Checked build speeds

[Fearitself]

Mayans build city in 26 sec.
After CONSTRUCTION, in 23/24 sec.
After ARCHITECTURE, in 21 sec.
After ENGINEERING, in 18 sec.
.
Other civs build city in 40 sec.
After CONSTRUCTION, in 36 sec.
After ARCHITECTURE, in 32 sec.
After ENGINEERING, in 28 sec.
.
It would apear that each research lessens build time by 10% off the original build speed.

[Skanky Burns]