As we head into the first few laps of a New Year, it may be an appropriate time to reflect on some "what if" questions that need to be considered. After all, our chosen sport/hobby/business/profession operates (or should) on an evolving landscape populated with activities that include innovation, exploration, creativity, competition, and a hunger for winning. Was it not, from where would the motivation to do what we do come? That said, let's examine some possibilities for the future. And just so we don't fail to make mention of its objective, that concern formed the basis of what has now become Circle Track's Project G.R.E.E.N. Hopefully, this became clear many months ago. So for now, we invite you to think about the following.
What if the powertrains of today's weekend race cars were not exclusive to carburetors and gasoline? What if there was an opportunity to shave the costs of running a competitive race car? Specifically, in the course of reducing the cost of maintaining a competitive race car, what if less frequent engine rebuilds and lower fuel prices were possible?
What if there were ways to explore optimizing power levels that embraced new and affordable technologies? What if new classes of racing were made available that not only enabled responsible changes but rewarded those who engaged in such progressions? What if we collectively came to the conclusion that racing, long-term, as we know it today could benefit from embracing changes that combine to not only improve present conditions but also help ensure future growth and longevity? We already know that there are verifiable declines in certain areas of our chosen sport, so what if we recognize the value in, and need for, examining where we go from here?
If you chose to address virtually any of these "what if" questions, and since the objectives of CT's Enginology column are directed to powertrain topics, this may be a good time to examine ways that changes to this part of a race car can be evaluated.
Based on elements that were foremost in developing the magazine's G.R.E.E.N. project, stepping out of the box to explore electronic fuel injection and alternative fuels was "square one" in putting the future powertrain puzzle together-which brings us to this month's "what if" subject of how to analyze and optimize the effects of an alternative fuel.
You may recall that roughly a year ago, this column contained information about a method for evaluating the combustion process in a running engine. It was called "Engine Cycle Analysis" or ECA and focused on real-time measurement of in-cylinder pressure vs. crankshaft angle during combustion conditions. In fact, we provided a simplified graphical trace of cylinder pressure as a function of crankshaft position throughout one combustion cycle, showing when the burn began and the pressure history following that event.
Emerging largely from the academic community that spawned its origin, ECA has become more commonplace among engine builders and race teams seeking to fine-tune their engines for optimal performance. But here's the point. In its quest to evaluate potential fuels of the future, while determining ways to optimize their power potential, Circle Track has elected to use ECA approach.
To that end, the GM CT-525 which has been featured in a number of editorial efforts the past year will be the subject engine for the combustion analysis of E85 vs. race gas. Because of the inherent differences in energy content and burn characteristics between these two fuels and changes to engine hardware (cylinder heads, camshaft, ignition timing, intake manifolding, and so on) that could help enhance the use of E85, a study of this fuel's combustion properties (compared to race gasoline) could be both revealing and helpful.
Specifically, the engine will be sent to Michigan Technological University's Engineering R&D department, which houses a lab complete with advanced analysis equipment such as the combustion vessel pictured above. Following the required machine work that enables installation of a network of in-cylinder (combustion space) pressure transducers, it will be instrumented to facilitate the ECA process and subjected to a rigorous testing program. Right now, it might be worthwhile to review how ECA works and what can be derived from the process, particularly as it relates to Project G.R.E.E.N.
Typically, an encoder is attached to the crankshaft snout, from which incremental crankshaft positions (in degrees) can be determined, relative to piston position. In order to examine small but finite crank positions, it's possible to create increments as small as fractions of a degree. At very high data sampling rates, this approach enables a virtual "real time" flow of information. Then, within the cylinder, high-rate pressure transducers record cylinder pressure variations that are specifically linked to crankshaft position. So, as a function of crank angle, it's possible to tie specific cylinder pressures with equally specific piston positions relative to crank position.
As a result, it's possible to record and evaluate any pressure changes that occur in the combustion space at a very high rate of recording. Further, since we know that net cylinder pressure is the primary ingredient to producing crankshaft torque (computed as horsepower by including time), the study of what we're calling "real time" combustion pressure history provides a targeted look at the foundation of combustion efficiency and its effects on power.
More importantly, since we're dealing with what could functionally be called a "single-plane" intake manifold (all runners joined in a common plenum volume), the net influences of reversion pulses and other pressure excursions that are both normal and unavoidable in such a design can be examined. To do this requires all cylinders (combustion spaces) be fitted with pressure transducers linked to the crankshaft's encoder device. That's exactly what will take place in our G.R.E.E.N. engine while at MTU.
Now, why is this particular exercise of value to the project? Primarily, it's because we can determine more than cylinder pressure histories vs. angular crankshaft positions. By applying certain thermodynamics calculations and related computations, we can develop cylinder pressure vs. cylinder volume, as each changes (relative to the other) throughout complete combustion firing cycles. And by calculating the first derivative of the pressure/crank-angle equation, we can also evaluate the rate of cylinder pressure change. Also as a function of crankshaft angle, we can estimate the rate of combustion heat release, if we assume that heat transfer (and leakage) to the cylinder walls can be neglected. Not a problem.
It's also possible to create a graphical trace depicting combustion space temperature (again as a function of crank angle), notably from the time of intake valve closing to intake valve opening; a data stream that includes peak combustion space temperature that is generally just past TDC on the power stroke. Even though we may elect to perform similar calculations beyond these, we'll make certain to convert the rate of heat release data to a percentage of air/fuel charge burn which will allow us to define the length of the burn, time to fully develop combustion and ignition delay...all critical elements in the study of what transpires in the combustion space.
Since part of the project (by design) involves fuels that are alternatives to racing gasoline, it's reasonable to assume that such fuels may have different combustion characteristics. That's patently fundamental. However, ECA will allow us to not only quantify the different characteristics but also provide information that can be linked directly to modifying or designing "alternative fuels" hard parts like cylinder heads, intake manifolds, piston crowns, camshafts, and (very likely) ignition systems. It's projected that by analyzing specific combustion characteristics of the various fuels to be evaluated, windows of opportunity will be opened to parts manufacturers seeking to match hard parts with the use of alternative fuels.
This collection of thoughts and information is just a preamble to what we'll share with you a few months from now. What's important to recognize and keep in mind is that this pioneering project is dedicated to creating an awareness of what may, or should, be included in the future of circle track racing in particular and motorsports in general. The fact that you're reading about and following this particular initiative is a credit to your hope and belief in our chosen profession or avocation. Clearly, the readers of this magazine are at the core of what lies ahead and any comments you'd like to share are more than welcome. In the end, isn't it all about "what if"...?