Review & Pics:
My friend and I installed the Stillen Underdrive Pulley this past Friday. The installation wasn't too bad overall. It took a total of about one hour, but that includes the time taken to get the car up on jack stands, remove the undertray, etc. The hardest part of the installation was getting the stock pulley off, because they torque the bolt from the factory really, really tight. My mechanic had to hold the starter in place with a pry bar while I loosened the stock pulley bolt with a torque wrench, and it took a lot of effort/strength to loosen that thing. It would have been easier if the car was on a lift, because I would've been able to use my body weight to pull down on the wrench. Doing it while laying on the ground though, I had to rely on muscle alone.
Driving Impressions:
My butt dyno hasn't noticed any huge gain per se. What is most noticeable to me, however, is that responsiveness has improved, especially off the line. Now, keep in mind that my Z is a 6MT. You know how when you launch off the line there's like a sort of momentary 'dead spot' or 'lag' when you initially engage the throttle and clutch? Well, this is where I notice the most change. That dead spot is virtually gone. My launches feel much more immediate now. The light goes green, I step on the gas and let the clutch out and BAM!! It's on! And I'm not even talking about hard launches. Just with regular around town type of driving, the responsiveness off the line is just more clean and crisp, if that makes any sense.
Also, you know how if you're driving with the AC off and then turn it on, you can actually feel the load the AC is putting on the engine? Like you can feel a bit of power being sucked away. Well, that feeling is noticeably reduced. It's not gone entirely, but it is reduced to a very significant degree.
Dyno:
Okay, enough with the butt dyno. Here's the real thing. I went and put my car back on a DynoJet this morning to see if there are any measurable gains from this thing.
So peak HP goes up from 324.61whp to 330.23whp (+5.62). Peak torque also went up slightly, but I'd say that the peak torque increase is negligible. What is more significant, torque-wise, is the positive effect this has had on the curve. Compare the old and new torque curves carefully. It looks like I've gained back some of the low-end torque that I lost when I installed the headers. (This would be consistent with my perception of sharper response off the line.) Also, if you look at the top-end, it looks like the torque isn't dropping off as sharply as before! I'm keeping it up longer!!!
As for horsepower, I don't think a gain of 5.62 is half-bad, considering that I've already got the full intake and exhaust mods (i.e., my returns should be diminishing big time by now). All in all, I'm pleased with the results.
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