New true dual exhaust - now what is resonating so bad?


Sevensecondsuv

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Hi all:

**LEGAL: The subject truck is used off-road only and is therefore emissions exempt**

I just finished putting true duals on my '92 explorer. I cut the factory Y-pipe apart and added some bends to it to get dual 2-1/4" pipes running right next to each other along the passenger side of the transmission. They run about 4 feet and then end in a 2-1/4" X-pipe. From there, dual 2-1/4" pipes run over the axle and in to dual thrush welded (knock-off Flowmaster 40) mufflers. The mufflers have turn downs half cocked to each side.

Anyways, at idle, it sounds great, with a very deep, pulsating rumble. From about 3000 RPM to redline, it once again sounds awesome, pretty much the best sounding six I've ever heard. My complaint is 1500-3000 RPM, where something starts resonating terribly. It's resonating so bad that it sounds like one of the pipes is rattling on the frame of the truck. I've checked and double checked all clearances and have at least 3/4" everywhere, so it's not rubbing.

Anyone have any suggestions? I'm thinking maybe I should put some glass packs in the 4' section before the X-pipe...
 
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Surrey

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Ahhhhhh, I love how emissions exempt means the environment doesn't matter anymore...

If you are going to put something on there, I would do some universal cats over glasspacks.
 

BlueChariot

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A cow does many times the environmental damage of a car's exhaust, so could we not split hairs over emmissions?
 

Sevensecondsuv

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Ahhhhhh, I love how emissions exempt means the environment doesn't matter anymore...
Your 2.9L breathing through cats has worse emissions than a 4.0L without cats - it's a proven fact (and also why 4.0L's didn't even have EGR for the first couple years). If you care that much, you should consider driving something newer and cleaner.
 

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May be because the exhuast exits under the passenger compartment of the truck?

May also be a V6 being a V6? My 2.8 used to like to drone a lot with a louder exhaust, kinda made me decide the best sounding V6 is one you can barely hear (in my case to know if it was still running) With just a glasspack it sounded neat at idle, and at higher RPM, but really just noisy with no definition between, it had pipe running out behind the rear passenger side tire. That setup didn't stick around too long... my solution was more muffler.
 
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RangerFabWorks

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just extend the pipes out a lttle further. dumps resonate the exhaust under the truck. running the pipe all the way out will eliminate this.

and will sound better.
 

bobbywalter

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or run two different size mufflers. or add resonators

i assume you have 20 psi of boost with that exhaust system on that 450 hp engine so i can see where its a mystery as to why it resonates. it seems the turbo should quiet it a little through those echo chambers.:icon_confused:


err...:icon_confused:
 

177CIOfPureLove

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Your 2.9L breathing through cats has worse emissions than a 4.0L without cats - it's a proven fact (and also why 4.0L's didn't even have EGR for the first couple years). If you care that much, you should consider driving something newer and cleaner.
I am not going to disagree with your statement, Although something I found really shocking was when my 2.9 passed state emissions with fully hollowed out converters. I had just swapped it in my truck, it had 127,000 miles and I had done a full tune up on it as I swapped it in. I had ordered new cats but had not gotten them yet, just wanted to bring it up so it would fail, and drive around on my rejected sticker until they were installed. You would not believe the surprise I had when the guy scraped my old sticker off and put a new one on. I had passed with flying colors. 1988's don't even have EGR valves! I had to take all that stuff off of the motor (a 1986) before I put it in!
 

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just extend the pipes out a lttle further. dumps resonate the exhaust under the truck. running the pipe all the way out will eliminate this.

and will sound better.
This.
 

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I figured this kind of fit with his question so i thought i should ask it for both of us lol... How much will running it out the back effect the sound? Will it lose/add some rumble or anything?

Many people on here say they like the turndowns and i was considering doing that when i do my exhaust. But if it is pretty mucht he same thing without so much drone-ing, i wont lol.
 

cammeddrz

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a friend of mine cut his cat out on his 4.0 bII, he then straight piped it to his muffler. he also complains of a "resonation".......
 

Sevensecondsuv

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I too suspected the turn downs. I just tried fitting some 18" long pieces of pipe on the ends of the turn downs. It did help kill the resonating quite a bit, although it's not quite as deep any more. Looks like I'm going to have to think of a way to fit some more tail pipe in. The problem is that the mufflers are currently occupying the space that the spare tire used to. I can cut and rotate the turn downs and add the 18" pieces of the pipe to them pointed out the side, but that's about it. Right now the turn downs end about 2" from the back of the bumper...

For anyone thinking of going with a loud exhaust on a 4.0L, I have the following advice:
1) A 4.0L has enough displacement, the correct firing order, and a 60° design; all of this combines to create enough depth and definition in the exhaust pulses that it sounds good at all RPMs with a loud exhaust. Many V6's (especially the smaller ones) sound like crap with a loud exhaust, the 4.0L doesn't. It's not exactly the classic V8 pulsating roar, but a sound that is a little different yet equally pleasing to the ear.
2) I do not recommend a loud exhaust on something that gets driven regularly. Loud exhaust is great fun when you're in the mood for it (as with my off road toy Explorer), but gets annoying fast when you're just trying to get from A to B.
 
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bobbywalter

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i love the 4.0.




one dislike of wheeling with rbv's.....loud 4.0's or any stock rbv engine



4.0 or 2.8....never seen a big difference in range of sound. when i run into the ones that sound good, its still relative. cause mine would be quiet if i were to own one..


best sounding ford v6 i have ever heard are the current ones in the 150/stang.:dunno: its all opinion with these types of subjects. i know guys that hate v8's, especially american v8 noise. almost feel bad for the poor closet bastards.:D



i was serious about two sized mufflers.

order stock mufflers for a fox anything v8.
 


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