Renault Power Unit Hardware & Software

[Blackout]

For the ones who speak german better than me; didnt understand the last sentence http://www.auto-motor-und-sport.de/form ... 40482.html
The last part talks about the Renault PU qualities, backpressure, MGUH to MGUK energy transfer etc

[gandharva]

They say that the best part of the Renault engine ist the MGU-K. So the power from the battery lasts really long compared to competition. A Mercedes engineer told them, that after corner 16 the batteries are done in Spa and the system has to switch to MGU-H. But MGU-H usage comes at a cost. It takes away power from the combustion engine because of exhaust back pressure.

[Blackout]

Thanks but that's the part I understood What isnt clear to me, is the last sentence "Das so genannte Clipping kommt bei uns in Spa nicht eher als sonst." "clipping'?" "nicht eher als sonst"? what does he mean with that?

[Thunder]

Clipping is the Point where all MGU-K Energy is used up and the MGU-H has to jump in. And that Point doesn't come earlier on the Lap in Spa than on the other Tracks, which speaks for a good ERS. The other PU's seem to have had Problems with that.

[Blackout]

okay thanks. Interesting

[Tommy Cookers]

They say that the best part of the Renault engine ist the MGU-K. So the power from the battery lasts really long compared to competition. A Mercedes engineer told them, that after corner 16 the batteries are done in Spa and the system has to switch to MGU-H. But MGU-H usage comes at a cost. It takes away power from the combustion engine because of exhaust back pressure.

are they speaking of a race lap or a qualy lap ??

[Abarth]

Clipping is the Point where all MGU-K Energy is used up and the MGU-H has to jump in. And that Point doesn't come earlier on the Lap in Spa than on the other Tracks, which speaks for a good ERS. The other PU's seem to have had Problems with that.

You mean all the Energy in the ES, directed to MGU-K is used up, isn't it?

[bergie88]

Clipping is the Point where all MGU-K Energy is used up and the MGU-H has to jump in. And that Point doesn't come earlier on the Lap in Spa than on the other Tracks, which speaks for a good ERS. The other PU's seem to have had Problems with that.

You mean all the Energy in the ES, directed to MGU-K is used up, isn't it?

That is what they mean with clipping, but I don't think it works exactly in that way. In my opinion the usage of the MGU-H or the battery to power the MGU-K is optimized. It is always a tradeoff between generating power with the MGU-H (to drive the MGU-K) and losing power due to exhaust backpressure. At the moments when a lot of power can be generated by the MGU-H without creating too much backpressure the MGU-H is used, otherwise the energy will come from the battery.

[Tommy Cookers]

yes, but .....

....... It is always a tradeoff between generating power with the MGU-H (to drive the MGU-K) and losing power due to exhaust backpressure. ......

substantial power from gu-h action is available without any exhaust backpressure
(as long as the exhaust system is designed to preserve exhaust 'pulses', as even the 2014 Merc substantially was)
ie taking power from blowdown to ambient ending at bdc, this is truly free power
(16000 Wright 1950s aircraft engines got 6% free at 1.15 bar map and 18 % free at 2.2 bar map at CR around 7:1 this way)
exhaust tuning of reflected pulses also helps to reach ambient pressure by bdc

recovery powers above this blowdown power will only be available by raising exhaust pressure generally
such powers can loosely be seen as power moved from the crankshaft source to an electrical source

[bergie88]

yes, but .....

....... It is always a tradeoff between generating power with the MGU-H (to drive the MGU-K) and losing power due to exhaust backpressure. ......

substantial power from gu-h action is available without any exhaust backpressure
(as long as the exhaust system is designed to preserve exhaust 'pulses', as even the 2014 Merc substantially was)
ie taking power from blowdown to ambient ending at bdc, this is truly free power
(16000 Wright 1950s aircraft engines got 6% free at 1.15 bar map and 18 % free at 2.2 bar map at CR around 7:1 this way)
exhaust tuning of reflected pulses also helps to reach ambient pressure by bdc

recovery powers above this blowdown power will only be available by raising exhaust pressure generally
such powers can loosely be seen as power moved from the crankshaft source to an electrical source

Thx for the information Tommy! So if I understand correct, energy can be generated "freely" up to a certain power, after which there will be a trade-off between generating and losing power?

[Tommy Cookers]

yes
my post at 520 April 27 2014 page 15 in the TERS thread should have links to various source material for this position and
my post at 720 July 21 2015 page 25 in the TERS thread
(also there's been a wider argument over raised exhaust pressure)

[trinidefender]

yes, but .....

....... It is always a tradeoff between generating power with the MGU-H (to drive the MGU-K) and losing power due to exhaust backpressure. ......

substantial power from gu-h action is available without any exhaust backpressure
(as long as the exhaust system is designed to preserve exhaust 'pulses', as even the 2014 Merc substantially was)
ie taking power from blowdown to ambient ending at bdc, this is truly free power
(16000 Wright 1950s aircraft engines got 6% free at 1.15 bar map and 18 % free at 2.2 bar map at CR around 7:1 this way)
exhaust tuning of reflected pulses also helps to reach ambient pressure by bdc

recovery powers above this blowdown power will only be available by raising exhaust pressure generally
such powers can loosely be seen as power moved from the crankshaft source to an electrical source

Wouldn't the much lower compression ratio have helped with blowdown energy as less energy is expended pushing the piston down?

[Tommy Cookers]

yes - (that's why I always point out the CR)
though remember the exhaust pressure at EVO (if the EVO is correctly chosen) will be the same whether eg the CR is 7 or 17

[ringo]

yes, but .....

....... It is always a tradeoff between generating power with the MGU-H (to drive the MGU-K) and losing power due to exhaust backpressure. ......

substantial power from gu-h action is available without any exhaust backpressure
(as long as the exhaust system is designed to preserve exhaust 'pulses', as even the 2014 Merc substantially was)
ie taking power from blowdown to ambient ending at bdc, this is truly free power
(16000 Wright 1950s aircraft engines got 6% free at 1.15 bar map and 18 % free at 2.2 bar map at CR around 7:1 this way)
exhaust tuning of reflected pulses also helps to reach ambient pressure by bdc

recovery powers above this blowdown power will only be available by raising exhaust pressure generally
such powers can loosely be seen as power moved from the crankshaft source to an electrical source

You say this more than once, but i still cannot agree with it.

You may have to explain this in bullet points for me. As i don't see how it makes sense as the generator is an inertial load and an electrical load.

[Tommy Cookers]

sorry ringo, I can't understand which bits (if any) in my post you accept and which you don't

in my post earlier 1147 am yesterday I refer to earlier posts of links to the source material
the NACA source material shows migration of power from crankshaft to recovery turbine as turbine load (& exhaust pressure) is raised
I thought people were anyway taking that position as common sense