I just purchased an RV8 today and planed on installing GAMI injectors. I was advised to install AirFlow Performance injectors instead. Does anyone know which size I will need? Not sure where to find it but I haven't been able to after digging online. Lycoming IO-360-B1F 180HP. Thanks
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Airflow Performance Injector Size
- Thread starter TheNewGuy
- Start date
No one can recommend sizes until you do a test. Pick your favorite cruise condition, and slowly lean recording the fuel flow as each individual cylinder hits peak EGT. Send the data to Don and he will recommend sizes. Some iteration may be needed.
Ok. I’ll give them a call and follow the process they have. Just heard of them today.
Edit: Better yet, I just saw they are 30 minutes away from me. I’ll give them a visit
Forget GAMIs. They are for the certified crowd.
Read this: https://airflowperformance.com/wp-content/uploads/2015/12/Nozzle-Tuning-Instructions.pdf
Go up and fill out this: https://airflowperformance.com/wp-content/uploads/2016/03/Engine-Data-Form.pdf
Send the above form to Airflow Performance. They will advise next steps, if any.
Read this: https://airflowperformance.com/wp-content/uploads/2015/12/Nozzle-Tuning-Instructions.pdf
Go up and fill out this: https://airflowperformance.com/wp-content/uploads/2016/03/Engine-Data-Form.pdf
Send the above form to Airflow Performance. They will advise next steps, if any.
Call Don first. He may recommend changing them all to .024" before running the test. That's what he had me do and then send him test data. Just changing to .024" from .028" helped. Then he spec'd the sizes needed to make it exactly right. Easy and his restrictor nozzles are fairly priced.
Just another data point, I did LOP fuel flow spread test on my RV10 at 6500 ft DA @ 65% power (ROP) with Lycoming stock nozzles (0.028). I got 1gph spread
#2 peaked at 11.3 gph
#5 peaked at 11 gph
#4 peaked at 10.9 gph
#6 peaked at 10.8 gph
#3 peaked at 10.7 gph
#1 peaked at 10.3 gph
Changed #2 to 0.0285 and #1 to 0.0275, now the FF spread is reduced to 0.5 gph which I can live with. I may do another iteration to further reduce the spread. #2 still is the leanest, needs up size a bit.
#2 peaked at 11.3 gph
#5 peaked at 11 gph
#4 peaked at 10.9 gph
#6 peaked at 10.8 gph
#3 peaked at 10.7 gph
#1 peaked at 10.3 gph
Changed #2 to 0.0285 and #1 to 0.0275, now the FF spread is reduced to 0.5 gph which I can live with. I may do another iteration to further reduce the spread. #2 still is the leanest, needs up size a bit.
As a general rule I recommend builders never go larger than the stock 0.028 nozzles. For how we fly this nozzle is much larger than ever needed. As Don Rivera discusses, the small nozzle to start (like his recommended 0.024’) provides a better spray pattern for our standard cruise settings but can still flow all the fuel the engine could ever drink. Here a call to Don is recommended to discuss.
So for your data, as a SWAG I might start with:
- 0.028 for #2
- 0.028 for #5
- 0.027 for #4
- 0.027 for #6
- 0.027 for #3
- 0.026 for #1
Go fly and get another set of data. For all my builds it takes one iteration to get in the ball park (like your 0.5GPH result), two to get close and three to get to a GAMI spread of 0.0 to 0.1GPH. While I can leaned to engine cutout with the engine running smooth, I strive for about the same LOP numbers on all the cylinders. I find the 20 to 30 degrees LOP to be the sweet spot for cross country efficiency while still going RV speeds.
Keep in mind changing one nozzle will change flow in all the others. Thus an iterative process.
Side note - after all the tuning over the years I had a collection of left over nozzles (mostly 0.028” but smaller ones as well). They went on to a second life in other builder’s RVs for their tuning process.
Side note #2. A buddy (RV-14A) spent the money on GAMI injectors. The resulting GAMI spread was ~0.5gph which I consider not good enough.
Carl
Please just be careful when switching to the .024 orifice nozzle from the .028 nozzle. You should check that you have enough fuel pressure to make the switch. If you system fuel pressure is not up to the task, you may not have pressure to supply enough fuel at high power settings.
While don does recommend.024’s for the 4 cylinders, he recommends.025’s for the 540’s.
Kyle pushed me to 0.024ish for my 540. They actually recommended starting with (IIRC) 0.0235's in 1&2, 0.024's in 3&4, and 0.0245's in 5&6. I ended up swapping nozzles around and ultimately ended up buying 3 additional nozzles to get things matched up.
After some consultation with AFP and experimentation with different size restrictors, my IO-360 is running the stock .0280" injectors on 3 cylinders, and a .0275" on one jug that wanted to run slightly rich. For my engine that got me a nice tight EGT spread when running LOP.
Out of curiosity I emailed Kyle at AFP to ask what he thought about the recommendation to use .024" restrictors... bottom line, there isn't any blanket recommendation, it really depends on a lot of other factors about your engine and fuel system that I won't try to summarize here. For my engine he recommended sticking with what I've got since it's running great. Best thing to do is consult AFP, they are a wealth of knowledge.
Out of curiosity I emailed Kyle at AFP to ask what he thought about the recommendation to use .024" restrictors... bottom line, there isn't any blanket recommendation, it really depends on a lot of other factors about your engine and fuel system that I won't try to summarize here. For my engine he recommended sticking with what I've got since it's running great. Best thing to do is consult AFP, they are a wealth of knowledge.
interesting. maybe they have learned more. They gave me a similar spread, but centered around the .025.
