By the time you read this, chances are you'll already have had an opportunity to see and digest results from the New Smyrna testing of Circle Track's Project G.R.E.E.N. proposed alternative fuel and powertrain package. From the results collected during the engine dynamometer testing at Mast Motorsports several weeks prior to the track experience, project participants were projecting the probability that lap times would be quickest with the EFI/E85 combination.
Even back then, during the engine dyno work, the fundamental re-shaping of the E85 fuel and EFI-based torque curve predicted improved corner exit rates of acceleration and speeds would be the areas of on-track performance gains. And, as you've likely now seen, that prediction turned into reality. But aside from reviewing and absorbing the track-derived data, it may be worthwhile to bring a couple of additional thoughts into discussion.
The first is a basic comparison in the quality of air/fuel charges delivered by EFI versus carburetion. On more than one occasion, this column has discussed the power-enhancing benefits of mixture quality as related to fuel particle size uniformity. Air/fuel charges do not "explode" in the combustion process. They need time to combust, even though such time spans are very brief. Large fuel droplets require more time to combust than smaller ones, often causing excess fuel to pass directly through an engine when unspent fuel has not had sufficient time to be converted into heat (power).
By comparison to EFI air/fuel charge quality, carburetors are not known to provide charges of equal quality. Consequently, not only is there a reduction in power from failure to burn all the fuel that's delivered, but on-track fuel economy tends to suffer. There's also a chance engine oil dilution will be higher than with EFI, resulting in shorter ring, cylinder wall, and valve guide life.
Taking another perspective to this, we could say a power improvement (and less oil dilution and wear) will occur as air/fuel charge quality improves, simply because more of the fuel delivered is converted into power, rather than passing out of the engine unburned or having it become routed into the oiling system.
In addition, air/fuel charge quality as provided by electronically-operated injectors is not engine speed dependant. Carburetor atomization efficiency can be linked to airflow rate, thus tending to be less atomization efficient at lower engine rpm and better as rpm increases...up to a point. Arguably so, you could say that regardless of the method of atomization (carburetor vs. EFI), there will be some level of air/fuel separation downstream of where fuel is introduced. But it's pretty clear that the mechanical shearing of liquid fuel that is produced in a carburetor will produce air/fuel charges of lesser quality than what is delivered by an injector that "sprays" fuel into the incoming airstream.
So, are these observations intended to be a slam at carburetors? Not in the least. Rather, they are meant to point out certain features to consider if or when a choice (or opportunity) comes to use EFI in a racing environment. To say it will not become more common in the future would be risky, at best.