well, I finally installed my true dual. Took the cats off, custom 3" mandrel bent pipes, X-pipe, and two custom 21inch mufflers, dumped.

I got some pictures here:
https://www.performancetrucks.net/fo...8/#post4886511

With the previous exhaust I had absolutely no drone, but with this one DAMN it drones at idle as well lol

So im looking for a fix. Went through the how to eliminate drone thread and pulled out as much info as I can from that thread and came up with this. I will put a vacuum valve - hooked directly to the intake manifold, on ONE side of the exhaust, right after the muffler. This way the x-pipe will direct all of the exhaust flow out of one tip, which "should" quite it down, but the interesting part is the pipe with the vacuum valve on will act as my "resonator tube" so it should theoretically kill alot of the drone.

Now the only problem is, if I place the valve BEFORE the muffler it will be too short of a resonator tube, and after the muffler might be too long, but id rather place it after the muffler because I have alot of drone everywhere, basically I most concerned with drone which spans from idle to 2000rpms, so I will target it right at the center or about 1400rpms.

What do you guys think? How much will the exhaust quite down just by blocking off one side of the exhaust during cruise? The vacuum valve will kick in instantaneously at 0 boost or more.

 

ahaa....

 

I dont think it will work, but feel free to give it a shot....can you be more specific about the valve you are using?

Having the mufflers dumped is not helping your drone...

 

why dont you think, it makes perfect sense, block one pipe with a vacuum valve, all the exhaust will be routed out one pipe, and the pipe with the valve will act as my resonator tube. I will place the valve xx inches away from the x-pipe to tune my resonator tube for the lengh I want.

It will make much more sense if I draw it.

 

Seach for Helmholtz drone fix, on various forums. camaro 5 forum has a good read on it, and I think i've seen it on tech too. Are just trying to get rid of the drone, or quiet the exhaust down too?

 

Not sure how a resonator tube will respond to being inline versus perpendicular like they usually are. Is that valve 100% open with zero pressure applied to it (normally open) and closes with vacuum, or is it normally closed and opens with application of boost? If its the former then your "resanator tube" will never be fully sealed which will drasticly reduce its effectiveness except at deep vacuum, like decel, when you dont have drone anyway.

If its the later, running a blown 427 through a single 3" exhaust any time its not boost is still very restrictive...

 

Something like this.

 

true, its a valve that is normally open and will shut with vacuum during idle and partial throttle cruise. It will crack open even BEFORE it reaches zero vacuum, I think a 3" exhaust will be fine for idle and partial throttle, I was living with an exhaust that necks down to 2.75" at the y-pipe and has two "high flow" cats.

On the other hand if you look at the x-pipe picture I have in my build thread, the resonator tube will be perpendicular to the exhaust flow

 

I'd say cap off one of the mufflers temporarily to see if the idea gets rid of the drone. If so then buy the valve.

 

this is what im doing, with a twist