Periodically, you've been exposed to some notions in this column that were linked to an engine's individual cylinder tuning or optimization. In some instances, we've hinted about certain ideas while at other times more specific information has been shared. Those of us who have spent any time on a farm might say we've managed to "plow up a snake" on the subject, and we felt it might be time to delve a bit further into the subject, if for no other reason than there is clear merit to and benefits from this approach. Now, let's provide a bit of background.
In the early 1970s, Edelbrock introduced a small-block Chevrolet intake manifold design that was unlike any previous concept for a V-type engine. They called it the "Tarantula" and it amounted to a single-cavity (plenum) manifold with runners that all connected directly between intake ports and the plenum. For reasons not important here, the design incorporated four runners measurably shorter than the remaining four. From an intake manifold "tuning" perspective, those skilled in the art/science know this factored into where torque boosts occurred in the engine's overall rpm range. That design changed the landscape among V-type street performance and racing intake manifolds. It also introduced some "flaws" that could be considered opportunities for how engine packages are power-optimized. Specifically, it suggested there should be ways an engine's individual cylinders could be optimized for power (particularly torque).
In 1988, Edelbrock obtained a U.S. patent that focused on linking the power output influence of intake and exhaust passage dimensions to specific ranges of engine speed and introduced the possibility of how valve timing played into the engine performance equation. In fact, and concurrent to that period, there was direct OEM involvement with certain NASCAR Cup teams to zero in on how this type of engine could benefit from single-cylinder optimization. At that stage, there was a measure of camshaft exploration capitalizing on the performance of the type of intake manifolds just described. Even ignition system modifications were employed for further benefits.
The point in recapping these events is to support the idea that treating individual cylinders as engines unto themselves is neither new nor snake oil. While intake manifold designs applicable to circle track engines have continued to improve and are on the threshold of including the "folded hands" concept found in many EFI induction systems, the notion of single-cylinder power optimization continues to emerge with obvious benefits to circle track racers.
Not to the exclusion of engines using common-plenum induction systems and collected exhaust headers, those fitted with individual runner fuel injectors and exhaust pipes are less complicated to apply this technology. Such engines are void of tuning interferences that result from intake and exhaust flow "cross talk" from pressure pulses and related dynamic disturbances common to plenum chambers and exhaust collectors.
If you don't think pressure excursions exist in an engine's plenum-type intake manifold, I recall during a particular engine dyno test when an intake valve head in a 351C Ford racing engine's No. 2 cylinder broke off and wound up embedded in the crown of piston No. 7. But even given these type of reversion pressure pulses, it's possible to improve net engine output by studying individual cylinder performance.
Here's an idea that's in current practice when seeking to optimize single cylinder output. Suppose you located a Lambda (oxygen) sensor in each primary pipe of an engine's header system, 8 to 10 inches downstream of the cylinder heads. As opposed to simply measuring exhaust gas temperatures which, by the way, can be misleading when trying to determine effective air/fuel ratios during combustion, these devices measure oxygen content in the exhaust. They are thus positioned to determine net air/fuel ratio during combustion. Early versions of such a system used CO (carbon monoxide) measuring devices with slower response times than current Lambda sensors. Unless you're blessed with an opportunity to use engine cycle analy-sis (ECA) or comparable in-cylinder pressure measurement methods, oxygen sensors are a worthwhile substitute.
Is this a useful tool? To be sure. For example, achieving equal runner-to-runner (or cylinder-to-cylinder) airflow equality in terms of quantity is only a step toward optimizing individual cylinder power. Even if the same amount of air (and fuel) is delivered to each cylinder, air/fuel mixture charge quality can result in variations in effective ratios at the time (and during) combustion. Individual cylinder spark timing variations can also become demons. By the analysis of post-combustion exhaust gas, you can more accurately determine the potential for optimized power per cylinder. In prior Enginology columns, we've discussed the importance of creating and maintaining good mixture homogeneity, effective fuel atomization and proper airflow quality. By the latter, we mean airflow that aids both fuel suspension and fuel atomization. All of these ingredients are necessary if you intend optimizing individual cylinder power.
If you need further evidence, here's a real-world example as shared by Dennis Wells (Wells Racing Engines), no stranger to readers of CT. According to Dennis, "We'd been burning the same piston in an alcohol engine and decided to check individual cylinder timing. We degreed the balancer and discovered the problem cylinder was getting two degrees more timing than the others. Especially in an alcohol motor pushing about 15:1 compression ratio, this much timing can cause problems, and it did. So, I got one of those distributor reluctors that you can bend and adjusted for the timing error. Then we decided to look into the intake manifold situation by installing O2 sensors in all the header pipes. In the process of making distribution mixes in the manifold, we discovered the problem cylinder (previously burning pistons) was also the leanest, so it's no wonder we were having burned piston problems. I'm a strong believer in tuning cylinders on an individual basis."
Once again, what's the point here? Essentially, we're discussing ways to evaluate upstream changes to intake paths, fuel routing, and spark timing to specific cylinders. I've also seen distributor cap plug wire terminals "modified" to either advance or retard spark timing, thus enhancing single cylinder output. At least for now, let's stop and turn to valve timing.
Can camshafts be "optimized" by incorporating multiple lobe designs and placement on a given shaft? Certainly. Has there been experimentation and validated results using this technique in the past? Same answer. What you may want to do is continue reading future issues of this magazine because there are projects and plans in the making that will likely include ways the general circle track populace can benefit from engine analyses and experimental ideas that might seem unobtainable to this audience. It remains an objective of CT to find, explore, and share ways so-called Saturday Night engines can be either built or modified. Including ways that identify and lead to the optimization of single cylinder power optimization is definitely on our list of upcoming topics . . . both in this column and elsewhere in the magazine. But for the time being, that's about as specific as we're able to be.