Well, I finished my Bendix FI installation. The good news is the high power aspect works great. Need a tweak or two on the restrictors, but pretty close already. Performance is great.
My problem is hot idle. I had been struggling to get the mixture set. I finally adjusted to lowest MAP/highest RPM. this resulted in a 20-30 RPM drop when going to ICO. I did this with the engine hot, but the cowl top off. I was able to have it idle for several minutes without a hiccup. Nice, smooth and stable.
It was 75* OAT today. On initial flight, it idles great and all is good. Once it gets hot under the cowl, the idle is horrific. It will initially go to idle from a higher RPM. After 15-20 seconds it gets a bit rough then it starts to drop out (just about dies and comes back). It will keep doing that until I run it up. If I leave it there too long, I can barely get it up to RPM and it will not clear itself until about 1600 (seem this is the point completely off the idle circuit or FI compliment).
I just tried a whole bunch of different mixture settings (re-cowling each time) and always the same result. I even got it lean enough that it stumbled on acceleration. I suspect this has to be heat related and boiling gas somewhere. However, I don't know how you guys could deal with what I am experiencing. Taxi is quite difficult to keep it running and even had some rough running on short final 1000-1200. Landing roll out is also difficult once I am below 30 mph or so and windmilling effects slows.
The feeling is like it is "loading up." After the idle event, leaning at higher RPMs helps to clear it faster, further supporting that. However, I don't see how I am getting too rich at idle. I have it perfectly set and it purrs with the cover off. I have tried leaning with the mixture knob at idle to get a RPM rise, but I still get the same results.
please help. I messed with this all day and don't know how to address it. I really don't want to pull this all out and put the carb back, but this just doesn't seem safe.
EDIT: BTW, the EGT are all very consistent while this is happening, so I don't believe it is a single cylinder issue. However, I do notice that when trying to clear things out at higher RPM, 3 & 4 come back to higher EGTs much faster than 1 & 2.
Larry
My problem is hot idle. I had been struggling to get the mixture set. I finally adjusted to lowest MAP/highest RPM. this resulted in a 20-30 RPM drop when going to ICO. I did this with the engine hot, but the cowl top off. I was able to have it idle for several minutes without a hiccup. Nice, smooth and stable.
It was 75* OAT today. On initial flight, it idles great and all is good. Once it gets hot under the cowl, the idle is horrific. It will initially go to idle from a higher RPM. After 15-20 seconds it gets a bit rough then it starts to drop out (just about dies and comes back). It will keep doing that until I run it up. If I leave it there too long, I can barely get it up to RPM and it will not clear itself until about 1600 (seem this is the point completely off the idle circuit or FI compliment).
I just tried a whole bunch of different mixture settings (re-cowling each time) and always the same result. I even got it lean enough that it stumbled on acceleration. I suspect this has to be heat related and boiling gas somewhere. However, I don't know how you guys could deal with what I am experiencing. Taxi is quite difficult to keep it running and even had some rough running on short final 1000-1200. Landing roll out is also difficult once I am below 30 mph or so and windmilling effects slows.
The feeling is like it is "loading up." After the idle event, leaning at higher RPMs helps to clear it faster, further supporting that. However, I don't see how I am getting too rich at idle. I have it perfectly set and it purrs with the cover off. I have tried leaning with the mixture knob at idle to get a RPM rise, but I still get the same results.
please help. I messed with this all day and don't know how to address it. I really don't want to pull this all out and put the carb back, but this just doesn't seem safe.
EDIT: BTW, the EGT are all very consistent while this is happening, so I don't believe it is a single cylinder issue. However, I do notice that when trying to clear things out at higher RPM, 3 & 4 come back to higher EGTs much faster than 1 & 2.
Larry
Last edited: