Mod list, how much gain?

[Rara]

Not sure if I buy the crank harmonics not being as bad at high rpm---at least thats not what I remember.
And that 4V Cobra info. is interesting---you rarely see those cranks hurt.
I respect your knowledge and you give very good information, but all the searches (and I did many on the UDP vs. DMD) never convinced me that the UDP will harm my engine. More hearsay and piling on like I see around here on various topics (my cutting springs post for ex.).
Either way, I'm running it and look forward to a decent gain at all rpm.
-J

http://www.atiracing.com/products/dampers/damper_dinan.htm

Read that. Not terribly technical, but from a respected source. And take note that few crankshafts have thier natural frequency near the engine's peak rpm, hence my statement. And I don't really care what searches you did here or anywhere on the internet, because you won't find a back to back test like you seem to imply you would need to see. That kind of testing is extremely expensive so people outside of the OEMs almost never run them. Look up things like crankshaft harmonics, and metal fatigue. I will say that the duratec does have a particularly strong crank, much like the modular 4V, but it doesn't make it immune. Plus, like I said before, with the susceptibility of the duratec to wipe rod bearings, I wouldn't want to do anything to help the process along. And again, this is nothing against UDP's, this is against UDPs that don't include a harmonic balancer.
In regards to cutting springs, I recall only saying that you shouldn't do it unless you already understand all the factors you are changing by cutting them, and you wouldn't be asking if you did.

 

[Rara]

How about the lighten fly wheel on the other end of the spectrum here? Doesn't this play a roll on the other side of the shaft? Does it not have that much of a change going from 21lbs to 13 lbs?? or w/e the lighten flywheel is.

All that would do is change the natural frequency, and remove some of the mass damping from the crank system. Don't count on a lighter flywheel to help change anything for the better in crankshaft harmonics.

 

[Harrry]

All that would do is change the natural frequency, and remove some of the mass damping from the crank system. Don't count on a lighter flywheel to help change anything for the better in crankshaft harmonics.

Not for the better but for the worse, is what i am trying to get at. They weigh in at 8-9lbs.
That is a huge change is what i am saying and people recommend these alot on these boards.

 

[Rara]

The lightweight flywheels may help or hurt a little depending on the particular application, but not terribly significantly in most cases, and likely very little in the case of the duratec. The change in mass does have an affect, but its more about the damping frequency; a harmonic balancer has a mass that is allowed to oscillate at a particular frequency to dampen out harmonics in the crank. Look at your damper, the pulley has an extra steel ring mounted to the outside attached by rubber. The density of the rubber (combine w/ the mass and diameter of the ring) determines the damping frequency of the balancer.

 

[Harrry]

Now this is over, lets continue because this is getting alot of views which means others are learning as much as we are. Lets not go and ruin this for others.



Rara i see your point with the rubber outside, i always thought that the flywheel also created a slight balance on the other end of the car. Do they not pre determine the weight ratio of either ends when they R&D the crank?
Or is everything planned around the crank?