Figure 4 - Somewhat exaggerated, and while you may not observe quantitative values consist
In fact, this method encompasses the ability to help quantify combustion efficiency (exhaust-diluted combustion, mechanically-separated air/fuel charges prior to and during combustion, etc.) by measuring the amount of unburned fuel (HC) and air/fuel ratios (CO) in cylinder-to-cylinder exhaust passages. Whether you can afford or have access to such equipment, I've seen some pretty useful data produced by the use of emissions sampling equipment from automotive repair shops. At least some information is better than none.
We touched on some of these in early sections. Here are some more you can consider. A few might seem rather rudimentary, but you'd be surprised how often they are overlooked.
First of all, test all the parts you plan to run on the track. While both temperature and related factors encountered on the track may not be duplicated in the test cell, at least you'll get a sense for where in the speed range power is made. That's critical to trackside tuning and gearing choices. Plus, unless you're using the same parts, you'll be tuning to some other combination instead. For example, even though the "dyno" headers you might be using are dimensionally the same as the racecar system, bends, radii, and other little idiosyncrasies can sneak up on you and produce off-target results, by comparison.
One area where dynos may be somewhat lacking in helping you "tune" components is the intake manifold. Consider the following piece of information. Let's say you've conducted back-to-back dyno tests using two essentially different manifolds. Further, let's also say they contributed to corrected power curves that are essentially the same, quantitatively. However, you noted that even though you minimized the BSFC curves (once plotted), one is trending numerically lower than the other. So, which manifold should perform better on the track? What this comes down to might be called "transient" horsepower or torque. The latter may be preferable.
Essentially, you'd like an engine to accelerate quickly (under load) throughout its operational rpm range. And, obviously, the quicker it can do this the greater the chance for a racecar to accelerate, all else being equal. Over time, it has been demonstrated that the engine operating with the lower BSFC will also tend to produce the quickest acceleration. Interestingly, you can apply this same logic when evaluating other major engine components, including headers and cylinder heads.
How do you compare this evaluation technique with so-called "acceleration" tests performed on the dyno by which a time-based and controlled unloading of the power absorber is applied? Not certain you can, even though this method does provide useful brake power data (for test-to-test comparison purposes) at minimum wear and tear on an expensive race engine. Unless an engine is accelerating a mass (load) and experiencing the changes in dynamics this involves, you've not basically brought the track to the dyno. However, programming throttle positioning as a function of load, if properly done, can create an operational environment that simulates specific track conditions. Higher-end engine dyno facilities do this on a routine basis.
There's clearly a limit to what can be accomplished in the pages of a magazine. Explanations often create unanswered questions. Editorial attempts to cover all aspects of a given topic or sub-topics can suffer the same consequence. However, even recognizing these limitations, this Series was intended to minimize those handicaps and attempt stimulating both thought and reason about and for the subjects discussed.
Make certain you spend a few minutes with the sidebars attached to this month's wrapup. Both are stuffed with helpful tidbits, particularly the one from Charles. And, finally, he and I hope you'll allow this Series of stories to be a stimulus for telling CIRCLE TRACK'S Editor (firstname.lastname@example.org) what else you may want to explore. You might be surprised at the response and pleased with the results. Meanwhile, thanks for your interest. It's been a pretty good run and hope you've enjoyed it as much as we have.