How does F1's PU quali mode obtain more power?

[Xwang]

How does F1's PU quali mode obtain more power?
Why is the same power rate not always available?
Let's speak about it!

[63l8qrrfy6]

Other than negative SOC, more extreme ignition advance and potentially even leaner mixtures. The downsides are higher level of knock and misfire, both of which are damaging (knock is straight forward and misfire can result in part of the unburnt mixture combining with the full mixture on the next firing cycle and producing very high cylinder pressures).

If the air massflow is increased by increasing turbo speed and also potentially introducing occasional surge events the life of the turbo can be reduced too.

Other than the ICE I know they have different gearshift harshness modes too which decrease the shift time at the expense of gear and bearing life.

[Tommy Cookers]

How does F1's PU quali mode obtain more power?
Why is the same power rate not always available?
Let's speak about it!

undercooling relative to any power state (temporarily) gives more power
undercooling means more energy is available for expansion in-cylinder

an amount of cooling which is undercooling at Q power is the equilibrium amount of cooling at normal power

the head/block heat transfer 'time constant' is tens of seconds
tens of seconds episodes is what a Q lap is made of

[Holm86]

Wastegate is constantly open, so the turbo is driven electrically all the time. Less exhaust back pressure gives better efficiency.
You can't run like this for long as it depletes the battery

[MtthsMlw]

Wastegate is constantly open, so the turbo is driven electrically all the time. Less exhaust back pressure gives better efficiency.
You can't run like this for long as it depletes the battery

Yep, for ~20s and if you add in the energy recovered over the lap maybe 30s.

[gruntguru]

Wastegate is constantly open, so the turbo is driven electrically all the time. Less exhaust back pressure gives better efficiency.
You can't run like this for long as it depletes the battery

As mentioned elsewhere the power required to run the compressor is in the 60 - 100 kW range depending on boost and whether blowdown pulses can be utilised to generate some turbine power without backpressure on the exhaust stroke. The Wright Turbo Compound was able to extract 20% of crankshaft power, additional from the exhaust at take-off (10% at cruise) without adding to back pressure during the exhaust stroke.
With 120 kW to run the MGUK, the total ES draw is around 200 kW. Any time the power requirement reduces, the wastegate will close and the K and H can both generate (assuming no per/lap harvest limit on the K).

At 4 bar boost, the piston engine output will increase by about 10% due to the "air motor" effect where the ES is used to drive the compressor and the piston engine uses that pressure to drive the crankshaft during the intake stroke.

[Tzk]

There's several reasons why teams got a "qualy" pu mode. Some of them are already mentioned above:

1. wear
if you run the engine in the highest mode for the full race distance, then the engine won't survive until the target lifetime is reached. Usually the engines last about 5000km, maybe longer. Older race engine usually become "friday" fp1/fp2 engines.

2. fuel consumption
In qualy you can afford to burn a lot of fuel per lap, ofc not exceeding the flow limit of 100kg/h. In the race you are limited to 110kg per 300km (race distance) and usually the teams even underfill because running the max. allowed fuel amount mostly isn't the fastest strategy. Starting the race with less fuel and then using lower power modes is usually faster overall.

3. battery charge state
In qualy you usually start the timed lap with a fully charged battery and end the lap without any charge left. In the race you run the engine in a sustained mode, that means that you start and finish the lap with the same amount of charge.

---

How the teams generate additional power is another story. I guess they use part- and off-throttle sections of their hotlap in qualy to charge the ES, sacrificing fuel. In race you can't affort that (see point 2 above).

[Tommy Cookers]

... As mentioned elsewhere the power required to run the compressor is in the 60 - 100 kW range depending on boost and whether blowdown pulses can be utilised to generate some turbine power without backpressure on the exhaust stroke. The Wright Turbo Compound was able to extract 20% of crankshaft power, additional from the exhaust at take-off (10% at cruise) without adding to back pressure during the exhaust stroke.

the Wright TC had rather early EVO and a CR of 6.7 or so (and axial recovery turbines)
F1 has presumably later EVO and a CR 16 or so
so wouldn't we expect F1 to see 8-10% turbine blowdown recovery not 20% ?

