Performance Crank Pulleys

[YarisSi]

What are they meant to do? Is it just for weight reduction?
Also just thinking the other day but not planning on doing it (only a yaris) can you bore out a throttle body or even buy bigger throttle bodies (single) to get more air in the engine.

[Marquis_Rex]

The crank pulley kits are usually of a lower rotational inertia than the original. It's a similar theory to a lightened flywheel but has less of a marked effect. It doesn't increase horsepower, but makes the throttle response sharper and also makes acceleration better. This is a definate quantifiable effect, but by how much and whether it is worth it- is another story.

I don't know what is availiable for a Toyota Yaris, but a bigger bore throttle body CAN increase the airflow to the engine, assuming the original was restrictive in the first place. If the original throttle body was NOT the bottle neck you'd be wasting your time. The thing to watch for when going for a bigger bore throttle body is an uncontrollable "tip-in" response (non progressive) when you put your foot down initially which could make the car quite difficult to live with in trafic. Air leakage through the bigger throttle would also be more so your idle speed could be effected, although usually with modern applications the idle speed control should take care of this.

[YarisSi]

Thanks for that