Smokey said, “If you ain’t thinking, you probably ain’t winnin’. Photo by Trish Yunick
In an attempt to set the stage for upcoming in-cylinder combustion analysis for the CT G.R.E.E.N. engine project, there's a good chance we inadvertently broached the second subject before what should have been the first. Aside from an apology for that, we decided to put things back in order this month. What brought this particularly into focus was the Advanced Engineering Technology Conference presentation made by Dr. Andy Randolph (Engine Technical Director for Earnhardt Childress Racing) at the recent PRI Show in Orlando.
Actually, we were exposed to the wit and technical prowess of Dr. Randolph some years ago, also at an AETC, when he discussed the intricacies of in-cylinder combustion analysis. There are teachers and there are teachers. Unless you've had an opportunity to observe his delivery, it's difficult to describe its effectiveness. You would marvel. Having had experience performing test procedures of the type he discusses, I'll underscore the value and benefits they can produce.
That said, this month we'll discuss what is widely believed to be the real focal point of making engine power; the combustion space. In fact, you may want to concentrate on how a variety of conditions and causes outside this space will help toward understanding "what affects what" in determining combustion efficiency.
Briefly stated, we urge you to focus on the combustion space while changes outside this window are made, be they changes to valve or ignition spark timing, intake/exhaust system configurations, port flow quantity/quality, combustion space modifications (heads and piston crowns), method of fuel delivery and type, and related factors that can materially impact how fuel is converted into heat (power).
The intent here is also to link what we previously discussed concerning the in-cylinder tests soon to be conducted at Michigan Technological University with the following bits of information. Hopefully, in combination with the prior discussion, you'll have a reasonably solid basis for following and understanding why the MTU data stream was gathered and the potential impact on how you optimize power in your own engine projects.
For purposes of discussion, we'll assume the subject engine has the ability to evaluate and control basic functions on an individual cylinder basis, such as the current CT Project G.R.E.E.N. version we hope you have been following the past year or so. We'll let your creative imagination figure out how the same results can be obtained from engines that don't incorporate such contemporary technology. Surely you've heard about variable HEI distributor reluctors (for individual cylinder spark timing) and mechanical fixes (fuel dams, slots, and runner entry modifications) for non-EFI intake manifolds. No? Well, it might be worthwhile.
OK, to the business at hand, square one involves the assumption that a multi-cylinder engine can be viewed as a collection of individual engines. That is to say, each cylinder can and should be optimized for its own combustion efficiency.
Since typical induction systems allow inlet excursion pulses to be "felt" or shared among all cylinders (based on port design, valve timing, backpressure influence, reversion pressure, spark timing, combustion contamination, engine speed, and fuel enrichment), there can be variations among cylinders in the potential for how power can be gained through optimization of one cylinder at a time.
However, the first part of this step involves determining what overall spark ignition timing produces the best power; e.g., conventional total ignition spark mapping. Then it becomes a matter of finding out optimal spark settings for individual cylinders. In the course of the MTU testing project, this step will be