Honda Power Unit Hardware & Software

[xpensive]

Unless they for some reason were given the nod anyway, wouldn't be the first time, would it now?

[wuzak]

Unless they for some reason were given the nod anyway, wouldn't be the first time, would it now?

Even if they were "given the nod" it is a clear breach of the regulations, and should another team protest the system the Mercedes would be thrown out of the races and, possibly, the championship. Danny Ric for WDC!

[xpensive]

A clutch is allowed by the rules and the difference in speed could be xplained as an unxpected side-effect by the split-turbo.

Think the Brabham BT46, a cooling-fan that as it happened also generated downforce, it was declared legal even if it was
violating the rules on movable aerodynamic devices and only withdrawn voluntarily by MrE for political reasons.

[henry]

So, yes, it is possible to use a clutch to disengage the mguh from the shaft, but the turbine and the compressor have to stay connected all the time.

I haven't seen any discussion of why this option is written in to the regulations.

I have assumed it is to allow for situations when it is undesirable to have any current flowing in the MGU. For instance if components in the control system are overstressed you might want to stop generating. In which case you could disconnect the MGU-H and manage boost with the waste gate.

[mrluke]

If your mgu-h failed or overheated it would be good to declutch it rather than retire the car due to a turbo that cant rotate.

[wuzak]

A clutch is allowed by the rules and the difference in speed could be xplained as an unxpected side-effect by the split-turbo.

A clutch is allowed to disconnect the MGUH from the turbo.

An unexpected side effect would still render it illegal. How hard is it to design a shaft system of approximatley 300-400mm in length such that one end rotates at the same speed as the other?

Think the Brabham BT46, a cooling-fan that as it happened also generated downforce, it was declared legal even if it was violating the rules on movable aerodynamic devices and only withdrawn voluntarily by MrE for political reasons.

In the BT46's favour was that the fan did actually draw air through the cooling system.

The car was withdrawn because Brabham were told it would be disqualified at the next race.

[henry]

If your mgu-h failed or overheated it would be good to declutch it rather than retire the car due to a turbo that cant rotate.

Agreed that is a failure mode for which a clutch would be useful.

I wonder if Mercedes de-clutched the MGU-H in Canada when the MGU-K controller failed. I guess it would depend on whether they could still manage the link between MGU-H and the energy store.

[xpensive]

...
The car was withdrawn because Brabham were told it would be disqualified at the next race.

Incorrect, to Gordon Murray's disappointment, MrE withdrew the car for political reasons to keep his FOCA together, this is well documented. But again, the clutch itself is legal and I believe that MHPE for some obscure reason were given green light by the FIA for the split turbo design even with the mentioned consequence, the latter which was somehow overseen at the time.

And finally, I am aware of position 5.1.6 in FIA's technical regulations.

[Tommy Cookers]

In term of log exhaust, you are loosing on volume efficiency, but gaining more on turbo efficiency because of shorter piping and higher temperature. So i think that all team will run lo style manifold in 2015. Another big benefit is aero package, and less cooling requirements. The PU106A uses the turbo efficiency better than the other two, and is able to harvest more energy from the MGU-H and power the MGU-K direct.

the short, unequal length headers of the log exhaust don't give an rpm-specific 'free supercharging' element as the tuned system does
but log path length differences are trivial, so the pressure pulses after blowdown remain rather evenly-spaced, thus well conserved
IMO with F1 rules this is vital, regardless of whether or not a raised mean exhaust pressure ('backpressure') is used
ie we must have blowdown running of the turbine or a blowdown + pressure running mix (not pressure running only)

a raised mean exhaust pressure would anyway undermine the effect of a tuned length exhaust ?


btw amusingly to we oldies the current so-called log exhaust is the opposite of what a log exhaust was
as drifting is now the opposite of what drifting was

[mrluke]

btw amusingly to we oldies the current so-called log exhaust is the opposite of what a log exhaust was
as drifting is now the opposite of what drifting was

Could you expand on both of those (sorry its OT)

[gruntguru]

a raised mean exhaust pressure would anyway undermine the effect of a tuned length exhaust ?

I don't believe so. Whether mean exhaust pressure is atmospheric or some other value doesn't reduce the benefit of blowdown energy.

[trinidefender]

a raised mean exhaust pressure would anyway undermine the effect of a tuned length exhaust ?

I don't believe so. Whether mean exhaust pressure is atmospheric or some other value doesn't reduce the benefit of blowdown energy.

Just thinking this through in my head. Blowdown energy is energy captured from the kinetic energy of the mass of the exhaust gasses. Usual Kinetic energy formula applies KE = .5*m*v^2.

So in the exhaust the mass of gasses is relatively constant throughout each cycle so that is fine. What we can alter is the velocity (v). The velocity of the exhaust gasses is created by the pressure differential in the cylinder vs in the exhaust. The greater the pressure differential, the greater the velocity. The greater the velocity the greater the kinetic energy available to be converted to blowdown energy.

If we increase the exhaust back pressure then we reduce the pressure differential and reduce the speed and hence KE of the exhaust gasses.

Feel free to tell me that I am talking out of my ass but please explain what would actually happen then.

[gruntguru]

Any decision to increase the designed mean exhaust pressure would normally be part of a decision to increase cycle pressures overall i.e. higher intake pressure and consequently higher cylinder pressure at E.O. So the pressure differential across the exhaust valve will be similar.

[toraabe]

Don't forget that the shorter the manifold is, the higher the temperature is when the gasses enters the turbine. Although the log manifold takes around 15 hp from the engine, you are able to harvest more energy through the MGU-H and deliver it direct to the MGU-K than you are loosing...

a raised mean exhaust pressure would anyway undermine the effect of a tuned length exhaust ?

I don't believe so. Whether mean exhaust pressure is atmospheric or some other value doesn't reduce the benefit of blowdown energy.

Just thinking this through in my head. Blowdown energy is energy captured from the kinetic energy of the mass of the exhaust gasses. Usual Kinetic energy formula applies KE = .5*m*v^2.

So in the exhaust the mass of gasses is relatively constant throughout each cycle so that is fine. What we can alter is the velocity (v). The velocity of the exhaust gasses is created by the pressure differential in the cylinder vs in the exhaust. The greater the pressure differential, the greater the velocity. The greater the velocity the greater the kinetic energy available to be converted to blowdown energy.

If we increase the exhaust back pressure then we reduce the pressure differential and reduce the speed and hence KE of the exhaust gasses.

Feel free to tell me that I am talking out of my ass but please explain what would actually happen then.

[mrluke]

There is a limit as to how low the pressure in the exhaust can be due to the restriction caused the turbo