we are going to be comparing inline four-cylinder engines with boxer 4-cylinder engines and talking about the individual advantages and

直列式和水平對臥引擎之間的差異, 以及他們各自的優缺點

disadvantages of each engine layout. We have a 3D printed EJ20 Subaru boxer engine as

影片中會使用兩具3D列印的引擎模型

well as a 22RE Toyota inline four-cylinder engine

一具是水平對臥的Subaru EJ20, 另一具是直四的Toyota 22RE

we'll start fairly basic and work our way through several different topics for each layout

我們會從最基本的部分開始, 慢慢地和大家討論兩種引擎排列方式的各種差異

including the four strokes the firing interval and order the

其中包括四行程的點火時間和順序, 不同引擎排列所產生不同的振動,

vibrations of each layout the packaging differences the cylinder head differences and finally a bit about the sound of each engine.

汽缸頭的差異還有排氣聲浪的不同

Looking at either layout, they're both based on the same four strokes intake, compression, power, and exhaust.

這兩種引擎的排列都是基於四行程運作 - 進氣, 壓縮, 燃燒和排氣

Both engines fire one cylinder for every 180 degrees of crankshaft rotation

兩種引擎也都是在引擎軸每180度時會點燃一個汽缸

but they have slightly different firing orders on each engine. We can see cylinders 1, 2, 3, and 4

但是兩種引擎的點火順序不同, 畫面上可以看到引擎的1,2,3,4 缸

for the boxer engine the firing interval is 1, 3, 2, 4 while on the straight four it's 1, 3, 4, 2.

在水平對臥的引擎上, 點火順序是 1, 3, 2, 4. 在直列的引擎上則是 1, 3, 4, 2

So the order of the last two cylinders firing is switched.

後面兩缸的點火順序是相反的

Now these layouts matched with the firing interval make for some interesting differences as far as how the engines are balanced on the

在這兩種不同的引擎排列上, 這兩種不同的點火順序也會衍生出不同的特性

boxer engine you'll notice the pair of pistons move in and out together

在水平對臥引擎上我們能看到兩邊對立的活塞會同時向內或向外移動

this means that the primary forces when the pistons reach the top of the cylinder as

所以當活塞走到汽缸頂或汽缸底的時候

well as when they reach the bottom of the cylinder are canceled out on the inline four-cylinder engine

兩邊活塞的相對主動能是能互相抵消的

it's the same story the primary forces cancel out as the pairs of pistons reach the top and bottom at the same time

在直四引擎上也同樣能看到在汽缸頂和汽缸底的位置時, 兩兩一對的活塞主要動能會互相抵消

when we get into secondary forces however the engines begin to differ.

但是次要動能在這兩種不同排列的引擎上就有不同的表現

Secondary forces are created due to the piston traveling faster at the top half of the cylinder then at the bottom half something

次要動能來自於活塞在一個循環的前半圈速度比在後半圈快 -

i'll include a link to in the video description

影片敘述裡有關於次要動能的影片鏈結

that breaks it down in great detail what you need to know though is that?

次要動能的重點是, 當活塞來到汽缸頂或汽缸底的時候

when the piston reaches the very top of the cylinder or the very bottom the secondary forces point up we're out from the piston

動能是由引擎曲軸指往向活塞的方向

now with the boxer engine since the pistons point opposite each other these forces are balanced out

在水平對臥引擎上由於活塞的方向是相反的, 次要動能也會被互相抵銷

resulting in a very smooth running engine for the inline 4 all of the forces point in the same direction

所以引擎整體是非常平順的 而在直列引擎上, 四個活塞的方向都相同

and thus do not cancel each other out causing the engine to vibrate unless balancing shafts are used the boxer engine isn't perfect however

所以次要動能並無法被抵銷, 在沒有平衡軸的情況下就會造成引擎的震動

because the pistons do not perfectly align with each other it creates a rocking moment which makes the engine want to rotate back and forth along the vertical axis.

