@philrob This is one that got me into modding, I absolutely must push it further. After this I must slow down may modding spree , I am doing way too much of it for two months now. But this is an apex of Jaguar, it is so unfortunate it didn't race, I think if it did race, Jaguar would have stayed on top. @Emery Yes Sayer definitely was bold about low drag. Besides that obviously proper aero balance, control of total lift produced. Supposedly, he even insisted that Jaguar badge needs to be painted on, because anything else disturbed aero too much, well that is a little strange with all of the rivetting, but maybe rivets don't spoil flow too much. However the problem is that they absolutely would have had to do K version to be more competitive everywhere else besides tracks of long straights. The same Porsche was doing with 907,908 and 917. Real problem must have been the Engine displacement regulations. And I think neither of those two had downforce But they probably had nearly neutral amounts of lift. Of course they both had measures to pick more airflow up above car at front, and force air flow upwards at the rear. That Porsche in particular probably had excelent aerodynamics. I think Jaguar would have had detachable tail too. Maybe slight lowered front end, and more body work coverage of frontal tire area. I wish Malcom Sayer worked for more decades on race cars. I think he would be known similarly like Norbert Singer is. There is no reason he wouldn't have been capable to change his mind from being all about low drag, to having some downwards force from aero effects. I think while looking at cars, in the 80s cars were obviously already all about downforce, but they also still cared a great deal about top speeds as long as there was full Hunaudieres in use at LM.
GT40 had a lot of work done over the years to reduce lift, but it was still lifting. Mk II had 100 lbs of lift total at 150 mph and the Mk IV had 148 lbs of lift total at 150 mph. Porsche had entered aerodynamic testing after the 906. The 908LH had 86 lbs of downforce total at 150 mph after testing with different nose designs. Obviously they were still learning lessons before they got the 917 right, but that might be because they were reaching new speeds.
Out of curiosity I just made a quick modelling to see how "more modern" lines would have fitted XJ13, I think it wouldn't have been ugly. Although I must admit rear end is difficult to style when lookign from rear angles. And for front end it is just very simple air dam and it works visually, and I am certain aerodynamically too, just question would be at how much cost of drag, it would have deflected air out away from front wheels, so that probably could have compensated. Reduced pathway downwards at rear end in angle and length would have already elimianted bunch of lift, and little spoiled would have eliminated some more. I wonder if some diffuser effect could have been extracted, but thats difficult with all the mechanicals in the way. To me it looks like if it could have been late 80s - early 90s supercar with these few small modifications. Hmm. Interesting, I can't believe though that MK4 had worse lift thatn MK2 at same speed. Perhaps taken the one of more slip streamed MK4, with rear deck that had stronger slope downwards and Gurney flap lowered way down. While MK2 with Gurney flap on more aggressive position + bigger front splitter lip (can be seen in photos they used them). It is always unclear with what particular setting these cars had those stated aerodynamic figures. Supposedly early GT40 had about 300kg of lift. Lola T70 supposedly had 200kg of downforce, but I assume it was with the most aggressive setup, like this one:
Working on shading and optimisation of model, also experimenting with new tire model. Not easy to balance it out.