V8 burble... how does it work?

mrthingyx

mrthingyx

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Hi, all.

Just a quick query regarding silly engine noises.

Could somebody please watch this video (http://www.youtube.com/watch?v=Y8qGSwS3SCA) and explain how the V8 gets that awesome, slightly off-beat gravelly burble which seems absent from German V8s?

It seems typical of big American V8s - Shelby Cobra (427ci) makes the same noise, etc.

Is it literally displacement or a combination of carbs, cubes, and exhaust?

And yes, pretty much any excuse to post a video of a 60s Mustang.
 

Hate

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I'm guessing a combination of pushrods and size

Or rather, NFI :p

I'm sure you can make a german v8 sound like that if you really wanted to.
 

Durzel

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I'd say it was the cam profile, I've heard Jap motors burbling with extreme lift cams. That said I don't really know enough about American motors to know for sure.
 

Dandle

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Part of it is the size of the engine along with the timing. The main bit though is the exhaust, look at TVRs some of those have a fantastic sound to them with much smaller engines than the yanks use. German V8s are normally in prestige cars and part of that is making the engine as quiet as possible.
 

Zip

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A regular V8 like you see in the Americans and Australians and even Toyotas 1UZ-FE and many V8s around the world use a Cross plane Crank Shaft.

The burble comes from the un efficient design of them when they fire and its the exhaust gasses not coming out Smoothly because 1 Cylinder on each bank fires completely off to all the other 3 on that side.

The Reason Ferrari and i think even a few of the Germans dont have the burble is they use a Flat plane Crank. Which makes one each bank fire at a time in an Order, Pretty much like 2 4 Cylinder engines working hand in hand:)
It helps with Scavenging a lot and thats why they dont have the burble,because the Air flow is even through out the firing.

Or You can do what the GT40 did and use a 180 Degree "Header"(Thats probably an American word for manifold but its all ive ever heard it be called) to get the same effect as a flat plane engine but using a cross plane crank. Its just a hell of a lot of maths and creates a hell of a lot more weight due to the way the exhaust has to cross over so they can grab the Cylinders gas which fires out of order on each bank.


Both have there advantages, Flat Planes seem to get lots of Vibration at idle but they save weight due to not having as many/much balancers and they can rev Freer because of it

Hope it helps.
 

Zip

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MagicBoy said:
Yours is easier to read tho. ;)

Same sort of reason the 90's Subaru Imprezs's have the distinctive offbeat sound I think?
Click to expand...

They have an Uneven manifold that does it.

Boxer engines are some of the smoothest in the world and just wouldnt make that noise with out the manifold being uneven IIRC.

Just have a look how smooth this Boxer Diesel is running, Damm fine:cool:

http://youtube.com/watch?v=uo9wRfd4QkI

The Flat 6s are even smoother then the Flat 4s aswel:cool:
 
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Dogbreath

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Zip said:
Both have there advantages, Flat Planes seem to get lots of Vibration at idle but they save weight due to not having as many/much balancers and they can rev Freer because of it
Click to expand...

One of the big advantages of a flat plane V8 is that you get even firing intervals on each bank that makes it much simpler to design a tuned length exhaust manifold. On a cross plane V8 you have odd firing intervals, so an effective manifold would be a spaghetti junction of pipes crossing over between the banks.
 

Zip

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Dogbreath said:
One of the big advantages of a flat plane V8 is that you get even firing intervals on each bank that makes it much simpler to design a tuned length exhaust manifold. On a cross plane V8 you have odd firing intervals, so an effective manifold would be a spaghetti junction of pipes crossing over between the banks.
Click to expand...



Like the GT40 did:)

Heres its Complex bundle of snakes:)

bundleofsnakesacl1.jpg
 
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