IO550N Fuel system adjustment

[Adam Molny]

I've been having trouble controlling my CHTs on climbout lately, so I went back and checked my engine logs. Max fuel flows are around 25.2gph, but SID97-3E says the range should be 25.6-27.3. I want to increase the high end fuel flow using my fuel flow gauge (which is accurate to withing 1%). I found the "adjustable orifice" but I can't figure out what kind of tool to use. It looks like a Torx screw but I tried T-10, T-15, and T-20 and none of them fit.

Does anyone know what kind of tool to use on that adjusting screw? Is there a cap screw that has to be removed first?



Thanks,
Adam Molny

[George Wehrung]

I used an Allen wrench. I think it had the ball end on it so it could get a grip as the wrench goes in at a slight angle


Sent from my iPhone using Tapatalk

[George Wehrung]

Here’s from the SID97-3G which has been superseded by the M-0. It’s too hard to find in the M-0





Sent from my iPhone using Tapatalk

[Adam Molny]

A 5/32" allen wrench did the trick, thanks. A 1/2 turn increase raised my fuel flow to between 27.2 and 27.5gph at takeoff power so I'm satisfied with the result. The idle RPM increased a bit so I backed off the idle stop screw, and will play with the idle mixture screw if necessary.

Thanks again,
Adam Molny

[George Wehrung]

Glad it helped Adam!

Remember changing one adjustment requires re checking the other two parameters as they are all tied together


Sent from my iPhone using Tapatalk