TO SELF Wright showed 6% in sea level cruise (endurance ?) and 9.5% in (another ?) slcruise 1840 total hp 2400 rpm

btw if F1 did 400 mph all the time natural exhaust thrust would make nonsense of turbine recovery

[saviour stivala]

Facts about Wright turbo compound. It is incorrect and therefore not possible to compare the wright turbo compound (Exhaust blow-down turbine geared directly to the crankshaft through a fluid coupling) to a turbo-supercharger system. One part of the system used by F1 power unit.
The turbo-supercharger, like the blow-down turbine is an exhaust power recovery device. However, it has a different purpose that of allowing the engine to develop sea level power at high altitude. Therefore, it utilises a different method of performing this duty. In a turbo-supercharger installation, all cylinders exhaust into a common collector with two exit paths, one through a variable opening waste-gate, and the other through nozzles aimed at a turbine wheel. With the waste-gates fully open, there is no restriction, and collector pressure is nearly atmospheric. However, as the waste-gate is closed, pressure builds-up in the collector. The gas is forced through the nozzles, turning a turbine, which drives a supercharger. No power recovery is possible in such a system unless the collector is above exiting at atmospheric pressure.
The turbo-supercharger, therefore, utilises a ‘pressure’ turbine. It is basically different from a blow-down turbine since it converts blow-down velocity energy into pressure energy in a manifold collector. The conversion to pressure energy reflects on the scavenging ability of the cylinders.
The use of a pressure turbine to recover exhaust energy is quite inefficient, this is due to loss of basic engine power which accompanies the increase in exhaust system pressure. The increase of exhaust pressure also has an adverse effect on engine cooling and detonation margin.
The F1 additional system to the turbo-supercharging that of operating the supercharger in electric mode, called FREE LOAD MODE. Produces the maximum power output from the power unit. In this mode with ICE at full fuelling and with waste=gates fully open the supercharger is operated by the ‘H’ with the ‘H’ sharing battery power with the ‘K’.

[gruntguru]

You are conflating different concepts which are in fact independent. The flow path of mechanical power has nothing to do with the turbine type. The Wright compound system has many similarities to a turbocharger system in fact the only thing that disqualifies it as a "turbocharger" is the fact that both turbine and compressor are connected to the crankshaft. If the Wright TC is run at an operating point where turbine power equals compressor power, the overall effect is identical to a turbocharger.

Turbine type - whether reaction or impulse - is a separate issue. Modern turbocharged engines with less than 4 cylinders per turbine entry are a mix of the two types and the exhaust header is designed to deliver blowdown pulses all the way to the turbine nozzle. This system significantly reduces average pressure in the header without loss of turbine power.

Whether it is possible in the current F1 engines, to convert any blowdown energy to turbine power, while maintaining atmospheric pressure during the exhaust stroke is still unclear. It would certainly be an advantage - requiring less electrical energy to operate in Electric Supercharger mode and therefore permitting its use for more time each lap.

[saviour stivala]

You are making a total mess out of the two different concepts.
There is no such thing as a compressor connected neither to the crankshaft nor to the turbine of the Wright turbo compound system.
‘Turbo supercharger system’. When exhaust gas is at atmospheric pressure or near atmospheric pressure. (waste-gate open) no power recovery by exhaust turbine is possible.

[63l8qrrfy6]

You are making a total mess out of the two different concepts.
There is no such thing as a compressor connected neither to the crankshaft nor to the turbine of the Wright turbo compound system.
‘Turbo supercharger system’. When exhaust gas is at atmospheric pressure or near atmospheric pressure. (waste-gate open) no power recovery by exhaust turbine is possible.

https://en.wikipedia.org/wiki/Wright_R- ... ex-Cyclone

The blowdown pulse will be well above atmospheric pressure regardless of what the waste gate is doing. There is recovery with the wastegate fully open.

[gruntguru]

You are making a total mess out of the two different concepts.
There is no such thing as a compressor connected neither to the crankshaft nor to the turbine of the Wright turbo compound system.

See that thing at the back of the engine? That's a compressor/supercharger.
https://aviatechno.net/constellation/r3350_ecorche.php

Both the compressor and the turbines are connected to the crankshaft.

[godlameroso]

You are making a total mess out of the two different concepts.
There is no such thing as a compressor connected neither to the crankshaft nor to the turbine of the Wright turbo compound system.
‘Turbo supercharger system’. When exhaust gas is at atmospheric pressure or near atmospheric pressure. (waste-gate open) no power recovery by exhaust turbine is possible.

https://en.wikipedia.org/wiki/Wright_R- ... ex-Cyclone

The blowdown pulse will be well above atmospheric pressure regardless of what the waste gate is doing. There is recovery with the wastegate fully open.

True, seen many turbo setups where the wastegate was improperly sized and couldn't flow enough exhaust gas to lower boost pressure even wide open. I wonder to what extent the wastegates on these turbos are slightly under sized.

[saviour stivala]

‘Turbosupercharger system’ As to the possible energy recovery by the exhaust turbine reference should be made to:- Facts about the Wright turbocompound Oct 1956 engineering department Curtiss-Wright corporation. Wright aeronautical division Woods-ridge. New Jersey USA. (pdf file).

Mod edit to add link:
http://www.enginehistory.org/Piston/Wri ... CFacts.pdf