GAMI Injectors

[nigelspeedy]

The mechanical fuel injection crowd will likely be aware of GAMI injector nozzles. When I first started flying my GAMI spread was ~0.8 gph and LOP it ran very rough, as in it felt like it was going to tear itself off the mount rough. I went through about 6 iterations of injector nozzle changes, each time adjusting the most rich or lean injector. Rather than aiming for 0 gph GAMI spread I set them such that every cylinder achieves 25 LOP as close as possible. Not much different but it seemed to make more sense to tune the system for the operating point rather than peak where I never run it. I can see the benefit of using GAMI spread as an easy to understand and measure parameter though. Being a mechanical system I see a little variation in the GAMI spread depending on operating condition and one leaning event to the next but only in the order of 0.1 - 0.2 gph.

I found GAMI to be helpful and responsive, although I think I tried their patience as a customer searching for a perfect setup.

Just to put it in financial perspective, the kit for my 4 cylinder Lycoming was $600. In the first year replacement nozzles are free as you tune the system, you just return the original and unused ones.

Today at 9000' PA with an OAT of 19C (ISA + 22C) I got the following in my RV-8 with constant speed prop:

100F ROP, 10.6 gph, CHT's 375F, 185 KTAS, 17.5 nm/gal.
25 LOP, 7.7 gph, CHT's 345, 175 KTAS, 22.7 nm/gal.

Running LOP results in a 30% improvement in specific range (nm/gal) with CHT's 30F cooler, at the expense of a 5.5% speed reduction. The good thing is I now have the choice to run ROP or LOP as the situation and mood dictate.

Lets say you fly 100 hours per year, and 75 of those are in the cruise where you lean the engine and fuel is $5/gal. By running LOP you would save over $1000 per year. So for me it was worth it to have the option, save money on gas and learn a bit about how my engine operates on the way.

A couple of things I would do differently. First I used the standard Vans 3 lever throttle quadrant and I find the mixture lever to be a bit coarse. I would use a single lever for throttle and vernier knobs for prop and mixture if I did it again. Second I hacked and chopped the baffles in front of cylinder #1 & #2 early on as they were the hottest. Not realizing that mixture has a such a great effect on CHT's these ended up being the coolest cylinders once I had the fuel injection tuned, and subsequently I had to add back baffle that I had earlier removed to match the CHT's. So in future I would solve the fuel distribution problem before starting on the baffling adjustments (not to say that you should not do as good as job of sealing the baffles as you can).

Overall if you are have mechanical fuel injection I would say that balancing the nozzles is a worthwhile exercise from an operational flexibility and economic point of view.

Cheers

Nigel

[Mark Dickens]

I've had GAMIs on 2 different Bonanzas, including the turbo-normalized set up, and am a strong believer in running LOP. One of the first things I plan to do after phase one is get to Airflow Performance and go through their nozzle tuning process. If I can't achieve less than a 0.3 spread doing that, then off to Ada I go.

[Jesse]

And, for an experimental, you can do it much less expensive than the certified GAMI's.

[cccjbr6]

+1 for Airflow Performance. Make the trip to Spartanburg for a tuning session, if you can. Don Rivera is an excellent teacher. You will learn a lot about your engine. He has a fascinating facility and the tour is great. After sale service is great too.

[DanH]

Originally Posted by Jesse

And, for an experimental, you can do it much less expensive than the certified GAMI's.

+1. Have not priced restrictors lately, but they were about $25 each from AFP. Typically might need two for a 4-cyl. Don't need the entire nozzle and restrictor assembly unless you have the old pressed-in style (here at bottom, cutaway nozzles and restrictors without screen and shroud):

[TS Flightlines]

+2 for Don at AFP. I had the pleasure of attending their FI class last fall, with a few other members of this forum. His knowledge and facilities can tune most any of the engines we typically see----and a bunch we dont see.
Outstanding customer service. I highly recommend that if you are using a mechanical injection, give Don and Colleen a call.
Tom

[Abraham]

Originally Posted by Jesse

And, for an experimental, you can do it much less expensive than the certified GAMI's.

And how do you do that? With what company?

[Rupester]

+ 3 for the great folks at Airflow Performance. After attending their FI 101 school in Spartanburg, I got my IO320 down to a 0.2 gph spread. Don and Kyle are superbly knowledgable and helpful.

[koupster]

Nigel,

Thanks for all your informative posts. I'm just now doing cruise performance testing.

Could you provide a few more numbers about your performance (Today at 9000' PA). Engine displacement (360, 390, or other), RPM, and MP.
Thanks.

Cheers, David
RV-6A O-360

[amekler]

i also give Don a vote. i started with gami on my tmxio540 and never got a small enough spread. They had be send the spider out ,etc. After months of frustration I went with Don and after only a couple of jet changes can fly LOP smoothly
GAMI would not give me a refund and said something was wrong with my engine.
What in reality was the fuel flow transducer location giving flucuatiing readings.
Don had me lean by moving the mixture one bump at a time.

Alan
N668G