Exhaust drone...resonator help

Between the bottom of the firewall to just forward of the rear tire, under the car, is the X member of the frame, made of 6" I beams.
This forms two right angle triangles on each side of the car. The hypotnus (46") of each triangle is the X member, the long leg of each (42") is the side of the car, the short leg is 19".

The mufflers are outlet to inlet in this triangle area, two mufflers per bank of cylinders. That is a 27" case+6" connector+a 34" case into TP.

A resonator box (900+ ci) fits forward of the firewall and X member per bank.

 

inMOtion, I'd say, if you can clamp it, you can try anything. We've done testing with those kinds of things forward, reversed, etc. You can only try it and see what you like.

Jon,

I don't have any experience with the spirals. Sorry, I'll see if I can find someone at GM tomorrow. I've got to run up for a meeting and I'll be next to the exhaust guys. Most of them are racers of some sort anyway!

 

Not having first hand experience, the lore is to paint the pipe from the collector back, lightly, then go for a ride. The paint will burn off at the first resonant point and that is the most efficient place to put an H or crossover. With your frame limitations, I dunno what you'd do.

H and X pipes can make a _dramatic_ difference in a motor. C5 Corvettes (which is what I'm most familiar with) have a 'motorboat' gargling idle with their m*** produced (sloppy) H pipes. Changing them out for a better crossover REALLY improves the exhaust note.

 

Anybody else have any experience with Moroso spiral mufflers? Not the auger inserts, but somewhat of the same design.

Wondering how they stack up against an elcheapo burned out gl***pack.

 

RocketSled ... I hear ya on the crossover placement location ! I'll try the burnt paint trick .. read of it before. Thanks

Danimal ... I have just realized the case volumes I have computed are wrong. The case shapes are oval not rectangle in shape. A volume reduction of 11-12 % on the Magnaflows, 10% lower on the DynoMax (end of case shape differences).

I acknowledge your concern of using 3" pipe straight through mufflers as the drone frequencies will remain. Would the drone remain if two 3" three chamber mufflers per side were fitted, then into a 2.5" TP ?

 

Whenever you change a diameter, you'll change what dominates. The smaller you go, the higher it will sound. I'd see what you've got to start with, it should flow pretty well. Then play with TPs to see what happens.

One thing for Jonny O is to make sure you blend your pipes well in that H. With the flow you have, you've got to make sure you don't have anything sticking into the primary flow that can cause a whistle. Not a mega deal destroyer or anything, just something that I have heard happen before. That is why many of the mufflers talk of what great perforations they have rather than louver patches. The louvers stay in the flow and CAN (not always) introduce the possiblity of a whistle.

 

With an X? Going from an H (old system) to an X. The piece I have is a Summit label. Weld joins the two pipes at the apex of a 45. Not exactly as smooth as I would like it, should I look into a real smooth opening between the two pipes in a X or were you speaking of the H pipes sticking into the collector pipe too far?

Thanks man.

 

Thanks Danimal for your help with this system planning. Eng/trans mock up in the ch***is start tomarrow. I'll keep you posted on the process and end result .

 

After getting engine/trans located and mounts made (4" back & 2" down) the three header styles were tried, only the block hugger will fit. The difference in the primary lengths suggest a dual pattern cam unless a crossover pipe at 19" after the collector flange can be fitted.

Wednesday I will reinstall the mock up engine/trans with pans to see if this is possible. 3" pipe out of the flange may dictate a front sump pan to allow this pipe to cross.

 

How in the HECK do you guys know this kind of stuff. I am amazed every time I get on the board.

 

Can I get some exhaust advice?

I have a 1960 F-100 with a stock 390 and iron exhaust manifolds.

I want a bit of a "racy" sound with a nice deep growl on the gas, and a slightly rumbly idle.

I was thinking about 2 1/4 or 2 1/2 going to Thrush DYNOMAX ULTRA FLO WELDED MUFFLERS and fairly short pipes turned down, coming out at an angle in front of the front wheels.

Whaddya think?

 

I am puzzled as to why you want to locate the exhaust in front of the front wheels on a RWD vehicle.

 

I think most trucks look way too redneck having pipes straight out the back, and there's not enough room to have them turn out the sides.

 

I would think the noise and fumes would be a problem up front.

Some cast iron manifolds can be swapped side for side making the exit at the front, which would be a help in your arrangement.

I have seen exhaust exits in front of the rear wheels .

 

HELP!! new here and this is a great discussion...Ok, a question, I have a serious drone issue with an old corvair, 6 cylinder. I have straight pipes and cats. The pipes exit about 16 inches from the cats out the back. 2.5 inch pipes. Between 2000 and 2800 rpm I get a horrible drone. I was told that a closed end resonator off each pipe would kill the drone, but what length must it be and where do I mount it. I know that these pipes are acting like an organ pipe and resonating, and they are short, so I am thinking that putting the resonator near the end would work best, but what length must it be??

