Performance Trends, Inc.

1) Valve Spring Tester Update  

Manual USB Spring Tester                 Automatic USB Spring Tester
         for specs on our valve spring testers.

Our popular Valve Spring Tester is available in several versions:

• Manual Spring Tester
• Automatic (pneumatic) Spring Tester
• Manual Spring Tester Kit (you provide arbor press)
• PT-200 Retro-Fit (you have a PT-200 spring tester)

Engine builders are continually getting the valve's open height closer to the spring's coil bind height.  Bind clearances are getting very low.  The theory is that the valve can not loft very far should valve loft conditions occur. 

When the spring gets close to coil bind, it goes very non-linear.  This is also true of the new, popular beehive springs and tapered springs, even if you are not running very close to coil bind.   For most of the spring compression, the spring is quite linear.  The non-linearity occurs only in the region of maximum open height, before coil bind.  

See the graph below of a spring force curve for a tapered spring.  The spring height starts high on the right side with force starting to go up at a spring height of approximately 2.6 inches, when the tester just starts to compress the spring.  As the height gets smaller, the force gets higher as you would expect, following almost a straight line at about 40 degrees.  At about 1.5 inches of height, the graph starts to bend upward at 50, then 60, then 70 degrees.  The vertical jump in force (90 degrees) on the left side is coil bind, where force shoots up with no change in spring height, at about 1.3 inches.

We've recently made some enhancements to the software to better handle this non-linearity only in the region of maximum open height.  If you are running these types of springs, or are running your springs very close to coil bind, do this:  In the Test Options screen there is an entry for Test Type.  Choose the Test Type of "Bent Data w bind", or "Bent Data, no bind" if you do not want to push the springs into bind.  The program can better follow this non-linearity and produce more accurate results.  

See figure below, where the green line called "bent" can follow this non-linearity, but the "smooth" blue line does not.  The largest difference in the results is primarily in the region of the maximum open height.  The error typically reports the Open Force to be lower than it actually is.

The latest software also checks for this type or non-linearity during testing, and calls this to your attention.  See message below:

Assuming you own the Plus version of the software (which 95% of customers do), here's the cost if you want to update.  If you already own v1.1C, this is a free update.  If you own v1.1B, it is $150 and if you own v1.1A it is $250.  Click on links below to see other enhancements in updating from these earlier versions.

  for info on enhancements in v1.1B and 1.1C.