Exhaust system with no drone

[robomatic12]

What exhaust systems are you guys running with little or no drone? The drone is the awful vibrating noise when you are cruising on the highway at about 2k rpms.

I've got quite bad drone, but I'm not sure of any of the manufacturers of the stuff as it was all on the car when I got it.
Currently:

Stock JDM downpipes (different design to USDM, no precat)
2.5" testpipes with resonators where cats would be
2.5" h pipe with ebay resonators I welded in
3" kakimoto catback with large single tips out back

[DCaff300ZX]

Far as I know this is the result of our free-flowing exhausts, although I would also enjoy a reduction in that area if it exists...

[Z-owned]

stock exhaust is always an option 2+0's have more options than the 2+2 greddy sp2's jwt genie (hard to find) are two of the quiter ones but those don't help the 2+2

[elninoloco7]

There is actualy a write up on 3ZC on how to cancel out your Drone in single Tipped Exhausts. I am definitely doing this mod when my car is up and running.

THIS WRITE UP WAS DONE BY "CHRIS" 3ZC user name : "Greavous"
After installing my catback exhaust last week I pleased with the whole deal except the noise it made at low rpm launch and coming of a light throtle and giving it some gas. Im talking about that low range obnoxious drone sound. Well, I posted about that and the options were get something else or add silencers in the ends. Silencers were what I was after, but all the ones listed were for name brands like Greddy and Borla... no listings for eBay catback, go wonder. LOL!

If you have a name brand exhaust yet dont like the drone have a look here for a silencer that might fit your application http://www.autocarparts.com/parts/Exhaust/Silencers/

I stumbled upon the info that the maker for the ebay exhaust was TopSpeed in Dallas. They make a silencer for the system for 27 bucks each. If you want some of their silencers here is their site http://www.topspeedauto.com/ProductC...gory=27&page=3


If they had some on-hand when I called I'd bought 2 of them and never stumbled onto what im fixin to get to...

If you want to kill the obnoxious drone...and retain a very HEALTHY rumble read on.

You will need:
-One hour of time
-hacksaw
-Drill and sharp 1/16" and 3/32" drill bits
-2- 1/8" x 3/4" long bolts & 4 nuts
-one 18" long exhaust pipe section from parts store (i used the 2 1/4" od stock, measure your pipe ID before you head to the store)
-tape measure and pencil
-some sand paper maybe (I used 220 grit)

This is the system im working with off ebay for about 400 bucks, I had removed the mufflers from the resonators to do this project on my work bench rather than on my back. This can be done while the exhaust is on the car although the fastening bolt will have to be relocated to a location where you can access with a drill under the car.


I went to autozone to measure me some pipe. Seems all autoparts stores have a small collection of pipe and fittings to size up. I only actually used 8 inches off a 18" long section that cost about $4 and tax. I used some dial calipers to measure the ID (inside diameter) of the tubing at the location that the Big tip is welded to the muffler. In this case it was 2.223 inches. I went to autozone and using my calipers checked the short lengths of tubing the had on hand. The 2 1/4 was 2.224 inches so even though it was a tad large (0.001) when you are dealing with diameters that is only really 0.0005 inches interference and some sandpaper will take care of that.

Back at home, I then checked it for fit into the tip if the muffler and it was tight. So i lightly sanded the outside and beveled the edge where i just sawed it into lengths. It was then a nice snug fit. (Doing a write up hadnt occured to me yet so no pics here .

I cut my tubing into 4 inch long lengths as seen here using a lazymans tool. A hacksaw will do fine.


Then used an exhaust pipe flaring tool to make a slight flare on one end. The idea was to make it extra tight when i drove the 4 inch section into the muffler opening. This might have been needless but I didnt want any rattles or buzzing going on. My guess is some plyer action along the edges would render the same results. Just flaired it out a tad.


Once I drove the piece into the muffler (no pics and needs 2 hands and a bench vice or a buddy to hold) using a leftover piece of tubing as a drift and rubber mallot. I then center punched and drilled a 1/16" pilot hole and then a 3/32" hole at the top of the tip just before where the insert and tip entered the muffler.

Drilling stainless steel takes a pilot hole and a SLOW drill speed. If you try to drill the hole at full blast you will screw the drill bit well beyond what the word "dull" describes. Drill will consistant moderate pressure and slow twist speed and it aint no thing...And wear some safety glasses, damn it.

Then I passed a stainless bolt and double-nutted it in place to hold the insert in place.


Once installed it was the moment of truth... Fan-damn-tastic!!! The obnoxious drone is totally gone however it is nowhere near silent! There is the perfect raunchy rumble the car should produce, it sits there and makes a proper V engine alternating idle sound too. On the road its very pleasant at all speeds. Under load it gets just roars and blast off with plenty of a too-doo and excitement. As you see, you cant really see them either, and as far as backpressure phobia goes, yes there is some added pressure. That extra only happens at the very end of the exhaust pulse and with this little restriction the gasses are then forced into the muffler a little more.


I strongly recommend this 4 dollar wonder cure to kill the drone.

ORIGINAL POST LINK >> http://www.300zxclub.com/showthread.php?t=89818

[robomatic12]

Great find, thanks! Ive read it a couple times and from the looks of it the pipe he adds extends back into the muffler so isn't as easy for the exhaust to escape?

[DCaff300ZX]

Hmmmmm...not sure I'm too thrilled with the science of that mod...

[Z-owned]

Hmmmmm...not sure I'm too thrilled with the science of that mod...

It's why I didn't post it, seems that back pressure would be created.

[elninoloco7]

well...its not that long its probably half way of the muffler section it self...i have already tried it out...and it works wonderfully i just haven't screwed it on...(i need a better drill to drill through my stainless steel muffler. Here is another picture he had posted up there..the longer it is the more silent it get...and the pipe you insert in shouldnt be that thick, so it should't restrict air flow that much, or at least i would think. Just buy a pipe from autozone (my pipe was 2.50 so i had to buy a 2.25)...and rent out that pipe extender thing Chris used, to get a tight fit. Autozone, Advance auto parts, have those things you can rent it for free for 2 days

[robomatic12]

I wouldn't be able to use that idea I don't think because of the way my muffler is designed differently. The 5.25" tip goes right into the muffler main body, it does not step down before.



The red is the silencer's I do have for the exhaust but they choke the outlet down to 1.5" which seems very restrictive to me.

What I'm wondering is how much of a difference have you guys noticed between testpipes and the oem cat converter pipes? I'm wondering if I should swap back to those if it makes the drone any better.

[Z-owned]

Cats will help quite the drone yes, will it be gone no.

[robomatic12]

Im trying to weight the options in terms of noise decrease vs power decrease.

1) Factory fitted exhaust silencers 5.25" --> 1.5" outlet at the muffler

2) Custom silencers I'll have to make 5.25" ---> 3"/2.5" outlet at the muffler

3) Reinstall oem cat pipes

4) Buy a quieter catback system, saw a Labree 2.5" for about $600 new