Renault Power Unit Hardware & Software

[gruntguru]

Thinking again about where PU peak power may sit.

At 10500rpm+ we can release the energy from 100kg of fuel.

The energy is used to turn the ICE crank and excess from this is harvested to drive the MGU-H and stored for use later.

Energy harvested from the MGUH is more often sent direct to the MGUK for immediate consumption.

So, the more we burn the more we can use and store, so it seems obvious that for peak performance, 10500+ is where the ICE needs to be.

Above 10500rpm we have increasing friction, so ICE output will fall an this would be detrimental to car performance, to the point where a higher gear and lower rpm (<10500) would produce more power.

Can we not massage MGU-K assist to equal out the friction losses of running over 10500rpm, whist still utilising H harvest when we are using the most fuel?

No more than we can at any other rpm. You only need to consider the total of crankshaft power plus MGUH power (AKA "self sustaining power"). This figure will peak somewhere slightly above 10,500 rpm. No advantage running higher rpm.

There may be a short term advantage running at a different rpm (or different operating point WRT ign timing, AFR, intake geometry, WG position, MGUH load etc) since the maximum that can be sent to the rear wheels is crankshaft power plus 120 kW MGUH. In other words the rpm for peak crankshaft power does not necessarily coincide with that for peak self-sustaining power.

In the long term however (eg not in traffic), you want to operate near peak self-sustaining output because that is where you get the maximum total energy per unit time (peak power) and also per unit fuel (peak efficiency)

My question is, is the added friction from 10500 to 11500rpm greater than the power gained from MGU-H harvest at 100kg/hr as opposed to friction at 9500-10500 but having less fuel to burn and presumably less waste heat to harvest?

Peak self sustaining output is entirely dependant on the relationship between ICE efficiency and MGU-H efficiency. Could there be a set of operating conditions where ICE efficiency could be sacrificed (such as running above 10500rpm) to enable better MGU Harvest?

Err, probably not. A 1% drop in ICE efficiency is 6kW. That would be what, 10% of MGU-H output?

Besides - higher rpm does not guarantee more waste heat in the exhaust. Higher rpm with same fuel flow and same AFR means same air flow and therefore less air/cycle therefore less boost and lower turbine PR (which is one of the most important factors in determining turbine power).

[trinidefender]

Energy harvested from the MGUH is more often sent direct to the MGUK for immediate consumption.No more than we can at any other rpm. You only need to consider the total of crankshaft power plus MGUH power (AKA "self sustaining power"). This figure will peak somewhere slightly above 10,500 rpm. No advantage running higher rpm.

There may be a short term advantage running at a different rpm (or different operating point WRT ign timing, AFR, intake geometry, WG position, MGUH load etc) since the maximum that can be sent to the rear wheels is crankshaft power plus 120 kW MGUH. In other words the rpm for peak crankshaft power does not necessarily coincide with that for peak self-sustaining power.

In the long term however (eg not in traffic), you want to operate near peak self-sustaining output because that is where you get the maximum total energy per unit time (peak power) and also per unit fuel (peak efficiency)

My question is, is the added friction from 10500 to 11500rpm greater than the power gained from MGU-H harvest at 100kg/hr as opposed to friction at 9500-10500 but having less fuel to burn and presumably less waste heat to harvest?

Peak self sustaining output is entirely dependant on the relationship between ICE efficiency and MGU-H efficiency. Could there be a set of operating conditions where ICE efficiency could be sacrificed (such as running above 10500rpm) to enable better MGU Harvest?

Err, probably not. A 1% drop in ICE efficiency is 6kW. That would be what, 10% of MGU-H output?

Besides - higher rpm does not guarantee more waste heat in the exhaust. Higher rpm with same fuel flow and same AFR means same air flow and therefore less air/cycle therefore less boost and lower turbine PR (which is one of the most important factors in determining turbine power).

Less air per cycle but more cycles. Theoretically if it's the same fuel flow and AFR then the exhaust mass flow will remain the same. Same blowdown energy.

Each pulse will be smaller but more pulses. This doesn't get into the realm of exhaust tuning though which can potentially shift the peak power rpm range through fairly minor changes.

