I haven't seen anyone flogging the dead horse for a very long time, but it still seems like people didn't understand the concept of the car.
Put very simply, it wasn't FWD. It was a reversed layout - a traditional hybrid P1 has an electric/IC split. This had an IC/electric split. In putting the layout back to front, it opened up a world of aerodynamic possibilities.
Everything you've mentioned is a very basic explanation of simple fundamentals of vehicle dynamics, which aren't entirely off base - they just can't be applied to this example.
I was replying to someone banging the drum of drivetrain layout not being the problem, rather than trying to resurrect a dead horse myself. I understand how LMP hybrid systems are arranged and the GTR LM's concept, and as an engineer myself I've tried to to understand why those involved thought the aerodynamic possibilities were great enough to justify using an extreme weight distribution and inferior drive layout.
As far as whether it was FWD or not: is it 100% FWD? No. Is it heavily FWD-biased? Yes, and Nissan themselves
always described it as being FWD. Even in the 8MJ hybrid class, cars are permitted well over 100MJ of fuel energy per lap, so the effect of the electrical system's energy is relatively small (contributing 4 sec in a ~3 minute 20s lap,
according to Nissan, and certainly less than Nissan were losing at Le Mans). You can't argue that the drivetrain is anything but a mildly augmented FWD. I'm happy to call it "FWD-bias" if that makes it clearer what we all mean.
I could have happily got into the deeper maths and physics but chose not to, precisely because the simple fundamentals
can be applied to the GTR LM. The decision to use a front-biased layout (in terms of aero, weight, and power distribution) necessitated rear tyres with a significantly smaller contact patch than their rivals in order to balance the car. To reclaim the lost mechanical grip and overcome the dynamic limitations of FWD-bias, Nissan would have needed a huge chunk more downforce than other LMP1s, and that's assuming that such downforce levels would not further over-work the tyres. One of the development problems mentioned in a few articles was difficulty defining a tyre compound that worked.
It would also take a massive jump in aero efficiency for that level of extra downforce not to increase drag. The greater downforce would impact front suspension settings over and above the specific requirements of FWD, further limiting any gains. Let's not forget that out of a slow corner the aerodynamics can't do much anyway - exactly the type of corner where a driver of a RWD-biased car will neutralise understeer with the throttle whilst the Nissan drivers would have been trying to balance tyre loads from steering and accelerating. Even the best diff and TC settings are not going to be good enough to match the inherent balance of a RWD when chasing fractions of a second through a corner. Trackside reports from LM in 2015 indicated that not only was it slower through the corners, the Nissan was unsurprisingly leaning harder on its TC than other cars.
Inherent limitations will always exist, but an engineer will always try and minimise their effect. That is how motorsport engineering will always work. FWD platforms make up a very considerable amount of competition platforms the world over, and they continually achieve success in various fields - there are some regulations that favour certain layouts, and some that favour others.
The "significant loopholes" you've alluded to, ironically, are what the current LMP1 regulations offered.
Where regulations favour FWD it is not usually through a loophole in the rules but rather because organisers have actively chosen to artificially balance the performance, as in touring car racing. FWD is normally used in motorsport only for cars based on FWD road cars, and I can think of nowhere in recent memory that it has been truly successful against RWD without performance balancing.
I remain unconvinced that unrestricted front aerodynamics was a
useful loophole. It seems that Audi, Porsche, Toyota, and the privateer chassis-builders would agree, since none of them bothered with that approach. An un-named German apparently told
Road & Track that he thought the Nissan project was no more than a marketing exercise.
The fact that the rules permit something does not necessarily mean that it is a loophole, nor that it is advantageous to make use of it. If the rules had also allowed unlimited front tyre width, it may have been something worth exploiting to make FWD work; for aero reasons alone there was not enough reason to go Nissan's route because of the significant compromises of FWD.
Bowlby is a highly accredited motorsport engineer with decades spent working in several very high profile positions within the industry. Someone in the position he was in at Nissan, being both the principal and technical director of a racing programme at the very highest level of international motorsport, will not have gone ahead with a project developed on hunches or random ideas. That's simply not how the motorsport business works. Regardless of how the cars materialised on track, and the performance issues they encountered, there will have been very sound engineering theories - going much, much further beyond basic vehicle dynamics concepts - applied at every step of the project.
I'm not suggesting that Bowlby's designs came from hunches or random ideas - even the best engineers make mistakes and pursue dead ends that originally came from solid engineering principles and concepts. I believe the GTR LM had the same problem as the Deltawing. Despite their outward differences I can see how the thinking behind the Deltawing's design led to the GTR LM. Both offer great aero efficiency numbers in a windtunnel or CFD analysis, and both start from a point of a fairly extreme weight & aero distribution. But both also have a reliance on one end of the car to be working much harder than would normally be the case for anything but a dragster. You can apply all the sound engineering theories in the world to that starting point but that approach is fundamentally inefficient, and for the GTR LM in particular it resulted in a cascade of negative consequences. Perhaps it's fairer to blame the front-engine layout and philosophy, but FWD was a big factor in the GTR LM's failure.
