Comparing powerunits, understanding early season issues and the real reason why Mercedes AMG F1 are ahead
2014 has thus far provided us with the backdrop to several drama's but for me it has been the source of major frustration. 2014 marks a point in Formula One that not only see's the largest rule change in the sports history but hinges on a major technological leap forward. Unfortunately I'm left aghast at the poor coverage supplied by the UK broadcasters (at least) which not only borders on propaganda/misinformation but moreover shows their disinterest in covering what makes the sport tick.
The latest signal of this was the Skysports feature over the Bahrain GP weekend claiming an exclusive as to why Mercedes were so fast compared to their rivals. The piece although great from the perspective they were actually covering the technical side of the sport was good, however their claim on an 'Exclusive' is somewhat incorrect. Myself, @ScarbsF1, @RacecarEngineering amongst others have all talked about this in the past via Twitter (albeit with the exception of Racecar Engineering who actually published it in their magazine on 5th March). Furthermore pretty much anyone who looked over the regs ahead of 2014 would have realised that splitting the turbo and installing the MGU-H between it in the V was a great way to package it. I even drew it way back in 2011/12 and published it in January 2013 when I took a look at the PU's and packaging on the blog.
The insinuation that the works team are the only ones that could fully utilise the advantages of this turbo layout however are unfounded. I actually corrected misinformation that Crofty gave via twitter during his '#AskCrofty' after the Bahrain GP.
#AskCrofty @richardh105 Err, no. Hence it's one of the secrets of Mercedes success so far
— Sky Sports F1 (@SkySportsF1) April 6, 2014
@SkySportsF1 @richardh105 incorrect the turbo is a homologated component and so all Merc teams have the same Turbo / MGU-H installation..(This is part of my frustration, if you don't understand or know about these sort of things then don't comment, I try to stay away from bum steering people and although I know a fair bit I'm always learning...)
— Matt Somerfield (@SomersF1) April 6, 2014
The Homologation process covers the ICE, Turbo, MGU-H and MGU-K meaning that the split arrangement is run by ALL Mercedes powered teams.
Don't get me wrong, the advantages gleaned by Mercedes (works team) are reliant on the split turbo configuration but it's how it's been used to package other items that stands them apart from McLaren, Force India and Williams. I won't go on to tear down the rest of the Sky package but suffice to say there are other technical elements that are incorrectly displayed during the presentation.
So what are the differences between the teams?
I'll start out with cooling options and for those of you uninitiated in the realms of turbocharging, a charge cooler (air to liquid to air) used to be seen as an inefficient way of cooling the inlet charge with most applications utilising an Intercooler/Aftercooler (air to air). This is because most people perceive the additional items required by a chargecooler to equate to additional weight. However over recent years opinion has swayed with the design of them (air to liquid to air) going back to the drawing board rather than just thinking of them as an air to air cooled, water jacketed. Air to air coolers are most effective when able to be placed in freestream air and so you'll usually see them front mounted on road cars. Air to air coolers for a single seater with a singular centreline turbo however brings forth some compromises in terms of pipework with much larger diameter pipework needed to carry the boost into and out of the cooler. Symmetry is an important aspect for Formula One teams as not only do their initial calculations (CFD) run with 1/2 a car mirrored (obviously Lotus are an exception to the rule this season) but having a differential in drag/aero performance on one side of the car can of course be detrimental to performance. This really brings rise to several layout options for the teams:
- Twin engine radiators (smaller than their usual capacity due to the downsizing of the engine) with twin air to air coolers mounted in conjunction with them, keeping the aero status quo. The downside of this is the increased level of pipework, especially the larger diameter boost pipes.
- A singular engine radiator, obviously larger than the one used in the setup above mounted in one sidepod, with a singular but similarly sized air to air cooler mounted in the opposing sidepod. The issue here would be the difference in core thickness between the water filled radiator and boost filled after cooler. Symmetry would also be lost in terms of the boost pipe sizings vs the water hoses.
- A charge cooled (air to liquid) setup would allow for similarly sized water radiators to be placed in either sidepod (one for engine cooling, the other for the chargecooler) with the water jacketed cooler placed between the turbo's compressor and the inlet. This setup has a few drawbacks which invariably outweigh the positives, the jacketed cooler's weight is placed relatively high up (increased CoG) but the shorter tract between the compressor and the inlet means you have less pressure drop (increased performance). The use of the pre-rad to support the chargecooler means that there isn't the packaging issues associated with the larger diameter boost pipes used with the air to air setups.
- A charge cooled (Air to liquid to air) setup with an engine radiator (smaller than the iteration above), pre rad and a chargecooler, either side of the car.
Force India's approach is perhaps the most obvious choice in terms of the air-to-air variants and from the image above we can see the effort that has been made in order to get the coolers ahead of the ICE, therefore the heat generated by the exhausts is less of a factor. Force India have opted for the more conventional laid back coolers to maximise airflow passing over their surface. Bear in mind that the arrangement of the cooling fins have to be orientated to take this into effect too as otherwise it wouldn't be worth tilting them.
Pictures of the FW36's internal packaging are a little rare, but what I can make out from the limited information is that they have gone for the conventional laid down orientation of the coolers. I'd also surmise that like Force India they have opted for the engine radiator in one sidepod and air-to-air cooler in the other option but I'll verify this when I have the proof.
