Log VS Tubular exhaust, which one is more efficient ?

[Powerslide]

Log obviously for packaging, think riff_raff said this first, definitely aerodynamically emphasized but can we be certain its a log design? If it is it has to be real clever, Formula One clever. Is it a tight system that is borderline log or symetrical? If it was a log system, it may not share too much of an opening per three cylinder. Take 240 degree duration exhaust cam and it won't suffer returning pulses as one valve will open and the others closes as 240X3 is 720 degree. Say they run 300 degree cams, that would have an overlap of 180 degree but both at marginal opening and closing lift.

Looking at those comparison pictures, even the three into one collectors look as if the far cylinder headers are nearly facing each other and that could be even worse that a log if sound waves were to be taken more seriously.



Image edited clearly shows Red Bulls design that log exhaust for aerodynamic advantage where the lower than log section is obviously inflated for a flow passage. All those inflated sections of carbon fiber going around the cylinder head as well looks to be passages to redirect air towards prefered exits. Just look how restricted the other design is

[wuzak]

There you go gg, think turbine - clutch - MGUH - clutch - compressor. Ingenious and its all within the rules.

As you said, this is where their poweradvantage is coming from. De-clutching the compressor and sending all turbine power to the MGUH whenever it's not needed is your other alternative. Superswift electromagnetic clutches makes it possible.

Leaving aside the legalities, when would they be able to "park" the compressor and still be able to drive the MGUH with the turbine? I would think with the compressor de-clutched the exhaust energy would be very low. And wouldn't the intake be rather inefficient, with all the air being ducted through the stationary compressor?

[xpensive]

This is the discussion that ended with this, a one year flower, allowed by the powers to be out of know who?



Same fate with the twin-clutch, though it was allowed out of necessity to retain the last big name in F1.

[idfx]

I'm reading about something else - Variable Turbine Geometry. I don't know if it's legal (I read the regulation but has certain "gaps"). The idea is practical.
Variable Turbine Geometry
articles
http://turbomachinery.asmedigitalcollec ... ID=1769698
Variable-Geometry Turbochargers
http://large.stanford.edu/courses/2010/ph240/veltman1/

image



source: http://paultan.org/2006/08/16/how-does- ... etry-work/

Variable Vane Turbo gif animate


source: http://www.fastmotoring.com/index.php/2 ... turbo-vgt/

Variable-Geometry Turbochargers

source: http://large.stanford.edu/courses/2010/ph240/veltman1/
Vgt

video
Variable turbine geometry
[youtube]http://www.youtube.com/watch?v=t2GrVS-sGdQ[/youtube]
[youtube]http://www.youtube.com/watch?v=i8R8rMVisCU[/youtube]
[youtube]http://www.youtube.com/watch?v=CbdY1rymBJg[/youtube]
Turbo à géometrie Variable. ( TGV)
[youtube]http://www.youtube.com/watch?v=Hg5FJuIBGNY[/youtube]

[dren]

It is not legal per the regulations.

5.9 Variable geometry systems :
5.9.1 With the exception of devices needed for control of pressure charging systems, variable geometry exhaust systems are not permitted. No form of variable geometry turbine (VGT) or variable nozzle turbine (VNT) or any device to adjust the gas throat section at the inlet to the turbine wheel is permitted.
5.9.2 Variable valve timing and variable valve lift profile systems are not permitted.
5.9.3 Variable length intake trumpets are forbidden in 2014 only.

[idfx]

It is not legal per the regulations.

5.9 Variable geometry systems :
5.9.1 With the exception of devices needed for control of pressure charging systems, variable geometry exhaust systems are not permitted. No form of variable geometry turbine (VGT) or variable nozzle turbine (VNT) or any device to adjust the gas throat section at the inlet to the turbine wheel is permitted.
5.9.2 Variable valve timing and variable valve lift profile systems are not permitted.
5.9.3 Variable length intake trumpets are forbidden in 2014 only.

ldfx wrote:
Yes, I agree that are illegal parts. I think it can be done a new idea while respecting the rules.
Small details on turbo can make a big difference. The turbo is something fascinating.

[Powerslide]

I think the MGU-H device is more practical in preventing lag than Variable Nozzle Turbo, mind you, which has been a highlight of AUDI's diesel charge in sports prototypes. I also suspect F1 engineers have been playing with ignition to make it easier for the MGU-H unit to prevent lag thats probably why the cars sounds different when low throttle. Cold blow, since now optimal fuel consumption is more important than before for overrall race pace

[gruntguru]

There you go gg, think turbine - clutch - MGUH - clutch - compressor. Ingenious and its all within the rules.

As you said, this is where their poweradvantage is coming from. De-clutching the compressor and sending all turbine power to the MGUH whenever it's not needed is your other alternative. Superswift electromagnetic clutches makes it possible.

Leaving aside the legalities, when would they be able to "park" the compressor and still be able to drive the MGUH with the turbine? I would think with the compressor de-clutched the exhaust energy would be very low. And wouldn't the intake be rather inefficient, with all the air being ducted through the stationary compressor?

