Don Rivera at Airflow Performance is one of a small handful of people whom I consider to be true masters of their craft. I've had various correspondence with Don off and on over the past few years, and the guy sure knows his stuff. That, and he makes a friggin' kick butt fuel injection system (the AFP FM-200 that I run on my RV-7). Anyway, I've been touting the somewhat amazing economy that I've been able to get out of my airplane. A few weeks ago I think I posted a page here that showed me getting well over 30 miles per gallon while still cruising along respectably. Anyway, Don saw this and sent me some email, letting me know that there is potentially even more economy to be eked out of this already phenomenal setup. I'm already taking full advantage of LOP (lean of peak) operation, so how else can I improve economy (other than drag reduction or "major" engine tweaks)? The idea is basically to try using injector restrictors with a slightly smaller orifice, the goal being improved fuel atomization. By decreasing the size of the injector orifice, at the same fuel flow it should increase pressure slightly and thus have an effect on the nature of the "squirt." Improving atomization of the fuel would increase surface area and thus "improve" combustion (I'm no expert by any stretch, but I believe that's the layman's explanation).
Long story short, Don sent me some restrictors to play with. I have stock .028" restrictors currently, so he sent me some .025" restrictors to test out. On the right you can see one lone .028" (no markings), and on the left you can see the .025" ones, which are marked numerically and also with a band.
In case you haven't seen restrictors for injector nozzles before, here's another view or two. These puppies slip down into the body of the injector, and the stainless tube from the flow divider compresses right into the flare.
Even though it's only a .003" difference in orifice size, you can see the difference.
.028" on the left, .025" on the right.
Ditto.
I need to find the time to do some lean test flights. The goal is to develop a full set of leaning data (EGT per fuel flow for each cylinder) and send it to Don for computer analysis. Apparently he has software that will optimize the orifice size for each cylinder based on this data. I've already done basic lean tests to determine that my current setup peaks simultaneously (all cyls reach peak EGT at the same fuel flow), but I need to get some really detailed data for Don. Soon...
This year for my birthday, my family pitched in and got me some cool back-saving doodads. First is this Bogi-Bar from Bogert Int'l. This sucker makes pulling the plane into the hangar trivial. Previously I'd push on the horizontal, pushing the plane back. Now I can just clamp this onto the tailwheel axle and pull safely and securely. My back is muy grateful.
This is the 4-RV model, which works on any tailwheel RV (I believe).
The lever pulls the steel arms out to place it on the tailwheel, then you pull the arm back to release pressure...the arms clamp right onto the axle.
And now for the really cool stuff...continuing right along with the theme of saving my back. More birthday generosity from the family included this Tail-Mate tailwheel hoist. At more than $200, this sucker is not cheap. It's not even that complex. But some ingenious dude out there is making a small fortune because we "buy versus build" folks are willing to spend the bucks. At least our family is willing to spend the money on us (thanks guys!).
At the base is an adjustable cradle for the tailwheel. It's designed to work with just about any size tailwheel. The smallest adjustment works great on the RV.
Just wheel it right on up to the tailwheel...
...give it a shove (or a kick), and the cradle slides right under the tailwheel.
Now just crank the ratcheting winch, and the tail is hoisted skyward in a most painless manner.
Wanna see how easy it is? Check out the little video below...