TSIO-360LB - proper way to do a GAMI check on a turbocharged engine - TSIO-360LB

[tmo]

So according to page 2 of the Savvy flight test profiles the GAMI spread flight test  on a TC engine is supposed to be run at or below 65% power AND at an altitude where ambient pressure is equal to the MAP (so basically the engine is turbo normalized).

So, being the chicken that I am, wanting to do the lean test at 55%, I:

 - assume ambient pressure is ~30" (QNH) at sea level and changes -1" for every 1000 feet (from the Saavy doc)

 - look at page 5-20 of the POH and see that for 55% power at 2500 RPM and 6000 feet the MP should be ~24" (30-6)

 - start leaning, while adding a little MP as it drops (no auto wastegate), then richen, while reducing MP, repeat 3+ times, do LOP mag check

If QNH is 32, a high pressure day, I'd need to go up to 8000 ft, if it was 28, on a low pressure day, 4000 ft would have been appropriate, correct?

Anything I got very wrong?  Anything I am missing?

5-20-rotated.pdf

[gsxrpilot]

Did you upload the results to SavvyAnalysis? If so, post the link and we can verify it's done correctly.

It sounds right to me though. I actually think you might be over thinking the process. In my experience the ambient pressure is not that important. 

Just do the leaning very slowly so that the peaks are clearly defined. Also do the LOP, in flight, mag check for 60 seconds on each mag. Again to get good data.

Finally the 1 or 2 sec resolution on the JPI is also important. By default it's 6 sec which isn't fine enough resolution.

[tmo]

I didn't run it yet, the EDM is not yet installed.  Just planning and daydreaming...

Wilco on all the additional advice (slow lean, long mag check, quick sampling).

[kortopates]

If you start with a 60-65% ROP power setting, or just under, you should be fine since as you start leaning your power will drop. 

The reason for the running your target MAP at the same altitude that it equals ambient atmospheric pressure it to essentially eliminate any induction leak(s) from ruining your gami spread data. Once we have good baseline data its not so critical, but induction leaks are so common with our new clients that doing it this way really helps us get better data consistently. We have other ways to look at/for induction leaks.

With the 231 without a automatic controller, to get good data, its critical to use your AP and preferably with 2 people on board, so you can use both hands to manipulate the controls. You want to continuously change mixture as slowly as you can, and in both directions. But while doing so, you'll also see MAP changing and you'll need to make small adjustments to keep MAP as constant as possible as you go from the rich side to the lean side and vice versa. This will take some practice and frankly this is the hardest engine to collect good data because of the lack of an automatic controller to keep MAP stable for you. But if you do nothing, you'll see your MAP change over a couple inches and that really interferes with getting good data. The whole point of the test is to see only mixture change since we're measuring differences in cylinders peaking in GPH.

[tmo]

Thank you for the "why" behind seeking roughly equal pressure.  Makes sense, and, also, makes life easier, because I now know I don't have to get it exactly right in terms of percentage of power, just hit 6k, 2500, set MAP equal to outside pressure, make sure it's below 60% power, voila.  Looking forward to it.