V8 conversion exhaust question, over or under? Options

[ringerdc]

What are the "pros and cons" of routing the exhaust pipes over or under the axles in a V8 setup? I see that most V8 conversions choose the "over" configuration using an "s" pipe. However, the "under" route is more of a straight path. In both the 4 and 6 factory setups the pipes are routed under the axle as well. Hmmmm..

Inquiring minds want to know

[Maltese Falcon]

Here is my old setup. Over the axle.

Try to keep Square Joints out of the equation (like at these muffler discharges) Realizing space requirements and sharp turns , square bends =power loss, almost like Press-bending Vs. Mandrel bending.
If your muffler shop is building a system for you and does not understand exhaust flow, nor have tight radius bends, I'll be happy to send you some random mandrel bends no cost (you pay shipping). I usually recycle remnants every week, but available if on hand (IMG:style_emoticons/default/welder.gif)
Marty

[andys]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

[Bruce Hinds]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

Andys - what kind of gearbox is that?

[andys]

Andys - what kind of gearbox is that?

Audi 01E 6 speed.

Andys

[Mike Bellis]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

Awesome craftsmanship! (IMG:style_emoticons/default/wub.gif)

[speed metal army]

I went over.

[bulitt]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

Fmasters= drone city.

[andys]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

Fmasters= drone city.

It only drones in about a 200RPM range, so I wouldn't categorize that as "drone city." I can easily drive around it. Any pieced together exhaust has the likelihood for droning, but it can be cancelled out. Production car systems are engineered and developed and tested to avoid/cancel drone. Much of the time, they can design chambers within the muffler that can cancel the drone of a specific engine configuration; one size does not fit all! In my case, knowing the RPM range of the drone, I can now configure a 1/4 wave drone cancelling chamber. To help soften the exhaust note, I can also cut the exhaust tips at an angle, but I don't think I'd like the look in my particular case.

Andys

[messix]

I was just thinking [I know... dangerous] an easy way to build a "anti-drone" exhaust, use 2 1 in 2 out mufflers like these http://www.summitracing.com/parts/mpe-1328...CFVJhfgod6RkAoQ and use one of the outlets on each to use as a cross over where the stock muffler would be.

I would draw up a picture but crayons don't upload

[mgp4591]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

I really like this setup- compact and well done. Do you have any sideshots of this or is it in a link for your build? (IMG:style_emoticons/default/smilie_pokal.gif)

[rick 918-S]

Under, tuck them in slightly as they pass the axle to clear the axle swing path. Never had an issue with the ground in 10's of thousands of miles. I installed a balance pipe between the mufflers just above the exhaust outlet. Simple. (IMG:style_emoticons/default/assimilate.gif)

[v82go]

I too went under on both of mine (one sbc and a LS6),
On my first one I tried the dual flowmasters and grew
tired of the drone, after building 3 or 4 more exhaust
systems, I ended up with a good sounding Porsche GT3
muffler (ebay), not too loud and no drone.

On my LS I have 2 Corvette C5 mufflers, I gutted and
shortened and tied together. These have 2 hidden outlets
and a exposed center outlet. No drone, but rather loud
and rowdy sounding. I have had no issues by going
under the axles.

[Amenson]

How dare you not include a sound clip!
(IMG:style_emoticons/default/smile.gif)

I agree, we must have a sound clip!

Cheers,
Scott

[bulitt]

I went over the axles for most of the reasons many have already stated. Notice the heat shielding. The muffler shields are available from Flowmaster. I get a drone at 2000RPM. Perhaps the next time I drop the motor/trans, I may add Helmholtz chambers to cancel out the drone. Granted a cross-over would reduce some of the noise, but a lack of a tidy solution will probably keep me from doing it. BTW, those Flowmaster's are three chambered, and according to the literature, they greatly reduce interior noise.

Andys

Fmasters= drone city.

It only drones in about a 200RPM range, so I wouldn't categorize that as "drone city." I can easily drive around it. Any pieced together exhaust has the likelihood for droning, but it can be cancelled out. Production car systems are engineered and developed and tested to avoid/cancel drone. Much of the time, they can design chambers within the muffler that can cancel the drone of a specific engine configuration; one size does not fit all! In my case, knowing the RPM range of the drone, I can now configure a 1/4 wave drone cancelling chamber. To help soften the exhaust note, I can also cut the exhaust tips at an angle, but I don't think I'd like the look in my particular case.

Andys

Had them on a pickup. It was unbearable.

[andys]

[quote name='mgp4591' date='Jan 17 2015, 08:53 PM' post='2135435']


Andys
[/quote]
I really like this setup- compact and well done. Do you have any sideshots of this or is it in a link for your build? (IMG:style_emoticons/default/smilie_pokal.gif)
[/quote]

Here's a link to my retrospective build thread. If you don't see what you're looking for, let me know.
http://www.914world.com/bbs2/index.php?sho...4625&hl=ls1 retrospective

Andys

[BIGKAT_83]

I'm running Magnaflow glasspacks under the axle and have no problem with drone. These are great mufflers I had them on a new mustang and when I sold the car I replaced them with the stock mufflers. I think the stock ones were louder

I tried some Flowmasters 40's Used them for less than 1 mile. Way to loud.


Bob (IMG:style_emoticons/default/shades.gif)

[speed metal army]

I'm running Magnaflow glasspacks under the axle and have no problem with drone. These are great mufflers I had them on a new mustang and when I sold the car I replaced them with the stock mufflers. I think the stock ones were louder

I tried some Flowmasters 40's Used them for less than 1 mile. Way to loud.


Bob (IMG:style_emoticons/default/shades.gif)

+1 on Magnaflow. Best sounding, least drone.

[andys]

I'm running Magnaflow glasspacks under the axle and have no problem with drone. These are great mufflers I had them on a new mustang and when I sold the car I replaced them with the stock mufflers. I think the stock ones were louder

I tried some Flowmasters 40's Used them for less than 1 mile. Way to loud.


Bob (IMG:style_emoticons/default/shades.gif)

Bob,

Mine are Flowmaster 50's. According to their literature (interior/exterior db charts), they're a lot quieter than the 40's. Just FYI.

Andys

[BIGKAT_83]

I kinda figured yours were 50's they look a little longer.


Bob