I just picked up a Stillen OEM sized pulley. I'm not worrried about installing it. I had a UR underdrive crank pulley and alt pulley on an older Acura and ran that for well over 150k miles with no issues.

 

I'd advise people to research the differences in cross plane vs flat plane crankshafts. Our engines don't use a harmonic balancer like v8s and other engines. There is a lot of old knowledge of old engines being expressed in this thread that doesnt have anything to do with our engines.

And , underdrive pulleys come with a bigger alternator pully to bring your alternator to factory rpm.

so either is 100% fine on a VQ.
yes I know this thread is older but still the top result for g37 lightweight pully on Google.

 

I've been running the Agency Power light weight crank (under size) and the alternator (over size) kit on my 2013 G Sedan since June of this year with zero issues:




"Off Topic" - Although on their website it says it fits our cars it doesn't without modification. Had to take both pulleys to a machine shop to have them mill off some material, but at the end it's been worth it for sure. Shoot I may even be the only G running this setup

 

Flat plane crankshafts?? I don't think anyone is running a GT350 or Ferrari motor in their G. All kidding aside, the topic of harmonic balancers was covered about 8 years ago in this thread.

It's good to hear that most underdrive pulley kits are now coming with a bigger alternator pulley as well to cancel out the fun headlight dimming effect at idle. But I would imagine that would add back some weight. Gaining back roughly 5 hp is pretty tough to notice on the butt dyno and not really worth it to me. I think your money can be much better spent on something else, like a rear differential brace.

 

Just pointing out that our engine is internally balanced.
And the point isnt feeling 5hp , it's about being 5 more to go with all the other hp you gain with this that and the other. Right?

 

I haven't thought about LW pulleys in a while. Pretty much dismissed it years ago thinking a 3hp gain at the wheels was pointless on a car with over 330 hp.

But this guy here makes a good point about the collective impact of incremental changes.

I had an Unorthodox Racing LW pulley in my old 2003 Maxima 6MT. For a few days afterwards, I swear the car would rev quicker in neutral, which meant something was different.

Anyway, 10 year old bump for a good read.

 

Yes, this is one small piece of the puzzle of many parts that add up to bigger gains.

 

IHMO you get more gains with lighter wheels/tires and smaller than OEM (slightly)

Edited to add: I get the draw of a pretty anodized pulley over the stock ones... but internal resonances are a thing for sure. With V8s the Fluidamper was a good lighter-but-still-damps option.

Just changed the belts and tensioner on the CX5 so been up close and personal with that area of the car recently...

 

Absolutely! And let's not forget stickier tires.