That's impressive. I didn't know the plain vanilla MK5s were torsionally weaker than the triple choc cooking models. Interesting, thanks for sharing
What always impressed me was the difference in torsional stiffness between MK4 and MK5. MK5 is 120% stiffer! Normally, newer models of the same car are usually only around 15% stiffer, but such a massive difference just goes to show how floppy and soggy the MK4 really was.
Anyway, I would hazard a guess the extra strength comes from thicker and/or more steel plates around the rear subframe floor/strut towers/inner arch structure, as that is generally where you notice it the most on turn-in. The MK5 Jetta must be even stronger as it has a built-in rear turret brace, aka, steel parcel shelf
The front of the car isn't all that strong where track driven race MK5s are concerned. Race teams often have to seam weld the chassis rails due to the grip of slick/track tyres and stiff suspension splitting the spot welds apart. That doesn't happen on road cars though.
As far as the MK5 is concerned, the steel plates that bridge the tunnel are there purely to stop the exhaust dragging on the floor if it parts company with the engine, they are not stiffening braces.
Crash testing is more to do with how the car folds up in accident and how that behaviour impacts occupant safety, rather than torsional stiffness.
Are you more interested in crashing or handling? I'm slightly confused by this topic, as interesing as it is
An old trick to determine bodyshell twist under hard cornering is to tie some cotton thread tightly across the strut towers. Go out and give the car death in the corners. Upon your return, if the cotton has snapped, there are improvements to be made.
