a bit more.

Do what I did, and just take the muffler off completly.

Add some dynmat in the boot, and you pretty much get no drone at cruising speeds :)

i'm running a 3 inch stainless cat back with a cannon and have no drone at all...

no resonator just straight to the cannon. nice deep note to it.

I thought resonators and hotdog's were the same thing???

Also what brand is the resonator you got?

Pity Mitsubishi have closed, you could have sold them your drone solution for big $$$ :bowrofl:

Ollie

I hope this attached diagram sheds some light on mufflers, resonators and hot dogs. Cannons are typically a hot dog in design but can contain much more glass packing for slightly better absorbtive noise reduction - but not typically much at all.

The AWD suffers (?) from having a long straight exhaust pipe from the cat to the diff which is good for performance as bends slow gas flow down, however bends also help reduce noise by slowing gas down and providing reflective cancellation of noise.

Recommendations for the AWD

Select a quality round bodied resonator with louvred tube perforations inside the pipe. If you look inside it you will see hundreds of little 'Opera Houses' raised up off the pipe, arranged in a spiralling fashion to reduce gas turbulence.

The only sensible place was to locate it ahead of the rear diff as per the pics.

Again the rear muffler should be as large a bodied muffler as you can sensibly install, of a straight-thru design or offset/straight or offset/offset (whatever you prefer to locate your tip/s etc) as long as there are no baffles or triflow piping etc. Must be straight thru. If you want it really quiet at the expense of performance then install a baffled or triflow muffler.

Cat Converters

I thought that my 3" hi flow when installed made my drone worse - because there was less restriction to exhaust gases and of course the corresponding noise. The factory cats have a decent volume but a 200cpi (cell per inch) high flow unit will improve power at mid and top. Expect a touch more note through the exhaust.

Extractors

The AWD is a heavy car with a less than enthusiastic gearbox. Short length extractors such as the Advance Headers, HM Headers are not useful for our cars. Hurricanes are the best available system (so far) for the AWD. Why? The primary pipes are very long which helps the low and mid range torque that our cars desperately need. The downside is the primary pipes are 1.5/8" diameter which are quite large. Good for top end power. So the Hurricane is the better of the crop despite having a bet each way with it's primary length vs diameter debate. Sure the exhaust ports are 1.5/8" from the head, but stepping them down to 1.1/2" would enhance exhause gas velocity for low and mid range - while retaining the long primaries would be a nice combination. Pacemaker utilise the 1.1/2" primaries with good long pipes. Unfortunately they don't support the AWD model yet.

In summary:

Good: Hurricanes
Poor: HM, Advance, other clones of. Sure they're an improvement on the stock manifolds but are they worth your hard earned cash for such little useful top end gain?

What brand of resonator did you pur in?

I have a big lukey in the center but only a perf and it does SFA, was gunna pput in a hot dog after it to reduce some noise but now i dont know if i'm waisting my time....

That's a tiny rear muffler :shock: . An additional hot dog is dead money. You need a larger rear muffler. The location you've specified for the hot dog is where most aftermarkets systems including Redback locate them. Redback systems now seem to come with a Resonator AND a hot dog. The Redback rear muff is a pretty hefty unit with good glass packing. Most people are quite pleased with there Redback systems if not a little downcast that the system seems too quiet for some.

Incidently the replacement rear mufflers from every supplier who's catalogue I've opened are almost the largest physically that can be crammed under the bumper. Must be something to it hey?

I had 2x 18" x 2.5" hot dogs that did jack you-know-what. They just don't have enough glass packing to take anything useful out the note. The raspy note has improved big time but I'm still not going to rev up at the foreshore :redface: Might need my old stainless muffs back on. Stainless often gives a quality note assuming there's a solid amount of glass pack too!!


I went througfh the 3 types of Redback mufflers on my AWD and ended up going to the stock sports muffler with the single tip due to the unbarable droan with all 3 of them.

I have a standard system to the cat then a 2.5 inch pipe through to the rear muffler.

I tried combonations of hot dogs being 1 then 2 then in different places and they did absolutely nothing. Took them all out completely.

The car sounds great at idle and soft driving, with only a very slight droan which is ok but as soon as you load it hard or rev it hard it sounds like absolute crap. It has a real raspy thrashy sound. It sounds that bad that i never drive hard round people.

Any suggestions without changing mufflers again?

Would hi flow cat make it any better or worse again?

I found when the hot dogs were on, it made that thrashy air noise even worse. Taking them off opened it up a bit more.

Hey, you diddnt answer my question.... i asked what BRAND the resonator was...

I'm quite aware that the rear muffler was small hense the large lukey in the middle of the car behind the cat.. But still seems a liittle loud for my missus liking.

I think i may have to replace the Rear muffler when the money permits. Have already bought the hotdog so il try it anyway. might change it just enough.

I think it would be just over legal, but mechanics have told me its not THAT loud......:nuts:
And passed me.... Go figure.

my awd has hm headers they seem ok not like im out for drag race performance !! other than that systems stock with 3in twin tip muffler on back but drones big time (sounds like a vs v6 commodore or skyline bahhh)

A closed Xforce Varex also removed all of the drone on my old AWD.

Gotta keep the Mrs happy - Lord knows that lesson has been drilled into me :doubt: . The reso I've used is a Stallion, from Tamworth. But I stress that there are many manufacturers such as Walker/Lukey that you can source a good resonator - louvred tube with LOTS of glass pack.

Most mechanics don't want the fuss - just want to get paid and move on. Fair enuf I suppose.


Hey, you diddnt answer my question.... i asked what BRAND the resonator was...

