I usually throw on a 77mm upper pulley and leave the stock crank pulley alone. I would like to try running a different setup of a 168mm lower and 83mm upper instead of just the 77mm alone. My reasoning for this would be to try and gain more surface area for the belt to grip, see if the 83mm allows for smoother engagement, and just honestly to try something new although boost should theoretically be around the same levels.

I've seen people say that with 180mm or bigger, that pinning the crank is necessary for safety. With a smaller 168mm crank, is pinning still necessary? I'm fine with changing out the crank pulley as I've done it on other cars with no problem. However, I've never pinned one and don't think I'd be comfortable drilling a hole into that area as it looks like you have to be extremely precise with the placement. Lastly (without bias), is there an aftermarket crank pulley that is designed better than the rest of the competition? I see products from ASP, UPD, Weistec, Kleemann etc and am not sure why one is better than another.

 

My advice: Leave the crank pulley alone and get a belt wrap kit: that will do a lot more to reduce belt slip than different pulley combos. (It's also cheaper, easier, and safer.)

However, to answer your question: Pinning shouldn't be necessary at that boost level: plenty of people have run that combo without any problems (if properly installed). Be sure to replace the bolt and torque it properly (it's very tight: 200NM then 90 degrees). Pinning is good insurance, however, so I definitely wouldn't recommend against it if you were up for it. There isn't much precision involved: you need to use a jig to guide the drill bit. The only problem is that drilling into the forged steel crankshaft is very difficult. You will need a good drill bit and a lot of patience. If you were to go any bigger, I would strongly recommend pinning. I can speak from experience that 175mm+77mm definitely does need to be pinned.