For those that are interested in the fine points & minor details of the Chrysler Engineering designs I'll provide more info here to explain the reason for the surge coil found in hydraulic clutch lines on Dodge trucks. I'm always surprised at the amazing depth of Chrysler engineering in adressing even apparently 'minor issues'. Seem to me that's what made them a breed apart from the also-rans of automotive engineering. It's lonely at the top...

I'm not certain that links will be live because I did a cut/paste from Microsoft Word, sorry!

Hopefully this will help explain things about the surge coil design:

As fluid/liquid flows in a straight line in a tube or channel of constant diameter at constant level with no rise or fall the velocity & force of flow stays the same unless flow encounters resistance. When the diameter is restricted but force behind the flow remains the same the liquid is accelerated. We see this in the venturi of a carburetor, or in air flow across an airplane wing, or in the Kamm effect of an airfoil.

Where liquid is flowing through a channel or pipe at constant pressure and there's a bend in channel or pipe the flow & velocity of liquid changes. On the inside of curve the flow is much faster than at outside of curve, having differing distance of travel, and this differential of velocity changes for any location from innermost to outermost location on the radius of the curve. Again this is seen in airplane wing surfaces & this change of velocities is what allows man to fly!

These velocity changes create frictions along the walls of the pipe or channel or conversely against the liquid, depending on the friction coefficient of the wall material, further influencing flow changes. Obviously some materials are rougher than other which would have differing effects on flow, velocity or relative friction. This friction in combination with speed changes in bends can impart turbulence. Over time the flow of liquid in pipes/tubes removes particles from the wall of tubing causing gradually increasing friction against fluid flow.

The radius of the bend will change the intensity of velocity change effects. Progressively smaller radius increases effects, and larger radius is less change. We normally think of a 'bend' as being somewhere between 1 and 90 degrees [off the top of our heads] but of course it may be anything from 1* to 359*. 360* is a circle, so we think of 'bends' as something less than a circle. But this hydraulic effect of slowing the fluid velocity in a bend is constant, so if a 360* circle is encountered the effects found in say a 90* bend are greatly magnified to have more severe change in velocity of fluid. Concentric or multiple circles have a huge effect.

A surge coil takes advantage of these effects, being specifically designed to slow a fluid's motion or intentionally impart friction. By doing this shock waves in the fluid flow caused by sudden acceleration/deceleration are mitigated or entirely eliminated. In the case of non-compressible hydraulic fluid at relatively low speed it can prevent foaming or aeration and hammer effects and reduce wear on some components.

Soft rubber seals & boots don't take kindly to sudden changes in velocity from zero to maximum and the accompanying shock waves in fluid in pipe can deform the rubber momentarily, causing a leak or loss. That leak may be fluid going out or air coming in, and in hydraulic systems we don't want either one. A properly designed surge coil can help balance a system to remove or control this shock wave, deformation & accelerated wear factor.

This linked page explains the theory well & includes diagrams & equations. The pictures show the science of it without any complicated math:
[www.roymech.co.uk]

Here's a link with mention of velocity change in bends with reference to engineering materials on how to calculate same:
[www.ei.org]

This page mentions velocity change through bends and offers test apparatus & procedure for calculation of changes in differing radii:
[www.jfccivilengineer.com]

More background on the effects of bends on fluid flow:
[www.abzinc.com]

A Yahoo search engine search under 'fluid velocity loss in bend' kicks back all kinds of info in the results. One would see that this surge coil effect on fluid motion is extreme and requires complicated engineering procedures to successfuly address all the related issues. We also see that was no problem at all for Chrysler Engineering....