Exhaust guru’s: restrictive x-pipe muffler?
Discussion
I’m looking for ways to quieten down my modified AMG and thought that a combined x-pipe muffler might do the trick. I purchased a Magnaflow, but on receiving it today it would seem that it merges both 3” exhausts by combining them into a single 3” pipe.
This is a turbo 5.5L so back pressure is not needed/wanted. I’m looking for as free flowing exhaust as possible.
Here is a pic:
Do you think this will restrict flow, or does an engine fire in such an order that the flows will merge rather than crash into each other? Further, as the pipes in the muffler are perforated, is the volume (as in size) of the pipe increased beyond what would be considered a restriction?
This is a turbo 5.5L so back pressure is not needed/wanted. I’m looking for as free flowing exhaust as possible.
Here is a pic:
Do you think this will restrict flow, or does an engine fire in such an order that the flows will merge rather than crash into each other? Further, as the pipes in the muffler are perforated, is the volume (as in size) of the pipe increased beyond what would be considered a restriction?
A cross pipe will always merge? hard to see if it really restricts down to 3" or is opened up a bit at the pinch point.
Anyway, I thought with cross plane cranked V8s the firing order is such that exhaust pulses alternate between banks, and thus in theory it could be 3" all the way back down from the cross pipe and not have a major effect.. but keeping the split in the exhaust allows the pulses to be 'halved' down the rearward section after the cross-pipe..
In real terms I massively doubt you will feel any power loss at all.. I wouldn't worry..
Anyway, I thought with cross plane cranked V8s the firing order is such that exhaust pulses alternate between banks, and thus in theory it could be 3" all the way back down from the cross pipe and not have a major effect.. but keeping the split in the exhaust allows the pulses to be 'halved' down the rearward section after the cross-pipe..
In real terms I massively doubt you will feel any power loss at all.. I wouldn't worry..
tejr said:
A cross pipe will always merge? hard to see if it really restricts down to 3" or is opened up a bit at the pinch point.
Anyway, I thought with cross plane cranked V8s the firing order is such that exhaust pulses alternate between banks, and thus in theory it could be 3" all the way back down from the cross pipe and not have a major effect.. but keeping the split in the exhaust allows the pulses to be 'halved' down the rearward section after the cross-pipe..
In real terms I massively doubt you will feel any power loss at all.. I wouldn't worry..
The pinch point isn’t really a pinch. The two pipes angle and narrow down into a single 3” pipe in the middle. All of the inside of the muffler is perforated, but if it were not it would be like pushing 6” of volume into 3” for about 12” length of tubing.Anyway, I thought with cross plane cranked V8s the firing order is such that exhaust pulses alternate between banks, and thus in theory it could be 3" all the way back down from the cross pipe and not have a major effect.. but keeping the split in the exhaust allows the pulses to be 'halved' down the rearward section after the cross-pipe..
In real terms I massively doubt you will feel any power loss at all.. I wouldn't worry..
If it were a traditional x-pipe with just two pipes pinched together it’ be more like 4-5” wide at the pinch point, but obviously with no perforation.
How much power are you making, that you believe it will be a problem ?
How much noise are you making, that an already turbocharged setup is making too much ? By nature, the turbos should already have killed a lot of noise.
What is the rest of the exhaust like, are there no other silencers ? Was there any form of X or balance in before ?
And you can be sure, if the silencer is mounted reasonably close to the front...all the material inside will burn away in a pretty short period of time, leaving a fairly open chamber with holes anyway.
I've had a few Magnaflows on my car over the years, and those closest to the engine always seem to lose the material inside quite quickly. Those at the rear seem to last a lot longer.
How much noise are you making, that an already turbocharged setup is making too much ? By nature, the turbos should already have killed a lot of noise.
What is the rest of the exhaust like, are there no other silencers ? Was there any form of X or balance in before ?
And you can be sure, if the silencer is mounted reasonably close to the front...all the material inside will burn away in a pretty short period of time, leaving a fairly open chamber with holes anyway.
I've had a few Magnaflows on my car over the years, and those closest to the engine always seem to lose the material inside quite quickly. Those at the rear seem to last a lot longer.
stevieturbo said:
How much power are you making, that you believe it will be a problem ?
How much noise are you making, that an already turbocharged setup is making too much ? By nature, the turbos should already have killed a lot of noise.
