Scooby "thud thud thud" signature engine sound
08 January 2013, 10:51 PM
#2
The burble/rumble comes from having unequal length exhaust manifolds, usually manifolds are the same length so when the gases pulse out of the exhaust ports on the engine they come out in sync, the subaru boxer engine sounds fantastic due being different to this. If you were to fit equal length manifolds, your car would sound like a regular turbo'd motor, similar to an evo etc, we couldnt be having that!
08 January 2013, 10:54 PM
#3
the sound comes from the horizontally opposed 4 cylinder, or H-4, or pancake motor. The engine's pistons are directionally opposed at 54 degrees. That is what gives the engine the loping sound, however it is also in addition to unequal length header piping to the turbo. If you put straight back headers on a Subaru with a 3" back pipe you will notice it sounds more like a Honda...
09 January 2013, 07:44 PM
#9
Scooby Regular
Eh?
The Boxer has a pair of horizontally opposed pistons (180' degrees not 54'). The cylinders are offset so the crank actually looks very much just like that in an inline four cyclinder motor. As the 1st and 2nd throw are at 180', and the cylinders are too, the pistons act in pairs, i.e. the front pair move opposite and so do the back pair, as in fronts push out, rears go in, etc. This creates a nice primary balance and makes a very smooth motor. there is a small rocking secondary motion but not much.
Now, the firing order is just like an inline four too, so the pulses come out at 180 degree intervals and with equal length primary exhausts the sound is just like any inline engine, absolutely no different. If you took a 2.0 litre inline in say , a Corsa or 206GTi and put the header lengh as the Impreza has, it would sound like an Impreza.
However, quite a bit of the sound is due to the muffling of the turbo as well as the size of the pipes too. Cosworths sound similar as do Evos.
A Japanese spec STi has equal pipes to drive separate split up pipe secondaries into the twin scroll turbo, hence it doesn't burble like usual. However a lot of the sound is still the big 2 1/2" outflow from the turbo and large back box volume.
A Ford Cossie with unequal headers would sound just like a Scooby, but that can't happen because like nearly all inline cars, the exhaust manifold is a cast, 4-1 unit driving into the integrated Turbo housing.
It really is the Subaru engine layout that has intake on top and exhausts under the car that means the Ehaust is so long to the turbo itself. Longish primaries to secondaries that wrap round the sump mean unequal length, and the secondaries go into the up pipe that goes to the Turbo. It was the sump that caused it, but 2.5 motors have the narrow sump to allow equal length pipes again.
The Bangs happen at 180 degrees perfectly evenly, bang-bang-bang-bang. always have and always will. Unless you fit a Yamaha M1 crank.
The Boxer has a pair of horizontally opposed pistons (180' degrees not 54'). The cylinders are offset so the crank actually looks very much just like that in an inline four cyclinder motor. As the 1st and 2nd throw are at 180', and the cylinders are too, the pistons act in pairs, i.e. the front pair move opposite and so do the back pair, as in fronts push out, rears go in, etc. This creates a nice primary balance and makes a very smooth motor. there is a small rocking secondary motion but not much.
Now, the firing order is just like an inline four too, so the pulses come out at 180 degree intervals and with equal length primary exhausts the sound is just like any inline engine, absolutely no different. If you took a 2.0 litre inline in say , a Corsa or 206GTi and put the header lengh as the Impreza has, it would sound like an Impreza.
However, quite a bit of the sound is due to the muffling of the turbo as well as the size of the pipes too. Cosworths sound similar as do Evos.
A Japanese spec STi has equal pipes to drive separate split up pipe secondaries into the twin scroll turbo, hence it doesn't burble like usual. However a lot of the sound is still the big 2 1/2" outflow from the turbo and large back box volume.
A Ford Cossie with unequal headers would sound just like a Scooby, but that can't happen because like nearly all inline cars, the exhaust manifold is a cast, 4-1 unit driving into the integrated Turbo housing.
It really is the Subaru engine layout that has intake on top and exhausts under the car that means the Ehaust is so long to the turbo itself. Longish primaries to secondaries that wrap round the sump mean unequal length, and the secondaries go into the up pipe that goes to the Turbo. It was the sump that caused it, but 2.5 motors have the narrow sump to allow equal length pipes again.
The Bangs happen at 180 degrees perfectly evenly, bang-bang-bang-bang. always have and always will. Unless you fit a Yamaha M1 crank.
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