2026 Hybrid Powerunits

[nevill3]

I beleive that the "at ambient temperature" clarification was possibly requested by one or more of the engine manufactureres that have designed their engine to be as close to 16:1 when measured ( before operating temperatures are reached) because previously they maybe left more headroom when it was 18:1, possibly with an operating temperature CR of 18:1 to comply with the old regulations.

If that was the normal philosophy across the board (ie not exceeding 18:1 by design) before but in searching for "loopholes" a clever engineer has re-interpreted the rules potentially giving their team or customers a small advantage.

This is possibly an old trick that has been secretly used by certain engine manufacturers that has now been passed around with the movement of personel between teams.With the reduction in CR this year it has become a hot topic as teams are striving to find everylast bit of performance.

The timing of the clarification is also significant because if the relevant teams that are using this new method requested this addition to safeguard themselves too early other manufacturers would have been alerted to this potential gain (no matter how small it may turn out to be)

[mzso]

The timing of the clarification is also significant because if the relevant teams that are using this new method requested this addition to safeguard themselves too early other manufacturers would have been alerted to this potential gain (no matter how small it may turn out to be)

Apparently Audi missed it, judging by reports coming from them. Underperforming engine and a team only realling beginning a transition doesn't scream good results for them.

[Hoffman900]

dbl post

[Hoffman900]

As I posted in the other thread;

V8 drag race and circle track builders set P-H around .040in (1mm) with steel rods which in practice is near zero Piston to Head clearance at redline (the goal is to run around 0.1mm running clearance). This isn’t out of the realm at all.

For a typical racing US domestic V8 with a 4.25in bore, 64cc chambers, and a 10cc dome, that’s a change from to 12:1 to 13.9:1.

This has been a “thing” for decades in race engine building. No fancy degrees or materials needed and certaintly not an industry secret.

All engines are limited by piston to head clearance. You can’t modify this, at some point, they meet, and it’s expensive. Now depending on the rods being used, it may matter. For example, on an American V8 drag race engine, aluminum rods may require 1.50mm p-h clearance ambient vs the 1mm for steel rods. Both will end up around .1mm near redline if you’re doing it right. Both will measure slightly different geometric compression ratios (aluminum being lower) but the same running compression ratio.

Binotto as an engine guy should know this. People building engines in their garages who struggled through high school even know this. This sounds more like sour grapes than anything.

[dialtone]

I have no clue why forums always think they are the smartest.

Binotto has more experience building racing engines in his pinky than people here have in their life. He obviously knows all of this, he built the Ferrari 2019 engine and plenty other ones.

The issue is the rule was written in absolutes, then it was changed in October 2025.

The problem is not Binotto not knowing but the rule being written badly and some teams being rewarded for taking a risk, while others got shafted for doing so. To make it worse Binotto was punished not long ago for taking risks on the engine rules.

Any comment trying to go for “how could they not know?” Just highlights the commenter arrogance. Simplistic comments like “everyone knows” are extremely insulting to the sport.

[FW17]

But it also includes part throttle and full throttle recovery.

How does driver do part throttle recovery?

Will the driver apply full throttle and use the brake peddle to control the torque to wheels by the amount of generation from MGUH?
Or do you mean a throttle map which sends only part of the power to the wheels?

[BorisTheBlade]

But it also includes part throttle and full throttle recovery.

How does driver do part throttle recovery?

Will the driver apply full throttle and use the brake peddle to control the torque to wheels by the amount of generation from MGUH?
Or do you mean a throttle map which sends only part of the power to the wheels?

The latter one. While the rules restrict the degree of freedom, as a rule of thumb you can harvest around 100 KW while the driver torque demand is below what the ICE is able to deliver.

[wuzak]

It will be part of an ECU map.

[Tommy Cookers]

I have no clue why forums always think they are the smartest.

The problem is .... the rule being written badly .....

Any comment trying to go for “how could they not know?” Just highlights the commenter arrogance. Simplistic comments like “everyone knows” are extremely insulting to the sport.

all the cars are illegal and have been illegal all the time since 1.1.2014
(and many have been illegal since 1914 when 'capacity' was first limited)

since 2014 the maximum ICE swept volume is 1600 cc - and the MINIMUM ICE swept volume is 1590 cc

a 1599 cc car (measured by FIA rules) has well over 1600 cc swept volume at race rpm
(even a 1590 cc car is over 1600 cc at race rpm)
because the upward semi-stroke and the downward semi-stroke are increased at TDC and BDC by inertial etc forces
by about 3000 ppm of the con-rod loa (plus the deflections of the crank throws etc)
ie more than 9 parts per thousand of the semi-stroke (and so by more than 9 cc per litre)

further ....
the swept volume limits are & have since 1914 been further breached by the thermal expansion of pistons & cylinders


.... UNLESS THE RULES ARE UNDERSTOOD NOW THE SAME WAY THEY HAVE BEEN UNDERSTOOD SINCE 1914

[Hoffman900]

I have no clue why forums always think they are the smartest.

