"five times faster" is correct and usable in written English.
You can use it to compare the speed of two things. For example, "I can run five times faster than my brother."
"The service is four or five times faster.
We could go five times faster without these committees".
Bankers' pay in London is rising five times faster than the pay of the average worker.
There may already be pigs genetically engineered to grow up to five times faster.
Median prices have risen five times faster than earnings since 1997, rents soaring faster still.
A child can heat up as much as five times faster than an adult.
First, the number of openly gay households is growing five times faster than the population as a whole.
A child's body temperature rises three to five times faster than an adults due to lower water reserves.
4G networks provide access to the internet up to five times faster than the current 3G networks.
Nursery prices have risen by nearly a third over the past three years – almost five times faster than wages.
Harper claims his crops grow five times faster than they would outdoors, and need 90% less water while doing so.
