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  #61  
Old 06-29-2007, 02:57 PM
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  #62  
Old 07-04-2007, 03:48 AM
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My turn to ask a question:

In this cutaway of the volvo (yamaha developed) V8;

1. How does the variable valve timing, cam phasing mechanism work?

2. All other V8s are 90 degrees (crossplane or flatplane) but this one is 60 degrees. I have noticed that this has a balancer shaft in V gulley (like 60 degree V6's and all V10s) suggesting this engine has end to end imbalance issues (unlike other 90 degree V8's). Furthermore i think i see splayed crankpins. so - my conclusion is that this the balancing technique in this engine is closer to a 60 degree V6 and not a regular V8. Does anyone else agree?
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  #63  
Old 07-04-2007, 05:05 AM
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intriguing. There's clearly a mechaism on the end of the camshaft which I suggest links the chain driven outer to the camshaft inner. Very interesting ... off to do some googling
"Now at 4.4 L, the V8 engine, made at Ford's Bridgend Engine Plant in Mid-Glamorgan in Great Britain, is unique in Ford's wide range of V8 engines in that it is designed for transverse use and has a V6-like 60° bank angle."
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  #64  
Old 07-04-2007, 05:09 AM
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1. Well in the cutaway of the large drums on the ends of the cams shows a grey/blue vaned piece inside, this is attached to the cams directly (it screwed in by the looks of it). The cam gears are kept in sync with each other because they are all on a common outer casing that floats. The connection between the cam shafts and the cam gears happens inside the large drums. Basically high pressure oil is pumped into the drums. The drum has vanes (probably 4 by the looks of it) built into it pointing in towards the grey/blue vane and the oil is kept inbetween the vanes on the drum and the vanes on the cam shaft. To change the phasing is a simple case of changing the amount of oil on either side of the vanes in relation to each other.

2. I agree. it defintately looks like there are splayed crank pins and the balance shaft suggests end-to-end vibration. So basically balanced like a V6.

I am guessing they built it like that to make the engine more compact? Either that or they built it up from a modular V6 design?
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  #65  
Old 07-04-2007, 05:17 AM
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Quote:
Originally Posted by hightower99 View Post
1. Well in the cutaway of the large drums on the ends of the cams shows a grey/blue vaned piece inside, this is attached to the cams directly (it screwed in by the looks of it). The cam gears are kept in sync with each other because they are all on a common outer casing that floats. The connection between the cam shafts and the cam gears happens inside the large drums. Basically high pressure oil is pumped into the drums. The drum has vanes (probably 4 by the looks of it) built into it pointing in towards the grey/blue vane and the oil is kept inbetween the vanes on the drum and the vanes on the cam shaft. To change the phasing is a simple case of changing the amount of oil on either side of the vanes in relation to each other.

2. I agree. it defintately looks like there are splayed crank pins and the balance shaft suggests end-to-end vibration. So basically balanced like a V6.

I am guessing they built it like that to make the engine more compact? Either that or they built it up from a modular V6 design?
Thanks, thats an interesting VVT mechanism, This is supposed to be compact, but I cannot think of ay V6 it can made along side. This must be a unique build.
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  #66  
Old 07-04-2007, 05:28 AM
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Quote:
Originally Posted by jediali View Post
Thanks, thats an interesting VVT mechanism, This is supposed to be compact, but I cannot think of ay V6 it can made along side. This must be a unique build.
The majority of cam phasing systems out there use a system like this... normally only difference is the number of vanes used 3 and 4 being the most popular.

AFAIK:

Alfa/FIAT has it called Variator in the twinspark engines
GM with their DCVCP
Honda uses it as the i in i-VTEC
Subaru AVCS
And I am pretty sure that Toyota has it as part of there VVT-i and VVTL-i systems
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  #67  
Old 07-04-2007, 06:00 AM
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Quote:
Originally Posted by jediali View Post
Thanks, thats an interesting VVT mechanism, This is supposed to be compact, but I cannot think of ay V6 it can made along side. This must be a unique build.
It share a lot of the dimensions and external points with the Duratec V6.
Yamaha woked with Ford on the V6 engine, so inevitabel that their will be "similarities"
The engine was originally dropped fron production in the 90s and Volvo resurrected it for the XC90 --- for some obscure reason
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  #68  
Old 07-04-2007, 06:05 AM
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aah..sounds likely. seems we owe a lot to the humble duratec then.
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  #69  
Old 07-05-2007, 08:06 AM
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My turn for a question:

If you got the exhaust to flow at super sonic velocities through a relatively straight exhaust manifold....

