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#51 MatsNorway

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Posted 22 November 2013 - 16:04

Koenigsegg aluminum 5.0L V8, 4 valves per cylinder, DOHC, titanium connecting rods, dry sump lubrication, with negative crank pressure functionality

 

http://www.koenigseg...models/agera-r/

 

1200hp from their 197kg 5L V8



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#52 desmo

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Posted 22 November 2013 - 19:45

Don't dry sump systems ordinarily run at nominally below ambient crankcase pressures?  Again I'd like to see actual pressure data vs. crank angle.



#53 malbear

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Posted 22 November 2013 - 21:48

And it will also be very heavy. More batterys, bigger charging systems and why? So we can fit more uneeded electric gizmos

I think that the battery could be about the same size or smaller than the conventional 12 volt just that it would have 18 small cells rather than 6.

also alternator not any different in size . more volts less amps lighter wiring. but I guess that it is very hard to buck the prevailing insitue infrastructure.



#54 bigleagueslider

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Posted 23 November 2013 - 03:09

Don't dry sump systems ordinarily run at nominally below ambient crankcase pressures?  Again I'd like to see actual pressure data vs. crank angle.

With a minimum volume sealed crankcase on a dry-sump race engine, the ambient pressure is highly dynamic.  The trapped volume within the crankcase constanly varies as the pistons move up/down in their bores.  The pressure in the oil circuit between the scavenge pump discharge and the air/oil separator is typically several times the ambient crankcase pressure (ie. at the scavenge pump inlets).



#55 desmo

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Posted 23 November 2013 - 03:53

Does one really want the scavenge pumps evacuating the cases as both pistons are rising? A rotary valve(s) timed to crankshaft rotation between the pump and scavanging inlets might reduce pumping losses perhaps?  Anyone ever tried to model the fluid dynamics of a sealed dry sump highly scavenged crankcase at high rpm? 



#56 Catalina Park

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Posted 23 November 2013 - 04:25

When a piston is rising there is often another piston falling at the same rate, so the pressure difference is not really that much.



#57 desmo

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Posted 23 November 2013 - 14:43

I would think the crankcase volume would change rather a lot in an F1-type segmented case between the crankpin being at top and at bottom, and that as a result the pressure would fluctuate wildly.  Not so much probably in your non-segmented street engine obviously.

 

The dearth of data on the 'net suggests to me that it is either essentially a non-issue or a major issue nobody wants to discuss publicly.



#58 Wuzak

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Posted 23 November 2013 - 23:50

I would think the crankcase volume would change rather a lot in an F1-type segmented case between the crankpin being at top and at bottom, and that as a result the pressure would fluctuate wildly.  Not so much probably in your non-segmented street engine obviously.
 
The dearth of data on the 'net suggests to me that it is either essentially a non-issue or a major issue nobody wants to discuss publicly.


But, in an F1 engine ther are 2 cylinders in the same segment. So, one is going up while the other is going down. Not at the same point in stroke, however. But that would surely reduce the fluctuations?

If they had stayed with the 4 banger for 2014 then it would be only one cylinder in th esegment and the pressure would fluctuate.

#59 desmo

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Posted 24 November 2013 - 02:53

But, in an F1 engine ther are 2 cylinders in the same segment. So, one is going up while the other is going down. Not at the same point in stroke, however. But that would surely reduce the fluctuations?

If they had stayed with the 4 banger for 2014 then it would be only one cylinder in th esegment and the pressure would fluctuate.

 

Obviously the smaller the v-angle the more the crankcase volume fluctuates as the crankshaft rotates. A 90 degree v engine will still experience significant crankcase volume changes with every crankshaft rotation, and an F1 engine with its case segments shrunk wrapped around the crank even more so.

 

engine_animation.gif

 

Nobody has any data?  This seems like a pretty fundamental thing any engine designer or tuner should be well versed in given its potential effect on pumping losses.



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#60 Lee Nicolle

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Posted 24 November 2013 - 03:04

I think that the battery could be about the same size or smaller than the conventional 12 volt just that it would have 18 small cells rather than 6.
also alternator not any different in size . more volts less amps lighter wiring. but I guess that it is very hard to buck the prevailing insitue infrastructure.

Which equals more weight!! Plus the extra weight and power drag of a larger alternator to charge the battery.

#61 gruntguru

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Posted 24 November 2013 - 23:52

Probably not. A 48V battery would be slightly heavier than a 12V battery of the same energy capacity. The 48V alternator would be lighter than its 12v equivalent. For a given resistive energy loss, wiring would need only 1/16 the copper and weigh considerably less. (insulation would not reduce by the same 1/16)



#62 gruntguru

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Posted 25 November 2013 - 02:09

Obviously the smaller the v-angle the more the crankcase volume fluctuates as the crankshaft rotates. A 90 degree v engine will still experience significant crankcase volume changes with every crankshaft rotation, and an F1 engine with its case segments shrunk wrapped around the crank even more so.

 

 

Nobody has any data?  This seems like a pretty fundamental thing any engine designer or tuner should be well versed in given its potential effect on pumping losses.

Pumping losses would only occur if the displaced air was forced through a restriction on each stroke. (A V8 with 4 semi sealed crankcases would be an example) Simply compressing and expanding the crankcase air as in a single cylinder engine does not produce significant losses.

 

A crankcase pressure trace would be easy enough to simulate - roughly the inverse of a crankcase volume trace (which is near sinusoidal)



#63 malbear

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Posted 25 November 2013 - 08:05

on my sixstroke ducati I used a one way valve on the crankcase breather and a small venturi in one of the exhaust pipes. this stops any oil leaks and keeps negative pressure in the crankcase . no oils escapes into the exhaust because of the labarinth path of the breather. A poor mans scavenge pump.


Edited by malbear, 25 November 2013 - 08:52.


#64 bigleagueslider

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Posted 27 November 2013 - 06:44

I would think the crankcase volume would change rather a lot in an F1-type segmented case between the crankpin being at top and at bottom, and that as a result the pressure would fluctuate wildly.  Not so much probably in your non-segmented street engine obviously.

 

The dearth of data on the 'net suggests to me that it is either essentially a non-issue or a major issue nobody wants to discuss publicly.

While F1 engines use segregated crankcases (ie. between mains), the crankcase volume is still large enough that the compression/expansion ratio produced by the V8 piston motion is probably only about 2:1 at most.  As I noted above, the primary reason for over-scavenging the crankcase is to remove as much oil as possible.  The hydraulic losses resulting from the crank and conrods passing through an air/oil mixture at high velocity can be significant.  And having less oil present in this air/oil mixture will greatly reduce these hydraulic windage losses.



#65 RogerGraham

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Posted 01 December 2013 - 01:21

Probably not. A 48V battery would be slightly heavier than a 12V battery of the same energy capacity. The 48V alternator would be lighter than its 12v equivalent. For a given resistive energy loss, wiring would need only 1/16 the copper and weigh considerably less. (insulation would not reduce by the same 1/16)

 

Autosport is reporting that the 2016 5-series might use a 48V electrical system.


"A further development, albeit one that is yet to receive the final go-ahead, is a new 48-volt electrical architecture.  Driven by ever-increasing electric consumption, it is deemed necessary to handle added functions, including a semi-autonomous driving system that allows partial hands-off operation, a more sophisticated anti-collision system with fully autonomous braking, a new infra-red night-time warning system and all-LED headlamps."