DEPAC Windows Interface: DEPAC LINK4 Windows program to run in Wndows 2000, XP, Vista, and Win 7, 8 PCs.

 DOWNLOAD and Install Latest LINK4 Program. 17 megs.. Save file, Locate file, then run it.

Has 4 different examples of Results discussed below.

LINK4 can read, and update both Vers2 and Vers3 CFGs and Test Files and Convert to LINK4 format..

System requirements:
Windows version 2000, XP, Vista, and Windows7, 8, 10
Minimum Monitor resolution 1024 x 768
Works best on High Resolution LCD Monitors
Spreadsheet and GrafPlots fill to the full monitor's resolution (more Numbers and finer Curves).
Works with standard Windows B&W and Color Printers (Portrait and Landscape formats).
Program is small and should run fast on most newer PCs.
Fast Install and easy Uninstall (Start > Programs > DEPAC-Link4 > select un-install)

You can view any DEPAC test run ever produced to edit , display, and print.

Below are 10 GIF files of DEPAC GrafPlot screens from LINK4 illustrating several inertia correction results.

Note: Our DEPAC stands out as the only system precise enough to reveal these important details and results. Proof is in the results.

 NOTE: All these tests and screen dumps were from using our DOS demo3.exe download from

There are many dyno makers who do not (or can not) do inertia correction accurately. Steady state testing has no inertia errors BUT these tests are not valid on any engine that accelerates fast in any application. Steady State tests are good only for engines, like those that drive a constant speed generator. Our Standard is to sweep the engine as it would be accelerated in the application, very fast for drag racing engines and slow for NASCAR Cup engines. Really slow for marine engines and generators.

DEPAC is a pioneer in transient engine testing showing how it can be done right (with our advanced ADL Control) and with meaningful results and precise inertia corrections.

 Introduction: There are 4 groups of Tests included as examples in the LINK4 .. Load the corresponding Configuration (CFG) File to explore.

1. NASCAR CUP engine with Fast 500 RPM/sec sweeps Up and Down over a wide range.

  Load CFG file - - - DEMO3.CFG   Tests done a Stuska 800.
  CUP-1, -2, -3 are of a NASCAR 350 CI CUP Engine at Ernie Elliotts Engine shop when at Concord, NC in 2004.

2. An NHRA Pro-Stock 500 CI engine illustrating the DEPAC looping test to Set the Inertia Factor.

  Load CFG File - - - LOOPS.CFG Tests done on a DTS Power Mark dyno.
  PS-LOOP-1, -2 NHRA Pro Stock engine of J&J Racing Greenville, TN

 3. Results of a very bad running engine where the flywheel effects smooth out the erratic engine performance. When we remove the inertial smoothing effects of the flywheel the engine's true erratic performance is revealed.

  Load CFG File - - - BAD-ENG.CFG   Tests done on a Stuska 800 dyno.
  BAD-ENG-1, -2 Bad Running engine from a client who thought there was something wrong with our system,showing erratic curves.. Yes, there was.. The engine was running very badly and the DEPAC system simply showed the real truth.

 4. An NHRA Pro-Stock 500CI. Three fast sweeps up at 600 RPM/sec with and without Inertia corrections.

  Load CFG File - - - PRO-STK.CFG   Test done a SuperFlow 901 dyno.
  PRO-STK-1, -2, -3 are NHRA 500CI Pro Stock fast pulls up at different times during the day. Air conditions changed as much as 1% but results were still corrected to 1/100th %.

Please look at GrafPlots CUP-1, -2, -3.

CUP-1 shows Torque curves of two fast sweeps UP and Down at about 500 RPM/sec. Normal sweep tests on CUP engines are usually much slower (100-200 RPM/SEC), but these were done for illustration of the power of the DEPAC system. These 2 pulls were inertia corrected and the average between these pulls is within 0.1 Ft-Lb or a difference of 0.02%. This particular engine ran much the same both up and down but usually most engines run differently up and down.

CUP-2 shows the same two curves with a re-play of the DEPAC Machine-Gun (MGun) dots. Red dots are Down in RPM and White dots are UP in RPM.

