Ian,
Different insurance companies have different ways of assessing risks associated with car insurance applications. Engine size is one of the factors used and normally a bigger engine results in a higher quote. However there are other factors which are taken into consideration as well and these factors may have outweighed the engine size factor.
I understand that you've put your mother's name to see different quotes but remember that the car insurance should be in your name if you're going to be the main driver, otherwise you will be doing fronting.
Car insurance for 17 year old males are more expensive because men tend to drive less carefully than women. There's nothing much you can do in your first year and if you don't have any claims at the end of the policy, you will earn your no claims discount which will entitle you to a huge savings on your renewal.
Right now what you can do is check car insurance comparison websites and go to
Direct Line Car Insurance (not listed on comparison sites but offering cheap quotes for young drivers like yourself) to see where you can get the best deals.
