Eliminating Exhaust Drone to quiet exhaust

[mudbilly]

Well, the mechanic that has done lots of work on the 73 and my other vehicles is convinced that he can tune the exhaust to make it quiet and eliminate the drone. ::shrug::

I am taking the car in early next week.

 

[Hemikiller]

OK, but what mufflers are on the car?

 

[mudbilly]

OK, but what mufflers are on the car?

Currently Hush Thrush is installed. with 12" long resonators in front of them and an H-Pipe connection in front of those, with Hedman shorties in front of those

Over the axle pipes take the exhaust out the rear. I've read that having long tail pipes has something to do with the drone, and it does appear the sound is actually coming from behind the mufflers.

2-1/4" pipes.

I'm going to give the guy total freedom from the heads to the exit.

I talked to Phoenix Engines, who built the motor, and they said with the dual exhaust, I could put on ANY type of mufflers. It will not affect performance or hurt the engine any, won't run lean, rich or whatever.

This has become a quest.................

 

[Stanglover]

I didn't see what you're running for mufflers, but in my experience, Flowmasters are pretty horrible for drone. I switched to Dynomax Super Turbos and was very happy with the noise level. I normally run them on just about everything now. Also had good luck with Hooker AeroChambers on a friends 383 Roadrunner - completely changed the car....

Hemikiller, a side bar question; How would you compare the exhaust tone of the mentioned mufflers at the rear of the car, to the Flowmaster 50"s I am running? I like the throaty sound of the Flowmasters, but not the drone, especially under 50 mph, when it disappears. I will be replacing my exhaust next winter, so your opinion would be helpful.

Thanks,

Geoff.

 

[mudbilly]

After the shop said there would be no issues with installing stock mufflers, I called the engine builder and they confirmed that I will see no difference with the stock mufflers, they did want it to stay as duals.

So the cam and headers are still on the car.

The shop was able to find OE Mustang mufflers and installed them. Although I am not where I want to be yet, it is heading in the right direction.

Before installing the new mufflers, I had:

73 Db at idle in drive

76 Db at idle in park

85 ish driving around

93-95 @ 2200 RPM under load.

With the new mufflers

73 Db at idle in drive

76 Db at idle in park

78 ish driving around

84 @ 2000 RPM under load ( the peak sound shifted)

At cruising speed, (78DB) the exhaust is only a little bit louder than the road noise. shifting into neutral only drops sound by about 1 Db.

Even though the Db is the same at idle the tone is much more mellow (hard to describe, it sounds muted, as compared to banging). It is muted throughout the RPM range & I drove it about 100 miles back and forth to work and it is a world of difference. I like it much better ( That being said, I loved the old sound for 10 years )

The power of the engine build is definitely working its way through the exhaust as compared to a stock engine.

My next step is to box in the trunk (it is currently wide open) with plywood and heavy duty sound deadening material. I'm hoping that I can stop the sound from getting into the cabin.

I'm also going to revisit the dead end sound eliminator with this shop, because they are much more knowledgeable than a stand alone muffler shop. I didn't quantify if there is a peak frequency that I can try to eliminate with the spectrum analyzer app yet. So I don't know if this is even the issue or if it is just louder overall due to the cam overlap, or whatever.

I'm also going to keep trying out various devices to see how quiet I can make the exhaust. This has become an engineering journey.

I ordered a set of these to slip into the tail pipe.

http://www.demon-tweeks.co.uk/motorsport/universal-exhaust-silencers/decibel-slayer-bolt-on-exhaust-noise-decibel-reducer-insert

And I have a phone call into this place to see if they think that adding this will make any difference on a full mufflered engine.

http://www.carchemistry.com/silencer-insert/

 

[Hemikiller]

I didn't see what you're running for mufflers, but in my experience, Flowmasters are pretty horrible for drone. I switched to Dynomax Super Turbos and was very happy with the noise level. I normally run them on just about everything now. Also had good luck with Hooker AeroChambers on a friends 383 Roadrunner - completely changed the car....

Hemikiller, a side bar question; How would you compare the exhaust tone of the mentioned mufflers at the rear of the car, to the Flowmaster 50"s I am running? I like the throaty sound of the Flowmasters, but not the drone, especially under 50 mph, when it disappears. I will be replacing my exhaust next winter, so your opinion would be helpful.

Thanks,

Geoff.

Geoff - We were both running Flowmasters. He had two chamber 40, I had the three chamber 50. The sound all around was great, but the drone in his car would drive you bonkers. With 4.11 gears and doing 60mpg, you couldn't carry on a conversation and this was a stock body car with full interior. After he put the Aerochambers on, the car was very pleasant inside. It still had a drone, but it wasn't a full body experience like the FM40's. The sound outside was much more refined, that brassy, metallic Flowmaster rap was gone, replaced by a much smoother, throaty sound that turned into a deep, nasty sounding snarl at WOT.

 

[mudbilly]

Drone is GONE! 

​

Finally got these mounted right after the headers....... ::thumb::     Work like a charm. 

