This latter condition can also have influence on peak power (compared to a single-plane manifold with inlet runners shorter than the EFI manifold), and you can see the effect of this factor at peak rpm. However, there is evidence of where in the engine speed range an improvement in torque can build a case for better on-track performance potential using the EFI system. Also note that neither of these tests was conducted with catalytic converters in place. More on this a bit later in the story.
Catalyst vs. No Catalyst Interesting stuff here. If you'll refer to the previous graph (Carburetor vs. Fuel Injection), you'll note that peak torque for the EFI and 100-octane Street Blaze gasoline was a corrected 496 lb-ft. Compare this with the configuration (catalyst vs. no catalyst) of EFI, 100-octane street blend and the 100 cpi (cells per inch) catalysts and you'll see only 5 lb-ft of torque were lost at peak torque. Plus the previously broadened and flattened torque curve (from around 3,250 to 5,500 rpm) was retained as a function of the EFI manifold design.
So for those who might believe the addition of catalysts would have a materially negative effect on overall torque output, here's some data to consider. The fact peak horsepower and torque output (with and without the catalysts) was virtually the same again points to other factors, including maximum volumetric efficiency obtainable (at higher rpm) with this parts package. Once again as a reminder, at this stage in the project, no attempt was made to optimize either functional integration of parts or best ECU calibration.
with 100 street blaze
catalysts vs. EFI
with E85 and 100 CPI
catalytic converters You may want to spend a little time studying these results. The baseline data was recorded using a carburetor, 100-octane Street Blaze racing gasoline, and no catalytic converters. Note peak horsepower was a corrected 552 hp, compared to a corrected 539 peak horsepower for the EFI, E85, 100 cpi catalytic converters package. Admittedly, given the current parts configuration, peak power decreased 13 hp. But before you condemn this outcome, pay attention to the way the EFI parts combination affected corrected torque from about 3,500 to 5,500 rpm (plus-22 lb-ft). Given how a particular circle track car might be geared and the track layout, this span of rpm could fall within a very desirable range of on-track engine speed.
In addition, if you will refer to the Carburetor vs. EFI data graph, you'll discover peak torque (EFI, E85, and no catalysts) produced a corrected peak torque value of 498 lb-ft. Compare this value with peak torque (carbureted baseline with 100 street blend gasoline without catalysts vs. EFI with E85 and 100 cpi catalysts) for the EFI, E85, and catalysts package at 499. Maybe this comparison sheds light on some conventional thinking that suggests catalysts will materially decrease power.
Catalyst Substrate Density Comparison While these data get into the minutia of how pumping losses can affect power and the effects of catalyst density on such losses, you can see that increasing substrate density by a factor of three (from 100 to 300 cpi) still allows the higher density, EFI, E85 catalytic converters combination to produce superior torque when compared to the carbureted, 100-octane Street Blaze, no catalysts package (by a higher peak torque value of 12 lb-ft).