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Old 01-04-2012, 02:11 PM   #1
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Join Date: Jan 2012
Location: Plano, TX
News AST 4150 Series Damper Announced - Tech Thread

Hello NASIOC! This is our first thread on this forum as a supporting vendor. We first talked about this shock on Dec 23rd, elsewhere, but were not a vendor here yet. We really wanted to get some additional technical information out to the Subaru community about the AST products, this new series of shocks we've helped develop with AST-USA, as well as our Vorshlag camber plates - so we ponied up and joined this forum. Feel free to PM, email or call us if you want to know more - our knowledgeable staff is here to help.

All New AST 4150 Damper

Vorshlag is here to pass along the announcement from AST Suspension and AST-USA about the all new AST 4150 Series Damper. The 4150 design builds on the basic architecture and market success of the AST 4100 series monotube single adjustable damper, and brings experience learned in the recent wins in GRAND-AM Continental Tire Sports Car Challenge, including new technology developed specifically for GRAND-AM racing teams. There is also some technology sharing from proven Moton Suspension dampers that have made their way into this strut, which is detailed below.

You can read about this new 4150 damper in the Official AST-USA Press Release, but I will post all of that and more in this forum post, with pictures, details, and my first hand impressions from driving on these new updates in my own 2011 Mustang test mule for the past couple of months. First, let's start with an exploded view picture of the 4150 strut that points out all of the updates over the outgoing 4100 design (which has been in production from 2006-2011, with several running updates along the way).

Here it is...

You can click that picture above for an even larger image. Its a 3D rendering AST made last week but that I marked up today, showing a cut-away view of the production 4150 version. All of these upgrades and new parts have been tested on various race and street cars, including the DDP pistons, low drag seals, and top guide. Let's look at some of the new components and explain what has been changed.

DDP Technology Piston

AST's latest digressive piston was developed for GRAND-AM and gives drivers and race engineers the best of both worlds. Drivers love the low speed damping response and body control, while race engineers love the “blow off” (the knee point digression, shown in the dyno plot below), with a tapering off of the rebound forces at high shaft velocities.

When the rebound adjustment is set to soft, the damper curve looks similar to an OEM street shock profile. When the rebound adjustment is set to firmer settings, the damper curve looks like a race shock. The most critical portion of the dyno plot area is affected the most - the portion at low shaft speeds. So much in racing happens at 0-3 inches per second shaft velocities, and that's where these pistons really step up the damping forces, when adjusted firmer.

Those two documents above list more details, and you can click them for larger images. The graphed rebound curve shown on the right shows the large amount of adjustment from full soft to full firm, and the super-digressive curve shape that these new DDP pistons can achieve. This “Jekyll and Hyde” personality is exactly what AST 4000 Series customers want: soft street ride and firm race car track performance in ONE shock - all with the turn of a knob.

Vorshlag's 2011 Mustang GT track testing with DDP pistons and 4150 valving at the bumpiest track in Texas (ECR)

And let me tell you from first hand experience - it works. Adjusting the knobs on the prototype ASTs in our 2011 Mustang with the DDP pistons makes a night and day difference - with more adjustment potential and valving change than I've ever seen in any shock. We were driving it at one of the bumpiest tracks around last week and were able to get the track set-up dialed in quickly, still soaking up the bumps but with sharp turn-in and controlled braking. When turned down to full soft for the drive home from the track, and it rode like stock. We have taken a number of people for rides in the car on the street at full soft and they think it is the OEM suspension. Those rides alone have pre-sold several sets of 4150s already - these shocks make you a believer.

Lower Drag Seals & Stronger Top Guide

High performance seals are a challenge for any damper. They must balance friction and sealing ability while not impacting shock performance and not leaking; All of this makes for a difficult balancing act. While the seal was originally developed for GRAND-AM road racing, AST is taking their knowledge from the track to the street once again.

These newly redesigned shaft seals have a low-friction polymer inner liner and an outer jacket with the appropriate amount of stiffness and flexibility needed in a street strut. This gives the low seal drag characteristics usually only seen in a race shock, with a street-worthy seal. These new seals reduce hysteresis in the damper plots by decreasing seal drag over 50%.

One of the benefits of AST and Moton being owned by the same parent company is technology sharing - when there is one design element obviously superior, it can and should make its way into another model across brand lines. There isn't much of this cross-pollination going on between AST and Moton, but one improvement to the 4150 strut design is the addition of the longer and stronger top guide from the Moton Motorsport strut. This Moton top guide is a TANK, and will help minimize shaft deflection under extreme racing loads, and is a welcome addition to the 4150 AST strut. This is another reason why the 4150 will work well on the street and on the race track.

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