The author was pleased with...
The author was pleased with the results from the DynoSim software.
To make a good comparison of DynoSim and measured dyno data on my engine, I will attempt to read data from the DynoSim graph and plot it on the same scale as the measured dyno data. Figure 5 shows the results. As you can see, the curves match nicely.
I am impressed with the ease of operation of the DynoSim software. For the most part it is easy and fast and has a nice display. If you want to learn about performance engines without spending a ton of money and time, DynoSim will get you up on the learning curve quickly without having to spend a lot of time reading the instructions. It can show you the proper order to spend money on your engine to get the most performance. In an engine, everything must work in harmony, and it's not always obvious in what order work should be done. For instance, on our test engine, I put on a big carburetor and then a good manifold. The manifold didn't help at that time because the heads and the exhaust were restrictive. When these were opened up, the manifold started to work. Knowing the rpm range at which your engine makes good power is essential for you to select the correct gear ratio for your car and track.
You can develop an understanding that peak power and peak torque are not as important as the area under the power curve between the rpm limits that your engine will see on the track. Knowing torque and gear ratios will help predict when you'll have wheelspin.
There are many things a real dyno test will do that a software simulation will not do. An actual running test will find oil leaks, water leaks, parts interference problems, fouled plugs, bad wires, low oil pressure, insufficient fuel delivery problems, ignition breakdown problems, and poor fuel mixture and distribution problems. You can tune your carburetor and optimize the spark timing. You can see the effects of valve lash settings and cam indexing. The DynoSim software assumes these items are optimized already.
The software does a decent job evaluating these items if you use the Cam Manager feature. If you made an error in assembly or have a weak part that won't withstand the load or rpm you plan to use, the engine will blow up on the dyno stand. Otherwise, it will blow at the racetrack in front of all your friends, and you'll lose points toward a track championship. Of course, it is painful either way. Also, the dyno operator hates to clean up the mess. From my experience, the dyno operator wants to shut down a test as soon as the horsepower noses over. I have to tell him the rpm at which I plan to run the engine and request him to test it to that point. It makes both of us nervous, but if that's how you're going to use the engine, you might as well test it that way.
The sound of a sweet-running engine is an experience that is hard to beat, but the cost of the software is probably one-third the cost of a half-day of dyno testing. I recommend you invest in the software first to learn how to build your engine and learn what to expect. Then, if you can afford it, you can't beat good data from an actual test.