Under Drive Pulleys...?
 

I have read through a few threads here and I can't see a clear yes or no as to whether these things are ok to run. I don't have a huge system, and the car is stock. Just wanting to free up as many horses as possible. What are the negatives to running a UDP?

Bump...

I too am having trouble deciding on whether I'll be getting pulleys or not. It seems like they aren't very detrimental to the accessories, but I also haven't seen too many (if any?) dyno results posted along with each set of pulleys these companies are putting out. I'd like to see some hard data and hear people chime in who have them installed.

Yeah I wanna stay N/A and would like to get as much power as possible. So if these help without hurting anything I will be all over it.

I have a friend who is running the NST ones in his 350Z and convinced me to buy them after feeling gains throught the powerband with his butt dyno. Said it was night and day. Im just waiting for NST to get some in stock, then Ill try to get a before and after dyno.

As far as safeness, the NST thread explains that they have never had any issues with pullies getting welded to the crank and never had problems with harmonic balance issues.

Ok now we are getting somewhere! Any extra info?

Yep, NST :excited:... We have been waiting for a month now:happydance:.. Can't wait to get them on:driving:.

I looked at Stillen, also some pulleys on ebay Unorthodox Racing Crank Pulley Nissan 350z 370z GTR G37 | eBay GlockWorks put one on his car http://www.the370z.com/parts-sale-pr...nk-pulley.html

Stillen and NST R&D is top notch. I went with NST because they sell kits for a butt load of cars, they have long history in racing. :stirthepot:

I've read the threads here and researched at each vendor's site and at other links found on google. I have friends that have gone this way on other cars, e.g. dodge charger. I can't because I am in a lease.

When I buy out the lease I will definately buy as many of the lightweight pulleys as there are. Unorthodox has the crank, idler, and alternator pulleys for the 370z. NST has crank and alternator pulleys.

Unorthodox claims about 10-12 WHP gain for the underdrive crank pulley alone, with 15% of that being contributed to the 20% underdrive. So the OEM size lightweight crank pulley would be 8-10 vs. 10-12 WHP. They also claim another 1-2 WHP for each of the other pulleys, idler and alternator.

Did they have anything to back that up Kcquinn?

NST Pulleys are awesome. Better throttle response, gas mileage, rev matching is faster, it makes power ALL the way through the rev range, and it's inexpensive. It's one of my favorite mods. It's worth a good 7-10 whp everywhere. Pair it with a light flywheel and that's a slice of heaven.

BTW, no issues what so ever and that's with about 8k miles on them. The last couple pages of the NST pulley thread, I have A LOT of info on my experience with them.

I've had NST Pulleys on for over a year 10k+ mi, and have had zero problems.

Dyno feel doesn't really change, but I do notice the fact that the engine revs much faster and smoother... Like there's 'less' of a strain to do so. Granted changes are minute and can be attributed to seeing what you want to see, but it's noticeable to me.

The primary concern comes down to how they're installed. If they are installed correctly by a competent technician, then you'll be fine. If not, then you'll have problems. So trust your mechanic or don't get them.

I've seen dyno comparisons. I just can't locate them right now. Those were for NST pulleys. I can't access the unorthodox racing site for some reason. You have to google and find retailers that carry their products. There is an NST thread here that I believe has dyno charts.

For the accessory pulleys I've not seen any dynos, and who would expect a dyno to show a 1-2 WHP gain anyway? Maybe if all of them were changed you could see the difference.

I did a before after dyno on the NST. Gained 7-10 hp.

Here is the dyno results after the install

http://www.the370z.com/attachments/e...arts-dyno1.jpg

Was this the two pulley set with under drive crank pulley?

Two pulley set. This is also with CAI installed at the same time. This explains the bump in power at high RPM's. the 10whp average everywhere else is from the pulleys

So u went on the dyno after u installed a CAI and the pullies?

Yes

Spent $372 for the CAI and $214 for pulley and belt. The bang for buck ratio is strong. I had gotten a deal on both. Probably won't find a deal that sweet anymore, but if someone spent another $100-$200 for the combo, it's still a great buy. It's showing 10whp all the way up, and up to 16whp at 7000-7500... After I installed Long tube headers, HFC, exhaust, and no tuning.

So then you really dont know what the gains where then? It could be all intake or all pullies or just maybe 1 or 2 pulley

I went with the Stillen lightened and underdrive, as I trust their quality over the other options. Just wish it was available black anodized.

Dyno gains were 6hp 9tq peak and overall quicker revving.

Look man, it's common knowledge in this forum that cold air intakes have no benefit and show negligible gains below 6500 rpm. As I've stated, the delta increases exactly at that RPM on the dyno charts. You've posted 2600 times, you can't be ignorant of this. I know exactly where the pulleys made power.... EVERYWHERE. And I know where the CAI's made power, over 6.5k. I really was not trying to spell this out.:shakes head:

i have to agree.anytime you can remove unsprung weight (pullies,wheels ect),power increase is guaranteed and is something the ecu CANNOT adjust for !

You don't know at all where the pulley made power because you installed it at the same time as your CAI. Your claim means nothing.

There is a dyno somewhere around here the nst pulleys did 5- whp if I recall, Ill see ifI can find it........

http://www.the370z.com/engine-drivet...370z-dyno.html

You must mean rotating mass, and I agree with you there.

Unsprung weight is attached to the suspension and not supported by the springs.

wow even in hotter weather! Thanks for the dyno chart upload +rep

I put my stillen pulley on today, its been raining so I cannot romp on it, but throttle response seems improved. I am not sure why people find this hard, with the right tools ots a snap, 1/2 drive with 2 foot + breaker bar and a large prybar to hold the pulley and some elbow grease puts this on in little to no time. Granted I did mine on a lift, it took me all but 20 minutes from lifting to putting down. for 165 bucks, and if I get 5 whp, quite worth it IMO.

How hard is it to align it when installing. Not sure what im looking for.

Not an issue, it's keyed. Remove belt and pulley, install pulley and belt.

I did not need a puller either, it wiggled off as did my 350z with 70k at the time.

I have the Stillen pulley because I WANTED 20% under driven... Mike at NST will make you one if you NEED NST... But in all honesty if you or your installer is component, there is no risk in running it... I've had it for 3000 miles now, and it feels great, I MIGHT down the line order a 10% overdrive for the alternator from Mike@NST, but as of now I don't see any reason

It took my mechanic 20 min to work out where the belts go (as I didn't have the diagram for it) then he put a breaker bar with I think 3/8" on the tensioner, moved that out of the way then took the belt off... Then he had this bitching contraption to put over the stock pulley with a torn belt over the stock pulley (to prevent damage) then he used a breaker ba on the bolt and once he undid it the pulley slid right off... Car had like 23k miles on it and was 3 years old at the time... And honestly I have no damn idea why the notches are on the pulley for alignment... I can only see it being necessary if you're rebuilding the motor