The cake turned out to be burnt at top, did not rise completely and the bottom half have a kueh-like texture.
After a few clicks here and there on the Net, i soon found out the likely causes for those problems. It puzzled me at first why i burnt the cake even though i followed the temperature 170°C. Soon, i learnt some important lessons about ovens and baking:
i. Each oven bakes differently depending on the size, type etc. So the temperature and time needed may vary.
ii. Temperature set on the oven dial may not be the ACTUAL temperature INSIDE the oven. Thus, it's best to use an oven thermometer.
Next is why my cake is shrunken and did not rise properly. The problem lies in this three words
"beat until stiff"
Being an absolute beginner with completely no experience at baking, i had no idea what this three words signify. I found out that beating of egg whites is one of the most important step in making chiffon cakes and i had just overlooked it. I only beat the egg whites until frothy and not until STIFF. Here is a perfect guide on how to beat egg whites.
Also, i learned something about mixers.. My standing mixer does not reach the bottom of the bowl. So the egg whites at the bottom remain unbeaten, resulting in the double layer of the cake with the bottom half tasting like kueh. So for my 2nd attempt, i removed the mixer from the stand and used it like a hand mixer, making sure that the egg white is fully beaten.
Next, i found out the correct way of folding the mixtures and its importance. The egg white must be folded slowly and carefully to prevent the egg whites from collapsing.