What is the rest of the exhaust like, are there no other silencers ? Was there any form of X or balance in before ?
And you can be sure, if the silencer is mounted reasonably close to the front...all the material inside will burn away in a pretty short period of time, leaving a fairly open chamber with holes anyway.
I've had a few Magnaflows on my car over the years, and those closest to the engine always seem to lose the material inside quite quickly. Those at the rear seem to last a lot longer.
750whpHow much noise are you making, that an already turbocharged setup is making too much ? By nature, the turbos should already have killed a lot of noise.
What is the rest of the exhaust like, are there no other silencers ? Was there any form of X or balance in before ?
And you can be sure, if the silencer is mounted reasonably close to the front...all the material inside will burn away in a pretty short period of time, leaving a fairly open chamber with holes anyway.
I've had a few Magnaflows on my car over the years, and those closest to the engine always seem to lose the material inside quite quickly. Those at the rear seem to last a lot longer.
Enough noise to make a whole street of strangers turn around in symphony when I go above 3k rpm. The turbos only mute the sound up to about 2k rpm.
Previously it had 2.75” pipe, two sets of cats, a very large muffler in the mid-pipe and a rear muffler.
Now it has 3” pipe and only the rear muffler. Everything else is gone.
I was planning on putting the MagnaFlow about half way down the mid-pipe (roughly where the original mid-muffler was)
Obviously an X-Pipe is supposed to help scavenge...by design. But some can neck down quite a bit and ultimately may become a restriction. Whether enough to worry about is another matter.
The one I had on my own car would have necked down to around 3.5" diameter from a pair of 3", TBH even at that it can easily do over 4 figures.
Although it did always bug me and I opened it up last year, not really had a chance to try it without breaking other stuff though.
TBH, I wouldnt even bother with the X, just go for a pair of pipes, as big silencers as you can fit and it'll be fine.
Maybe add in a balance pipe as opposed to X, but whichever is most convenient. But unless the X is fairly open it's going against what you probably want, so teh X could almost become like an X/H combined really.
I also bought one of these last year for a nosey, very cheap really. It does neck down again being an X, but it isnt too bad at all. Certainly good value if nothing else.
But it's still squeezing down full 3" pipes into a smaller area, then opening up again, but not as bad as some.
https://www.ebay.co.uk/itm/3-76mm-Exhaust-Stainles...
The one I had on my own car would have necked down to around 3.5" diameter from a pair of 3", TBH even at that it can easily do over 4 figures.
Although it did always bug me and I opened it up last year, not really had a chance to try it without breaking other stuff though.
TBH, I wouldnt even bother with the X, just go for a pair of pipes, as big silencers as you can fit and it'll be fine.
Maybe add in a balance pipe as opposed to X, but whichever is most convenient. But unless the X is fairly open it's going against what you probably want, so teh X could almost become like an X/H combined really.
I also bought one of these last year for a nosey, very cheap really. It does neck down again being an X, but it isnt too bad at all. Certainly good value if nothing else.
But it's still squeezing down full 3" pipes into a smaller area, then opening up again, but not as bad as some.
https://www.ebay.co.uk/itm/3-76mm-Exhaust-Stainles...
stevieturbo said:
Obviously an X-Pipe is supposed to help scavenge...by design. But some can neck down quite a bit and ultimately may become a restriction. Whether enough to worry about is another matter.
The one I had on my own car would have necked down to around 3.5" diameter from a pair of 3", TBH even at that it can easily do over 4 figures.
Although it did always bug me and I opened it up last year, not really had a chance to try it without breaking other stuff though.
TBH, I wouldnt even bother with the X, just go for a pair of pipes, as big silencers as you can fit and it'll be fine.
Maybe add in a balance pipe as opposed to X, but whichever is most convenient. But unless the X is fairly open it's going against what you probably want, so teh X could almost become like an X/H combined really.
I also bought one of these last year for a nosey, very cheap really. It does neck down again being an X, but it isnt too bad at all. Certainly good value if nothing else.
But it's still squeezing down full 3" pipes into a smaller area, then opening up again, but not as bad as some.
https://www.ebay.co.uk/itm/3-76mm-Exhaust-Stainles...
I think I'm gonna get back under the car tomorrow and see if I can fit a pair of these under the car somewhere:The one I had on my own car would have necked down to around 3.5" diameter from a pair of 3", TBH even at that it can easily do over 4 figures.
