Mercedes Power Unit Hardware & Software

[AJI]

An engine driven alternator also loads the engine and puts extra friction + weight +inertia

Exactly. If you already have one mega engine driven alternator and another mega exhaust driven one, why have a pissy little one for ancillaries when it is clearly stated that you can use the ES for this purpose.

The ancillary alternator conversation really started (for me) with the suggestion that they may be using one to charge the ES or send extra power to the K and H, which makes absolutely no sense when you already have a K and an H…

On a similar note, Mercedes and Audi have both ditched the starter and alternator in some of their road cars in favour of a single 48v MGU-K. It does the job of the starter and the alternator and also gives the cars a short hybrid boost.
F1 tech is officially road relevant.

[Zynerji]

An engine driven alternator also loads the engine and puts extra friction + weight +inertia

Exactly. If you already have one mega engine driven alternator and another mega exhaust driven one, why have a pissy little one for ancillaries when it is clearly stated that you can use the ES for this purpose.

This all started with the suggestion that they may use an ancillary alternator to charge the ES, which makes absolutely no sense to me...

Actually, I brought it up while questioning if it could be used in reverse to drive the crank in short bursts by reversing the polarity. I had the thought when RBR was frying them in the V8Hybrid days, and was asking if they still had them installed, and possibly using them as a secret second MGUK.

[AJI]

Actually, I brought it up while questioning if it could be used in reverse to drive the crank in short bursts by reversing the polarity. I had the thought when RBR was frying them in the V8Hybrid days, and was asking if they still had them installed, and possibly using them as a secret second MGUK.

This makes sense in the pre PU era, but not anymore. An ancillary alternator used in the way you describe is effectively a second K and they're only allowed to have one...

[Zynerji]

Actually, I brought it up while questioning if it could be used in reverse to drive the crank in short bursts by reversing the polarity. I had the thought when RBR was frying them in the V8Hybrid days, and was asking if they still had them installed, and possibly using them as a secret second MGUK.

This makes sense in the pre PU era, but not anymore. An ancillary alternator used in the way you describe is effectively a second K and they're only allowed to have one...

Obviously. My point is that we know that the MGUH and K are often reversed at like 40khrz or some nonsense, it shouldn't be difficult to make an alternator behave similarly without the FIA knowing...

Just speculation as always...

[AJI]

Just speculation as always...

Hey, that's what I love about this site. None of us 100% know what's going on, but there are plenty of very insightful educated guesses.
I'm all for a 'creative interpretation' of the rules, and I dare say using the alternator as a tricky second K was explored pre the PU era, but I can't see any reason to pursue it now, mainly because I don't think they have one. Just my opinion of course, and as I said, I'm happy to be proven wrong...

[Mr.G]

An engine driven alternator also loads the engine and puts extra friction + weight +inertia

Exactly. If you already have one mega engine driven alternator and another mega exhaust driven one, why have a pissy little one for ancillaries when it is clearly stated that you can use the ES for this purpose.

This all started with the suggestion that they may use an ancillary alternator to charge the ES, which makes absolutely no sense to me...

Actually, I brought it up while questioning if it could be used in reverse to drive the crank in short bursts by reversing the polarity. I had the thought when RBR was frying them in the V8Hybrid days, and was asking if they still had them installed, and possibly using them as a secret second MGUK.

I'm still in doubt that there is no low voltage alternator.
- I'm not sure how much power demand the car have for the low voltage supply but it would be up to 500W as this about 30kJ which are allowed.
- supplying 500W for ~2h solely from battery (separate) is not good
- converter from 1000V to 12V won't be small either
- when you damage the 12V circuit you need to opt for new engine parts = penalty
- power generators H/K will generate lot of disturbances = noise in low voltage circuits/issues
- from el. eng. point of view if possible they would opt for galvanic insulation between power electronic and control electronic...
- you can drive the alternator with hydraulic if you want

[AJI]

I'm still in doubt that there is no low voltage alternator.
- I'm not sure how much power demand the car have for the low voltage supply but it would be up to 500W as this about 30kJ which are allowed.
- supplying 500W for ~2h solely from battery (separate) is not good
- converter from 1000V to 12V won't be small either
- when you damage the 12V circuit you need to opt for new engine parts = penalty
- power generators H/K will generate lot of disturbances = noise in low voltage circuits/issues
- from el. eng. point of view if possible they would opt for galvanic insulation between power electronic and control electronic...
- you can drive the alternator with hydraulic if you want

Sure, I'm guessing too, but I see no need for an ancillary alternator for the reasons stated previously, but mainly because the flow diagram shows a legal unlimited path from the ES to the ancillaries…

- Yes, we don't know the actual power demand of the ancillaries, but we can assume they are tiny compared to the K and H demand. The external ancillary buffer is actually 300kJ. I must have accidentally written 30 and didn't notice until today... Sorry for any confusion
- The power for the ancillaries isn't solely supplied by the external 300kJ, it's supplied from that 300kJ plus the ES plus the K and the H.
- Converting from any voltage to another voltage isn't difficult. The physical size of the unit is, in very simple terms, directly proportional to current demand, which is minimal for ancillaries.
- I don't see anything in the rules suggesting there are any penalties for replacing anything in the low voltage part of the system?
- Re: noise, interference, insulation, etc… Whether there is a 12v alternator or not, there is still a ~1000v system and a 12v system simultaneously running on the cars. The 12v system works just fine, it's clearly not a problem. If it were we wouldn't have TV pictures and I doubt the commercial rights holders would be happy with that. The 1000v system on the other hand, clearly has room for improvement...
- Why would you drive an ancillary alternator hydraulically when you don't even need one?

