2025/2026 Hybrid Powerunit speculation

[johnnycesup]

Just to add to the previous discussion, using a common LHV for gasoline (44.3MJ/kg), the previous ruleset had a total fuel energy flow of 1230kW. If the 1000hp rumours are true, that would be a total thermal efficiency of 60,6%, which is pretty incredible.

The 1,000hp includes power (up to160hp) from the battery system, so should not be included in the TE calculation.

TE would be around 51%, assuming all power for the MGUK comes from the battery.

It would be ~56% if about half the energy comes from the MGUH to MGUK.

But didn't the maximum power occur when the MGUH was being powered by the battery, and not recovering energy?

Actually it makes a lot of sense that the MGUH couldn't power the MGUK with pure harvesting, haven't really thought of that before. So peak efficiency should be around 56 or so %, that seems more reasonable.

As for max power, what difference does driving the compressor with the MGUH makes? Genuine question, since the ICE will be providing plenty of air to spin the turbine. Is it a back pressure reduction, and if so, how significant is it?

[Abarth]

[...]will still render the exhaust turbine a 'pressure turbine'. The fact that a variable opening waste-gate is used, provides the exhaust gases from cylinders to turbine with two paths, when the waste-gate is opened exhaust gas pressure is at atmospheric pressure, and no turbine recovery is possible, When it is closed, exhaust gas is above atmospheric pressure and turbine recovery is possible.

This is circular reasoning.
For example, if the pulses are at 25% and the 'constant' pressure is 75% of the total energy that the turbine can convert into mechanical work, opening the waste gate will lead to
a) the engine experiencing almost zero backpressure (it was an important feature for engines with MGU-H).
b) reducing turbine speed and charge air pressure to manageable levels, but not necessarily to zero. This was also the goal of introducing twin-scroll turbos: maintaining a higher turbine speed at low loads and harvesting pulse energy without negative effects on scavenging.

Lower backpressure at equal compressor power increases MEP without a consumption penalty, which is an obvious goal of engineering in this field.