Stillen Underdrive Pulley - Review/Pics/Dyno/Vid
 

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.

Here's the Stillen UD Pulley, front and rear:
http://www.the370z.com/members/semte...1-p1000920.jpg

http://www.the370z.com/members/semte...7-p1000918.jpg

Here's the stock pulley, viewed from underneath the car:
http://www.the370z.com/members/semte...2-p1000922.jpg

We used a small gear puller slightly modified with one of the arms shortened (we were following wstar's lead on this, so credit goes to him (see http://www.the370z.com/members-370z-...html#post59072 for more details if so desired)):
http://www.the370z.com/members/semte...9-p1000924.jpg

Stock pulley with the puller attached:
http://www.the370z.com/members/semte...0-p1000925.jpg

Here's how the engine looks after the stock pulley is removed:
http://www.the370z.com/members/semte...3-p1000927.jpg

And here's the new pulley, installed:
http://www.the370z.com/members/semte...8-p1000936.jpg

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.

Here's my previous DynoJet dyno:
http://www.the370z.com/members/semte...09balanced.jpg

Here's the updated one:
http://www.the370z.com/members/semte...ced-052009.jpg

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.

Video

YouTube - Stillen 370Z Underdrive Pulley Dyno Results


Don't forget to rep if you found this informative/useful! ;)

I'm really disappointed you couldn't find a spectacular bedspread to shoot the product photos on.. boo!

I don't think you can fairly compare the low end on those charts, the previous dyno runs were started at higher RPM so you just see the spool up lag.

The high end you can see the distinct change, you picked up 10 ft/lbs at red-line which is impressive. Thanks to the reduced falloff you would probably see a benefit from bumping up the red-line slightly.

semtex journal is back at NUMERO UNO!! haha. congrats on the install.

This is one mod any make of car that nobody dynos individually. Thank you for actually going about and doing it. Its good to see some hardcore proof of gains from an UD pulley.

Thanks man!

I'm only comparing the small bit from 2500-3000 rpm. I think it's fair to compare at those points. But prior to 2500 rpm I agree that it's due to the runs starting at different rpms. Having said that, the delta between the two from 2500 - 3000 rpm isn't much. But I'll take what I can get!

Nice work man. You'll be hearing from my lawyer shortly re: theft of my patented gear puller modification :p

LOL....hey, I've got a stack of gun magazines for a backdrop this time. Gotta change it up every now and then, you know? :p

HA! I'd better get my checkbook ready for the royalty checks I'm gonna have to write, huh?

Yep, fair enough. Now that you have the software figured out you can overlay the old best run with the new best run to really compare.

:icon14: Ditto. Unless Semtex acquiesces and at least throws a cigar magazine into the mix I'll have to stop reading his threads and force him to return my journal.

Thanks for a great writeup. I wonder how the lightweight pulley would compare to the underdrive one in performance. I'm most likely supercharging my Z in the future so an underdrive pulley would be inaptopriate for me.

Skorch, I was wondering the same thing, but have decided I will probably go underdrive for now then swap if the supercharger thing becomes a reality for me. I'm sure the underdrive will be a quick sale to a fellow forum member.

*sigh* Tough crowd. Okay how's this? Surreal enough for you? :wtf2:

http://i618.photobucket.com/albums/t...0/IMG_2299.jpg

You, sir, just won every award there is on this forum. :bowrofl:

One more question: how has the synchro rev-match responded to the pulley assuming that you have the sports package?