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Discussion Starter #1 (Edited)
The idea came to me after researching Subaru flat 4's and what gave them their distinctive lope compared to conventional inline 4 motors, I discovered that was due to their unequal length headers. On a Subaru, Cylinder's 1 & 2 have shorter pipes than on Cylinder's 3 & 4, from my observations, cylinder's 1 & 2's pipes are roughly half as long as the ones on the opposing bank. The longer pipes cause a delay because the sound pulses have to travel further, however, the delay isn't long enough to sound like a v8, I reckon that if the pipes were four times as long as the short pipes, it would simulate the sound of a single bank of a v8 engine.
The only drawback would be heavily unequal exhaust pressure that could seriously weaken the longevity of the motor, but perhaps a larger diamater piping for the longer pipes would solve this potential issue.

It would be so simple to accomplish, you would simply need to collect cylinder's 1 & 2 together, have it going down wards, and have Cylinder's 3 & 4 collect into a really long pipe that travels behind and around the engine and merge with Cylinder's 1 & 2 like this

obsolete method


mew method


you don't actually need 8 cylinders to reproduce the distinctive v8 sound, you just need the pulses to fire in 90-45-90-135 degree sequences. On a subaru, though the firing order is 90-90-90-90, due to the unequal length of the pipes it sounds like it fires at 90-68-90-112, however if you double the length of the long pipes, you double the delay time, and it would most definitely bring you in or around the range of 90-45-90-135 degree rotational pulses. I've tried these angles on a wooden dowel with screws powered by a drill hitting a jug and re-produced each sound almost exactly.



I would like you all to hear this for yourself, Listen to the progression from Equal length pipes, to unequal length pipes, to a conventional 350 with a single open header.

Equal Length Pipes on a Subaru sound

Unequal Length pipes on a subaru sound

350 v8 single bank open header
 

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Although the thought process is admirable and I don't want to scoff....no. Subaru is horizontally opposed and an inline 4 is, well, inline. A V4 is still a 4 cylinder yet sounds different from the other 4 cylinder engine configurations. If you want v8 sound, record some v8 sounds and play them on your car stereo.
 

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Discussion Starter #3 (Edited)
Engine configuration plays no role in the way an engine sounds, a piston releasing air the same regardless of whether its vertical or horizontal, firing order is what determines the sound's harmonic value. A Horizontally opposed flat 4 with equal length headers sounds like any conventional inline 4 cylinder engine because the pulses travel an equal distance through each pipe, when you hear the "Boxer sound" as people put it, it's directly due to unequal length pipes, a quick search of google is all you need to validate that point, furthermore I've taken the time to record rotation angle pulses (as shown in the diagram) As for the v4, it doesn't sound any different than an air-cooled flat 4? Why? Because both used true dual exhausts which means you only had two 90 degree pulses per bank [Right bank 90-90-_-_] while on the other bank you'll hear [_-_-90-90] .

These are recordings of a dowel with four screws (and the corresponding angles below) that is being spun by drill, unfortunately due to lack of power the drill wont turn any faster than about 1,200rpm. These numbers represent pulses generated by each motor
90-45-90-135 (A single bank of a v8 engine)
90-90-90-90 (An inline 4 cylinder or a flat 4 with equal length pipes)
90-68-90-112 (The boxer sound generated by unequal length pipes, or stock subaru headers.

The issue here is not whether or not my system can produce a v8 sound, it would be impossible not to, the issue has more to do with unequal back pressures leading to engine destruction, and the length of pipe needed to offset the sound.
If you're still skeptical, please, listen to this acura, it has unequal length pipes and sounds exactly like a horizontally opposed flat 4.
 

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I've always been a Toyota fan and that is what I've mainly owned the last 15 years. I did by my first Subaru for a winter car, and once I heard the UEL header sound I had to have it. So I just installed a UEL header on the 2.5L in the Subaru. I like the unique sound it produces, kind of the lobing sound a V8 makes, but not quite, mixed with the 4 cycliner sound.

I have to laugh because I was thinking the same thing you were!!! I like the Boxer sound so much how can I get that on an inline 4 cylinder. I thought the same thing you did, well make a custom header with the same phase timing as the Subaru header. It will never sound like a V8, but it will sound like a Subaru.

The crank of an engine and the way the valves fire also give it its exhaust note. All V8s don't sound the same either. A Chevy is going to sound different than a Lamborghini due to the 90° piston separation of the Chevy and the 180° piston separation of the Lambo.

How did you come up with the degree timing of the single V8 bank and the Subaru?
 

