the stock spoiler isn't really sufficient to keep the tail down when cornering (sweepers) around 90+ mph. it could use a larger wing or rear defuser to keep the tail down and not wash out.

The OEM rear spoiler is not designed to produce downforce. In general, most factory wings and spoilers are for aesthetics only. In the cases of the Z they are functional, but aside from the NISMO they only serve to clean up air flow and reduce lift. The NISMO kit as a whole produces around 150 lbs of downforce at 70 mph.

If you really want rear downforce you need to go to a proper wing like what Mike is running on his Z. But start adding downforce at one end of the car and you really need to be careful that you're not upsetting the aero balance of the car.

what about the add on spoiler like the one made by mines. Do they help?

Honestly I have no idea. The Mine's spoiler is just an aesthetic piece. Just by looking at it you can certainly tell that it increases drag, but does it benefit the car in any way? No one knows without putting it in a wind tunnel.

It's safe to assume that all it does is look good. :tup:

so that's why i see FWD civic's with those huge arse wings on the trunks..! :icon17:

Interestingly enough, the last gen Celica came with the option of a functional (but odd looking) hood spoiler.

Wasn't a fan of it, but at least it would be more in keeping with a FF setup.

it looks cool :)