CUP-3 Shows the same two runs BUT with no inertia correction applied. Note the large errors caused by even light rotational inertia at fast sweeps. Note the MGun dots show less scatter because of the smoothing effect of the flywheel. Look back at CUP-2 to see the MGun dots with more actual real torque scatter. These curves are different by 7 ft-lbs, as compared to 0.1 Ft-Lb with the corrected results (see these averages on the top-left next to the test run names. Note the pop-up menu at the bottom where we can change the inertia correction number any time after the test run.

Please note that these torque curves have a subtle 'finger print' in the curve due to the complex cross-over, under the car, exhaust system (same as they have in the car). Only DEPAC can show these small subtle effects whereas many other dyno systems routinely apply curve smoothing (curve fit), primarily to make up for the poor accuracy of the method of A/D sampling used.

 Please look at GrafPlots PS-LOOP-1, -2.

These plots show an actual DEPAC Inertia LOOP Test for inertia. PS-LOOP-1 shows the MGun dots as the throttle is picked up to full. Then we quickly modulate the Load to cause the engine to rapidly sweep up and down showing the effects of inertia on the Torque dots (with no correction). The dots loop CCW with the Red dots coming down in RPM and the White dots sweeping up. This one simple looping test took only a few seconds to do.

Now the engine is shut down and we then can replay these MGun dots and type in different numbers for inertia, as a guess. Then you replay the MGun dots to see effects. The object is to enter a number that will cause the Red and White dots to mix together with no visual looping seen (that is No Inertia errors). Very quickly you can fine an number that makes this happen. Refer to PS-LOOP-2 to see that entering 0.385 results in near perfect cancelation of inertia on the engine under test.

Please look at GrafPlots BAD-ENG-1, -2.

Now we have an engine that is running very badly. In this case the flywheel inertia effect makes the engine look smooth (filtering effect). BAD-ENG-1 shows both the upper Inertia Corrected Torque curve and the lower Un-corrected smoother curve. We have played back the MGun dots for the curve with no inertia correction. The MGun dots look good and not much scatter.

 But now look at BAD-ENG-2 where we now play back the MGun dots for the inertia corrected curve (0.26). Now the flywheel no longer smoothes out the erratic running engine. We are now seeing how bad this engine is really running without a flywheel to smooth out the performance. Note also the different colored dots Yellow and Purple. These are tags the DEPAC system appies to periods with anomalies, like an ignition mis-fire or erratic fuel distribution. The DEPAC system can tag these MGun dots to show problems during this integration period.

 Notice that the inertia corrected curve is not smooth since we are now showing the true behavior of this bad running engine. Any further test run overlays will also show that this engine just does not run the same way twice. DEPAC brings out this true behavior and never applies curve smoothing, like so many other dyno systems.

 Please look at GrafPlots PRO-STK-1, -2, -3.

PRO-STK-1 shows three fast sweeps up at 600 RPM/sec on a NHRA Pro Stock from 2001. These tests were run at different times during the day where the air quality changed by 1% but these three no-change backups are still within +/- 0.02% with our air correction system. The upper Torque and Power curves have been inertia corrected to 0.331. The lower curves are the same three runs with no inertia correction. Errors are dramatic and erratic since the sweep rate fluctuates during the sweep on this SuperFlow 901 dyno. This is a very well developed engine that does become smoother as the inertia errors are corrected (top curves) and observe the average torque shown on these three runs on the upper left in green.

PRO-STK-2 is the same curves but we have hit the insert key to plot the MGun dots for the corrected upper curves. Note in particular the left, start end of the curves. Note that the Red dots and the White dots have merged. Dynos like the SuperFlow, and most all others that use speed controls, will overshoot the RPM set point and then pull down to the setpoint (Our ADL Control does not do this). We then use this natural behavior to set the inertia correction.

PRO-STK-3 shows the MGun dots for the uncorrected curves. See the upper Red MGun dots as the dyno overshoots the start RPM setpoint and rapidly pulls down to begin the sweep up. We use this half loop to set the inertia correction, without needing to perform any looping tests. Also note the uncorrected curves are spiky and inconsistent with the inertia errors (with erratic sweep rates).

NOTE: Our technology is available to other dyno companies who wish to upgrade the performance of their Dyno Instrumentation and Controls.

DEPAC Dyno Systems, 404 Red Bud Trail, Sparta, TN 38583