Review of Stillen Underdrive Pulley for 7thgen Maxima

Member Credit: MaximaDrvr

Well, here is what Stillen says:

STILLEN has long manufactured precision pulleys for our supercharger kits. We have used this expertise to produce a new line of high performance crank and accessory pulleys.Each pulley is machined from 6061 aerospace grade billet aluminum with a bold new design to maximize performance, strength and minimum weight. 304 stainless steel sleeves are used for main seal contact points for durability. Stock timing marks are maintained and keyways are precision broached. All pulleys are CNC turned, milled and balanced based on computer generated designs. Up to 80% lighter weight than stock steel and up to 10% lighter than other aftermarket pulleys, we’ve seen power gains of up to 10+ HP at the wheels.Both underdrive and stock diameter applications available for most popular Nissan / Infiniti vehicles.

Product Features

I had been very against Underdrive pulley installation in the past. On my previous vehicles, this instal would mean that the harmonic damper was removed, and vibration and engine wear were increased. I had also seen limited improvement or gains from the mod, and felt it was purely aesthetic while potentially harming the engine and limiting alternator output.

Then I found that the VG 3.5 has an internal damper and the crank pulley is only a pulley. I have read arguments that the delrin insert in the stock pulley helps act as a damper. Based on my knowledge of the insert material, I didn’t see this as a concern.

Underdrive/ light weight pulleys work by reducing rotational mass. They do not add power to the engine. They do, however, reduce what is known as drivetrain losses. If less power is needed to spin the pulley and accessories then more power is available to be sent to the transmission. What that means is that my Engine HP did not increase at all. WHP will go up though.

I have been looking for mods to add, that don’t require taking the engine apart. I picked up one of these pulley and belt combos from the classifieds as NIB, for a much better deal than new from Stillen. I was very skeptical that this would work, but for the fairly small amount of money involved I figured I would try it.

I had my dealer install this. Generally I do the installs myself and document them for the forums, but I was feeling lazy and the dealer price wasn’t that out of line. My dealer charged $157 to install the pulley and new belt. This involves removing the wheel and fender liner, the starter, and then the pulley itself. Book time is 1.5 hours.

Impressions:

First thought: Interesting.
Second thought: the throttle limit till 30mph really limits this car.
Third thought: holy crap, this actually worked.

When not really on the gas, and at lower rpm this isn’t noticeable. When I am on the gas, above 3k rpm, there is an increase. Rule of thumb is that 5hp is the smallest increase that is registered on the butt dyno. I fully believe the 10hp claim, and feel this probably added as much as my RacingLine y-pipe. The engine does not seem to rev faster, and I attribute that to the transmission. The car does accelerate better, and I would say slightly smoother as well.

$135+$43= $178 
Installed by dealer would be $335.

Is it worth that? Potentially. I am very happy with this mod. Knowing what I know now, I would probably do it again, and have no problems recommending this to everyone on the forum. If you are looking for a fairly cheap power adder, and for one of the few things available for this engine, then this is a very good option.