Author unknown:
For those of you with IO-360 engines, you might want to consider the GAMI fuel injectors as a way of cutting down fuel burn. I just got a set in my Bonanza, and while the IO-520 is a smooth running engine, it’s even smoother with the GAMI injectors; especially when running Lean Of Peak.
Editor:
I don’t want to rub anyone the wrong way, but I’m compelled to make mention on this. As most of you can appreciate, what’s great for one engine isn’t necessarily great for all.
I’ll begin by saying that the folks at GAMI are great guys, with great products; they are doing some of the best aircraft engine performance engineering going right now, and I am avidly looking forward to some of the products they are currently testing. Their engine management seminar is expensive, but is an eye-opening experience. I have talked with many people who have attended it, as well as with some of the GAMI folks, and I hope I can afford to go myself one of these days. I also installed GAMIJectors in my buddy’s V35A Bonanza (IO520 Continental), with great results.
Now the contrasting information. There may be someone out there with a different experience, but I have spoken with three people who installed GAMI’s in their IO360 200HP Lycoming. None of them felt they had experienced any benefit at all from the injectors. I can personally run my IO360-A1B6 at least 25 degrees lean of peak with minimal (and acceptable) roughness (along with the usual marked loss of power).
There is a reason for this disparity of results. The IO520 does not have a balanced induction system. As a result, each cylinder receives a significantly different amount of air. The primary reason the GAMIJectors were developed was to address this specific shortcoming on this particular engine. Of course, they will also help any similarly unbalanced-induction engine for which they were further developed.
The Lycoming IO360 200HP engine has balanced induction tubes, that project into the air plenum below the oil sump. These tubes pick up relatively cool air that is not surrounded by the hot oil. As a result, the IO360 cylinders receive a much more balanced air charge. They therefore benefit much less from injectors having different flow ratings.
The IO360 induction is so relatively well balanced that I offer you an alternative proposal. This assumes that you do have the 4-probe EGT capability that is required for the purpose. Next time you fly, slowly lean your engine to, and slightly beyond, peak EGT. This is best done at or above perhaps 7,000 feet, so that you can use full throttle and can control power using only RPM and mixture.. Use 2,400 or 2,500 RPM; whatever you are comfortable with, but stay below 75% power at this stage of your experience. Make a note of the sequence in which each cylinder peaks, and the temp spread between the first and the last (if you have something like a JPI-700/800 that inverts the display for LOP work). Let’s say that the cylinders peak as “3421”. Next time it is convenient, simply swap the injectors between 3 and 1, and between 4 and 2. Then run the test again. If you do this a few times, you’ll probably wind up with 90% or more of the GAMI benefits (on this particular engine), without the high cost of the new injectors.
While it is possible that you’ll get no benefits, and that your current injector placement is completely optimized, it is highly
unlikely. While the Lycoming injectors are manufactured to a high quality tolerance, there is a tiny flow variance between them. Since you are only dealing with tiny differences in fuel flow during this process, the manufacturing variance can be enough to gain an improvement.
GAMI is doing some very interesting work on engine controls. They are pursuing ignition and fuel management methodologies that could enable our “high compression” (8.7 to 1) engines to operate on unleaded high-octane motor fuel. In my opinion they are on by far the most promising track, by designing sensing for peak pressure pulses (and therefore detonation as well), and directly controlling engine timing to achieve best power or best economy on unleaded fuel. I hope to see their work pay off before we encounter any 100LL shortages due to tetraethyl lead elimination.