Caterham have followed a very similar path to Red Bull in terms of stacking twin ICE radiators in either sidepod with the chargecoolers pre rads, the angling of these is much sharper though in order to curtail their presence ahead of the exhaust manifold.
Lotus have also gone down the chargecooled route but have a different layout to the previous two Renault powered teams with the ICE radiators and chargecooler pre-rads mounted almost vertically/longitudinally with the chargecooler itself lying under the rear rad. To supplement the flow of cool air in that region the team have also utilsed a floor duct for the left hand sidepod due to the increased piping created by that exhaust (I'll explain this a little more later).
From these images I'd surmise that Marussia have opted to run a chargecooled setup with an engine radiator in one sidepod and a pre-rad in the other. This makes the Ferrari configuration closer to the Mercedes one than say the Renault one but it still holds a significant variation. Ferrari have not opted to separate the compressor and turbine and run the shaft through the engines V, however it would appear the boost pipe from the compressor is routed through there (through a donut in the airbox pipework), terminating at the chargecooler. The air is then cooled within and exits from the top into the inlets (pipework which has the green temperature stickers on it).
As you can see I have limited images of the C33 to work with but apart from the orientation of the radiators (in this car they are vertical) they appear to be using a chargecooled setup, the same as Marussia.
This next section may involve a bit of scrolling back to the pictures I've used above rather than filling the article with yet more images. One of the other areas that can be changed by each team in order to enhance performance is the exhaust. You'll note that from all of the images presented of Mercedes powered cars the teams are utilising a log manifold rather than the equal length ones we are used to seeing. Now this is an area of performance that is a trade off and so depending on where you are wanting to make gains it would change your approach. Furthermore there are still design considerations and marginal differentials in each design that can affect both torque and power curves. Add into the mix what the MGU-H is capable of doing in terms of spooling / supporting the turbocharger, what size and/or scroll your turbo is and you have some serious decisions to make.
All the other teams but Red Bull are utilising an equal length manifold which resides aft of their engine and charge air cooling solutions. Red Bull have laid their manifold flat underneath the chargecoolers in a configuration that lends itself towards an equal length variant, however with the limited vertical space it's difficult to ascertain whether it truly is equal length and could be a hybrid of both solutions, simply extending the header lengths. The advantage of the layout used by the Mercedes powered teams is the sheer amount of space saved by running the manifold directly to the turbine.
Wastegate(s) are another component that can be selected by each team but will likely take instruction from the manufacturer in terms of their installation and operation. Ferrari powered teams (above) have opted to have twin wastegates (one for either manifold) as part of the Turbo/MGU-H assembly with significant pipework diameters being proportioned off. All of the other teams are using a singular wastegate with significantly smaller pipework (usually running off the centreline), whilst Lotus once again do their asymmetric thing and run only one wastegate from the left hand exhaust bank. There are some plausible (but marginal) advantages that could be extracted aerodynamically from the wastegate that I've talked about before and this might be what Lotus are trying to do with their asymmetric layout. The wastegate is an important element for the new powerunits and must be robust, several of drivers/teams have had issues with them already, probably most famously Sebastian Vettel. Their control and effectiveness is important due to the way the MGU-H operates alongside it, with a decision to be made over which one curtails the turbo based on the cars current SOC (State of Charge, ERS language for the amount of energy being recovered and sent either to the ES or directly to the MGU-K).
Ferrari powered teams thus far seem to have fallen a little short of the mark with a large disparity in top end performance which was clear to see when it left Alonso a sitting duck for an attack by Hulkenberg in Bahrain. It seems their issues revolve around the way in which the two MGU's distribute power to one another and could be the result of mistakes made in selecting the size of their turbocharger. Towards the top end of the powerband it would be wise for the MGU-H to be harvesting power (ie curtailing power) and sending it directly to the MGU-K for additional power. However it seems that the Ferrari powered teams are unable to do this and instead are using energy from the ES which in turn is being depleted too rapidly, resulting in less top end horsepower.
Last but no means least is a question mark over exhaust bore, you'll note from the images that all the teams have different sizes, tailored to their own performance needs. It's not an area of massive potential due to the energy leaving the exhaust being lower than in previous seasons but still worth a mention as it can be adjusted by each individual team.
In summary the Mercedes powerunits split turbo arrangement is a performance differentiator but it's decisions that the team have made in the rest of the installation that sets them apart from even those teams that also run the Mercedes HPP unit giving them not only a power advantage but creating a more internally aerodynamic efficient car. It's quite clear to see by the behavior of the Mercedes powered cars that their ERS in it's entirety is much more mature than their counterparts, with the Renault and Ferrari powered teams struggling generally with the transition of energy under acceleration and braking. This affects the brake-by-wire system, as holes in the provision of energy or during harvesting will lead to communication issues between the MGU-H, MGU-K, ES, controller and braking system. All of these lead to a lack of feel/confidence for the drivers who then struggle to let the automation that should be going on in the background do its work.
With the Renault and Ferrari powered teams having issues that really revolve around larger packaging and problems with the ERS, fixing either of these issues during the 2014 season will not only be vast and expensive but come with their own compromises.