I disagree. My VQ was noticeably harsher above 5000rpms.

Also, when it comes to 1st and 2nd order crank vibrations, they can occur as low as 3000rpms, then dissipate, then come back at a higher rpm. Every engine is different and to label 10,000rpms as the breaking point is very misleading and simply not true. If that was the case, then BMW I6s and Contour SVT V6s wouldn't snap their cranks with UDPs at rpms well below 7000rpms.


Yes, the VQ block and lower block is extremely robust. However, balanced cranks have pretty much used since the dawn of gasoline combustion engine. The "balancing" has obviously gotten a lot better over the years though. Regardless, the VQ crank is perfectly balanced, but still doesn't stop the fact that the crank experiences varying loads when those explosions send the pistons down at various rpms and loads. The flywheel (6MT) or the torque converter (5AT) serves as a crank damper. But powertrain engineers also know the critical purpose of balancing the other end of the crank hence the reason for the elastomer infused crank pulley.

Never seen any proof of that, but I have seen race spec QRs, SRs, and VQs with fluid dampers.


Not any of the American motors I've worked on, and certainly not any American V8s. GM's L98, LT1, and LS1 V8s have the same exact elastomer ring crank pulley design. Same goes for the Ford Mod V8s (SOHC/DOHC), and Dodge's Hemi motors. Same crank pulley designs as the VQ.


True, I've never heard of a single VQ failing from an UDP. However, I have seen a case of where the UDP became worn at the crank key slot and spun on the crank, got wedged, and completely unbalanced the crank and blew the motor.

Trust your sources. Research. And certainly don't believe everything you're told from an aftermarket vendor.

 

DaveB, I am not here to pick a fight with you or anyone else. This was part of my hesitation in writing what I finally decided upon. I do not want to sit here back and forth picking at your points and then waiting for you to pick at mine.

Bottom line is this. I have used NST pulleys for a few years, I have seen great results with them, I have picked up throttle response, great accessory life, and even better MPG. I speak from experience, and that experience tells me I have had nothing to worry about on numerous cars.

Your car, do with it as you wish. I have said it before and I will say it again. There are those who DO, and then there are those who sit on the sidelines and throw in their two cents.

You see this in the world of sports, politics, etc etc. A few actually do things and others sit there and throw in their ideas, which are 99% of the time useless because they have never experienced any of the things they so pationately seem to be experts about.

Have a great time modding your car everyone

 

everyone has brought up good points - however they are points that have been beaten like a dead horse out here for years!

I hope this doesn’t end up another 20+ page debate... read post #21 and as VQguy said “Have a great time modding your car”

 

Do you honestly believe that, or am I missing some sarcasm? The g35 is a mass produced vehicle. As such, every engineering decision has been made measured against safety, emissions, performance, reliability, and most importantly, cost.

 

As Dave has already pointed out, many people make the same claims for lightened flywheels. To touch on your point, I noticed that the engine revs more freely in neutral, but there was absolutely no difference in gear.

 

I ran a Fidanza flyweel on my old maxima 18lbs down to about 11lbs. Very noticable difference in throttle response and ability to rev. But I read as the gear ratios approach 1:1, the advantages become less.

 

lighten flywheel w/ no clutch upgrade is pointless.
underdrive pulley is good - man, when i first came on here - i almost swore this was a " lowered on rims" scene- theres a lot of technically " savvy" people in here. def. a good place to learn about OUR cars. looking forward to STILLEN!

 

You missed the sarcasm. I was trying to make it obvious with the sentence before that, coupled with the fact that I was suddenly agreeing with the original poster. I think the excess sarcasm flipped back around at infinity and came back to perceived genuineness.

In defense of the lightened flywheel comment, note that lightened flywheels generally represent at least an order of magnitude change in inertia compared to a lightened crank pulley. The effects of many lightened flywheels are significant enough to generally be felt in first gear (5-10% gains in 1st).

Note that all my arguments against the pullies (gains and perception in the car) are based on non-underdrive.

 

MechEE......... Buddy, how the hell are you? Still going after these pulley guys huh. That's ok. Never liked this mod but I do like the flywheel one. Had one before and I'll have another soon. I will agree that most is felt in first then dies out like Jeff said higher up in the gears. I call this the "get out of the hole" mod. Good for take offs and going through the first couple of gears pretty much. I know Trey you feel it hurt your launch but with the flywheel, you need to re-learn all over again. We could all do like the "Rock Crawlers" and go even heavier so we won't stall or bog on takeoffs. 5hp??? I doubt with your butt you can feel the difference.

 

I don't want to pick a fight either. It's just when I read your post and towards the end read that most of all the information you posted came directly from the vendor raised my eyebrow. Also, the statements about balanced cranks and American V8 motors being externally balanced is one of those undying myths perpetuated by the informed import crowd and when I hear that statement, I pretty disregard anything else the person posts. It's nothing against you though because you're just relaying information.

Do what you wish with your cars and have fun. If the UDP gives you what you want, then it's good for you. For me, I bought an UDP because I believed the positive reviews; however my qualitative and quantitative results were wildly different than the accepted norm. I then began researching UDPs and realized it wasn't the mod it was cracked up to be, for me. Therefore I removed from my VQ30 and I will not install one my VQ35.

 

Haha... doing well, you? Yeah, lightened pullies have a special place in my heart, what can I say? They're such a perfect academic exercise with 100% application to the real world.

I agree on the flywheel comments: they're good for "get[ting] out of the hole", at least on a naturally aspirated car. Generally when I've modified a car to the point where I'm thinking of putting in a lightened flywheel, I've already broken down and added forced induction (last car was a turbocharged GTI VR6), at which point traction in 1st is already a problem and I want all of the rotational inertia I can get to prevent wheelspin.

 

This is one area where you and I differ. Like you, I've been fairly selective with my mods(just not as much). I research each mod until I have a high confidence. However, not one mod has given me the gains I've seen in countless dynos. I didn't have high expectations for anything but the test pipes, utec, or the mrev. But none of those gave me anything close to what some others are seeing.

But here's where we differ: I don't think these mods don't work. They just weren't as effective for me as for some others. Each car is different, and will respond uniquely.

 

Actually, the flywheel's benefit would also be felt even at a 1:1 gear ratio. It's just not amplified as much. So any gear from 1st to the 1:1 gear would show gains. Not just in 1st.

 

Sure, there are gains. The question is how much, and can they actually be "felt"?

Gains from inertia changes coupled to the motor scale from gear to gear with the square of the relative ratios (see an old page I wrote here that explains this math). That is, if you have gain G1 in 1st gear, the gain in the upper gears would be:

G2 = G1*(r2/r1)^2
G3 = G1*(r3/r1)^2
... where r1, r2, etc are the gear ratios for gears 1, 2, etc.

For the G35, the gear ratios are 3.794, 2.324, 1.624, 1.271, 1.000, 0.794. So the gains as a relative percentage of the 1st gear gains are:

2nd: (2.324/3.794)^2 = 38%
3rd: 18%
4th: 11%
5th: 7%
6th: 4%

So if you insanely lightened your flywheel to the point of a 10% gain in 1st gear, you'd still be down to a 0.7% gain in your 1:1 gear (5th), and there's no way you're feeling that (unless your name is DaveB).

 

Are those % gains relative to 1st gear? Ie.. over and above 1st gear gains? I'd take that. Expecially when these gains are more pronounced in the gears you actually care about.

And no, the flywheel was not "insanely" lightened. The everyday drivability was only minimally reduced. And this is someone that commuted everyday in stop/go traffic. Someone that brought his daughter to grandma's everyday.