What would happen when the super-sonic flow enters a turbocharger?

with the constricting area of the turbine scroll the flow will slow down and gain pressure but what happens when it suddenly slows down to trans-sonic and slower?
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  #70  
Old 07-05-2007, 09:11 PM
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If you have back pressure at the turbo inlet the air flow will return to subsonic.

Just an aside but something to think about with supersonic airflow...
By definition anything that happens down stream of a supersonic flow CAN NOT affect the properties up stream of the flow. No sounds, shocks, pressure changes etc can flow upstream through a supersonic flow. Now enough back pressure can reduce the flow rate and return the flow to subsonic. Conversely with more upstream pressure I can make the flow move even faster with the help of a divergent nozzle.

One more thing, I don't think you can make exhaust flow supersonic without a convergent nozzle. Beyond that my memory of the subject matter is fuzzy.
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  #71  
Old 07-06-2007, 04:45 AM
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Quote:
Originally Posted by culver View Post
If you have back pressure at the turbo inlet the air flow will return to subsonic.
What do you mean? which turbo inlet are you talking about? and I already know the velocity will return to trans-sonic/subsonic... My question was what happens if that happens inside the exhaust side of a turbocharger?

Quote:
Originally Posted by culver
Just an aside but something to think about with supersonic airflow...
By definition anything that happens down stream of a supersonic flow CAN NOT affect the properties up stream of the flow. No sounds, shocks, pressure changes etc can flow upstream through a supersonic flow. Now enough back pressure can reduce the flow rate and return the flow to subsonic. Conversely with more upstream pressure I can make the flow move even faster with the help of a divergent nozzle.
I already know that pressure waves cannot travel backwards against the flow if it is supersonic... What do you mean by "back pressure"? the flow will slow down if the cross sectional area of the flow is decreased... when the velocity decreases the pressure must increase... I also know about how a divergent nozzle can increase velocity (with increased pressure) I also know about de Laval nozzles...

Quote:
Originally Posted by culver
One more thing, I don't think you can make exhaust flow supersonic without a convergent nozzle. Beyond that my memory of the subject matter is fuzzy.
In order for a maintained supersonic velocity you would have to use a de Laval nozzle to achieve supersonic velocities... but you wont be able to get too fast as the pressure isn't very high or stable.
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  #72  
Old 07-06-2007, 12:20 PM
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Basically what I’m saying is if the turbo restricts exhaust flow then the pressure at the turbo inlet will increase. If that happens then the pressure difference across the manifold will drop and the flow will become subsonic.

If the flow was subsonic when it hit the turbo impeller then it doesn’t mater if it was supersonic beforehand, it is subsonic in the turbo housing.
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  #73  
Old 07-07-2007, 12:13 AM
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A turbocharger is always going to restrict the flow somewhat and at supersonic velocities the flow will slow down just because of the decreasing crosssectional area of the turbine scroll.

My question is if you have a supersonic flow that changes to trans-sonic what happens?
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  #74  
Old 07-07-2007, 04:05 AM
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Why do you want to make the flow supersonic for a short period to then slow it again to subsonic at the turbo?

How much energy will be taken in the speed change to supersonic that the turbo wont be able to use? Wont the pressure wave at the transonic boundary on the way to supersonic create more back pressure than the cylinders are ideal at?
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  #75  
Old 07-07-2007, 06:43 AM
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Quote:
Originally Posted by Cyco View Post
Why do you want to make the flow supersonic for a short period to then slow it again to subsonic at the turbo?

How much energy will be taken in the speed change to supersonic that the turbo wont be able to use? Wont the pressure wave at the transonic boundary on the way to supersonic create more back pressure than the cylinders are ideal at?
This is not something I actually want to do I was simply thinking about what would happen and I wanted to know if anyone here knew...

Very little energy is used to achieve supersonic velocity in a flow. Basically pressure is traded for velocity. So you get supersonic but only at low pressure.

Also there is no ideal back pressure...

and any pressure created before the point where it is supersonic will only "fuel" the velocity...
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