2025/2026 Hybrid Powerunit speculation

[wuzak]

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?

[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.

[mzso]

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.

Depend on how you look at it. All energy comes from the burning of the fuel. So if you're talking about the TE of the power unit, it should very much be included. If you only think about the ICE than obviously not, and it will be less.

[Hoffman900]

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?

Most of the quoted TE was never quantified in the sense that it was done in conditions actually used on track, or if the MGUH was involved, or it was a “hero” TE run in the test cell to maximize bragging rights.

[BassVirolla]

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.

Depend on how you look at it. All energy comes from the burning of the fuel. So if you're talking about the TE of the power unit, it should very much be included. If you only think about the ICE than obviously not, and it will be less.

But while draining the battery is not a sustanaible mode.

Real efficiency can be measured without taking into account the energy storage, as in the MGUH motoring the MGUK.

While draining the battery you take a false higher efficiency, which would be offset by a necessary lower efficiency (lower Torque x rpm net output) when recharging the ES.

Edit: Charging batteries with the MGUK by braking, in a whole, could be measured as improving efficiency, but muds the picture a lot while talking exclusively about the PU. At last, the inertia of the car comes from the fuel.

Take it this way: What could be the maximum efficiency with the PU isolated in a dyno?

[PlatinumZealot]

470kw from ICE would be over 56%

Show your calculations please.

I'm not the person you're replying to, but there's a 3000MJ/h limit to the fuel energy flow in the regulations. Now MJ/h (unit of mechanical work per unit of time) is obviously a unit of power, so 3000 MJ/h = 833 kW.

So considering the internal combustion engine can burn the fuel perfectly and nothing else is burned (so no oil burning shenanigans), a 470kW output is equivalent to 56,4% thermal efficiency. A bit optimistic IMO


EDIT:
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.

Ok thank you. I see why you guys are wrong. Please have a look at the 2014 engine threads.

Engines do not work like that. You can't just pluck some numbers from the regulations and work backworks ( or rumours for that matter!).

You take numbers from a known physical engine or known physical/lab derived phenomena.

The previous rules had a fuel flow limit of 100kg/hr. This is equivalent to 4350 MJ/hr or 1230kW (note 4350 is higher than the 3000 number). The ICE engines (not the power unit!) as was calculated before by many forumers here is around 630kW. This smacks you sqaure at 52% thermal efficiency.

We know the combustion behaviour of these engines and we have estimated the MGUH and addition to efficiency and MGUK addition to output over 12 years of observation. So you use that and extrapolate. We do know that they were at limiting returns.

What you do, you see, is listen out when the season starts if you hear Mercedes shouting from the mountain tops of any record in thermal efficiency. They used to do this each year as the hybrid V6 developed because it was good for marketing their brand and the sport. And indeed those efficiency increases were genuine. With this new engine i am almost 100% sure that you will NOT hear any announcement on breaking any efficiency records.

[wuzak]

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.

Depend on how you look at it. All energy comes from the burning of the fuel. So if you're talking about the TE of the power unit, it should very much be included. If you only think about the ICE than obviously not, and it will be less.

Bt that's using fuel that is outside the current fuel flow.

[mzso]

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.

Depends on how you look at it. All energy comes from the burning of the fuel. So if you're talking about the TE of the power unit, it should very much be included. If you only think about the ICE than obviously not, and it will be less.

But that's using fuel that is outside the current fuel flow.

It's still utilized for drive. I guess that just means you can't assess the efficiency of a PU by taking an arbitrary point in time.

[Tommy Cookers]

... I guess that just means you can't assess the efficiency of a PU by taking an arbitrary point in time.

yes
and you can't assess the efficiency of a PU if it recovers KE .... because ....
you've already counted the energy given by the PU - so recovery is double counting ....
double counting (as if it's PU-dependent) of something that is PU-independent ...
because recovery is recovering something that is vehicle/task dependent not PU-dependent

[BassVirolla]

... I guess that just means you can't assess the efficiency of a PU by taking an arbitrary point in time.

yes
and you can't assess the efficiency of a PU if it recovers KE .... because ....
you've already counted the energy given by the PU - so recovery is double counting ....
double counting (as if it's PU-dependent) of something that is PU-independent ...
because recovery is recovering something that is vehicle/task dependent not PU-dependent

Should be constant dissipated power, as in a dyno, where you can't recover inertia of the car.

[diffuser]

Why would they allow so much leeway on power on the ICE but a hard limit on electrical?

[karana]

Why would they allow so much leeway on power on the ICE but a hard limit on electrical?

