I hit a tire tread on the road and it broke my front bumper lip .Can I Drive my RX8 without the splash guard under the engine?

 

You can...but there will be issues with the radiator not working as efficiently and the potential to get rocks making holes in your A/C condenser.

You would be better to try and zip tie it all together until you can fix it

 

Mine came without a drivers side splash guard, beyond the slight decrease in radiator efficiency. Without the splash guard there's quite a bit more space for you to start flinging road grime over connectors sensors and other things. I've wondered if it was a major contributor to my steering rack failure.

I bought one of these for $20-25. It looks a little different than the OEM one, but it fits completely fine.

2004-2008 Mazda RX8 Inner Fender - Body Mechanical & Trim - Action Crash, Front Left - Driver Side 04-08 RX8 Inner Fender - 8610-04056087 - PartsGeek