i ordered the stock diameter underdrive pulley for my 07 G sedan.

getting it installed on next week thurs.
im going to get a base line dyno done with my current mods.
HFC, intake, groundwire.

and then they will install the pulley and do an after dyno. the tuner told me there wont be much of a "hp/tq" gain. it does use stock belts so all it is that its lighter, so the inertia moves faster making it a lot easier to spin and the result being faster uprevs. so my rpms will climb quicker giving quicker acceleration.

pics vids all in time guys

 

stock diameter is not an underdrive pulley, it's just lighter.

as you kind of said, a lighter pulley probably not show up in the hp and tq sheet, but you"ll notice improved throttle response and probably quicker revving. while it may not show up on a hp/tq chart, with just a few clicks they can produce a 'time vs. acceleration' chart off the same runs and it could very well show up on that. i'd ask them to do one of those as well.

on my drag quads, we use lighter flywheels a lot to help the motor rev freer and there is a visual difference in the time vs accel charts on those.