Frequently Asked Questions
This FAQ is divided into 2 sections: 1) applicability questions, and 2) operational questions. Check both sections, as there is sometimes some overlapping information.
Applicability
For what specific engine models has the FAA approved GAMIjector® fuel injectors?
Please visit our compatibility page for the latest FAA approval on both Continental Motors and Lycoming engines.
What about Continental Motors engines with top-mounted "tuned" induction systems, like the GTSIO-520 and IO-550-G? Would they too benefit from GAMIjector® fuel injectors?
GAMI has instrumented and flight-tested GAMIjector® fuel injectors in a number of these engines. While they have less uneven mixture distortion than other Continental Motors engines, the GAMIjector® fuel injectors provide noticeable improvement, although not always as much as with bottom-induction engines.
What about fuel-injected Lycoming engines? Could they benefit from GAMIjector® fuel injectors?
GAMI has gathered data on thousands of these engines, and found that injected Lycomings also have substantial mixture distribution imbalances that could be corrected with GAMIjector® fuel injectors. Among other things, we've found that Lycomings manufacturing tolerances on their fuel injector nozzles are extremely broad, causing them to have significant variations in flow. GAMI now is certified for almost all normally aspirated Lycoming engines. GAMI has also completed FAA-Certification Testing for the turbo-charged engines and has the STC in hand. For the latest on GAMIjector® fuel injector engine certifications, see our compatibility page.
My engine is still under factory warranty. Will installation of GAMIjector® fuel injectors on my engine void my warranty?
Excellent Question! Continental Motors' official position is that Continental Motors will not dishonor any warrant merely because of the addition of any STC'd part or modification. This has been publicly confirmed by several Continental Motors representatives. In addition with over 22,000 sets sold to date, GAMI is not aware of a single warranty claim by Continental or Lycoming where GAMIjector® fuel injectors were named as a contributing factor.
They do, however, reserve the right to dishonor the warranty if they can demonstrate that the failure was caused by the modification, with the burden of proof being on the manufacturer.
What happens with my GAMIjector® fuel injectors when I change engines?
Continental Engines:
At one time, with most Continental engines, you would get one of two possible nozzle sizes, depending on the "M" or "P" code on the fuel distribution manifold (aka fuel spider).
For example, in the IO-520-M, it was D12C or D12D. Depending on which nozzle size you had in the engine, you would get either the GAD12C or GAD12D GAMI kit.
Recently (post-2003), Continental has standardized that somewhat and most engines now use the smaller of the two sizes, though they use a different numbering system.
If your old engine had the size GAMI kit that is compatible with the new engine, we can recertify those nozzles for the new engine serial number for a fee, generally $349.
If the GAMIjector® fuel injectors from the old engine are not compatible with the new engine, we would offer you a 25% discount on a new set in exchange for that old set.
Lycoming engines:
We can recertify those nozzles for the new engine serial number for a fee, generally $349.
Operational
What should my temperature spread (EGT or CHT) be?
This question, or some variation of it, is the most common question we receive. The truth is, the temperature spread isn't very important. We want the EGTs to reach their peaks at close to the same fuel flow, or same time as you lean the mixture, but the absolute value of the temperatures is not very important.
However, we want to keep the CHTs under 400°F, and ideally even 380°F or less. We also want to keep the TIT under the typical 1650°F TIT limitation (some engine TIT limits are higher).
There is no maximum for EGT.
How high can I run my EGTs?
Similar to the question above, there is no maximum for EGT, nor an EGT that is too high for operation. However, it is important that the CHTs are cool enough (ideally 380°F or lower) and the TIT is below its redline (typically 1650°F).
It is also important that you are appropriately RICH or LEAN of peak EGT.
How RICH or LEAN of peak EGT should I set my mixture?
This is the second most common question we receive! Pilots tend to try and over-complicate this part. While the science of engine operation is fascinating, and the intricacies can take years to fully understand, setting the mixture in actual practice is fairly simple.
In most normally-aspirated (i.e. non-turbocharged) engines, setting the mixture ~100°F RICH of peak EGT or richer, or ~20°F LEAN of peak EGT or leaner will produce pretty good results.
In turbocharged engines, or higher-than-stock compression engines at higher power settings (75% and up), you need to be a little richer (125°F ROP) or a little leaner (50°F LOP).
If running RICH of peak, you want to use the FIRST cylinder to peak as you lean from the rich side, and if running LEAN of peak, you want to use the LAST cylinder to peak as you lean from the rich side as your reference cylinder.
As in the above questions, it is important that the CHTs are cool enough (ideally 380°F or lower) and the TIT is below its redline (typically 1650°F).
Another important note: On the RICH side, you RICHEN further to make things cooler. On the LEAN side, you LEAN further to make things cooler.
For more in-depth information, you should check out our articles page and the Advanced Pilot Seminars website.
Mechanical/Technical
I have some fuel staining around my nozzles. What is causing that?
I see that fairly regularly on both the GAMIjectors and the stock CMI and Lycoming nozzles. The fuel injector nozzles on a naturally aspirated engine have 4 air holes spaced around the periphery of the nozzle body (under the screen and shield). While the engine is running, engine vacuum pulls air into those air holes. That is what creates the atomization of the fuel spray as it leaves the injector.
There are a few conditions that can cause the fuel to exit those air holes. The most common is when the engine is not running. During the priming sequence and shortly after shutdown, fuel is present in the lines, but there is no engine vacuum to draw air through those holes. Although the outlet of the fuel inside the injector body is slightly lower than the air holes, and most of that fuel drains into the intake chamber of the cylinder head, there is still some opportunity for a small amount of fuel to be pushed into the nozzle air chamber and out of those air holes. That generally presents itself as a stain around the lower portion of the nozzle and the injector port in the head. That is generally no larger in diameter than about 1" when it happens at shutdown, though signs of fuel running down the fins of the cylinder can happen with heavy priming.
A less common occurrence happens in flight. The root cause is that there is not enough positive pressure differential (form outside to inside of the nozzle body) to create a constant, uninterrupted flow of air into the air bleed holes in the side of the nozzle. Some engines have, through either ram air or just really free flowing intakes at high airspeeds, the ability to almost equalize the pressure between the intake and the upper cowling at wide open throttle. In the case of ram air, the intake pressure may actually be higher than the upper cowling pressure. In aircraft such as Bonanzas and Barons, you'll most likely see this on cylinder 5 or 6, as they are the ones furthest forward in the cowling and may have less air pressure around them than further back in the cowling. On Comanches and RVs, you'll more often see this on #2 (for the same reason). This will present itself as staining on the upper cooling fins, baffling, or even upper cowling. In our estimation, there isn't enough fuel present to be a fire hazard, however in those aircraft that experience this you can eliminate that my very slightly closing the throttle (maybe 1/2 in. Hg).
If you have any questions that are not answered here please contact us.