Am I correct in stating that he exhaust manifold is not a homologated part, I.e. Teams can have track specific manifolds?

[FPV GTHO]

Energy harvested from the MGUH is more often sent direct to the MGUK for immediate consumption

You're suggesting they are harvesting over 6MJ per lap then?

The rules limit 2MJ harvesting from the K to the ES, so the remaining 2MJ allowed in the ES has to come from the H. Full discharge from the ES to the K is more powerful than self sustaining from the H to the K, so if theyre sending more direct from the H to the K than from the H to the ES, it would have to be more than 2MJ being harvested outside of the ES. Minimum.

If the driver demands full power, ie the K is motoring at 120 kW, it doesn't make sense to be sending energy from the H to the ES. It is less efficient. It uses up some of the "per lap" ES limit.

Thats assuming the K can run at 120kw under self sustaining conditions.

[Zynerji]

You're suggesting they are harvesting over 6MJ per lap then?

The rules limit 2MJ harvesting from the K to the ES, so the remaining 2MJ allowed in the ES has to come from the H. Full discharge from the ES to the K is more powerful than self sustaining from the H to the K, so if theyre sending more direct from the H to the K than from the H to the ES, it would have to be more than 2MJ being harvested outside of the ES. Minimum.

If the driver demands full power, ie the K is motoring at 120 kW, it doesn't make sense to be sending energy from the H to the ES. It is less efficient. It uses up some of the "per lap" ES limit.

Thats assuming the K can run at 120kw under self sustaining conditions.

I thought H -> K was unlimited? As in, could push well above 120kW. I thought the whole point was 120kW from battery + MGU-H feed as well...

[Tommy Cookers]

sorry if I'm missing something ....

the K is limited to 120 kW

(and less at low rpm due to the torque limit)
the 120 kW based on DC power factored by 95% efficiency - so just over 120 kW actual might be possible

120 kW is power
power x time is energy
energy (MJ) is of course also limited

[Singabule]

You're suggesting they are harvesting over 6MJ per lap then?

The rules limit 2MJ harvesting from the K to the ES, so the remaining 2MJ allowed in the ES has to come from the H. Full discharge from the ES to the K is more powerful than self sustaining from the H to the K, so if theyre sending more direct from the H to the K than from the H to the ES, it would have to be more than 2MJ being harvested outside of the ES. Minimum.

If the driver demands full power, ie the K is motoring at 120 kW, it doesn't make sense to be sending energy from the H to the ES. It is less efficient. It uses up some of the "per lap" ES limit.

Thats assuming the K can run at 120kw under self sustaining conditions.

K-H relation is not limited by megajoules, but limited by kilowatt. Sometimes manufacturer override the K and power H just to sent back to K in order to get higher MJ allocation (more than 4MJ) per lap. Honda confirm doing this and its called extraharvest strategy. MGUH to Es is back to H is free also, but from ES to K is limited. So you can see even FIA has difficulty to control this, luckily the CE is a standard part hence they can trace out energy used and transfered between K-H-ES

[muramasa]

Honda's Extra Harvest is MGU-K directly driving MGU-H to make energy recovery (by H-motor inertia, rapid on-off at 20-40Hz) to send electricity to ES, not sent back to K. This way they are effectively overriding 2MJ/lap limit for MGU-K - ES route. BTW they are harvesting at MGU-K in acceleration as well, by turning ICE more than needed to drive K in partial throttle phase.

Also as of 2016 Honda were not doing MGU-H -> MGU-K direct drive because thin/long is not effective, thick/short is the way to go so the energy generated at H was stored at ES once. That means Honda's max deployment amount was 4MJ per lap as ES -> MGU-K is limited to 4MJ/lap, and Honda's deployment was not inferior to others in 2016 so it can be considered that other makers were roughly the same (Honda's initial struggle in deployment in 2017 was due to increased speed of new wider faster car and not employing Extra Harvest until Monza).
MGU-H direct to MGU-K + ES to MGU-K would require power control to merge the two paths and perhaps that doesnt make performance sense, for now or at least at the point of 2016. Wonder how it is now and what other makers are doing.

