I have in front of me an article concerning the lotus elise.
The chasis is made entirely from aluminium alloy (6063 family for those
of you who care). The designers have used aluminium extrusions to build
the chasis which is then glued together using epoxy resin. They have
used glue aparently because if you weld aluminium you have to use
thicker extrusions to keep the strength at the joints. The entire chasis
weighs 143 pounds and is as stiff as a bmw 3 series saloon (sedan).
Brake discs are aluminium composite (aluminium.silico carbide).
It uses the rover k series engine of 1800cc capacity. The lightest four
cylinder engine of that size to be found anywhere. (there is aparently
room under the hood for a v6 lump yummy).
The renault aparently uses welds in it's structure and is therefore
heavier and is slower by comparison even though it has a two litre
150bhp engine under the bonnet.
I can supply the full ariticle if you want it. Just email me direct and
i will scan it in.