Yes, I agree. Not much to be gained by disconnecting the compressor drive. My original suggestion of disconnecting the turbine and driving the compressor with the MGUH would be difficult too. Without a large wastegate the turbine would likely overspeed and the back pressure would still be quite high.

[xpensive]

Obviously at lift-off, when you disconnect the resistance of a stalling compressor and let the inertia of the 125 kRpm turbine run the MGU-H freely.

As for disconnecting the turbine and run the compressor with the MGU-H only at spool-up, there's no reason for overspeeding the turbine, as the very reason for disconnecting it was that it's not up to speed, right?

Ain't argumentation great fun, even for the sake of it?

[wuzak]

Obviously at lift-off, when you disconnect the resistance of a stalling compressor and let the inertia of the 125 kRpm turbine run the MGU-H freely.

As for disconnecting the turbine and run the compressor with the MGU-H only at spool-up, there's no reason for overspeeding the turbine, as the very reason for disconnecting it was that it's not up to speed, right?

Ain't argumentation great fun, even for the sake of it?

If you want to use the MGUH to make power during lift-off (ie in a braking zone) then it makes sense to leave the compressor attached, since that adds to the angular momentum of the assembly and thus the amount of energy that can be generated.

I admit in the the 2014 engine thread I said I didn't think that blow-off valves were being used, but on this video the sound was clearly there - at least on the Ferrari engined cars. Maybe Ferrari use the blow off because of their braking/downshifting strategy, while Mercedes and Renault, who don't seem to have the blow off valve, brake the turbo hard to generate some power for the ES.

If the compressor was de-clutched during braking I would expect the blow off vale would be necessary?

[xpensive]

If you can de-clutch the compressor at lift-off and use the MGU-H for instant spool-up, why would you need the blow-off?

Besides, the inertia of the turbine is far more than the compressor, and the more I think about it, it might make sense to
make that even more so, as another ERS-source. Perhaps that's where it is, a flywheel...?

[gruntguru]

Obviously at lift-off, when you disconnect the resistance of a stalling compressor and let the inertia of the 125 kRpm turbine run the MGU-H freely.

As for disconnecting the turbine and run the compressor with the MGU-H only at spool-up, there's no reason for overspeeding the turbine, as the very reason for disconnecting it was that it's not up to speed, right?

Ain't argumentation great fun, even for the sake of it?

My original suggestion was for a temporary power boost - not spool up.

Spool up is not a problem with the MGUH available to accelerate the turbo.

[Brian Coat]

So back to the log manifold ...

I can see the packaging benefits but I think there might be a theoretical performance benefit.

It is well known that

1) The use of tuned length exhaust manifolds in race car engines is to improve volumetric efficiency (air flow) through the use of the pulsations induced in the pipework by the exhaust strokes of the engine but this tuning effect is possibly of lesser value in an engine constrained by fuel flow and boosted by a turbo-supercharger

3) High amplitude exhaust pulsations will alter the instantaneous gas speed through the centripetal turbine. Between the maximum and minimum portions of the pulse, the instantaneous gas speed impinging the rotor will vary a lot even though the impeller speed is more constant. Since, for a given geometry, the turbine efficiency can only be maximised over a narrow range of gas speed (at a given turbo speed), the pulsations could actually have the effect of reducing the efficiency of the turbine (averaged over the cycle)? Therefore it might be desirable to have LESS pulsation in the exhaust, in order to optimise turbine efficiency?

If someone said this earlier, my apologies.

[Tommy Cookers]

an exhaust system can attempt to conserve exhaust pressure pulses with or without giving 'tuned length/extractor' effects
though tuned length/extractor systems have always been used in F1 turbo engines
we don't know whether or not the design of the Mercedes system is eg attempting to conserve pulses without extraction

the attraction of conserving pressure pulses is power recovery by 'blowdown turbine' ie without raising mean exhaust pressure
raising mean exhaust pressure tends in the obvious way to reduce crankshaft power
though it helps in conserving pressure pulses so may increase combined (crank+turbine) power for a given fuel quantity (said NACA)
(regardless of design, pressure pulses are not well conserved when blowdown is against normal ambient pressure)

however caused, loss of pressure pulse energy gives a heating effect and so tends to raise mean exhaust pressure
this resulting steady 'pressure turbine' term assists the turbine both in recovery and response
and is usually achieved by exhaust system designed to cancel residual pulses so (and/or by restriction) to raise exhaust pressure

relative to a given induction pressure this raised exhaust pressure has cost crankshaft power
what matters is whether or not this factor is dominant (over the benefits of raising mean exhaust pressure)
presumably Renault and Ferrari think it is and maybe Mercedes thinks it is not

since raising exhaust pressure and raising massflow ie leaning are somewhat antagonistic ie tending to be mutually exclusive
one wonders which is being used when rpm is significantly over 10500

[Brian Coat]

I've learned from further research that the phenomenon I suggested is very real.

But my earlier statement "Therefore it might be desirable to have LESS pulsation in the exhaust, in order to optimise turbine efficiency?" is incorrect.

If there is pulsation energy available then you want to harvest it.