We're constantly reading about the gains associated with the UDPs, but everything I've read points to butt dynos and "feel". I'm just curious as to if anyone has done dyno testing or 1/4 mile testing before and after the UDP? I can't find anything with the search function. I'm amazed so many people put so much faith into something with no documented proof of working other than what others say.

 

What is a UDP?

 

Underdrive Pulley

 

EVeryone knows less mass is proven without taking the time to vet the mod on it's own at the track. I've yet to see anyone anywhere take the time to test this mod on it's own or wait to perform the mod at the track itself with before and after results while running at the same water temps and weather conditions. Who has time for this? - it's only 200 bucks and most people do it in conjunction with other mods.

Most people don't care enough to prove it since it has plenty of butt-o-meter value or we are not paranoid about physics failing us and not really that concerned if it's just slightly gaining power since it's cheap anyway. It takes one drive to see that it makes a difference..not everyone needs a proven hypothesis to spend 200 beans!

 

Agreed, but the reduced rotational inertia of the UDP is way overstated. With my Maxima I ran consistent low 14.6s@96mph with the stock 15" rims 40lbs and lower 2.2 60 foots. On the same day and track, I swapped on my much larger and wider 17" rims 42lbs. The car ran consistent upper 14.6s@95mph with lower 2.2 60 foots. The 17s had a lot more additional rotational inertia to overcome than the 15s did plus the 17s were slightly heavier. The result was about .07 seconds and 1mph. Then there's my G35. With the 17" Sport rims 46lbs, the car went upper 14.49@97.6mph with a 2.21 60'. On the same day and with the 15" drag radials 35lbs, the car went low 14.5s@96mph with consistent upper 2.1 60 foots. Not only were the 15s 11lbs lighter, but more of the weight was closer to the hub which is good. Granted I've figured that the 15" DRs are too short for ideal performance in the 1/4 mile, the result was that reducing over 22lbs in rotational inertia didn't make any real difference. The UDP is mounted directly to the engine and is only about 7" in diameter. A 24-27" tire combo has a lot more inertia than that little pulley.

That's fine if want people buy their mods based on heresay and butt-dynos, it's their money. But for some us, we like to see conclusive data supporting a mod and I was just curious if there was any proof of this thing actually working on the G/Z VQ35. I know on the VQ30/VQ35 in the Maxima/Altima community, it's a bit of a joke because of all the dynos and track time saying it doesn't work, but on the G/Z sites, it seems like the majority believes it's one of the best mods out there without any proof.

Some people like to add mods simply because it's "a mod" and it's something to do. Some other people like to buy mods that actually perform as intended. I spent way too much time and money on worthless mods including an UDP over the past 10 years of modding a Z28 and Maxima. The G35 is going to be different. I'm older and wiser now. If the aftermarket part isn't superior than the factory part, it's not going on my car. I've spent way too much money believing my butt dyno and other people's butt dyno only to be let down both at the track and in my wallet. Butt dynos suck, that's the truth. My G35 doesn't "feel" near as strong as my Maxima did, especially from a roll. Guess what? My almost stock G35 is only .18 seconds and 1.3mph slower than my modded Maxima was ....in much cooler weather. So much for believing my butt dyno.

 

Yeah but try not to compare the FWD platform to the RWD platform using the old butt dyno. The loaner i35 seems to be way faster than my G. All FWD's seem faster than they are supposedly. If after a year of owning the same car, you should be able to detect how your engine revs and gets to speed. Maybe rotational mass isn't reduced that much but it is reduced and with several other "minor" mods, should add up to a realizable gain. Mass is mass is mass. Less is less

 

DaveB, did your 15" rims and 17" rims have tires mounted that made their overall diameter identical? Even an inch can make a big difference in final drive ratio and especially times off the line.

 

No, the diameters were not identical. The 15" BFG DRs were 2.4" shorter than the stock 17s. The 15s increased gearing by about 8%. There was no change in 330', 660', and 1/8 mile compared to the 17s. After the 1000', the car slowed down, mostly because of the forced shift into 4th 150' short of the finish line. There was very little difference in 60' between the DRs and 17s. My best on the DRs was a 2.19 and the 17s did a 2.21. With either tire, there was barely a chirp on launch. The G35 autos lack the ability to come off the line hard.

 

This thread is OLD so you have probably found this dyno by now, but I figured I would link it for others doing searches on pulleys.

https://g35driver.com/forums/engine-...nk-pulley.html

This member had his UDP installed by the dealer and hasn't had any issues over the past 4 years.

 

None of the pics work in his thread

 

+1 I noticed that earlier, what exactly is a UDP? i know i'm a bit of a technical nub, but I'm trying to learn.

 

I will reach out and see if he still has the dyno graphs.

He does recap the peak gains though for someone looking through all the charts and getting confused. And through pm's he mentioned about an avg of 6-8hp in gains. What caught my eye was his 1/4 mile time for a DE auto.

 

https://g35driver.com/forums/engine/...take-look.html

Should give you more info.

As for the dyno charts, they should be reposted this weekend.

 

i'll post the dyno sheets tomorrow night. The dyno operator couldn't believe the gain either 4 yrs ago. I haven't had a problem with mine and I used to be boosted with it.

 

before the crank pulley best of 3 runs.

Mods:
Borla TD
Stillen Cab
TS reflash