2025/2026 Hybrid Powerunit speculation

[saviour stivala]

Regarding some preceding comments: Notice I wrote “the engine while it is declutched on the grid.” Ideally the clutch between a running engine & its transmission is open when the car is stationary, in lieu of, say, having a 1000000:1 gear ratio for first gear. What I was getting at was, if it was permitted to use the 500 hp MGUK to increase the crankshaft speed of the 500 hp ICE beyond what the ICE itself can provide, then this should help spool up the turbine more quickly. But as the video alluded to, it takes 5 seconds to spool--does this mean the K can’t be used during idle? There are limits, discussed earlier in this topic, about what the MGUK can do independent of pedal position. It's too bad they can't use two accelerator pedals! How much fun would that be. Fiddle-throttle has a nice ring to it.

As for relying on the MGUK & ES alone to compensate for lag, you’d be leaving performance on the table if there is a way to overcome it by another means.

I'd see it more logically the other way. Available energy to spin exhaust turbine is greatest with the ice at absolute full load, not being spun unloaded by a E contribution to crankshaft.
If the ICE were to be run against resistance with throttle wide open (against a "brake") as in a dyno facility, then it should spool the turbo into peak.
Could be start procedure, arrive at grid slot with 50% battery e.g. select first, clutch open, max regeneration selected, rev nuts off it at max regeneration for 5secs prior to lights out, away at full boost/battery IF strategy and load correctly applied.

Note to the pedantic, this is thinking out loud, and not after reading nuance of deployment regs

The MGU-K being part of the power unit's functionality for acceleration, it can be used in deploy mode on race starts.

[gruntguru]

1. It is unlikely that 5s turbo lag will impact startline acceleration. A well designed ICE would have at least 200 KW with zero boost - even at say 1.1 lambda. Add 350 KW from the MGUK (assuming the ES is well charged during the warmup lap) and you have 550 KW available - rising rapidly as boost increases.
2. The preferred anti-lag strategy will be to harvest during any period where boost might otherwise drop and where full power is needed shortly after. Aggressive harvesting will keep the turbo spooled without wasting fuel.

@Farnborough. I don't think the rules permit harvesting at zero road-load ie on the startline.

[diffuser]

1. It is unlikely that 5s turbo lag will impact startline acceleration. A well designed ICE would have at least 200 KW with zero boost - even at say 1.1 lambda. Add 350 KW from the MGUK (assuming the ES is well charged during the warmup lap) and you have 550 KW available - rising rapidly as boost increases.
2. The preferred anti-lag strategy will be to harvest during any period where boost might otherwise drop and where full power is needed shortly after. Aggressive harvesting will keep the turbo spooled without wasting fuel.

@Farnborough. I don't think the rules permit harvesting at zero road-load ie on the startline.

You can't use all that power off the line anyways. Probably not before you hit 130 kph. So I doudt that's a problem. Plus, you only start a race once off the line, most of the time.

[Farnborough]

It's the comments made in that RB PU interview (whether or not they are shared by other developers is not known) of this phase being very different to current PU application.

Worthwhile watching to hear what he says though. Briefly, thinks it's going to bring quite variable outcome, which could lead to significant difference in that element for race start.
Also noted that no excess fuel burning outside combustion chamber will limit traditional anti-lag methodology.

[wuzak]

1. It is unlikely that 5s turbo lag will impact startline acceleration. A well designed ICE would have at least 200 KW with zero boost - even at say 1.1 lambda. Add 350 KW from the MGUK (assuming the ES is well charged during the warmup lap) and you have 550 KW available - rising rapidly as boost increases.
2. The preferred anti-lag strategy will be to harvest during any period where boost might otherwise drop and where full power is needed shortly after. Aggressive harvesting will keep the turbo spooled without wasting fuel.

@Farnborough. I don't think the rules permit harvesting at zero road-load ie on the startline.

You can't use all that power off the line anyways. Probably not before you hit 130 kph. So I doudt that's a problem. Plus, you only start a race once off the line, most of the time.

MGUK can't start deploying until the car is above 50km/h.

[gruntguru]

1. It is unlikely that 5s turbo lag will impact startline acceleration. A well designed ICE would have at least 200 KW with zero boost - even at say 1.1 lambda. Add 350 KW from the MGUK (assuming the ES is well charged during the warmup lap) and you have 550 KW available - rising rapidly as boost increases.

You can't use all that power off the line anyways. Probably not before you hit 130 kph. So I doudt that's a problem. Plus, you only start a race once off the line, most of the time.

I certainly didn't mean "off the line" when I said "startline acceleration".

As for traction limit - they will be out of that phase after about 2 seconds - still 3 seconds more before they see full boost. Fortunately the ICE can make near full power with nowhere-near full boost - the extra boost is needed to maximise TE and eke out the last handful of ponies.