Sorry, I don't want this to go on forever, but I am genuinely intrigued as to whether the cars have an ancillary alternator or not?

EDIT: I started a new thread to discuss this outside of the Mercedes PU thread as it really applies to all PU's
viewtopic.php?f=4&t=27593

[Kevinkirk]

Bit of a newbie question. Could all the engine driven auxiliaries be electrically driven.eg hydraulics and water pumps etc?

[63l8qrrfy6]

5.13.1 All coolant pumps, oil pumps, scavenge pumps, oil/air separators, hydraulic pumps and fuel
pumps delivering more than 10bar must be mechanically driven directly from the engine
and/or MGU-K with a fixed speed ratio.

Not sure if the 10 bar limit only applies to the fuel pump or any of the pumps mentioned.

[Sierra117]

5.13.1 All coolant pumps, oil pumps, scavenge pumps, oil/air separators, hydraulic pumps and fuel
pumps delivering more than 10bar must be mechanically driven directly from the engine
and/or MGU-K with a fixed speed ratio.

Not sure if the 10 bar limit only applies to the fuel pump or any of the pumps mentioned.

Hmm quite tricky. Considering relations are supposed to be technical and precise and how one can easily rewrite to refer to all pumps requiring the 10bar limit, I'd say it's most likely only applied to the fuel pumps here. A simple change to having a comma before "delivering" and after "10bar" would refer to all pumps more clearly.

Wonder if this was used as a loophole by the teams though.

[Brake Horse Power]

I think from a drive side view of the auxiliaries you would prefer mechanical. It is robust, kind of simple, light and very efficient at first sight.

But when you drive auxiliaries separately you have more control, for example the rpm can be fixed instead of varying between 4? And 12k rpm. I dont know how large benefit this has if you talk about cooling and hydraulic pumps. Due to this steady rpm geometry might be optimized, which could be more efficient.

[63l8qrrfy6]

I think from a drive side view of the auxiliaries you would prefer mechanical. It is robust, kind of simple, light and very efficient at first sight.

Absolutely.

But when you drive auxiliaries separately you have more control, for example the rpm can be fixed instead of varying between 4? And 12k rpm. I dont know how large benefit this has if you talk about cooling and hydraulic pumps. Due to this steady rpm geometry might be optimized, which could be more efficient.

Despite the fixed gearing the oil and hydraulic pumps can have variable displacement. Actually I know for a fact that hydraulic pumps do since most teams use the same Parker axial piston pumps with variable swashplate angle. In most cases the hydraulic pump speed is dictated by the steering moog valve flowrate requirement at low engine speed (launch/ leaving the pits).

Traditionally oil pumps have been of external gear type with a PRV which is not particularly efficient but I'm not sure there's performance to be found by driving them electrically. Probably easier to switch to a variable displacement vane type pump.

[Big Tea]

I think from a drive side view of the auxiliaries you would prefer mechanical. It is robust, kind of simple, light and very efficient at first sight.

But when you drive auxiliaries separately you have more control, for example the rpm can be fixed instead of varying between 4? And 12k rpm. I dont know how large benefit this has if you talk about cooling and hydraulic pumps. Due to this steady rpm geometry might be optimized, which could be more efficient.

Would there be any advantage of an electrically driven 'external cam shaft' to power the pumps mechanically without loading the engine? I am assuming now that it is run off 'free' energy, not out of the allocation.
Possibly a motor-in-flywheel to give it inertia so the motor could run at fairly low average load. I realise this is all extra weight, but the weight allowance seems huge now and if it needs ballast it may be a reasonable trade off for position?

(perhaps we should have a section where stupid ideas are shot down properly )

[gruntguru]

I think from a drive side view of the auxiliaries you would prefer mechanical. It is robust, kind of simple, light and very efficient at first sight.

But when you drive auxiliaries separately you have more control, for example the rpm can be fixed instead of varying between 4? And 12k rpm. I dont know how large benefit this has if you talk about cooling and hydraulic pumps. Due to this steady rpm geometry might be optimized, which could be more efficient.

Would there be any advantage of an electrically driven 'external cam shaft' to power the pumps mechanically without loading the engine? I am assuming now that it is run off 'free' energy, not out of the allocation.

This would only be permissible for pumps producing less than 10 bar which rules out the higher power ones including (at least) fuel and hydraulic.

[Brake Horse Power]

Quite a cool picture posted by MtthsMlw in the Force India thread, which I thought was good to share in this thread as well. What is the carbon pipe from the gearbox towards the air box? Is it for venting / cooling? It is not a structural stud is it? I suppose the white part is flexible to make sure it is not cracking under deformation?

High res engine and gearbox