I'm quite aware that the rear muffler was small hense the large lukey in the middle of the car behind the cat.. But still seems a liittle loud for my missus liking.

I think i may have to replace the Rear muffler when the money permits. Have already bought the hotdog so il try it anyway. might change it just enough.

I think it would be just over legal, but mechanics have told me its not THAT loud......:nuts:
And passed me.... Go figure.

Thanks.... i know of lukey, mercury, walker, magna flow....etc

Just was curious as to who made it for reference :D

Do what I did, and just take the muffler off completly.

Add some dynmat in the boot, and you pretty much get no drone at cruising speeds :)

mines like that now::naughty: ...lol... dumps befor the rear axle.:2cool: .... lol this is true guys it does sound sweet though im getting my varex fitted on monday,,

Gotta keep the Mrs happy - Lord knows that lesson has been drilled into me :doubt: . The reso I've used is a Stallion, from Tamworth. But I stress that there are many manufacturers such as Walker/Lukey that you can source a good resonator - louvred tube with LOTS of glass pack.

Most mechanics don't want the fuss - just want to get paid and move on. Fair enuf I suppose.


Hi all, know this has been done to death, but it is big problem for all awd's, especially those of us with wives and kids, who still like to drive....
Has anyone tried to fit a Mangnaflow 5x11"x22"lg rear muffler (2.5" inlet, 2x2.25" outlets), instead of the 5x8" joby used by the fwd crowd. The unit is 1.5" taller, and 1" wider than stock mitsu (non sports) unit, and same length, hence 50% greater volume. Just wondering if the combo of std perf straight thru, and this larger volume rear muffler might also do the trick????
EZYBOY, what is longest centre muffler you have measured will fit??? AWD's have a small resonator after cat, and then a 14" lg resonator before diff. Wondering if we could replace this with a single say 20" perf glass packed straight through at 6" dia for same result as your louvered unit???????

Latest update.

I had a 2.5 straight through from the cat back to a genuine sports muffler.

Sounded ok, very thrashy when pushed hard. Made a very horrible buzzing sound noise under load. I had a small hot dog put on just after cat the same as in a genuine mid section. Got rid of the buzzing noise but still sounds horrible when pushed hard.

The latest update which i had done last fri is i had a 4" resonator installed just before the diff the same as in a genuine mid section. Now my mid section is the same spec as a genuine one with the same hot dog and resonator in the same place and the same size as the genine.

Believe it or not putting in the new resonator made the car droan a lot more. The car is dead quiet when cold but once it heats up, the droan comes along. I dont understand how adding another resonator increases the droan noise. Its not unbearable but is louder. The upside is that most of the thrashy noise has gone and the car has a much nicer note.

I was going to put in a 6" like EZ Boy but it would last 5 mins in our place hanging down so low. It would get collected on the first speed bump.

Latest update.

I had a 2.5 straight through from the cat back to a genuine sports muffler.

Sounded ok, very thrashy when pushed hard. Made a very horrible buzzing sound noise under load. I had a small hot dog put on just after cat the same as in a genuine mid section. Got rid of the buzzing noise but still sounds horrible when pushed hard.

The latest update which i had done last fri is i had a 4" resonator installed just before the diff the same as in a genuine mid section. Now my mid section is the same spec as a genuine one with the same hot dog and resonator in the same place and the same size as the genine.

Believe it or not putting in the new resonator made the car droan a lot more. The car is dead quiet when cold but once it heats up, the droan comes along. I dont understand how adding another resonator increases the droan noise. Its not unbearable but is louder. The upside is that most of the thrashy noise has gone and the car has a much nicer note.

I was going to put in a 6" like EZ Boy but it would last 5 mins in our place hanging down so low. It would get collected on the first speed bump.

I have fitted the following which seems to work quite well.....
Std Rear muffler replaced with Berklee 10"x6"x20" (BS0661).
Front hot dog (immediately behind cat) replaced with 5"x3"x14" 2.5"ID straight thru muffler.
Total Cost = $270.

Agree on comments re: quiet when cold, and vibration (drone) comes in when hot.
Better in tippy mode, when you can hold revs, but this is to do with resonant point of system.

Calcs show this vibration to be at about 85-100Hz, which is quite hard to tune out. Still have the option of a 2nd mid mount muffler (making it 3 in total) but doubt this will fix it. My focus is on the length of pipe between the front muffler, and the rear muffler and the fact it has no hangers, (i.e. the pipe has a resonance), and I need to find where the correct mounting point will be to cancel out the vibration from the pipe, based on wave lenghts.

Dynamat, etc.. helps to reduce the vibrations reverberating from the driveline tunnell, and the thin heat shield over the complete exhaust, but does nothing to kill off the problem.

Will keep all posted

You could use reflective cancellation to target the problem frequency:

You could use reflective cancellation to target the problem frequency:

Hi EZ Boy,
I agree that this is one solution, but it does introduce an interferance, may as well use a reflective muffler.

The problem we are actually talking about is a change in the amplitude of the pressure wave due to temperature that creates the vibration, as noted by Family Wagon ("...quite when cold...droney when hot.."). I also have the witnessed the same set of conditions.

If we tune it out at a specific frequency, we could introduce a different more annoying resonance. So far a 14" and a 20" oval mufflers of different ratio's in diameters seem to cancel almost all resonances, including the one referred to above. So we know that at least 70L volume of straight thru mufflers will remove 80% of resonances.

The problem is that at the specific frequency range that causes the resonance there is insufficient damping for the amplitude of the wave as temperature increases. There is a complex calculation required here and I am working on the model to calculate roughly the resonant pipe length due to temperature, which will assist in confirming the frequency, and highlighting the amplitude.
Will keep all posted on any developments...