不過即便如此, 水平對臥引擎也是有缺點

What's fascinating though,

因為對立的活塞並沒有對齊, 所以也是會引發一些左右的搖擺

is that if you add two cylinders to either of these designs whether it's a boxer six or an inline six you can

不過非常有趣的是, 如果我們用六缸引擎來討論

perfectly eliminate all first and second order forces and moments

不論是六缸直列或是六缸水平引擎, 主要和次要動能都能夠百分之百的被抵消

you might think the boxer six would have a rocking motion from the cylinder banks of three

你可能會覺得在水平排列上, 六缸引擎還是會有左右的搖擺,

but each bank of three cancels out the rocking motion of the other unlike in a V6 configuration

不過在一邊三缸的情況下, 左右兩邊的搖晃是會互相抵銷的

looking at the two engines both of these 3D printed engines are at 35% scales

現在我們來看看引擎的尺寸

you can actually compare them size-wise to one another

這兩具模型都是35% 的比例

because of the inherent vibrations of inline four-cylinder engines you won't tend to see engine size as much larger than about three liters

因為直四引擎天生震動的特性, 一般來說大於三公升的引擎很少見

so historically they have existed at much larger sizes one of the largest gasoline four cylinders currently made is in fact a Toyota engine a

現在常見的大直四引擎之一就是豐田Toyota Tacoma的 2.7 公升引擎

2.7 inline 4 used in the Toyota Tacoma only porsche and Subaru currently used flat engines in their vehicles

目前只有Porche 保時捷和Subaru 速霸陸有在使用水平對臥引擎

so the size doesn't tend to be any larger than typical inline 4 cylinders even though it does have better vibration characteristics

所以也很少看到比普通直四引擎還要大的水平對臥引擎

the other biggest advantage of the boxer engine is the low profile which keeps the center of gravity low and thus reduces the amount of

水平對臥的另一個好處是引擎的高度比較低

load transfer you have in the car during braking cornering or

這樣的設計讓引擎的重心較低

accelerating which improves grip with a lower center of gravity you can also reduce body roll and choose to use softer springs

所以在轉彎或加速的時候離心力也會比較低, 同時也能選用比較軟的彈簧

additionally in the event of a collision

另外當汽車遇上撞擊時,

it's easier to position the engine so that it goes underneath the passenger compartment rather than into the passenger compartment

水平對臥引擎也比較能夠往車室底下潰縮來保護乘客

for improved safety. Now that's not to say that the inline four doesn't have its own size advantages

不過直四引擎也有他的優點

generally, it's a bit more compact with only one cylinder head

一般來說直四引擎的體積會比較小, 只需要一個汽缸頭

and it's not quite as wide as the boxer engine

也會比水平對臥引擎窄

this leaves more room for

在引擎的左右會留下較多的空間

suspension geometry and can also allow for a better steering angle since the tires won't have as much of an interference at full lock

允許更多懸吊幾何設計的發揮空間和輪胎轉向的空間

moving on to the valvetrain although this particular inline 4 has a single overhead cam you'll much more commonly see dual overhead

這具直四模型是一具單凸的引擎,

like the boxer engine on modern vehicles

但現今較常見到的則多是和水平對臥一樣的雙凸設定

the big advantage with the inline 4 is that there's only one cylinder head meaning only one intake and one exhaust

直四引擎的另一個優點是只有一個汽缸頭

camshaft less moving parts

也就是說只有一套進氣, 一套排氣

and some weight saved. It's also far far easier to access the cylinder head for service, whether it's adjusting the valves or

更少的零件也意味著較輕的重量 同時直四引擎也比水平引擎容易維修保養

replacing spark plugs the I-4 design makes it a much easier task

不管是調整節氣門或是更換火星塞, 都比水平引擎要簡單許多

finally we get to the topic of sound and here's where most people will agree the box rumble is a better sound but it's not

最後我們來看看排氣聲浪, 很多人都會覺得水平對臥引擎得打鼓聲比較好聽

really a true advantage

但這並不是什麼特別的優點

The boxer rumble is a result of unequal length headers and because Subaru is moving away from this exhaust design

這個聲音來自於不等長的排氣頭段, 但是Subaru速霸陸漸漸的不再使用這個設計

New ones will generally sound pretty similar to other four-cylinder engines it would in fact be possible to design an inline

所以現在的新車聽起來和直四引擎差異不大

four-cylinder engine with different length exhaust pipes to create a unique rumble generally associated with Subarus.

其實在直四引擎上也是可以設計一套不等長排氣頭段產生Subaru 的打鼓聲浪

But it's not ideal for exhaust scavenging to have unequal pulses

但這不對等的排氣對排氣效能來說並不好

it's not the smartest way to route an exhaust or

這對四缸引擎來說並不是一個好的設計

four-cylinder engine

00:05:10,900 --> 00:05:11,470

however

00:05:11,470 --> 00:05:18,749 最後感謝Eric Harrell 提供這兩套3D列印的引擎

packaging does not the unequal header length seem appealing when paired with a boxer engine. And a big thank you to Eric Harrell for providing

有任何問題或意見歡迎留言喔

the 3D printed models you can find links in the video description. If you have any questions or comments feel free to leave them below,

謝謝大家觀賞

thanks for watching!