Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Dual Mode Dampener I Love You.....

In reply to:

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I lost a bit of power, but, the trade off is worth it. I lost 10hp/3-5tq from my last dyno, but my cat was also clogged. I will dyno again soon, with a new cat, for better numbers.

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I can't believe you are worried about a little bit of increased weight on one end of the crankshaft when there's a flywheel on the other end. It's the flywheel that governs the rotational inertia of the crank (and hence engine acceleration). The flywheel's combination of high weight and large radius leads to a large moment of inertia. The pulley's effect on engine acceleration is minimal, if not completely lost.

Engineers out there, do the math and you will see what I mean.

Well, seeing as the flywheel is only like 10 or 11 inches diameter, and the pulley is about 4 or 5 it's not as insignificant as all that (inertia increases with the square of the radius - 2x radius is 4x inertia). But you also have to consider that 80% of the pulley weight is at max radius (from the damper ring), compared to a roughly equal distribution on the flywheel so it gets even closer. I think 4 lbs off the pulley is roughly equivalent to 1.5 or so on the flywheel the last time I napkin-calculated it. Going up 5 lbs from UR UDP to DMD would without question be noticeable, going from stock up 1lb to DMD would probably be hard/impossible to feel - and well offset by the increase in smoothness.

Originally posted by 5speedSE170HP:

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ok whats the correct nomenclature for the DMD? is it damper or dampener?? its damper...right?

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"Damper"

...Ed

OK, here is how much the extra 1# weight will affect the DMD. a formula was given about a year ago but I recall that for a 10 lb lighter flywheel on focus (which has same stock weight as ours) gave benifit equivalent to...
260 lb weight loss in first gear (at 15 lb/HP this is like +17 HP)
90 lb in second gear (+6 HP)
50 lb in third (+3 HP)
30 lb in forth (+2 HP..this is the gear you dyno at, so you see +2HP)....but they light flywheel SEEMS to give a lot more kick especially in first/second because..IT DOES!!

But that is a 10# drop with a big radius..so if the DMD was as large in radius as a flywheel loss would be 10%..
First gear...+26 lbs or -1.7HP
second.... -0.6HP
third..... -0.3HP
forth..... -0.2HP

However, with the DMD being less than 1/2 the radius, you can cut those numbers by probably 60-75%...
...Max loss with DMD in first gear...less than 1 HP...unmeasureably small in second and above!!!

NOW, think about how much extra work/power lost by rapidly bending a forged steel crank....if a DMD can reduce that by even 50%....I think you get my drift..anybody who has one can attest to the smoothness..."roughness" costs power (how much I do not know).

I post this just in case power loss is a concern. It is possible that people removing UDPs will feel minor loss (but perhaps not) but this is because they are underdriving accessories. If they use separtate UDPs for P/S, alt, they will not lose anything.