I have converted this vehicle into an open wheel front end sort of like the dodge prowler, but the rear remains the same for now, the eventual plan is to make it open wheel all around. It looks terrible right now, hence my nickname Jasloppy, but it should be real nice when I am finished.

 

I would fit the largest case volume resonator as the space available will allow ..

 

Ok, I know this is an old thread, but was doing a google search and this one came up.

So I just had my exhaust done yesterday on my car and now have a drone that is unbearable at cruising speeds. I have a 350 with a thumper cam in it. Dual exhaust with some gl*** pack style mufflers. I had some new tailpipes put on from the mufflers back. The previous setup went under the axle and would drag the ground if I was cruising to low and would rest on the ground when it was laid out, so it had to go. The pipes were all the way out the back, hung pretty loose and didn't have much of a droan at all. I had them do some creative routing of the pipes to go over the axle and dump out under the trunk high enough and as far back as we could get it where it can't be seen at all. We also added an H-pipe as far forward as we could which is just after the tailshaft of the transmission and the mufflers are not to far from that point. maybe 10" or so. There are 6 hangers on the exhaust I think. They are all rubber mounted, but some are pretty tight.

I don't know what speed or RPM the drone comes in at, but it is at lower rpm cruising and is bad enough that you don't even want to try and have a conversation with the other person in the car because you are yelling at them.

Would loosening the hangers a little to let it move more help with the drone? Would it help the drone if I have them put the tips all the way straight out the back?

I called the shop and they said to bring it in and they would see what all they could do, but they are open 8-5 m-f which is when I work, so its hard to get in there. Figured I would get some information for ammo or see if there is anything that I can try at home to remedy the situation.

Thanks for any help.

Chad

 

I am ***uming : the 'car' is the 50 Ford Custom, the only part of the exhaust system changed is tail pipes and hangers + H pipe .

With rubber mounted hangers I don't think the fact that they are snugged up tightly is contributing to your drone.

The H pipe, for best result, should be located as near the end of the collector as possible and before the mufflers. Its diameter should be the same as the pipe it connects with, should not fit inside the exhaust pipe . (the H pipe acts as a pressure equalizer and sound frequency attenuator , does not primarily cross flow exhaust gas, does not have to be a straight H ..can be l~l for fitment purposes. If the H pipe dia. is less than 90% of the dia. of the exhaust pipe it connects with its effectiveness is reduced.

The first thing I would try is to extend the tail pipe fully to the rear, use an end piece made from a 90* bend which is cut off parallel with the ground, at the same plane as the lower edge of the tail pipe dia.. it turns down but doesn't extend down .. when installing this 'tip' rotate it so the exhaust (and the sound pressure) is directed outward and does not bounce back up into the floor/trunk pan causing them to vibrate like a drum (the p***enger interior = the inside of the drum).

This drone problem is often difficult to isolate. In this thread, posted earlier here, is a very knowledgeable contributer, Danimal, an OEM industry professional on exhaust systems design and packaging. I have read everything of his I can find by using the search function and looking for anything he has posted on this site. I do the same thing on other forums using key words such as exhaust drone, resonance, etc.

I hope this is of some help ..

Miles
.

 

Yeah, after talking directly with danimal I mocked up some exhaust pipes that went all the way out to the bumper and that solved 90% of the drone. I figure the rest of the drone I will have to live with till I get some actual mufflers instead of gl***packs.

As for using the search, I did the same thing. How do you think I came up with a thread from 2008. But even after reading what I had I still figured it doesn't hurt to ask the question to see if there are any other pointers from anyone else.

Later,
Chad

 

That is actually the way the brits did it. Muffler first then resonator right in the rear.

What you may try prior to going after resonators is just moving the mufflers to right in front of the axle give your tail pipes a chance to do their job. I know that you have ground clearance constraints but if you are going to put a resonator there anyway you are still going to have ground clearance constraints.

 

Hey Chad,
Thanks for reply and posting your results. There is one gl*** pack manufacturer, Jones Exhaust in Tennessee ...
http://http://www.jone***haust.com/ ... that makes a 40" case length muffler in 3", 3.5", 4", 5" body diameters. 2"-3.5" interior sizes, with and without end pipes. Available through Summit. Very reasonable pricing. I mention this as I am going to try using two different case /core sizes per side plus a resonator at the rear . I am dealing with 496ci, 11.8cr engine. Should this fail then I will go to Magnaflow XL series 3 chamber muffler.

Miles