Dave B

I was reading through some old Grassroots Motorsports magazines and an article in the May 2003 issues caught me attention. The article is entitled, "The Weighing Game". In it they discuss rotational inertia, static weight, piston and rod weight, crankshaft dampers, and lightweight clutches and flywheels. What really caught my attention was the section on crankshaft dampers and flywheels. Quoting and paraphasing the article:

Crankshaft Dampers:

"That round lump of steel and rubber on the front of your crank is not a harmonic balancer. There's no such thing. You can not balance harmonics. This piece is a crankshaft damper or torsional damper. It is commonly accepted that having the lightest possible damper may not be good for crank life, although it will allow the engine to deliver it's best performance. The reality of the situation though, is that in terms of power, the reverse is almost always true. A modern, quality camshaft profile is based on highly complex mathematical formulate intended to produce a profile that will generate a smooth, minimal-vibration lift curve at the valve. On a 400hp HP 5.0 motor, swapping out the 14-ounce aluminum crank pulley (definately not a stock pulley) for a 15-lb, but highly functional damper increased output by more than 11hp. In addition to less power, the lighter pulley that was removed allwoed the crank to flex as much as 250% more than with the damper. All this flex adds up to broken cranks, especially for inline sixes (BMW reference I'm sure). Okay, to sum up crank dampers, the rule here is simple: forget the weight and just make sure you get one that does what it's suppose to do- dampen. This will allow the car to go faster, longer."

Flywheels:

"The situation on the other end of the crank presents a dramatically different picture. Here we can shed some weight. During the summer of 2002 I spent a week with Fidanza Flywheels, dyno and track testing flwheels of different weights in three different Mustang 5.0 with power ranging from 390hp to 560hp. Out on the drag strip, the lightweight rotating assembly (20lb lighter clutch and flywheel) delivered more than tenth of second reduction in ET and almost 1mph of extra trap speed."


The article is far more lengthy, but I only quoted the highlights. I'll also note that NASCAR and big V8 racers use these super heavy dampers.

The reason the damper part caught my attention was that when I installed my UDP 1.5 years ago, I noticed more engine vibration, both at idle and throughout the rev range. 2 weeks ago I removed my UDP as an experiment and all the vibration disappeared and my driveability improved (easier take offs, smoother shifts). The VQ crank pulley is a crank damper (has a rubber ring sandwiched inside) and I won't be reinstalling my UDP. Who would have thought that adding a heavier damper to the crank actually could increase performance? The fact that crank vibrations can actually negatively effect valvetrain operation got me thinking.

I thought the info on the flywheel was pretty interesting too. On a 390hp Mustang, 20lbs removed from the flywheel/clutch assembly was good for .1 and 1mph. I'd imagine a much lower powered Maxima wouldn't reap nearly the benefits, but the flywheel can't hurt. The article really emphazied the advantages of the light flywheel/clutch on the road course.


Dave

MrGone

iTrader: (30)

I love my fidanza, and I cant wait to get a UDP, but I have a VE.

I've noticed no additional viberations, and the Fidanza doesnt really effect driveability, I mean I could see how it could, but some people are just picky.

Just keep in mind not all engines are the same, and what works for one engine doesn't always work for the next and vice versa.

SEmy2K2go

iTrader: (10)

I guess this is the only part of the article that I have an issue with. If there is no such thing, then Jegs and many many other aftermarket performance and non-performance retailers are incorrect in their descriptions of the following items.

http://www.jegs.com/cgi-bin/ncommerc...49&prmenbr=361

njmaxseltd

iTrader: (19)

Great article Dave!

mzmtg

iTrader: (11)

Shock absorbers shoudn't be called that because they dont absorb shock. Yet, everyone call them that anyway...

BEJAY1

iTrader: (19)

Interesting. Again Dave questions everything done over the past few years!

Just read it through and don't know how I missed that before. Maybe I just dismissed it at the time. Guess it wouldn't be that hard to swap pulleys and dyno back to back...

That ATI technology though is way over my head.
http://www.atiperformanceproducts.co...rs/dampers.htm

Stephen Max

iTrader: (59)

It really is a misnomer. For one thing, it does nothing to the balance of the crankshaft, unless it is poorly made, in which case it can adversely affect the lateral balance. But you can't balance a shaft torsionally. You can, however, dampen out torsional vibration and limit its amplitude, which is what the damper does. The net effect is a smoother running shaft, which people associate with a well balanced shaft, hence the name.

Ceasars Chariot

iTrader: (16)

dave what UDP do you have ?

h2kFrosty

iTrader: (3)

Probably the only one that's worth a damn and doesn't make your engine leak oil... a UR one.

ericdwong

Yeah thats what I always thought about those lightweight flywheels.... the cost is not worth the gain. For the $400+ you'd spend on one you're better off spendin that elsewhere...

Dave B

According to the article, removing weight from the flywheel won't cause vibration. It's removing weight and dampening from the pulley which will cause crank vibrations. I'd love to see a VE pulley in person because the pictures of the VE pulley in my Chiltons seem to show the same kind of design as the VQ's dampner. But Jeff swears the VE pulley doesn't have any rubber in it, so I'll believe him unless I see differently.

Most engines aren't the same, that's the truth. But seeing that ATI has their special heavy dampeners available for the Honda B-series, Toyota 2JZ, Nissan SR and RB26 series, BMWs, Infiniti Indy V8s, plus nearly very make, model, and displacement of domestic iron, I'm going to tend to believe that these things will work for just about any motor.

I had my UR UDP on for 1.5 years with no problems except for the minor increase in vibration and more willingness to bog/stall in the lower rpms and at part throttle shifts. I think it did gain some power on the dyno, but the driveability and vibration issues got to me after time. I spent way too many hours trying to figure out why my VQ vibrated more after the UDP. It turns out it was the UDP.


Dave

Dave B

You wouldn't believe how much money (~$1500) I've wasted over the years now modifying my Maxima. It's been a huge and expensive learning experience. At least I won't make the same mistakes on my next car.


Dave

Dave B

I use to have the UR UDP installed. Now it's sitting in my garage. Don't get me wrong, I think the UR UDP does increase the power and probably won't cause any mechanical issues with well-built VQ, but for me I wanted my driveability back. I may just go for the flywheel when it comes time to replace the clutch.


Dave

ohannon7

iTrader: (5)

Well that sucks-I thought the UR pulley was the "safe" one, Hmmm....

hacim105

iTrader: (6)

Now I'm in a delimma of whether or not to keep my UDP in. I mean it's not like i can feel much of a difference with it in but I know it's helping. This is tough. What is anyone else going to do?