NicoN Posted June 11 Report Posted June 11 (edited) Recently, my co-owner found a GAMI-spread of 1,0 ..1,2 gallons between leanest and richest cylinder 2 and 4. Our A/P cleaned the nozzles with ultrasound and MEK, but teh result is noo change. What to do in this case? Swap nozzles 2 and 4? BTW: my co-owners says not to fly LOP. Is our GAMI-Spread really too high? Edited June 11 by NicoN
Pinecone Posted June 11 Report Posted June 11 1) Do you have GAMIjectors? If so, someone put the wrong injectors in the wrong cylinders. 2) If you find the injectors are in the proper holes, you have some other issue like an intake leak. 3) Once you fix all the other issues, contact GAMI with the new data and they will adjust your nozzles for a small fee. If the answer to 1 is that you don't have them, then order them.
dkkim73 Posted June 11 Report Posted June 11 That's too high (the spread). I've heard some people caution against GAMIjectors for some planes, and experiment with swapping the Continental injectors. But I think most of the time the consensus is GAMIjectors/TurboGAMIjectors are better. I would imagine the best path is to collect detailed engine data and consult with GAMI (free). Very good point above about making sure something else isn't off (esp. air leak into the system) first. As for ?LOP at all? that's a broader question that will beget a forum riot soon. I think it's great and at the very least a fantastic tool to have in your quiver. Which tool you will not have with too high a spread... 1
Ragsf15e Posted June 11 Report Posted June 11 You could possibly still safely run LOP, but it’s unlikely to be smooth or efficient. You’ll have to get the richest cylinder past peak, by which time the leanest one is very lean and possibly not firing smoothly. You need a better spread to do it right. If nothing else is wrong, gami injectors will solve it. If you already have them, it’s cheap to fix by working with gami.
Wingover Posted June 11 Report Posted June 11 6 hours ago, NicoN said: Recently, my co-owner found a GAMI-spread of 1,0 ..1,2 gallons between leanest and richest cylinder 2 and 4. Our A/P cleaned the nozzles with ultrasound and MEK, but teh result is noo change. What to do in this case? Swap nozzles 2 and 4? BTW: my co-owners says not to fly LOP. Is our GAMI-Spread really too high? Talk to Justus at ACG Aircraft in Germany. 1
blaine beaven Posted June 14 Report Posted June 14 Make sure you are checking the spread at around 65% power. I did it once at 75% and it showed a spread of 0.5 gal. When I check the spread at 65% power it’s 0.0 to 0.1.
1980Mooney Posted June 14 Report Posted June 14 On 6/11/2025 at 4:52 AM, NicoN said: Recently, my co-owner found a GAMI-spread of 1,0 ..1,2 gallons between leanest and richest cylinder 2 and 4. Our A/P cleaned the nozzles with ultrasound and MEK, but teh result is noo change. What to do in this case? Swap nozzles 2 and 4? BTW: my co-owners says not to fly LOP. Is our GAMI-Spread really too high? You didn’t mention if there were any events prior to finding this: - How long/flight hours ago did you or partner last record tighter/normal spreads? - Was any work done on the engine recently or recent Annual prior to discovering the high spread?
NicoN Posted June 15 Author Report Posted June 15 In the meantime my partner analysed our JPI data and is of the opinion that in September 2023 the spread increased. I think a couple of month we had 2 cylinders replaced. At least one is in the group of leanest/ richest.
Rick Junkin Posted June 15 Report Posted June 15 20 hours ago, blaine beaven said: Make sure you are checking the spread at around 65% power. I did it once at 75% and it showed a spread of 0.5 gal. When I check the spread at 65% power it’s 0.0 to 0.1. Hmm. I do my GAMI sweeps at my cruise MP/RPM power setting to verify the spread is <0.5gph. My logic is this is the power setting at which I will be running the engine LOP and where I want to verify the fuel flow is balanced best for smoothest operation in cruise. I know I read a recommendation for this approach about 9 years ago when I initially set up my engine. I believe it was on the GAMI web site, but it might have been something from Mike Busch or John Deakin. The other checks Savvy suggests for induction leaks and in-flight mag checks I perform at a lower power setting, nominally 65%, to keep the temperatures under control. Minor thread creep, sorry about that. 1
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