2025/2026 Hybrid Powerunit speculation

[gruntguru]

I get your point. It is really only the ICE that converts fuel energy to mechanical - and that includes the turbo-compounding. Current efficiency of 50%+ includes a very minor loss converting turbine energy to electrical.

Does anyone have any thoughts on how the ICE might change and what efficiency might be possible, now that the only source of work is the crankshaft?

My initial thoughts:
1. Later EVO to increase in-cylinder expansion and minimise EGT.
2. Reduce or eliminate EIVC (Miller) to maximise pumping work done on piston during intake stroke. (This will be the sole means of returning recovered exhaust energy to the PU)
3. Larger turbine and housing to reduce backpressure. Minimise wastegating.

The way to totally avoid wastegating is achieving a steady state as in some old diesel engines, regulated by fuel flow (a.k.a. very lean burning).

Yes. Unfortunately unlikely, since the rules limit boost. The only way to run high boost over a wide range of RPM while ensuring boost doesn't creep above the rules limit, is a wastegate.

[wuzak]

There have been some reports that the best ICE will have about 420kW, which is 50.4% TE.

A while back, Tombazis suggested that the PU could have as much as 1,100hp peak power, which would mean ICE power of 470kW and TE of 56%!

Wow!

Just to clarify, Tombazis said that the 2026 PU could have up to 100hp more than the current PU.

Most think that the current PU has a peak power of ~1,000hp, which is why I said 1,100hp.

The current PUs may not actually have 1,000hp though.

Mark Hughes had an article where he suggested that the best would be about 450kW. That would be 54% TE.

But 400 - 420kW sounds like a more reasonable guess to me.

The current PUs have been frozen since 2022, so no development has gone into them.

That may be why it is possible for the 2026 ICE to be more efficient.

[JRodrigues]

Some news from Audi's camp regarding their engine: