Graph 5: CO emissions based on a five-lap average for each engine/fuel configuration. Uni
By reviewing these figures, you will find there is a significant reduction using the EFI/catalyst combination relative to the combination without catalysts. For the 100 cell-per-inch (cpi) catalyst, there is a 75 percent reduction in HC. For the 300 cpi unit, it was 87 percent. Interestingly, the HC emissions for the carbureted version without catalysts were lower than for all of the catalytic converter configurations (Graph 4). This seems counter intuitive. However, if you refer to Graph 3, these results become much clearer.
Since the carburetor exhibited large lean spikes, there was very little fuel to burn. HC and CO emissions always run inversely to NOx emissions with regards to relative A/F ratios-e.g. fuel-lean conditions create low HC/CO and high NOx, while fuel-rich conditions generate high HC/CO and low NOx.
By comparing the CO and NOx data shown in their respective graphs (5 and 6), you'll see this to be the case. The inherently lean A/F excursions recorded with the carburetor (which contributed to the reduced performance) generated less HC and CO emissions but generated more than five times the NOx emissions compared to the catalytic converter fuel-injected configuration (Graph 6). Therefore, a comparison of catalytic converter effectiveness could not be conducted relative to the carburetor. However, by focusing on identical engine and fuel configurations, this comparison was made.
Graph 6: NOx emissions based on a five-lap average for each engine/fuel configuration. Un
When comparing identical configurations and the emission reduction potential without the relative A/F ratio variations produced by the carbureted version, the picture becomes much clearer. Removing the carburetor results and focusing on identical Lambda values and measured emissions, the effectiveness of the catalytic converter becomes clear. Graph 7 summarizes the emission reduction, using both the 100- and 300-cpi catalysts, relative to the same configurations with no catalysts.
From these results, it appears that a modest CO reduction was produced by all of the catalytic converter configurations. However, significant HC and NOx reductions were produced. The 300-cpi catalyst produced notably greater HC and CO reduction, even though NOx conversion remained almost the same among the parts combinations. You can also see that the conversion efficiency between the Street Blaze, 100-cpi configuration is higher than the E85 version.
Graph 7: Catalytic converter emissions reduction efficiencies comparing 100 cpi vs. 300 c
A plausible explanation for this deviation is based on the design of the catalyst. Catalytic coatings are selected and tailored for specific fuels. Specifically, almost all converters sold are intended to be used with petroleum-based fuels. If we were to focus specifically on the emissions from an E85-fueled engine, converter cell count and formulation of the catalyst could be altered to address this specific fuel. As an example, since the relative fuel flow rates are on the order of 25 percent higher for E85 than race fuel (based on lower energy density or content), it is plausible that the length and size of the catalyst may need to be increased to address the relatively low A/F ratio, thus ensuring enough catalytic reaction surface to reduce the emissions.
Some Preliminary Conclusions
We use the term "preliminary" for several reasons. In particular, there are additional tests to be conducted. The Circle Track team has an implicit responsibility to conduct this project not only with a strong desire to report accurate findings but also do so using all available engineering skills and data reduction practices available to us. But even at this stage, there are some issues of significance. We'll mention only a couple of them.
For example, during the initial track tests, almost a full day was required to calibrate the carburetor, in order to optimize its performance and begin gathering meaningful lap data. Horace Mast (Mast Motorsports) tuned the EFI system in less than 20 minutes, once an initial few laps were logged with this combination. While we didn't attempt to quantify how this would impact the economics of long-term EFI use on fuel and tire costs, they would certainly be reduced. Also, as predicted from the engine dyno test session, based on improved brake torque below 5,500 rpm, corner exit acceleration and lap-time reduction proved out on the track.
In face of all this, it's worth repeating that along the path we've been taking, optimization steps have not been included. Chassis setup, gear/tire combinations, and changes to driving technique (among other factors) all have a role in maximizing the parts combinations we're exploring. As when racers begin experimenting on their own with the parts and fuels we have been and will continue investigating, there's little doubt further improvements will surface.
The overriding objective of the project has been to identify and examine environmentally-friendly additions to the current motorsports landscape. It remains for the race-sanctioning bodies and segments within the racing participant sectors to decide if, when, or how they want to begin using what the project is validating. Best of all, no immediate end is in sight for this exercise.