ProRacing DynoSim - Dyno Testing With A Computer

Real engine testing requires a dynamometer that can cost $30,000 or more-and you have to take the engine out of the race car and spend another day's labor to get some numbers. I have been fortunate enough to have a friend with a dyno, so I've tested many of my engines. It's always interesting, but it's hard work and costs some bucks.

However, a low-cost alternative is available. Several companies now offer engine dyno software to predict what engine performance you're getting with the parts you have and the parts you hope to buy. One such company is Motion Software Inc., which produces the DynoSim software. This is distributed by ProRacing Sim, LLC.

Following the directions included with the software package, it took me about 25 minutes to install the software.

Figure 1 shows the screen layout. On the left side is a section for inputting information about the engine to be tested. Information required includes the type of short-block and cylinder heads, the level of compression, the induction, the exhaust, and the type of camshaft. In each section, there should be asterisks indicating pull-down menus. Once you've made the selections, the software plots the performance, horsepower, and torque on a graph as a function of rpm.

For our test engine, I'll choose a Chevy 350 bought from a salvage yard. Here are the various menu selections I'll make:

* Under the Short-Block menu, I select Chevy eight-cylinder small-block and 350 V-8. This loads the proper bore and stroke. Having done this, the software puts a green check mark in the box beside Short-Block to indicate we have properly loaded the information.

* Cylinder Heads: I find the choices available and select Low Performance/ Stock Ports and Valves. I have to input the valve sizes and select 1.94-inch intake and 1.5-inch exhaust.

* Compression: I select 9.0.

* Induction: 350-cfm, two-barrel carb. It's also necessary to select the manifold type, and I choose a dual plane, standard flow.

* Exhaust: I select Stock Manifolds and Mufflers.

* Camshaft: I select Stock Street/ Economy. The lifter type is Roller Hydraulic. I guess the new 350s have a roller cam, but the old ones I find have flat tappet cams.

See Figure 2. Torque is in green and horsepower is in red. It says our engine makes 220 hp at about 4,000 rpm. Torque is 345 at 2,500 rpm. Performance is about right, but I don't think it will win any races. We have to breathe some life into this engine, so I put a big 750-cfm four-barrel on it. Now I have 250 hp. The peak is still below 5,000 rpm. It probably needs a better intake manifold, so I'll try a good single-plane aftermarket manifold. I select Single-Plane High-Flow, but that doesn't do anything. Then I try some headers and ditch the mufflers. I use small tube, open exhaust. Now I have 280 hp and 400 lb-ft of torque, which is much better. I need a better cam, so I select Drag Racing/Circle Track profile. Now I'm getting competitive-360 hp at 5,500 rpm. Our torque drops off a bit but it likes the higher rpm.

Time to scrap the heads. We will put on some old double-humpers with 64cc chambers. I select Wedge/Stock Ports and Valves. Also, I bump the compression ratio up to 10. Now we are looking at 400 hp, and this motor is still pulling good at 7,500 rpm, assuming it will stay together. Now we're getting some serious power. If we want to turn 7,500 rpm, we better invest in some new parts. An overhaul would be in order with new flat-top pistons, rings, bearings, and some better rods. Maybe some pink rods or Vortec-type rods will do. If we find a sponsor or hit the lottery, we can spring for some real racing rods.