The Portable Emissions Measuring...
The Portable Emissions Measuring System from Sensors Inc. is not much bigger than a case of oil. Here it is hooked up to the Project G.R.E.E.N. engine during our recent dyno test at Mast Motorsports. That long gray hose houses the wires for the a that are attached to the engine's headers which you can just see in the picture to the left.
In the early 1990s, the Superflow Corporation was attempting to commercialize a means for measuring real-time combustion pressure as a function of incremental crankshaft angles (positions).
Although the academic community and certain factions within the automotive OEMs had been previously perfecting this technology, nothing was then on the market that was practical and effective.
The engine research company I had at the time became a beta site for the development of Superflow's efforts, allowing our little "skunkworks" to become exposed to a fascinating method for combustion analysis. The technique was called Engine Cycle Analysis (ECA) and it has become an invaluable approach to combustion space evaluation in more recent times.
Prior to that experience, I'd had the benefit of designing major engine components affecting the combustion process by the use of rather crude (compared to today's methods) exhaust emissions measuring techniques.
Sensors' Dave Kalen reviews...
Sensors' Dave Kalen reviews the real time results from the PEMS unit during a dyno pull.
By evaluating the byproducts of combustion, as you might expect, some insight was possible about the efficiency of the "burn" as it related to power development. It made sense, and it worked to the extent limited by the measurement technology itself. Stated another way, the value of measured data was only as good as the equipment's accuracy, repeatability, and information collection speed. Stay with me, it gets more interesting.
Roughly two years ago, I learned about a newer technology that provided a way to measure on-board vehicle exhaust emissions in real time. Let me be more specific. The method enabled the collection of combustion byproducts under virtually any condition of vehicle operation. At this point, a light came on.
If this equipment was capable of quantifying the components in an internal combustion engine's exhaust byproducts, why wouldn't the technique be a window to optimizing crankshaft torque? So, based on this presumption, I had my initial conversation with Dave Kalen at Sensors, Inc. (a preeminent producer of portable emissions measuring systems or PEMS Account Executive and now a member of the Circle Track G.R.E.E.N. project team). That initial discussion led to meeting his company's president and CEO, Dr. Andrew Reading, and the information that follows. To the serious race teams and engine builders who may read this column, I encourage you to absorb the next few paragraphs.
Over time, engine builders and tuners have tended to focus on a number of combustion-influencing variables, particularly air/fuel charge ratios. According to Dave, "long-established ASTM fuel standards gave people known fuel concentrations for the combustion chamber. It wasn't until recent years when other factors such as real-time exhaust gas measurements allowed engine developers the opportunity to tweak and control the conversion of fuel into heat, causing some changes in conventional or old-school thinking."
What Dave is talking about includes the conditioning of air/fuel charges by various methods of mixture motion and how this can affect optimal spark timing, mechanical compression ratio and (ultimately) crankshaft torque. These factors alone provided evidence that maintaining specific mixtures of air and fuel under equally specific engine operating conditions was not sufficient to achieve maximum power.
However, given these additional techniques that can impact combustion efficiency, using time-honored ways to control the burn might not be insufficient. There is reason to believe we may now be at that stage of measuring and evaluating combustion efficiency in the general populace of racing engines.
Here's a close-up of the sensors...
Here's a close-up of the sensors used by the PEMS unit. They are attached to a tube coming off of the headers.
In the conversion of a hydrocarbon fuel into heat via the internal combustion process, there are multiple byproducts that constitute the "exhaust gas." Of them, unburned hydrocarbons (un-spent fuel or HC), carbon monoxide (CO), free oxygen (O2), and oxides of nitrogen (NOx) are particularly notable, not just for emissions reduction purposes but as data related to optimizing combustion efficiency. If you've been following Project G.R.E.E.N., you've likely seen we've begun including references to, and data from, the measurement of these emissions during initial engine dyno testing at Mast Motorsports. On-track emissions information is forthcoming.
Here's just one example of how such "emissions" can relate to the optimization of combustion efficiency in a racing engine. Oxides of nitrogen (NOx) are combustion heat related. At the risk of oversimplification, speed up the combustion process (by whatever means) and exhaust gas temperatures stand to be decreased.
In other words, if the burn rate is accelerated, more heat will be used to do work on the pistons, resulting in reduced e.g.t. when the exhaust valve opens. We know this often provides an opportunity to slightly reduce spark timing for additional gains in IMEP (net work on the pistons). Further (as you're "tuning" a given combination of engine parts), if you happen to be measuring several other components in the exhaust gas that includes CO (this relates directly to air/fuel ratio), you can begin quantifying the relative importance of enrichment and burn rate to net power.
Here's another perspective. If you are primarily focused on what's going into an engine and are only including exhaust gas temperature or a few emissions components, there's a chance you could overlook both subtle and significant changes affect-ing optimum power. It's generally believed that around 30 percent of the energy content in gasoline (even in a racing engine) is converted into useable heat (power), possibly less. Even if it was slightly more than this, it makes sense to be evaluating the impact that specific engine modifications (including tuning) are having on combustion efficiency, beyond the point of using time-honored brake-specific fuel consumption and exhaust gas temperature data as analysis tools. And while adding O2 sampling to the process of evaluating exhaust gas, would it not make sense to be measuring other combustion byproducts as well . . . notably oxides of nitrogen (NOx) and carbon monoxide (CO)?
And so that you don't get the notion that all this information is just a lofty academic perspective of what might be done through proper evaluation of exhaust emissions, here's a quote from Dr. Andrew Reading of Sensors, Inc. (a recognized information resource on internal combustion engine chemistry). "If we're talking about a hydrocarbon fuel, in a perfect world, we don't expect to see anything but carbon dioxide and water in the exhaust. Anything other than this indicates inefficiency in the combustion process. Analyzing combustion byproducts can be a key to optimizing engine output, which should be of interest to racers seeking to obtain the most power from their engine."
With that, we'll rest our case.