If I understand it correctly, there is actually no difference. Neither the ICE nor the MGU-K have a power limit, but rather an energy flow limit, for the ICE ~833kW and for the MGU-K 350kW. It's just that the MGU-K is extremely efficient and can get close to the 350kW.

[johnnycesup]

Show your calculations please.

I'm not the person you're replying to, but there's a 3000MJ/h limit to the fuel energy flow in the regulations. Now MJ/h (unit of mechanical work per unit of time) is obviously a unit of power, so 3000 MJ/h = 833 kW.

So considering the internal combustion engine can burn the fuel perfectly and nothing else is burned (so no oil burning shenanigans), a 470kW output is equivalent to 56,4% thermal efficiency. A bit optimistic IMO


EDIT:
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.

Ok thank you. I see why you guys are wrong. Please have a look at the 2014 engine threads.

Engines do not work like that. You can't just pluck some numbers from the regulations and work backworks ( or rumours for that matter!).

You take numbers from a known physical engine or known physical/lab derived phenomena.

The previous rules had a fuel flow limit of 100kg/hr. This is equivalent to 4350 MJ/hr or 1230kW (note 4350 is higher than the 3000 number). The ICE engines (not the power unit!) as was calculated before by many forumers here is around 630kW. This smacks you sqaure at 52% thermal efficiency.

We know the combustion behaviour of these engines and we have estimated the MGUH and addition to efficiency and MGUK addition to output over 12 years of observation. So you use that and extrapolate. We do know that they were at limiting returns.

What you do, you see, is listen out when the season starts if you hear Mercedes shouting from the mountain tops of any record in thermal efficiency. They used to do this each year as the hybrid V6 developed because it was good for marketing their brand and the sport. And indeed those efficiency increases were genuine. With this new engine i am almost 100% sure that you will NOT hear any announcement on breaking any efficiency records.

Sorry, how are we wrong exactly?

The 1230 kW for the previous ruleset (2014-2025) was in my post before you replied and in the conditions I assumed (1000hp without need to use the battery), the thermal efficiency of the PU would absolutely be around 60,6%, and I stand by that number. If, as some people said here, the MGUH is only good for around 60kW, you'd get around 56% (probably closer to the truth), and if you want to completely disregard the electric part and say the ICE produces 630 kW, that corresponds to a efficiency of 51.2%, sure (I don't think that number tells the truth about that system).

Now in the current regulations (2026), a peak output of 470kW from the internal combustion engine would mean a thermal efficiency of at least 56% in that point, for sure. The only way it could be lower is if the incoming chemical energy into the system was higher than the number in the rules (so cheating).

I mean, if you think 470kW would mean an efficiency value (and without the MGUH that is not something with different interpretations) lower than 56% , would you please show your calculations?

[PlatinumZealot]

The 1230 kW for the previous ruleset (2014-2025) was in my post before you replied and in the conditions I assumed (1000hp without need to use the battery), the thermal efficiency of the PU would absolutely be around 60,6%, and I stand by that number. If, as some people said here, the MGUH is only good for around 60kW, you'd get around 56% (probably closer to the truth), and if you want to completely disregard the electric part and say the ICE produces 630 kW, that corresponds to a efficiency of 51.2%, sure (I don't think that number tells the truth about that system).

Now in the current regulations (2026), a peak output of 470kW from the internal combustion engine would mean a thermal efficiency of at least 56% in that point, for sure. The only way it could be lower is if the incoming chemical energy into the system was higher than the number in the rules (so cheating).

I mean, if you think 470kW would mean an efficiency value (and without the MGUH that is not something with different interpretations) lower than 56% , would you please show your calculations?

No no no.

The previous rule set is 100kg per hour of fuel flow maximum. (Or about 4350 MJ per hour of energy flow or 1620hp of fuel power) The previous power units made 1050hp or so with ICE plus Electric motor. 840hp plus 160hp.

The previous engines thermal efficiency is 840hp/1620hp. Or about 52% to 55%

These new engines will be stripped of two major efficiency boosters... The MGUH (heat recovery turbine) and 18:1 compression ratio down to 16:1. Their efficiency WILL GO DOWN. No matter how you slice it even without doing the numbers.


Now...
MGUK is now 350KW. Or 470hp.
This leaves 530hp for the ICE if the 1000hp rumour is true. (I doubt it based on reports).
Total fuel input power is 3000MJ/hr or 1,117hp
Efficiency is 530hp / 1117hp = 47%

So you see now? Thermal efficiency will be lower.

I think the real figure will be lower.