Mercedes Power Unit Hardware & Software

[gruntguru]

“The turbo RPM is under full control of the ‘H’”. Nobody said it is not.

Your original statement suggested that increased turbine speed was a direct consequence of opening the wastegate which it is not. What happens to turbine speed and the opening of the wastegate are both consequences of signals from the ECU. It is highly likely that the turbine was already operating at the speed which produces optimum AFR and so will not increase when the wastegate opens.

When the waste gates are opened it is a call/demand for maximum power output from the ‘power unit’.

Nobody knows that for certain. It is possible other modes call for wastegate opening.

Maximum power output from the power unit calls for. Full fueling permitted. Maximum boost.

Nobody knows that for certain. Boost will be adjusted to achieve best power AFR which has little to do with "maximum boost"

Minimizing exhaust back pressure.
In this mode the compressor is being used in electric mode. Both the ‘H’ and the ‘K’ are sharing battery power. (The ‘K’ is also contributing to the output) that is why it is called maximum ‘POWER UNIT OUTPUT”.
When that call/demand is made (maximum power unit output) the turbo is certainly not running at full boost and full turbo RPM. So when the waste-gate/s open the turbo will be speeded up to it maximum RPM

Not necessarily. Maximum turbo RPM is limited in the rules to 125k RPM (since no teams use other than 1:1 MGUH gearing) and that speed is probably rarely used other than at high altitude tracks.

and boost.

[saviour stivala]

Yes turbine/turbo speed and boost will increase as a consequence of the waste-gates opining because when waste-gates open the turbo goes into electric drive to full boost, at max fueling permitted, which means that before waste-gates were opened the ICE was not operating at that level. was operating at a lower level.
Air fuel ratio/turbo speed/turbo boost, there is no doubt that the ICE is operated at best air fuel ratio at all time.
It is the fuel flow (fuel injected) which will be adjusted to best air fuel ratio and not the turbo boost.
Nobody said that turbo speed is not limited to 125k RPM. And nobody said that any team (engine manufacturer) uses other than 1:1/direct MGU-H/turbo drive speed.
There exist no gearing/gear drive between turbo and MGU-H.
--------------------------------------------
Noli nothi permittere te terere.

[henry]

Is it possible that they might reduce boost in eboost mode?

This would reduce the power required of the MGU-H to drive the compressor and whilst this would reduce mass flow to the turbine the loss in turbine power might be less than the reduced H power.

[saviour stivala]

FREE LOAD MODE:- Waste-gate/s open full fueling permitted turbo in electric mode with the ‘H’ and ‘K’ sharing battery power. In this mode maximum possible power unit output is produced.

Noli nothi perittere te terere

[gruntguru]

Is it possible that they might reduce boost in eboost mode?

This would reduce the power required of the MGU-H to drive the compressor and whilst this would reduce mass flow to the turbine the loss in turbine power might be less than the reduced H power.

Absolutely. I always felt that less boost would be optimal in electric supercharger mode. There is not sufficient charge to run "ES mode" for a whole lap so the small sacrifice in power from say a 10% richer (less lean) mixture would be offset but a significant increase in deployment time.

It should also be considered that the reduced back pressure in ES mode might improve volumetric efficiency and allow similar cylinder filling with lower MAP.

[NL_Fer]

What is the point of running supercharger mode with less than maximum ICE power?

Supercharger mode is chosen for absolute maximum peak power (at the beginning of a long straight). So supercharger mode should be combined with maximum ICE power.

[gruntguru]

Yes turbine/turbo speed and boost will increase as a consequence of the waste-gates opining because when waste-gates open the turbo goes into electric drive to full boost, at max fueling permitted, which means that before waste-gates were opened the ICE was not operating at that level. was operating at a lower level.
Air fuel ratio/turbo speed/turbo boost, there is no doubt that the ICE is operated at best air fuel ratio at all time.
It is the fuel flow (fuel injected) which will be adjusted to best air fuel ratio and not the turbo boost.
Nobody said that turbo speed is not limited to 125k RPM. And nobody said that any team (engine manufacturer) uses other than 1:1/direct MGU-H/turbo drive speed.
There exist no gearing/gear drive between turbo and MGU-H.
--------------------------------------------
Noli nothi permittere te terere.

Repeating the same sh*t doesn't make it one bit more correct. If the driver is at WOT, the engine will most likely be at maximum fuelling and optimum (not maximum) boost REGARDLESS of whether the wastegate is open. The decision to open the wastegate will be made based on the urgency of the additional power requirement and the charge state of the ES.

Turbo boost and fuel flow are both set by the engine management system according to the driver demand via the accelerator pedal. One does not follow the other. This is not a 1980's fuel injected engine with a throttle pedal working butterflies and the ECU setting the matching fuel flow. You need to reset your thinking.

At WOT (and assuming the mode is not fuel conservation) the fuel flow will be maximum and the turbo boost is adjusted to optimise AFR.

