Designing Building and Tuning Shocks - How It Works

AFCO Explains the Basics of Designing, Building, and Tuning Shocks for the Street and the Track.

Stephen Kim Aug 6, 2013 0 Comment(s)
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Single-Adjustable vs. Double-Adjustable

One of the most popular questions people ask all the time is whether they need a double-adjustable shock, or if a single-adjustable shock is sufficient for their needs. This is an issue we take very seriously, and it all comes down to the level of performance you expect from your car. AFCO single-adjustable shocks adjust the rebound only, or in other words, how quickly the shock pulls apart to control body roll. For street cars that will see occasional use at the dragstrip or at Pro Touring events, single-adjustable shocks are a great value. They're easy to use, provide great ride quality, and allow fine-tuning the valving to stiffen the suspension up at the track. Double-adjustable shocks control both compression and rebound, and are intended for max effort cars used in very competitive environments where you expect a higher level of expectation from your race car. The more power you have, the greater the need for double-adjustable shocks.

Designing Building And Tuning Shocks Shock Absorbers 2/11

Remote Reservoirs

Many race cars and an increasing number of high-end street cars utilize shocks with remote-mounted shock reservoirs. With this type of setup, a large quantity of fluid is held in a remote canister, and fed to the shock body with a high-pressure hose. The purpose of this arrangement is to isolate the effects of the shock's internal gas pressure from the shock valving. Mono-tube shocks are pressurized at 50 to 200 psi with nitrogen gas to prevent cavitation, but this pressure can have the adverse effect of increasing spring rate. Pro Touring cars are constantly transferring weight from front to back and side to side, so an increase in spring rate is undesirable. By holding the fluid in a remote canister, we can decrease rod pressure, which is the difference in force it takes to compress a shock with and without gas pressure.

Better Headers

Dynatech offers a diverse range of products for muscle cars, late-models, and race cars. For muscle cars, we have great-fitting line of stepped headers for first- and second-gen Camaros, and '68-and-later Novas, Chevelles, and El Caminos. They feature thick 3/16-inch flanges for good sealing, and a stepped tube design. Starting with a smaller-diameter tube near the header flange keeps exhaust velocity up, and from there the header primary increases in diameter for improved scavenging. Additionally, Dynatech headers are coated inside and out for looks and longevity, and also utilize a four-bolt ball-and-socket connector at the collector for leak-free operation. Traditional three-bolt flanges work themselves loose over time, and are much more prone to leaks. By using a sintered-metal gasket inside a ball-and-socket connection, which is identical to what the OEs use in late-models, we can ensure leak and maintenance-free performance. Furthermore, our MuscleMaxx headers for muscle cars include header bolts, gaskets, and a color-coded instructions. Our SuperMaxx headers for late-models feature stainless steel construction, triple-layer factory style gaskets, and oxygen sensor extension cables.

Stepped Advantage

Designing Building And Tuning Shocks 4 Bolt Ball And Sock Connecter 6/11

Stepped header primaries are often used in drag cars, and offer several advantages over non-stepped designs in street cars as well. If you think about an engine as an air pump, you can't put a fresh air/fuel charge into the cylinders until you have evacuated the spent gases out of them. That said, having properly sized primary tube gives you the best opportunity to remove these gases. If the header primaries are too large, the exhaust can become very lazy. Conversely, if you keep the exhaust compressed, it speeds up velocity and helps pull the exhaust out. At Dynatech, we have experimented with different lengths of smaller tubing in order to maximize scavenging. Despite their benefits, they're not ideal for every application. For instance, if you use stepped headers on a motor with lots of cam overlap or efficient exhaust ports, you can evacuate the air/fuel charge out too quickly before it has a chance to ignite. That's why it's important to have dialogue between the engine builder and header builder when dealing with a pro-built engine with great heads and a big cam.

Mufflers

To complement our line of headers, Dynatech offers both auger and split-flow–style mufflers. The baffling inside our auger mufflers looks like a coarse thread screw. They were developed to meet some specific rules requirements in Sprint Cars parts where race officials have implemented very strict maximum decibel levels. The tradeoff with mufflers is the more you dampen the decibel level, the more backpressure you create. Since the auger mufflers create minimal backpressure, they would probably be too loud for most street cars. For street applications, Dynatach's split-flow mufflers are a better alternative. They're essentially a straight-through–style muffler with a perforated core that's surround by stainless steel packing for absorption-style damping. The end result is the best of both words: high flow and noise reduction.

Designing Building And Tuning Shocks Exhaust Tip 7/11

Collector Tricks

In the past, collectors were simply seen as a tube that the header primaries dumped into, but collector design plays an important role in overall exhaust scavenging. Dynatech race headers are offered with merge collectors that start out at the same diameter as a standard collector, but then neck down in diameter before it hourglasses back to its original diameter. This creates a venturi or vortex effect to draw exhaust out of the engine more effectively. By speeding up the exhaust flow with merge collectors, they can make an engine more efficient. Similarly, if you want to run an open header exhaust but are concerned about the noise, Dynatech's Vortex insert cones are a great solution. These cone-shaped inserts go into the end of a collector, and utilize a perforated core to reduce sound by three decibels with little to no loss in horsepower. The core has a bunch of small holes in it, and noise is reduced as the exhaust hits the edges of the holes. Since the surface area of the holes is greater than surface area of collector outlet, there is little to no increase in backpressure.

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