The problem is .... the rule being written badly .....

Any comment trying to go for “how could they not know?” Just highlights the commenter arrogance. Simplistic comments like “everyone knows” are extremely insulting to the sport.

all the cars are illegal and have been illegal all the time since 1.1.2014
(and many have been illegal since 1914 when 'capacity' was first limited)

since 2014 the maximum ICE swept volume is 1600 cc - and the minimum ICE swept volume ic 1590 cc

a 1599 cc car (measured by FIA rules) has well over 1600 cc swept volume at race rpm
(even a 1590 cc car is over 1600 cc at race rpm)
because the upward semi-stroke and the downward semi-stroke are increased at TDC and BDC by inertial etc forces
by about 3000 ppm of the con-rod loa
ie about 9 parts per thousand of the semi-stroke (and so by 9 cc per litre)

further ....
the swept volume limits are & have since 1914 also been breached by the thermal expansion of pistons & cylinders


UNLESS THE RULES ARE THE WAY THEY HAVE BEEN UNDERSTOOD NOT THE WAY SOME NOW IMAGINE THEY ARE

This. Binotto isn’t dumb, but this just reeks of sour grapes to me. This is also on the FIA… when you regulate everything to the nth degree and have overly complicated rules, you open the door to this. For as much as the rules spell out, they just about might as well be spec engines.

[Juzh]

.. there is a limit of energy usage per hour. For a typical race that translates to around 70 kg of fuel and that is what Scarbs meant.

it doesn't translate to around 70 kg per race
it translates to around 100 kg per race
the limit to what could be used

the heat rate per hour has been cut by 30% but the kg per heat rate has been raised eg by 15%

Please elaborate. Thanks.

[Tommy Cookers]

.. there is a limit of energy usage per hour. For a typical race that translates to around 70 kg of fuel and that is what Scarbs meant.

it doesn't translate to around 70 kg per race
it translates to around 100 kg per race
the limit to what could be used

the heat rate per hour has been cut by 30% but the kg per heat rate has been raised eg by 15%

Please elaborate. Thanks.

from 2026
regardless of fuel manufacturer the fueling energy/heat rate must not exceed 3000 KJ/hr
(about 30% less than energy rate under the old 100 kg/hr rate rules and typical old fuel energy content of 44KJ/kg)

the new fuel can be anything between 38 KJ/kg and 41 KJ/kg
ie the fuel massflow rate for a competitor will depend on the KJ/kg of the fuel type used by that competitor

and eg with 38 KJ/kg fuel the massflow rate (and so the mass loaded) will be higher than eg with the 41 KJ/kg fuel
so eg a '38' fuel load to be 15% more mass than we might expect from familiarity with the old fuel

so I have suggested that some eg the '38' fuel usere might load about 95 kg
the '38' fuel rules give scope eg for a significant alcohol content - but alcohols are low energy per kg

[Juzh]

regardless of fuel manufacturer the fueling energy/heat rate must not exceed 3000 KJ/hr

3000 MJ/h, right?

the new fuel can be anything between 38 KJ/kg and 41 KJ/kg

Would it not be preferable to have as high energy density as possible (so 41 MJ/kg) to reduce weight?

so eg a '38' fuel load to be 15% more mass than we might expect from familiarity with the old fuel

I still dont understand where this extra 15% comes from or why is it needed when fuel density and energy flow are limited

[mzso]

Would it not be preferable to have as high energy density as possible (so 41 MJ/kg) to reduce weight?

I still dont understand where this extra 15% comes from or why is it needed when fuel density and energy flow are limited

If you have lower energy density fuel, you need more of it, don't you? So more mass flow.

But I don't think anyone would go near the lower end, it would be a catastrophic handicap.

[wuzak]

so eg a '38' fuel load to be 15% more mass than we might expect from familiarity with the old fuel

I still dont understand where this extra 15% comes from or why is it needed when fuel density and energy flow are limited

I think he is saying that the mass of the lowest energy density 2026 fuel (38MJ/kg) is about 15% greater than for a 2025 fuel with the same total energy content.

44/38 = 1.157.