Turbo is the only way to get a 7th gen celica relatively close to 10 seconds (by relative im talking maybe 11's). See, your faced with a really tough situation, FWD. You can have a celica that has 220 WHP running 12s along side a celica that has 400+ whp. The main reason for that is traction. Goin non-turbo is the best way to control traction, as the power doesn't hit all at once like Turbo. However, it is the more expensive route to get that power. For the sake of explanation I'll do both:
First step when building a nice power motor for Turbo is deciding how much PSI you want to run. This will determine the extent (and cost) your mods will run. For high boost I suggest picking up some reinforced rods and lower compression pistons (8.8:1) for the block. While your down there sleeve the cylinders. Now lets move up to the head. stronger valves, springs, retainers and a nice port polish are a must. Upgrade the injectors, fuel pump, oil pump and oil pan. To manage the fuel a PowerFC would be the best option. In fact an oil cooler wouldnt be a bad idea either. The transmission is gonna need stronger internals as well. I have heard many things about people's 6 spd trannies not being able to take the torque. Clutch and a chromoly flywheel should be installed as well. Depending on the PSI your gonna be running would I recommend an LSD.
The long fun road to N/A power. Im not really gonna go into too much depth here as there are too many physics of the engine to explain. Stroke the engine. Main focus here would be improve the low-mid range power while cause lift to scream. Cold Air Intake
, straight pipe exhaust, header, clutch, flywheel, lsd, valve springs, powerfc, ceramic coat your Intake
manifold, header, and full exhaust. Throw on a hondata heatshield gasket. Set the rev limit to a reasonable level (based on how you stroke the block). run higher compression pistons and play with the timing (powerfc allows this). Port and polish the head and Intake
runners. custom cams will be a must
For both of these. your gonna need to upgrade the suspension to handle the increase in power safely and allow a better transmission of power to wheels. Also sticky tires and wider rims are a must as traction will be ur biggest opponent.
also, your gonna have to do some minor
Lastly, you can have a 400 whp car and still run 14's if you dont know how to drive. So learn to drive the beast you build and then you will see nice times.