Although it did always bug me and I opened it up last year, not really had a chance to try it without breaking other stuff though.
TBH, I wouldnt even bother with the X, just go for a pair of pipes, as big silencers as you can fit and it'll be fine.
Maybe add in a balance pipe as opposed to X, but whichever is most convenient. But unless the X is fairly open it's going against what you probably want, so teh X could almost become like an X/H combined really.
I also bought one of these last year for a nosey, very cheap really. It does neck down again being an X, but it isnt too bad at all. Certainly good value if nothing else.
But it's still squeezing down full 3" pipes into a smaller area, then opening up again, but not as bad as some.
https://www.ebay.co.uk/itm/3-76mm-Exhaust-Stainles...
https://www.ebay.co.uk/itm/Magnaflow-14149-Race-Se...
If I can then maybe I'll have the exhaust guy weld in a H for me. I'm aiming to take the farty edge off my AMG exhaust note.
Magnaflow show this image on their site ? Although it looks different to what you have there. This looks like one of their basic X-pipes inside a silencer, so doesnt neck down that badly ?
I think it's Profusion Customs in the UK keep some Magnaflow stock. I'm sure I bought some from them and some from the US over the years
I think it's Profusion Customs in the UK keep some Magnaflow stock. I'm sure I bought some from them and some from the US over the years
stevieturbo said:
Magnaflow show this image on their site ? Although it looks different to what you have there. This looks like one of their basic X-pipes inside a silencer, so doesnt neck down that badly ?
I think it's Profusion Customs in the UK keep some Magnaflow stock. I'm sure I bought some from them and some from the US over the years
Thats a design I'd be happy with, but sadly the design of mine is very different. Here's another pic:I think it's Profusion Customs in the UK keep some Magnaflow stock. I'm sure I bought some from them and some from the US over the years
Resonators (absorbant-free, perforated wall straight-through boxes) take out the rasp/farty edge on any exhaust. With no loose absorbent to lose, these can be placed well upstream. manufacturers usu have them somewhere in the middle of the run to damp the pipe overtones from both ends. It's likely the cats you've removed were doing a lot of this work.
If you want quieter, you simply need the largest-volume rear boxes you can fit, as far back as you can. With resonators.
If you want quieter, you simply need the largest-volume rear boxes you can fit, as far back as you can. With resonators.
Huff said:
Resonators (absorbant-free, perforated wall straight-through boxes) take out the rasp/farty edge on any exhaust. With no loose absorbent to lose, these can be placed well upstream. manufacturers usu have them somewhere in the middle of the run to damp the pipe overtones from both ends. It's likely the cats you've removed were doing a lot of this work.
If you want quieter, you simply need the largest-volume rear boxes you can fit, as far back as you can. With resonators.
I've tested different boxes on my car....and straight through perforated tube were better and quietening things down than a chambered design ( both Magnaflow )If you want quieter, you simply need the largest-volume rear boxes you can fit, as far back as you can. With resonators.
Although as said, from a longevity point of view, a chambered silencer will probably do the same job for it's entire life.
The straight through types with absorbent material will eventually lose the material and effectively become a perforated tube inside an open chamber anyway. But when they work, IMO they do quieten better, at least from testing on my own car.
But yes...as large as you can, and further back generally helps. But if there are room for some up front, than that will help too.
One important point about acoustics in general. Density is king in quietening sound waves. So look for a thicker gauge metal on muffler construction, a thicker matting or wool packing, a thicker gauge straight through pipe etc.
You'll notice a lot of the aftermarket performance brand names are significantly lighter than the oem type ones.
Lighter isn't always better in this case.
You'll notice a lot of the aftermarket performance brand names are significantly lighter than the oem type ones.
Lighter isn't always better in this case.
TarmacRV8 said:
One important point about acoustics in general. Density is king in quietening sound waves. So look for a thicker gauge metal on muffler construction, a thicker matting or wool packing, a thicker gauge straight through pipe etc.
You'll notice a lot of the aftermarket performance brand names are significantly lighter than the oem type ones.
Lighter isn't always better in this case.
+1; Good point, well made. You'll notice a lot of the aftermarket performance brand names are significantly lighter than the oem type ones.
Lighter isn't always better in this case.
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