GAMIjectors & TurboGAMIjectors FAQ:
Answers to Frequently Asked Questions About These General Aviation Products

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A supplement to Mike Busch's AVweb review of the new GAMIjectors and TurboGAMIjectors from General Aviation Modifications.

GAMIjector cutawayLATEST FROM GAMI! GAMI has received its long-awaited STC for the installation of GAMIjectorsTM on TCM IO-360 and TSIO-360 engines found on the Mooney 231, Piper Turbo-Arrow and Seneca, Cessna Skymaster (including Turbo and Pressurized), etc. Only the TSIO-360-MB engine (Mooney 252) is excluded from the STC.

GAMI is also now offering GAMIjectorsTM for Lycomings! See AVweb's in-depth review by Carl Marbach.

QUESTION: For what specific big-bore TCM engine models has the FAA approved GAMIjectors?

    ANSWER: In STC number SE09217SC, the FAA approved GAMIjectors for use on all normally-aspirated TCM IO-470, IO-520 and IO-550 engines that employ a bottom-mounted induction system. This STC covers the following specific TCM engine models:

    • IO-470-A, -C, -D, -E, -F, -G, -H, -J, -K, -L, -LO, -M, -N, -P, -R, -S, -T, -U, -V, -VO, and L/IO-470-A.
    • IO-520-A, -B, -BA, -BB, -C, -CB, -D, -E, -F, -J, -K, -L, -M and -MB.
    • IO-550-A, -B, -C, -D, -E, -F and -L.

    In STC number SE09289SC, the FAA approved turboGAMIjectors for use on all turbocharged TCM TSIO-520 engines that employ a bottom-mounted induction system, as well as certain IO-520 and IO-550 engines equipped with aftermarket turbonormalizer conversions. This STC covers the following specific TCM engine models:

    • TSIO-520-A, -B, -BB, -C, -D, -DB, -E, -EB, -G, -H, -J, -JB, -K, -KB, -L, -LB, -N, -NB, -M, -P, -R, -T, -U, -UB, -AE, -AF, -VB, -WB and -CE.
    • IO-520-B, -BA and -BB turbonormalized with STC SE5222NM.
    • IO-550-B turbonormalized with STC SE5222NM.
    • IO-520-D turbonormalized with STC SE00215DE.

QUESTION: What about TCM engines with top-mounted "tuned" induction systems, like the GTSIO-520 and IO-550-G? Would they benefit from GAMIjectors?

    ANSWER: GAMI has instrumented and flight-tested GAMIjectors in a number of these engines. While they have less uneven mixture distribution than other TCM engines, the GAMIjectors provide noticeable improvement, although not as much as with bottom-induction engines. GAMI is applying for STCs for these engines as well, and hope to have them approved in late 1997.

QUESTION: What about small-bore TCM engines like the IO-360 and TSIO-360 engines in Mooneys, Turbo-Arrows, Senecas, Skymasters, etc.?

    ANSWER: We just received an STC (SE 09401SC) covering all TCM IO-360 and TSIO-360 engines, with the sole exception of the TSIO-360-MB engine in the Mooney 252. We are now shipping GAMIjectors for these engines. The 360-series Continentals have precisely the same sort of mixture imbalances as the big-bore engines, and would benefit from GAMIjectors in exactly the same fashion. And because many IO-360 and TSIO-360 installations tend to be tightly cowled and hot-running, the reduced CHTs made possible by lean-of-peak operation will be especially valuable with these powerplants.

QUESTION: What about fuel-injected Lycoming engines? Could they benefit from GAMIjectors?

    ANSWER: GAMI has done tests with a number of these engines, and found that injected Lycomings also have substantial mixture distribution imbalances that can be corrected with GAMIjectors, although for completely different reasons than in the TCM engines. Among other things, they've found that Lycoming's manufacturing tolerances on their fuel injector nozzles are extremely loose, causing them to have random variations in orifice size that sometimes exceed the variations GAMI intentionally engineers into a matched set of TCM GAMIjectors! GAMI now has STCs for a variety of Lycoming engines — contact the company for details.

QUESTION: I'm interested in ordering a set of turboGAMIjectors for my Cessna T210. However, my GEM shows that my #4 cylinder peaks first, not #1 or #2. Will turboGAMIjectors still work on my engine?

    ANSWER: GAMI gets questions like this all the time. The answer is: if your bottom-induction TCM engine does not exhibit the characteristic maldistribution pattern in which the rearmost cylinders (#1 and #2) are leaner than the others, then there's something wrong with your engine! You might have mismatched or out-of-tolerance or dirty injector nozzles. Or you might have an induction leak. GAMI says they have never seen a bottom-induction TCM engine with equal-flow nozzles and an airtight induction system that did not exhibit the characteristic rear-is-leanest pattern.

QUESTION: My engine is still under factory warranty. Will installation of GAMIjectors on my engine void my warranty? What is TCM's position on this?

    ANSWER: Excellent question! TCM's official position — as stated in public by their west coast technical representative Loren Lemmen in response to a direct question from a crowd of 100 Bonanaza owners — is that TCM will not dishonor any warranty merely because of the addition of any STC'd part or modification. 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 TCM.

    Given the fact that the Designated Engineering Representative (DER) who worked with GAMI to secure FAA approval of GAMIjectors is the former Vice President of Engineering for TCM, and he says that the mixture maldistribution problem fixed by GAMIjectors has been known and understood at TCM for several decades, it seems very unlikely that TCM would ever claim that a cylinder problem is a result of a GAMIjector, unless GAMI screws up and miscalibrates a nozzle badly. In that case, GAMI states unequivocally that it will stand behind its product and fix the damaged cylinder.

    GAMI now has over 1,500 sets of GAMIjectors and turboGAMIjectors flying, and all were sold with an absolute money-back satisfaction guarantee. So far, not one person has wanted their money back. (Actually, early on, one customer did get his money back, but about 30 days later he changed his mind, said he had made a mistake and didn't understand what he was doing, and had GAMI send him back his nozzles, and paid for them again.) To date, no GAMIjector-related warranty claims have come up with TCM.

STILL HAVE QUESTIONS? Contact General Aviation Modifications, Inc., by e-mail at, by FAX at 1-580-436-6622, or by telephone at 1-580-436-4833.

GAMIjector cutaway

General Aviation Modifications, Inc.
2800 Airport Road, Hangar "A"
Ada Municipal Airport
Ada, Oklahoma 74820