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I just re-read your first post, clever experiment using the dowel, screws, jug, and drill. Then recording the sound bits. Nice job.
 

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Discussion Starter #6
"How did you come up with the degree timing of the single V8 bank and the Subaru?"
The Timing came from a 350 v8 distributor, with the even numbers representing one side of a bank and the odd numbers represent the opposing bank, for the angles I simply removed the angles that corresponded with the opposing bank. Same applies for the subaru, except cylinder's 1 & 2 correspond to the bank with the longer pipes, but since they all converge in one outlet, the sound offset by the longer pipes changes the way we hear it.
 

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This is actually pretty cool.

As for engine destruction, I think it would be easiest to simply buy a cheap running 100-200 dollar 4 cylinder car and try it out.
 

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Engine configuration plays no role in the way an engine sounds


If you're still skeptical, please, listen to this acura, it has unequal length pipes and sounds exactly like a horizontally opposed flat 4.
While I understand what you're getting at, I have to ask; what are your credentials and what experience do you have first-hand at modifying vehicles? Your first point I'd have to argue...there's more to engine sound than a "piston releasing air". Actually, it's the valve which does that.

What is the point of this exercise? If it's to make your car sound like a Subaru, I can tell you right now that unplugging one cylinder will net you the same result. Also, if you want to spend time concocting a hundred-pound pile of spaghetti for an exhaust system, you go right ahead. But I'll stick to something that makes power.
 

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The guy is entertaining a harmless idea, don't be so hard on him.

I see how you got the timing for the 1 bank of a V8, but how did you get the timing for the UEL header on the Subaru. Wouldn't that be a matter of pipe length, and the difference of the distance? Did you have a header to reference.

Harmonics can play a good or bad role, you may cause harm to the engine, but I don't think you will. You might get the sound you are after if that is your goal, but you might loose power doing it. I don't think you would loose enough power to care or notice. You can't have your cake and eat it to.

If the unequal length header works on the flat 4 why wouldn't it work on an inline 4 without destroying it?
 

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The guy is entertaining a harmless idea, don't be so hard on him.

I see how you got the timing for the 1 bank of a V8, but how did you get the timing for the UEL header on the Subaru. Wouldn't that be a matter of pipe length, and the difference of the distance? Did you have a header to reference.

Harmonics can play a good or bad role, you may cause harm to the engine, but I don't think you will. You might get the sound you are after if that is your goal, but you might loose power doing it. I don't think you would loose enough power to care or notice. You can't have your cake and eat it to.

If the unequal length header works on the flat 4 why wouldn't it work on an inline 4 without destroying it?
I think he is worried about the significant difference in length between the Subaru sound and V8 sound (2 times as long compared to 4 times as long)
 

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I'm not busting balls, merely trying to invoke some critical thinking. Unequal length exhaust won't kill a 4-stroke engine. It will, however, hinder the exhaust scavenging so it won't run as efficiently.
 

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Discussion Starter #14
While I understand what you're getting at, I have to ask; what are your credentials and what experience do you have first-hand at modifying vehicles? Your first point I'd have to argue...there's more to engine sound than a "piston releasing air". Actually, it's the valve which does that.

What is the point of this exercise? If it's to make your car sound like a Subaru, I can tell you right now that unplugging one cylinder will net you the same result. Also, if you want to spend time concocting a hundred-pound pile of spaghetti for an exhaust system, you go right ahead. But I'll stick to something that makes power.
Maybe it's just me, but that sounds a little condescending, and in terms of credentials; simply put that's a genetic fallacy, ad hominem to be specific, but if it matters that much to you, let me save you the trouble of having to read through another second of my ludicrous, I have no credentials in the automotive world. I am however an automotive enthusiast who has taken time, a substantive amount time researching the sound properties of engines, And if you're skeptical to that a degree, than I implore you, try it out for yourself, prove me wrong by attempting my theory instead of trying to shoot it down with simple explanations that I've already taken into account long before you mentioned them.
 

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Any condescending interpretation is not implied or intended. As for ad hominem, that claim is baseless as I in no way used your character traits as an attempt to discredit you. Character is different from an inquiry of education. My question was merely to see from what experience your points are originating. If you take offense at that, well it would indicate a certain type of person. If, however, you want to learn from others' experience, this board is a good place to do exactly that.
A person is only qualified to give an opinion based on the realm of his own experience, correct? My questioning is based on my experience with a) growing up working on vehicles, b) I have owned, maintained nearly 50 vehicles, many of which I have modified quite heavily, and c) part of my career has been in an engine rebuilding shop, and I have personally built a winning race engine. Does all this mean I know everything? Not even close...but it gives me something on which to base my questions and arguments. That being said, my question still stands - what is the point of the exercise, the end you hope to achieve?
 

