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Old 11-20-2011, 03:20 PM   #1
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Fortune Auto Suspension - Shock Dyno Explanations - Suspension Consistency Tech Threa

Hello all! Decided to make a tech thread about shocks and shock dynoes. Also wanted to show case some of our shocks
and how they compare to the competition:

Shock Dynos:

There is tons and tons of mis-information on the Internet and forums in regards to shock dynos.
First we must understand that a shock dyno is not the end all be all of ride quality and performance.

A Shock dyno is only a tool to help determine how good a shock is in theory. Real world testing is also necessary in helping dial in how a shock rides and performs.
Shock dynoes primarily aid in determining hysteresis & cavitation. We also use a shock dyno for shock matching, durability tests and confirming damper adjustments.
At Fortune Auto North America we use a shock dyno in day to day operations for all of these tests. This helps us offer the end user a consistent and well tested product.

Many manufacturers shy away from displaying shock dynoes because they (a) do not have one or (b) are trying to hide their shocks characteristics. When we build all of our shocks we use a CVP graph to confirm if the shock was built properly. At Fortune Auto you can request a shock dyno when purchasing your shocks for an additional $100. We supply you with a PVP sweep graph. We normally do not provide this service free of charge because it takes about 45 minutes per shock to conduct a PVP sweep graph.

CVP shock dyno plot.
This plot helps a shock builder or manufacturer determine if a newly assembled shock is performing within its defined parameters.
Its also helps determine if there is excess cavitation (usually due to lack of nitrogen pressure) and more importantly hysteresis.

Hysteresis is shown by the separation of the 2 lines in the graph. Hysteresis is due to seal drag.
Generally a shock with extremely low seal drag (a good thing for performance) has a lower life span and will need to be rebuilt more often.
A shock with high seal drag (think oem strut) can go longer with out rebuilds. Its important to find a balance between the two.
A shock exhibiting a good balance between low hysteresis & seal drag does not need to be rebuild every few months or year.

The graph below is of a Fortune 500 series shock. The minimal gap between the 2 lines shows fairly low hysteresis. This test was conducted at 250 degrees..max heat that would be seen on a race or drift car.

The graph below is of a competitors shock that is popular in the 240sx community.
This really exhibits poor shock operation and is unacceptable in terms of hysteresis. Its actually worse then a oem shock. This shock was also tested at 250 degrees.

PVP shock dyno plot:
At Fortune Auto we like to use the PVP plot in determining the ride quality and ride performance of a shock.
It also helps determine how linear or digressive a shock is.

Below is a graph of a 500 series shock. The graph is separated into 4 quadrants. The top of the graph displays compression force and the bottom the graph displays rebound force.
The left side of the graph represents low speed speed and the right side represents high shaft speed. A common misconception of Low Speed and High Speed is that it is referring to the speed of the car.
Low speed represents driver inputs such as roll, pitch, squat and dive. High speed represents bumps, pot holes, rumble strips etc.

High speed usually will tell you how comfortable a shock is and low speed force helps give driver confidence. A linear shock has very little low speed force will not handle roll, pitch, squat and dive situations as good as a digressive shock that has much more lower speed force.

Generally everything over 2-3 inches per second is considered low speed and anything over 2-3 inches per second is considered high speed.

The graph below is of a linear shock. Again this shock is a competitors and very popular in the 240sx community.
As you can see there is very little low speed force.

The graph below is of a 500 series shock. As you can see the graph has a knee in it. The shock exhibits much lower force...again more control in roll and dive/squat situations.

Fortune Auto Shock graphs:

All fortune auto shocks have the same valving from our 500 series to our dreadnnoughts.
Below is a sweep PVP graph of one of our shocks from full soft to full hard. You can notice nice consistent damping changes. Many lesser shocks make little to know damping changes when the knob is turned.

Below is a sweep PVP graph of a race shock that a customer requested to build for their time attack car.
As you can see the shock forces are higher so they can cope with higher spring rates. In this case 15k and 12k.
Many entry level shock manufacturers use the one size fits all mentality. This results in a improper ride and even worse performance.

Consistency and repeatability:
It is important that a shock is tested, tested and then tested some more.
When we dyno a shock we dyno all of them at 90 degrees. This makes all of our tests consistent for comparison sakes.

However race/drift conditions can actually get a shock extremely hot. We have seen temps as high as 220 degrees on our race cars after 40 minute wheel to wheel races.
Usually a shocks characterises will drastically change when it sees high temps. This is due to small piston sizes, low quality shim stacks and non synthetic shock oils that cavitate-.

We are proud to announce that our shocks are extremely temperature resistant.
The graph below shows our shocks running through some extreme temperatures.
The graph shows how resilient our shocks are to massive temp changes.

Considering that it takes 160 degrees to fry an egg it is pretty impressive that our shocks perform virtually the same at 90 degrees to 350 degrees.
This is accomplished by running oversizes shock bodies (that hold more shock oil), high quality shims and synthetic oil.

Hope everyone enjoyed this little tech thread. If you have any questions in regards to shocks please let me know! I would be happy to answer any shock related questions. Even if you do not have Fortune shocks

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