[gruntguru]

What is the point of running supercharger mode with less than maximum ICE power?

Supercharger mode is chosen for absolute maximum peak power (at the beginning of a long straight). So supercharger mode should be combined with maximum ICE power.

I guess you didn't read the post.

Lets say ES mode with optimum boost delivers 5% power increase but can only be used 10 seconds per lap.

What if ES mode with reduced boost delivers 4% power increase but can be used 15 seconds per lap?

Which delivers the better lap time?

[Zarathustra]

Lets say ES mode with optimum boost delivers 5% power increase but can only be used 10 seconds per lap.

What if ES mode with reduced boost delivers 4% power increase but can be used 15 seconds per lap?

Which delivers the better lap time?

Depends on how long the track is...

[rgava]

Lets say ES mode with optimum boost delivers 5% power increase but can only be used 10 seconds per lap.

What if ES mode with reduced boost delivers 4% power increase but can be used 15 seconds per lap?

Which delivers the better lap time?

IIRC, in the Honda PU thread this was discussed and, with information released by Honda, it was clearly shown that "thick and short" is better than "thin and long".

So, once you are not traction limited is better to have 5% power increase during 10 seconds than 4% power increase during 15 seconds.

[digitalrurouni]

All I can say is Lewis has said the Red Bull is faster than the Mercedes at certain points and that was something we have not heard of iirc even once till now in the hybrid era lol. Honda PU supposed to have a spec 4 I believe? And their chassis is less draggy but very downforcey. Mercedes has some work to do and post summer break will be absolutely fascinating. Fuel efficiency is great but right now it seems longer periods of higher power deployment seems to be the key and Mercedes needs some more straight line speed so possibly less drag from chassis (probably not gonna happen) or way more power from the PU. I await to see what spec 3 of the Mercedes PU brings. Utterly fascinating.

[SiLo]

All I can say is Lewis has said the Red Bull is faster than the Mercedes at certain points and that was something we have not heard of iirc even once till now in the hybrid era lol. Honda PU supposed to have a spec 4 I believe? And their chassis is less draggy but very downforcey. Mercedes has some work to do and post summer break will be absolutely fascinating. Fuel efficiency is great but right now it seems longer periods of higher power deployment seems to be the key and Mercedes needs some more straight line speed so possibly less drag from chassis (probably not gonna happen) or way more power from the PU. I await to see what spec 3 of the Mercedes PU brings. Utterly fascinating.

It only seems to affect them in qualifying though. Apparently they still use a significant amount less fuel so they start a lot lighter and can run in higher engine modes for longer.

[saviour stivala]

(Sh*t and all that).
Everything on a F1 car including the dog and the puppies is set/controlled or monitored by the ECU.
Turbo boost is not adjusted to optimize air/fuel ratio, it is the fueling which is adjusted to optimize air/fuel ratio. Whatever the turbo is pushing out into the plenum it will have to get into the cylinders through the throttle butterflies which are controlled by the accelerator (torque demand) pedal which is operated by the driver ‘driving the car’. And apart from the permitted pit-lane speed limiter, anti-stall and VSC modes, Contrary to many believe the engine throttles butterflies does have a movement relationship with the accelerator (torque demand) pedal.
Yes, when the waste-gates open the turbo goes in electric drive, and full fueling is being used. In that mode the air/fuel ratio is at optimum, from start of mode to end of mode.
Extracting the maximum possible output from the power unit (free load mode) is the most inefficient way of putting power through the wheels. But it is a mode that not only is in use but the power unit was originally conceived with this mode.

Noli nothi perittere te terere.

[gruntguru]

Lets say ES mode with optimum boost delivers 5% power increase but can only be used 10 seconds per lap.

What if ES mode with reduced boost delivers 4% power increase but can be used 15 seconds per lap?

Which delivers the better lap time?

IIRC, in the Honda PU thread this was discussed and, with information released by Honda, it was clearly shown that "thick and short" is better than "thin and long".

So, once you are not traction limited is better to have 5% power increase during 10 seconds than 4% power increase during 15 seconds.

There is a difference. Honda are talking about the best way to distribute a given amount of energy. In the example I gave there is significantly more energy in the 4% power increase x 15 sec/lap.

[PlatinumZealot]

All I can say is Lewis has said the Red Bull is faster than the Mercedes at certain points and that was something we have not heard of iirc even once till now in the hybrid era lol. Honda PU supposed to have a spec 4 I believe? And their chassis is less draggy but very downforcey. Mercedes has some work to do and post summer break will be absolutely fascinating. Fuel efficiency is great but right now it seems longer periods of higher power deployment seems to be the key and Mercedes needs some more straight line speed so possibly less drag from chassis (probably not gonna happen) or way more power from the PU. I await to see what spec 3 of the Mercedes PU brings. Utterly fascinating.

Lewis is being disingenuous. He said this on a hot track. So it sort of brings into question how much compromised are Mercedes cooling and their resulting derating.