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Discussion Starter #16 (Edited)
Question my sanity, but, growing up, I was surrounded by american cars, mustangs, cutlasses, a silverado 6.2L diesels, and though my dad never owned a corvette, I can say I have had the privilege of riding in a 1976 corvette with a 383 stroker, two 750cfm holley carbs. I on the other-hand am only 20 and though Im no professional mechanic, I have worked with my dad on Volkswagen, silverado's, 350's and 6.2L diesels (I loved that old truck so much that I eventually bought a 350v8 Blazer, I couldn't afford the fuel.) Now I have 1991 Volkswagen golf that I want to convert into a rat-rod. I hope I didn't strike you as arrogant, and its a real privilege for me discuss a topic with someone with your expirience in engines, however I honestly believe I'm right, and maybe my vocabulary strikes as some uneducated kid who wants to make noise with "Pistons releasing air" as opposed to "Valves releasing combustion" but regardless of what you want to call it, the sound generated by that valve releasing combustion is the same whether its facing upright, on a 90 degree block or if its horizontally opposed, the determining sound factor is as you put it, exhaust scavenging, traditionally Flat 4's and V4's had true dual exhausts, while Inline 4's usually have a single exhaust manifold. Is the logic behind my assessment wrong? Are my angle findings with a dowel and a drill unrealistic and impracticable in the real world?
 

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Don't forget that there's another reason why Subarus have their characteristic sound. In a Boxer engine, as opposed to a flat-four, both cylinders on one side of the engine will fire before the cylinders on the other side can fire. This would make a difference when combined with a UEL header.

http://www.rahul.net/ddoudna/Subaru/

edit:

https://www.youtube.com/watch?v=WoqD6jMxU84 (visual)

The reason I posted this information originally is because in the original diagram, you do not have cylinders in sequential firing order grouped together, which is a difference from the Subaru design.
 

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You would get the same sound if you grouped the inline 4 cylinder pistons the same as the Subaru and made the pair of primaries longer than the other pair. The sound would be the same.

Subaru Boxer firing order 1-3-2-4. The UEL header groups 1 and 3 together, and 2 and 4 together. 1 and 3 have the longer primary pipes.


In line Toyota 4 cylinder firing order 1-3-4-2. Would have to group every other cylinder together. For a custom header with cylinder 1 and 3 grouped, and 4 and 2 grouped. Making either groups primaries longer than the others.

As long as the pipe length was figured out so the timing of the exhaust pulses worked out the sound could be made to sound like have a V8 or a Subaru Boxer. Some performance may be lost in the process.

Subarus end up having this sound because when a header is made to wrap around the front of the engine to meet the other side the pipes are longer and it offsets the sound. They do make equal length headers for the Subaru that make it sound like an inline 4 cylinder. I think the UEL header goes with the boxer engine just do to the design and one of the easy possible ways to lay out the piping. I think you don't see it on an inline 4 cylinder because it is more work, not that it can't be done.
 

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Your distributor/firing order diagrams make sense. I don't know how you came up with the Subaru timing though. Could you explain?

Also I know first had it works on a Subaru, but I'm still trying to wrap my head around the exhaust pulses moving down the pipes. You show the inline 4 with 90° spacing, usually cylinders 1 and 3/2 and 4 are connected at the primaries. At this point 1 and 3 are 180° apart according to how they are connected to the crank, 2 and 4 are the same way. Then when the primaries and secondaries meet the pulses slide between each other to make the 90° offset?

How would you set up the pipe length to get you 45° and 135° offsets?

I'm sure this is easier than what I'm explaining, but I'm hung up on it.
 

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Discussion Starter #20 (Edited)
I figured out the angles based off of what I heard, I basically took the in-between 45 and 90, which is 68. Right when I heard 68-90-112-90, Subaru was the first thing that came to mind, however, when as I got closer to the equal 90's range (when I tried 79-90-101-90 the firing order mid-way between a UEL & EL, it sounded like an inline 4 with bad timing, subaru'ish, but not quite enough )
And I found that once you cross over the 68-90-112-90 threshold toward the 45-90-135-90, it really starts sounding like a v8
Although I no longer have the dowel thingy to test it, I'll post these to give you an example of what I heard. Even if I can't the 45-90-135-90, I know that I can get somewhere close.

68-90-112-90

79-90-101-90
 
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