[trinidefender]

sorry if I'm missing something ....

the K is limited to 120 kW

(and less at low rpm due to the torque limit)
the 120 kW based on DC power factored by 95% efficiency - so just over 120 kW actual might be possible

120 kW is power
power x time is energy
energy (MJ) is of course also limited

The MGU-K has an energy limit when that energy is coming from the ES

There is no energy limit going between the MGU-H and MGU-K

There is no energy limit between the ES and the MGU-H

One form of qualifying mode is to have rapid switching of the MGU-H between motor (with energy from the ES) and generator modes (sending generated energy to the MGU-K) allowing a bypass of the 4MJ limit (although not very efficiently)



According to the picture there is only a restriction for use of the MGU-K below 100kph during race starts. There doesn't appear to be a restriction for its use below 100 kph for the rest of the race.

Can anyone confirm or deny this with the written regulations?

[Tommy Cookers]

ironically .....
this qually energy path and so-called 'extra harvest' path pass their energy via mechanical storage in the H/turbo rotation
and
all H generation 'directly' motoring the K passes via temporary capacitive storage inherent in MG 'drive' electronics


I was posting in reaction to someone's view (as it appeared to me anyway) that over 120 kW was possible from K motoring
the power rules apparently mean what they say but the energy rules don't

[Zynerji]

ironically .....
this qually energy path and so-called 'extra harvest' path pass their energy via mechanical storage in the H/turbo rotation
and
all H generation 'directly' motoring the K passes via temporary capacitive storage inherent in MG 'drive' electronics


I was posting in reaction to someone's view (as it appeared to me anyway) that over 120 kW was possible from K motoring
the power rules apparently mean what they say but the energy rules don't

Its like itemization in Diablo3. The wording on the items very rarely describes the actual in game effects of the item.

Its almost like they knew that the ES->H, and H->K would be exploited as a loophole, and they wanted it to happen.

[PlatinumZealot]

Less air per cycle but more cycles. Theoretically if it's the same fuel flow and AFR then the exhaust mass flow will remain the same. Same blowdown energy.

Each pulse will be smaller but more pulses. This doesn't get into the realm of exhaust tuning though which can potentially shift the peak power rpm range through fairly minor changes.

Am I correct in stating that he exhaust manifold is not a homologated part, I.e. Teams can have track specific manifolds?

The engine rpms make a difference. The air flow is the same yes, but the resistance to air flow through the engine is less at higher rpm since you have more cycles and less air per cycle. So should require lower boost.

[Tommy Cookers]

less air per cycle means the air will need to be less dense - so needs less compressor work ie less 'boost'
relative to this the (differences in) flow work done thereafter are trivial

[Mansell89]

How did people feel the Renault PUs performed in Baku yesterday?

It looked to me like the obvious part that perhaps fell short of Ferrari and Merc was the energy recovery. They seemed to just run out towards the end of the straight.

Other than that the PU doesn’t feel as far behind as it was. It would make a huge difference if Renault can close the gap.

[baybars]

How did people feel the Renault PUs performed in Baku yesterday?

It looked to me like the obvious part that perhaps fell short of Ferrari and Merc was the energy recovery. They seemed to just run out towards the end of the straight.

Other than that the PU doesn’t feel as far behind as it was. It would make a huge difference if Renault can close the gap.

Cyril Abiteboul, Team Principal: "We were not sure what to expect for this race, but fifth for Carlos is a great result, our best since returning to the sport two years ago. We have to admit it came in exceptional circumstances, but it is very positive. Carlos drove a very mature race, managing his tyres well, and fighting with multiple cars throughout the race. It is very encouraging to look at how the grid has changed since last year; the gap to Red Bull and from the Renault engine to the rest of the field is obvious evidence of all the progress we have made and continue to make every weekend

https://www.pitpass.com/61641/Azerbaija ... es-Renault

[toraabe]

How did people feel the Renault PUs performed in Baku yesterday?

It looked to me like the obvious part that perhaps fell short of Ferrari and Merc was the energy recovery. They seemed to just run out towards the end of the straight.

Other than that the PU doesn’t feel as far behind as it was. It would make a huge difference if Renault can close the gap.

Depends on the mapping they are using.