​

http://www.carchemistry.com/silencer-insert/​

 

[luxstang]

I checked your link at that sounds pretty impressive.

Might give it a try.

 

[Stanglover]

Yes interesting indeed. Something else to think about! I was leaning toward the Summit Racing mufflers that our Australian buddy was talking about in a previous post in this thread, too lazy to go look for his comment!, but they sound good, no drone he claims and cheap!! I like cheap as if they're no good, no big loss to change them.

Geoff.

 

[eddyw]

I find it expensive, 2 pieces $173 + shipping + import 21% + paperwork $15...

 

[mudbilly]

I find it expensive, 2 pieces $173 + shipping + import 21% + paperwork $15...

What size pipes do you have ? I bought a set to fit 2-1/4" OD pipes over a year ago. When i went to have them installed I learned that I have 2'" pipes and since it was so long ago they didn't want to take them back and I bought the correct size (which weren't even listed on their website and I had to call)

 

[eddyw]

I find it expensive, 2 pieces $173 + shipping + import 21% + paperwork $15...

What size pipes do you have ? I bought a set to fit 2-1/4" OD pipes over a year ago. When i went to have them installed I learned that I have 2'" pipes and since it was so long ago they didn't want to take them back and I bought the correct size (which weren't even listed on their website and I had to call)

Hi Mudbilly,

I use the brand pypes exhaust system 2.5" and the race pro mufflers in combination with Hedman hedders :

https://www.hedman.com/

http://pypesexhaust.com/c-946258-shop-by-vehicle-exhaust-systems.html

On the highway between 70 miles/hr - 80 miles/hr i have a drone sound.

I include pics from another member here for any idea.

Greetings from Belgium,

Eddy

 

[mudbilly]

I'm running Hedman shorties and have an "H" pipe instead of the "X" and a set of resonators between the H and the Mufflers.  I had the same problem with drone. The car chemistry device has cured it. I do have the 2-1/4" pair left over, ( it measures about 2-1/8 OD).  I don't think it will work with the 2-1/2 pipes you have.

 

[eddyw]

I'm running Hedman shorties and have an "H" pipe instead of the "X" and a set of resonators between the H and the Mufflers.  I had the same problem with drone. The car chemistry device has cured it. I do have the 2-1/4" pair left over, ( it measures about 2-1/8 OD).  I don't think it will work with the 2-1/2 pipes you have.

*Car chemistery : Eddy, thanks for inquiring. You would be looking at our 2.5". The fit into 2.5" pipe. They measure at 2 3/8".

Thanks again.

Ken

*Pypesexhaust recommend those mini catalytic converters:  (  CVM10K )

 

[mudbilly]

well, the CATs would also help with the environment, at 10 miles/gal I'm doing my share of polluting. But I have to imagine that these are expensive, at least late model standard CATs are.

I think that there are 2 things that got rid of the drone. The back pressure resulting from the baffle and the sound going through the baffle itself. The CATs may do both of those also.

I'm curious as to what you do and the results. I've spent a lot of time and $ working on this. ::thumb::

Now I can hear the wind noise going past the window/roof edge and all of the rattles in the car  ::shrug::. I can also hear the stereo   , I can't wait to build my Tweeter pods next.

 

[eddyw]

I have now email contact with :

http://www.carchemistry.com

I let you know what the best solution is.

 

[eddyw]

I have build in the new silencer inserts, what a difference... NO drone sound anymore and NO lost of engine power.

THANKS for this very good advice.

::thumb::

 

[Carolina_Mountain_Mustangs]

When I tore down the crashed 72 Vert couple weeks ago it had a Pypes 2.5 exhaust system and I guess Hedman ceramic coated headers. The part number on the headers starts with an H. The system had been welded but I got off in one piece. They had put on new two weeks before the crash. It is an X configuration. I forget which muffle it was. They had put about a 1/2" spacer between the floor and the plate that goes under the seat on a vert to clear the pipes.

Will use in the 72 Q build.

 

[Stanglover]

I have build in the new silencer inserts, what a difference... NO drone sound anymore and NO lost of engine power.

THANKS for this very good advice.

::thumb::

 This looks like another good solution. I'd like to know more about how and where they were built in. Any diagrams that are not copyrighted? I will contact the manufacturer as well, but would also like to hear from you.

This is definitely one the books for next spring, however, while the drone is bad between 2k and 2500rpm, I'd like to preserve the sound of my Flowmaster 40's which get lots of compliments. I actually had a guy email me to say how awesome my car sounded going past him the opposite way!!

Geoff.

 

[Stanglover]

When I tore down the crashed 72 Vert couple weeks ago it had a Pypes 2.5 exhaust system and I guess Hedman ceramic coated headers. The part number on the headers starts with an H. The system had been welded but I got off in one piece. They had put on new two weeks before the crash. It is an X configuration. I forget which muffle it was. They had put about a 1/2" spacer between the floor and the plate that goes under the seat on a vert to clear the pipes.

Will use in the 72 Q build.

 Nice score David. That will come in handy for sure.