How to make a 4 cylinder sound like a v8 - Toyota Nation Forum : Toyota Car and Truck Forums
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#1 Old 01-11-2014, 09:35 PM
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How to make a 4 cylinder sound like a v8

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



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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#2 Old 01-12-2014, 01:45 AM
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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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#3 Old 01-12-2014, 02:28 AM
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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.

Last edited by Jean-Luc; 01-12-2014 at 02:42 AM. Reason: spelling mistakes & ideas I forgot to write.
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#4 Old 01-12-2014, 02:25 PM
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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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#5 Old 01-12-2014, 02:27 PM
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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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#6 Old 01-12-2014, 02:49 PM
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"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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#7 Old 01-12-2014, 06:33 PM
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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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#8 Old 01-12-2014, 07:13 PM
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Quote:
Originally Posted by Jean-Luc View Post
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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#9 Old 01-12-2014, 07:31 PM
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This should get stickied

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#10 Old 01-12-2014, 07:56 PM
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^ Not sure if your cynicism is showing, or if serious...

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#11 Old 01-12-2014, 10:59 PM
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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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#12 Old 01-12-2014, 11:03 PM
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Quote:
Originally Posted by nogard View Post
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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#13 Old 01-12-2014, 11:33 PM
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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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#14 Old 01-12-2014, 11:58 PM
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Quote:
Originally Posted by DCM View Post
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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#15 Old 01-13-2014, 12:35 AM
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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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