Rotating the tires, I noticed that behind the front passenger side wheel, I could see the bottom of the motor, and there was a pully partly visible with no belt on it. Anyone know why it’s there?
i have wild speculation, but no facts. Lets pretend that this engine existed with belts in other cars, (Toyota Matrix/Pontiac Vibe) Toyota may have designed the harmonic damper (or balancer) into the pulley. Now, if they also use that engine block in the Prius, they could design an all new harmonic damper and track more parts, or use the same old harmonic damper and have an unused pulley. If my theory is correct, then they chose to stock fewer parts. Harmonic damper - Wikipedia - The harmonic balancer often serves as a pulley for the accessory drive belts turning the alternator, water pump and other crankshaft driven devices. Toyota ZR engine - Wikipedia - The Toyota 2ZR-FXE is a 1.8 L (1,798 cc) Atkinson cycle variant of the 2ZR-FE
That’s what I hope it is. I know of nothing belt driven on the Prius, and I don’t recall anyone making a fuss about this previously. Just caught a glimpse and did a double take.
Well, the Gen3 was specifically called out as beltless. And I do remember some previous discussion of this pulley, coming to the same conclusion expressed by Jimbo of reducing the number of unique parts in the overall supply chain.
It is there to reduce engine vibration. A four-cylinder engine has only two spark plugs firing per 360 degrees of crankshaft rotation because of the four-stroke engine cycle. The inertia of the pulley combined with an energy absorbent material such as rubber, helps to reduce crankshaft vibrations so that they will not become excessive, allowing the crankshaft to resonate at certain speeds and causing damage to it or perhaps the crankshaft bearings.
It's the harmonic balancer used on all Toyota 2ZR 1.8 liter engines, using belt driven accessories or not. Toyota does not need to manufacture a special part for the 2XR engine to use it without ant belt driven accessories. That would mean a new part and the cost of inventorying a and cataloging a special replacement part. It's basically a mater of logistics. Likewise, there are a starter mounting port and threaded mounting bolt holes for a starter. The holes are not used and a cover plate is bolted to the place where a starter would be.
I'm think that pulley is a glorified washer; a bolt is torqued against it. It served a purpose with applications having belts (Corolla, Matrix?), and it doesn't hurt to have it there. Doesn't seem like enough mass to be a damper or balancer, but I don't really know.
My previous four-cylinder cars had their belt-driving pulleys bolted directly to the crank, and no excessive crank vibrations, as far as I know. Amazing tech, huh?