[gruntguru]

MGUK can't start deploying until the car is above 50km/h.

Interesting. I guess 200 KW won't break traction at 50 kph - I guess it will have some boost by then.

[wuzak]

MGUK can't start deploying until the car is above 50km/h.

Interesting. I guess 200 KW won't break traction at 50 kph - I guess it will have some boost by then.

Current PU is 100km/h.

This is from the race start.

[Badger]

Could turbo sizes vary? Anyone know what the regulations say?

[Tommy Cookers]

MGUK can't start deploying until the car is above 50km/h.

Interesting. I guess 200 KW won't break traction at 50 kph - I guess it will have some boost by then.

yes

unboosted the ICE would need to be doing c. 10000rpm to deliver 200 kW ....
that wouldn't happen until the car is doing c. 100 mph (first gear)
like the Jim Clark era

MGU-K motor action seemingly clipped at 500 Nm won't reach 350 kW until c. 70 mph (& traction-limited anyway)
so at 50 kph only about 170 kW is available (& traction-limited anyway)

[wuzak]

MGUK can't start deploying until the car is above 50km/h.

Interesting. I guess 200 KW won't break traction at 50 kph - I guess it will have some boost by then.

yes

unboosted the ICE would need to be doing c. 10000rpm to deliver 200 kW ....
that wouldn't happen until the car is doing c. 100 mph (first gear)
like the Jim Clark era

MGU-K motor action seemingly clipped at 500 Nm won't reach 350 kW until c. 70 mph (& traction-limited anyway)
so at 50 kph only about 170 kW is available (& traction-limited anyway)

With the fuel flow allowed, 200kW @ 10,000rpm => TE ~25%.

I would have thought they could do something better.

[vorticism]

Could turbo sizes vary? Anyone know what the regulations say?

Not much, a window is spec'd. (dia, tip height)
Compressor:100-110, 30-35
Turbine: 90-100, 35-40
175mm max distance between the compressor front and the turbine end.

Should I read anything into them spec'ing minimum sizes? 150k max RPM, regardless.

I'd see it more logically the other way. Available energy to spin exhaust turbine is greatest with the ice at absolute full load, not being spun unloaded by a E contribution to crankshaft.

Yes, but the claim in the video is that the turbo is taking around 5 seconds to spool while the engine is unladen, and the generating modes available are limited (afaik). I was thinking the MGUK could be used to drive the ICE beyond whatever is limiting it at idle in terms of fueling and redline. I'm assuming the redline could raise with low or no fuel. Temporarily overdrive the ICE to f.e. 15k RPM for a 1/3 air mass flow increase beyond the typical 11k powerband. If the lack of exhaust heat nullifies all of this, use very late ignition to assist this such that the ICE can be fueled as though laden, while unladen. Basically maximize mass flow via higher than normal K-driven engine speed + fueling (within curve limit) & late ignition to achieve . ICE & K as temporary turbine engine starter.

If you only have one spark per cycle mandated, you might need to do something like this to impel the ICE since all the combustion energy would be produced after the expansion stroke. This is a longwinded way of explaining why I thought they must not be able to deploy the MGUK in a significant way while the ICE is at idle or declutched.

[gruntguru]

I should have watched the video sooner. Just watched it and realised that some of us (myself included) have misinterpreted the "5 second spool" comment. This is not turbo lag. This is the time they have to spool the turbo BEFORE the green light. So without knowing what strategy they use, they will have the turbo pre-spooled so that full torque is available from the start.

@Wuzak - under the rules is it possible they can run the engine in generator mode with the car stationary? What fuel flow would be available? They could certainly do this with radically retarded timing to generate hot exhaust gas.

[Vappy]

If cold blowing is re-used in 2026, perhaps this video could give us an idea of what that might sound like? These cars in testing followed the hot exhaust-blown ban.

[wuzak]

@Wuzak - under the rules is it possible they can run the engine in generator mode with the car stationary? What fuel flow would be available? They could certainly do this with radically retarded timing to generate hot exhaust gas.

It seems so.

C5.2.12 During a standing start from the grid the MGU-K may only be used once the car has reached 50 km/h.
C5.2.13 The amount of stored energy in the ES may not be increased by more than 100kJ whilst the car is stationary in the garage during the Sprint Qualifying and Qualifying Sessions.

C5.2.19 When the car is stationary on the grid prior to a standing start the MGU-K torque may only be negative (i.e. charging the ES) except for torque requested by an MGU-K active damping strategy whose sole purpose is to protect the MGU-K Mechanical Transmission.
C5.2.20 No off-board ES charger of any kind may be used whilst the car is in the pitlane

It looks to be specifically allowed!