Howdy Alan-
I should just say "Yeah, what Joe Person said."
But with the usual caveat of being a late starter and now finding myself somehow in the middle of the gaggle, I will offer a few details of my fairly stringent perusal of the Ellison up to the point of actually trying to obtain one, and then choosing instead to lengthen the carb induction on my current 0-290. My observations are worth what you are paying for them
First, the facts as I see them:
A. Some really fast guys use the Ellison throttle body. Some really fast folks use a carb, and fly a lot rather than tinker.
B. Several years ago I saw the letter from Ellison where the company denies any benefit to the 0-235 Lyc, which was my VariEze engine at the time. I gave this factor proper weight, keeping up the Ellison chase, but lowering the amount I was willing to pay for ‘nothing’ according to them, and expanding my pursuit, looking sideways at other forks in the yellow brick road to efficiency.
Second, Physics. The following details have been explained to me by some very patient people. I believe they are true:
A. The carb has a jet spraying to one side.
B. The Lyc carb induction system has a hard hill to climb from the get-go because of being located on the oil sump with only about 3 inches of flow before the split. That is a very short run, especially combined with the jet spraying more fuel to one side than the other. Not a big deal when I was putting around in a Cessna 120 at 70 mph where you never think of such things, but a very significant factor when thinking of lean of peak ops in a highly-refined steed. The Lyc sump design and its immediate fuel distribution imbalance became a sore spot for me.
B. The Ellison advantage would seem to come from using a spray bar rather than a carb jet, immediately being a step ahead of the carb in expanded fuel distribution. My imaginary vision of the spray bar was probably somewhat accurate and it intrigued and beguiled me for a long time. It still does, but I am easily distracted by more shapely curves, especially on intake tubes, so that hunt increased.
C. I heard that the Ellison advantage requires the equivalent of a straight, undisturbed two-foot run (probably less) into the inlet, or there is no benefit. I heard of a couple of things that folks had done to approximate this and made notes in my book of tricks, with visions of a two-foot inlet going through the firewall and up under the belly. Or not. Standing around at fly-ins invisibly listening in, it wasn’t hard to hear a story or two of an Ellison installed and finally replaced with a carb.
D. After many hours of listening to very knowledgeable people, I began to realize that this is kinda like the “law of thermodynamics” that I saw explained recently: “You never win, you always lose, and you have to play.” No free lunch. One step forward and two steps back.
As I saw it, if you have an intake that is long enough to enable equal fuel mixing, there is going to be some fuel pooling. Oh great. It occurred to me that it wouldn’t hurt for this longer intake that I was becoming more inclined toward to have some twists and turns to keep the mixture non-liquid to the greatest extent possible. So some turns and zigs and zags in the induction tube might not be all bad.
With several years of use and benefit now from the 0-290 extended intake tube, a recent observation made sense: Some folks were documenting fuel mixture characteristics looking through clear tubes, and observed that the fuel was not totally vaporized, but besides the vaporized fuel, some was liquified and flowing through the tubes like pencil-sized strings wriggling toward the carb. I can’t vouch for the veracity of that, but it makes as much or more sense as anything else I have observed and experienced.
The surprise for me was that my extended intake tube works, that there is no throttle delay or hesitation, and that takeoff power improved with the better fuel balance, as well as comfortable higher altitude lean of peak operation. If you haven't seen them there are pics here on ez.org at Featured Canards.
At the end I was at a place where the lengthened induction tube had become a solid element of my desired design. From what I had learned it would work as well with either a carb or throttle body, and provide what I wanted - even distribution. The chase ended, thankfully, as a boater-friend and I were blowing a couple of decades of settled dirt off of his old Evinrude outboard mini-carbs, holding them against the underside of the Lyc cylinder head intake ports.
All to say, my point of arrival with the Ellison hunt was that I wasn’t going have a perfect enough installation to allow the Ellison to truly do its thing. The over-riding fact is that many of the fast guys and gals have combined numerous meticulous elements that blend to enable their magical performance.
My journey is quite satisfying with the extended intake tube and carb. No issues. It is also true that from my study I have nothing negative to say about the Ellison throttle body, and would offer only positive comments and congratulation to successful users, with any negative issues being related the limits of the installation.
I would suppose that about half of what I have said here holds water. Thankfully my intent is to fly, not stand around holding water. Good luck with your project.
Next time I see you, you owe me $.02.
