This project is clearly getting some traction. While initial reader responses have largely been in support of CT's "green racing initiative," there has not been sufficient, hard data to support the project's viability . . . until now. In the following paragraphs, you'll have an opportunity to review the unwashed results for our first engine dynamometer session at Mast Motorsports. Fortunately, several of the players from whom you heard comments a month or so ago were present for and participated in the tests. You'll recall previous observations from Rob Fisher (CT's Editor), Forrest Jehlik (key project engineer from Argonne Laboratories), Dave Kalen (Account Executive and motorsports enthusiast from Semtech, the PEMS company), and Horace Mast (mechanical engineer and owner of Mast Motorsports). A follow up story with their comments relative to this test begins on page 40 immediately after this feature. You will likely be interested in what they reveal.
In order to help you derive the most benefit from the dyno results, we've chosen to focus our discussion on the graphical representations the data provides. The computer skills of Forrest Jehlik produced the graphs shown. Our belief is that by looking at the "visuals" and correlating them with the practical and theoretical perspectives they reveal, you'll come away with the majority of your questions answered, for now. At least that is our intent. We'll also tack on a few concluding remarks at the end of the story as we head into the project's next phases.
Fuels Comparison Although 93-octane gasoline was included to compare it with 100-octane racing gasoline (actually blended with 10 percent ethanol to raise the octane rating) and E85, a lack of performance resulted in its removal for the continued analyses. As a result, the 100-octane "Street Blaze" gasoline and E85 (both from VP Fuels) became the fuels used for subsequent tests.
As you will note, data from the "fuels comparison" tests show a torque and power degradation from about 4,000 rpm to peak rpm at 6,750 where the output from all three fuels converged to approximately the same value. Largely attributable to the engine's overall diminishing volumetric efficiency relative to net airflow at higher rpm, other factors played into this convergence. However, from 4,000 rpm to around 6,250, E85 tested marginally better than the 100-octane Street Blaze. (Note: At this point, it's important to know all tests were conducted using the same ECU calibration. For multiple reasons, parts-specific spark and fuel maps were not sought to optimization. Future tests will address that issue.) The data shown indicates only slight differences (w.o.t. throttle, full load) between the torque output comparing 100-octane racing gasoline to E85. As a result, power output differences you will see comparing data from various parts combinations (EFI, carburetion, catalysts, and so on) will be true to the differences such parts represent, not owing to variations in fuel performance.
VP's Street Blaze 100 gets poured into the tank for a round of dyno pulls.
Carburetion vs. EFI At the moment, there seems to have been two areas of particular interest among racers and engine builders regarding a shift away from the conventional use of carburetors and racing gasoline. One pertains to how much power might be lost, switching to EFI, and the other the extent to which catalytic converters would reduce on-track performance.
If you subscribe to the notion that torque is a major factor in race car acceleration, you may find the torque curves displayed in the attending graph of interest. In particular, aside from the approximate 7 percent gain in torque (at the rpm of greatest torque difference or roughly 4,500 rpm), note the general broadening and flattening of the overall torque curve produced by the EFI and 100-octane package. Part of this can be traced to improved fuel atomization (a topic discussed in previous "Enginology" columns) and in part to a basic intake manifold design that favors low- and mid-range torque.